Thesis Defense: Mapping and Estimating Expansion Rates of Arundo donax in Native Fish Conservation Areas of Central Texas
Major Advisor: Dr. Jason P. Martina
Committee Members: Dr. Jennifer Jensen (Geography), Dr. Paula Williamson
Tuesday, December 12, 2023, 10:00 am, Supple 257
Invasive species management is often hindered by delays in detection or knowledge gaps of species-specific expansion rates. When monitoring is irregular, disturbed and even protected natural areas become more vulnerable to advancing invasions. Such monitoring often requires labor intensive surveys, sometimes in remote locations, costing time and resources that could otherwise be used in the treatment stage of management projects. As small Unmanned Aerial Systems (sUAS) and accessible satellite imagery become more available to land managers and researchers, an avenue has been created for early detection of conspicuous invasive species. My aim was to map and assess the expansion rate of Arundo donax, an invasive giant reed that infests freshwater systems globally. Arundo donax poses a significant threat to the designated Native Fish Conservation Areas (NFCAs) of Texas where its tall stature and high biomass production threatens to alter water flow and its competitive propensity leads to decreased local native diversity. High resolution multi-spectral imagery collected around known populations of A. donax permitted the isolation of the species’ unique spectral response. This spectral response was then compared to satellite imagery with greater coverage –Sentinel-2 satellite – for the development of a classification map encompassing a 200 m buffer of riparian zones within several targeted NFCAs across Texas. Our model performance encountered some difficulty, attributed to variation of soil reflectance and vegetative seasonality, but performs acceptably within two Central Texas NFCA for the 2022 classification (overall accuracy: 71%, kappa: 0.46). These NFCAs have been emphasized for investigation of A. donax’s expansion rate. Expansion rates were highest in the Southern Edwards Plateau, increasing ~ 0.284 km2/year. Project products of the first remote sensing-based map of Arundo within these NFCAs, as well as elucidated expansion rates, will benefit land management agencies. Methodology for continued detection and reevaluation of expansion rates may be replicated in the future for identification of priority treatment areas.
Bio: Jenna DeMent is from Lake Charles, Louisiana but now calls Mont Belvieu, Texas home. She earned her B.S. in Biology with an Ecology emphasis from Texas A&M – Corpus Christi University, where she worked in various wetlands surrounding the “Island University”. Her investment in habitat and natural resource management stemmed from observing her home wetlands of western Louisiana and eastern Texas being developed into a sprawling suburban landscape. After working as a wetland specialist with agencies like the Texas Parks and Wildlife Department and The Nature Conservancy, Jenna joined the Martina Lab in 2021 to pursue a M.S. in Population and Conservation Biology. While she looks forward to returning to the swamps of the Southern Coast to improve restoration efforts, she is glad to first continue her work with Dr. Jason Martina at Texas State University for the completion of a Ph.D. in Aquatic Resources and Integrative Biology.
Dissertation Defense: It’s Not Easy Being Green: The Effects of Conventional and Alternative Agricultural Practices on Stress Physiology and Immune Function in Tadpoles
Major Advisor: Dr. Caitlin Gabor
Committee Members: Dr. Lauren Fuess, Dr. David Rodriguez, Dr. Jessica Hua (Binghamton University), Dr. Blake Hossack (USGS)
Tuesday, December 12, 12 pm, Norris Conference Room
Exposure to pesticides can cause a variety of adverse effects in wildlife including dysregulation of hormonal responses, decreases in immune function, and increased parasite prevalence. The glucocorticoid response modulates physiological and immune responses to environmental stressors. Conventional agriculture has been linked to both changes in glucocorticoid regulation and increases in Echinostoma parasite infections in amphibians. Organic agriculture is the most widely used alternative agricultural method, but organic farming often requires more frequent chemical application and more land to match conventional food production, leading to increases in agricultural encroachment. I studied the links between the glucocorticoid stress response and parasitic infections in Hyla sp. tadpoles in response to conventional and organic farming. In the field, I found that tadpoles from both organic and conventional farms had reduced stress responsiveness and increased negative feedback efficiency, which may help these tadpoles cope with agricultural stressors. Organic and conventional farms had less canopy cover and higher water temperatures, which were associated with higher Echinostoma parasite infection prevalence compared to tadpoles from natural ponds. In the laboratory, I exposed tadpoles to either the conventional herbicide glyphosate or the organic herbicide citric acid. Tadpoles exposed to glyphosate had higher survivorship than both citric acid and control tadpoles. Glyphosate exposed tadpoles were also larger than both control and citric acid tadpoles and had lower glucocorticoid release rates. Taken together our results indicate that organic agricultural methods are not less stressful to amphibians and that the increased risk of agricultural encroachment from organic farms may increase loss of wetland canopy cover and alter Echinostoma infection patterns in tadpoles.
Bio: Amanda was born and raised in Capac, Michigan where she conducted her PhD research. She received her B.S. from Michigan State University in 2015 and worked on reptiles and amphibians in Michigan, Nevada, Florida, and Guam before starting her Ph.D. in 2019.
Dissertation Proposal Defense: Hotspots, Self-Policing, and Charisma: An Exploration of Factors Influencing Recreational Disturbance to Texas Waterbirds
Major Advisor: Dr. Christopher Serenari
Committee Members: Dr. Clay Green, Dr. Leila Siciliano-Martina, Dr. Anthony Deringer, Dr. Elena Rubino (University of Arkansas at Monticello)
The number of people living and visiting global coastal regions has increased in the last fifty years. During this time, recreational disturbance to avian species has increased through human development and activities, resulting in a decrease in bird populations. While many recreationists may believe that mortality is the only type of harmful disturbance, direct and indirect anthropogenic activities as well as natural occurrences, such as storms, that cause stress to nesting birds, induce nest abandonment, and increase energy expenditure can also negatively impact species numbers. Waterbirds are most sensitive to human disturbance because of the sensitivity of coastal habitats and waterbirds reliance on these habitats. This dissertation addresses the decline in waterbird populations and efforts to reduce their disturbance in three ways. Specifically, the proposed study will identify recreation hotspots in waterbird habitat, the drivers of self-governance (the ability for a recreationist to police themselves), and the importance of species attributes on perceived species value. Data will be collected by administering a quantitative survey to anglers, boaters, and non-motorized watercraft users. Survey administration will occur in person push-to-web postcards, and via email, allowing recreationists who are potentially responsible for the disturbance to waterbirds on Texas’ coast to be contacted. Analysis will primarily include spatial analysis to reveal disturbance hotspots and inferential analysis using a series of multiple linear regressions to identify variables that help mitigate disturbance to waterbirds. Findings will aid advancements in theory while providing tools for management to potentially aid in mitigating disturbance to waterbird populations.
Bio: Abigail is from Virginia and graduated with her bachelor's degree from Michigan State University in Animal Science before getting her Master’s degree in Wildlife Science at the University of Tennessee Knoxville. Her love of the outdoors coupled with her desire to work with wildlife, leading her to focus on human dimensions of wildlife for her master’s and Ph.D. She is supported by her lab, friends, and family on this academic journey.
Dissertation Proposal Defense: Investigating prevalence of the anuran chytrid fungus, Batrachochytrium dendrobatidis, across three mainland regions of Ecuador (Coastal, Highlands, and Amazonian)
Maria Del Mar Moretta-Urdiales
Major Advisor: Dr. David Rodriguez
Committee Members: Dr. Chris Nice, Dr. Shawn McCraken, Dr. Dittmar Hahn, Dr. Ana Longo
Monday, November 27, 2023, 1 PM, Norris Room
Ecuador hosts more species per unit area than any other country on Earth. With an estimated 676 species of amphibians, Ecuador ranks third globally in amphibian diversity levels, and is home to 36% of the endemic amphibian species of the world. However, Ecuador is also experiencing severe amphibian population declines, with over 200 threatened species, which are primarily attributed to increases in habitat loss and emerging infectious diseases (EIDs). One such EID is chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd). This disease has been implicated in the decline of hundreds of amphibian species globally. Given its generalist nature and cosmopolitan distribution, Bd is considered amongst the most devastating wildlife pathogens in recorded history. For my thesis, I am investigating the prevalence of Bd and ecological drivers of infection across three Ecuadorian habitats: the Coastal region, the Ecuadorian highlands, and the Amazon. I am examining how phytotelmata act as potential reservoirs for Bd and what key factors influencing Bd prevalence in these systems. Additionally, I am studying taxonomic affinity and host-specificity of Bd prevalence through host mitochondrial DNA sequencing. Through this work I will clarify Bd dynamics across Ecuadorian habitats and host taxa shedding light on the role of phytotelmata in the persistence and spread of Bd in forest canopies.
Bio: Mar is a conservation scientist, tree climber, and a disease ecologist. As part of her research, she is studying the spread of diseases in amphibians living in the canopies of forests in Ecuador. Mar actively collaborates with Ecuadorian universities, NGOs, and local communities while offering research opportunities to Ecuadorian biologists, undergraduate students, and tree climbers. Her goal is to be a bridge between local communities, science, and conservation. Mar is interested in understanding and measuring amphibian disease dynamics and cryptic amphibian declines across the three regions of Ecuador, including spaces where amphibians are already affected by deforestation, such as urban forests. She works with local stakeholders to advocate protecting the remaining forests in highly disturbed ecosystems while continuing to teach and mentor Ecuadorian biology students.
Thesis Defense: Effects of nitrite and probiotics on physiology, olfaction, and disease susceptibility in channel catfish
Major Advisor: Dr. Mar Huertas
Committee Members: Dr. David Prangnell, Dr. Camila Carlos-Shanley
Friday, November 10, 2023, 8 AM, Supple 257
Fish farming is one of the fastest-growing food production methods in the world. Channel catfish are one of the main finfish produced for food and sport. The commonly cultured species Channel Catfish Ictalurus punctatus is threatened by the highly virulent bacterial pathogen Edwardsiella ictaluri, which causes the disease Enteric Septicemia of Catfish (ESC). ESC can cause up to 100% mortality in infected ponds. Additionally, continuous exposure to nitrite, a derivate from ammonia waste in fish that is common in intensive aquaculture practice, can exacerbate infection rates and lead to higher fish mortality rates. Our experiments aimed to see the protective effect of probiotics against E. ictaluri in fish chronically exposed to nitrite. We designed a probiotic diet for catfish using endogenous bacteria from the channel catfish olfactory organ and gut contents and exposed fish to nitrite, probiotics, and nitrite plus probiotics. Then, we challenged the treated fish with Edwarsiella ictaluri and looked at the effects of treatments on juvenile channel catfish mortality, nitrite content in tissue, olfactory function, and microbiome. Our results showed that nitrite accumulates in the organs. Also, the nitrite and probiotics affected olfactory function. Finally, we found that nitrite and probiotic treatments affected the olfactory rosette and gut microbial loads. The probiotic treatment increased bacterial presence in the olfactory rosette and gut. Nitrite had the opposite effect, wiping out the microbiome of the olfactory rosette and gut. For catfish aquaculture, our results found potential probiotic species that could be used to reduce fish infection by Edwardsiella ictaluri. We also showed that bacteria and nitrite significantly impact olfaction sensitivity in catfish, which farmers need to consider when maximizing feed conversion ratios. In fish management, nitrite is often overlooked as a stressor, so our study can persuade farmers to look at nitrite when considering overall fish health.
Bio: Ashley received her bachelor's degree in biology from Colorado State University in 2018 . She spent the next two years working in biotechnology. She hopes to use this Aquatic Biology master's degree in conjunction with a future chemical engineering degree from Colorado State University to aid in the development of clean energy systems.
Thesis Defense: Whole genome analysis of Escherichia coli and Pseudomonas aeruginosa mixed culture biofilms grown for 117 days in spaceflight
Committee Members: Dr. Kavita Kakirde, Dr. Davida Smyth (TAMU-SA)
Friday, November 10, 2023, 10 AM
Biofilms tend to have an increased tolerance to physical and chemical stressors. Biofilms are capable of damaging water-associated infrastructure not only on Earth but on spacecraft in space as well. In addition to damaging structures, biofilms could potentially act as a source of infections for crew members on spacecraft. In an unexpected event, an experiment where mixed-culture biofilms of Escherichia coli strain F11 and Pseudomonas aeruginosa strain PA01 sent into space with SpaceX CRS-21 to analyze the effects of microgravity were left untouched for 117 days. Upon arrival back to the Earth, viable cells were found. This situation led to a great opportunity to analyze the effects of spaceflight on extended growth and microbial evolution of the biofilms. Out of the 24 spaceflight samples returned, 17 still had viability. Of those, E. coli was found only in non-treated (0ppb AgF) samples while the P. aeruginosa was found to have survived the silver treatment (400ppb AgF). A total of 19 spaceflight isolates were chosen to undergo whole genome sequencing and were compared to the genomes of their respective ancestral strain. Illumina and Nanopore reads were used to obtain draft genomes via a hybrid assembly. Whole genome alignment was used to identify differences, including SNPs, amongst the spaceflight genomes. Genome annotation helped to identify proteins and their functions based on the draft genome predicted protein sequences. Differences amongst the spaceflight genomes were elucidated by comparing module completeness of metabolic pathways. A couple of E. coli genomes had minor changes in a lipid metabolism module. The P. aeruginosa silver-treated samples were the only ones that showed changes in module completeness while all others remained identical to the ancestral strain. Of the changes, all four shared a 75% completeness of the pyruvate oxidation pathway within the central carbohydrate metabolism compared to a 50% completeness in the respective non-treated and ancestral strains. The whole genome comparison of these 117-day spaceflight bacterial cultures reveals minor changes within the genome as a result of long-term growth in space. This project shows a glimpse of the effect spaceflight has on the direction of microbial evolution of biofilms. Future directions for this project include expanding the analysis of all viable spaceflight samples to obtain a more complete picture of genomic changes and within specific genes. Also, spaceflight samples should be compared to their ground controls to identify changes specifically caused by growth in space.
Bio: Aron Valdez is from San Antonio, Texas. She earned her B.S. in Biology from Texas A&M University-San Antonio in 2021. She had a desire to continue her education and perform research within the field of Microbiology. She joined the McLean lab in 2021 to obtain a M.S. in Biology. Her research focused on the study of bacterial biofilms through the use of Bioinformatics. After graduation, Aron plans to utilize her skills learned in graduate school to pursue a career in Microbiology with a focus on Bioinformatics.
Thesis Defense: Comparison of mercury concentrations in fishes and shellfishes from Matagorda Bay and San Antonio Bay, Texas
Major Advisor: Dr. Jessica Dutton
Committee Members: Dr. Timothy Bonner, Dr. Clay Green
Friday, November 10, 2023, 3:30 PM, on Zoom only
Mercury (Hg) is a toxic nonessential trace element that bioaccumulates in marine organisms and biomagnifies in marine food webs. Matagorda Bay and San Antonio Bay have several important commercial and recreational fisheries, yet little is known about the Hg concentrations in fish and shellfish in these two bays. Using a direct mercury analyzer, I measured the Hg concentration in seven fish [red drum (Sciaenops ocellatus), black drum (Pogonias cromis), spotted seatrout (Cynoscion nebulosus), southern flounder (Paralichthys lethostigma), hardhead catfish (Ariopsis felis), striped mullet (Mugil cephalus) and Atlantic croaker (Micropogonias undulatus)] and three shellfish [eastern oyster (Crassostrea virginica), blue crab (Callinectes sapidus), and white shrimp (Litopenaeus vannamei)] species collected close to Matagorda in Matagorda Bay and Seadrift in San Antonio Bay. I investigated the variability in Hg concentrations among species within each bay and for each species, how Hg concentrations varied between the two bays. I also investigated the relationship between Hg concentration and body length for each species at both locations; for fish, determined the percentage of each species that exceeded the adverse biological effects threshold level (0.5 µg/g wet weight); and determined the percentage of each fish and shellfish species that exceed state and federal Hg advisory levels. Overall, Hg concentrations were significantly different among species in both bays. Hardhead catfish had the greatest mean Hg concentration in both bays, whereas striped mullet had the lowest. There was a positive relationship between Hg concentration and body length for six species from Matagorda (red drum, spotted seatrout, southern flounder, Atlantic croaker, hardhead catfish, and white shrimp) and six species from Seadrift (black drum, spotted seatrout, Atlantic croaker, hardhead catfish, and white shrimp). Hardhead catfish and black drum had individuals exceeding the adverse biological effect threshold level and Hg advisory levels for human consumption. Results from this study indicate that apart from black drum above the maximum landing size and hardhead catfish, fish and shellfish from both bays are low in Hg making them a good seafood choice to reduce dietary exposure to Hg through seafood consumption.
Bio: Liam is from Massachusetts but now calls Maine his home. He received a B.A. in Communication from California Lutheran University in 2014 and a B.S. in Marine Science from the University of New England in 2020 where he studied microplastics in blue mussels. His interest in aquatic contamination began years ago while surfing in the Santa Monica Bay, where rainstorms would flush debris and bacteria into the bay and breakwater. Liam started his M.S. in Aquatic Resources in the Fall of 2021, where he was advised by Dr. Jessica Dutton. During his free time Liam enjoys photography/videography, surfing and mountain biking, and going on hikes with his girlfriend, Hannah, and black Labrador, Oliver. Liam works as a Marine Resource Specialist for the Maine Department of Marine Resource’s Division of Water Quality Program.
Thesis Defense: Effects of canopy cover and impervious surface on occurrence of coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) throughout the United States
Major Advisor: Dr. Joseph Veech
Committee Members: Dr. Butch Weckerly, Dr. Darren Proppe (TPWD)
Friday, November 10, 10 AM, Supple 257
Coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) are habitat generalist species that occupy similar ecological niches and compete for the same food resources. Urbanization may disrupt habitat resources and intensify interspecific competition. Therefore, there is a need to determine the extent to which coyotes and gray foxes require certain habitat elements, particularly in anthropogenic landscapes. A consensus on the habitat associations of each species has yet to be reached, as studies on occupancy and abundance of coyotes and gray foxes have found that each species' response to urbanization varies by region and spatial scales. My study examined the effect of canopy cover, presumably an important component of natural habitat, and impervious surface cover as an indicator of urbanization, on the occurrence of coyotes and gray foxes. Additionally, I determined whether associations with canopy cover and impervious surface cover differed between these species. I obtained data from 9,010 camera trap locations grouped into two spatial scales. At the local level, I had 3,920 groups and at the landscape level, I had 280 groups. I obtained percent canopy cover and impervious surface cover data from the National Land Cover Database. In ArcGIS, I calculated mean percent canopy cover, mean percent impervious surface, and standard deviation of percent canopy cover within buffers placed around each camera trap group at the local and landscape scales. Furthermore, covariates such as mean geographic location, number of cameras in a group, and number of trap nights per group were included in the analysis as these could affect coyote and gray fox detection. I constructed logistic multiple regression models to examine the effect of canopy cover and impervious surface on coyote and gray fox occurrence at the local and landscape levels. Coyotes and gray foxes occurred at localities and in landscapes with a wide range of canopy cover and impervious surface cover. However, for both species, probability of occurrence was highest at localities and in landscapes with an intermediate percentage of canopy cover and a low percentage of impervious surface. At the landscape level, gray fox occurrence sharply declined as heterogeneity of canopy cover increased indicating that the connectivity of canopy cover may be an important habitat variable for gray foxes. Understanding the habitat associations and avoidances of coyotes and gray foxes provides insight into their spatial distributions and possibly can advise better management strategies.
Bio: Danielle is from Hickory, North Carolina. She earned her B.S. in Fisheries, Wildlife, and Conservation Biology from North Carolina State University in 2016. Danielle worked for various government agencies in between degrees, focusing on wildlife conservation and nature-based education. She joined the Veech lab in 2020 to pursue an M.S. in Wildlife Ecology, where she found a passion for teaching and mentoring undergraduate students. After graduation, Danielle will be joining the Bucklin lab at Texas State to complete a Ph.D. in Aquatic Resources and Integrative Biology.
Thesis Defense: Impacts of Anthropogenic Stressors on Sperm Quality and Mating Behavior in a Live-Bearing Fish
Major Advisor: Dr. Caitlin Gabor
Committee Members: Dr. Andrea Aspbury, Dr. Mar Huertas, Dr. Emily Powell
Tuesday, November 9, 2023, 9 AM, Norris Room (Supple 376)
Human-induced rapid environmental change (HIREC) introduces novel challenges and threats for organisms, and understanding the behavioral and physiological mechanisms used to cope with these challenges is essential to assessing anthropogenic impacts on population dynamics, reproductive fitness, and species persistence. HIREC can take several forms, ranging from dense local-scale dynamics, such as urbanization, to broad global-scale phenomena, such as climate change. I used a live-bearing fish model, Gambusia affinis, to investigate anthropogenic impacts on reproductive potential in freshwater ectotherms. To assess the effects of urbanization of sperm quality in G. affinis, I collected males from six streams in Central Texas. I assessed sperm quality by measuring sperm motility, velocity, and path deviation. Of the measured sperm quality characteristics, only sperm motility had a relationship with the extent of urbanization, with sperm motility increasing as urbanization increased. There is also considerable divergence in straight-line velocity, sperm linearity, and wobble across populations without direct associations to the extent of urbanization. I then conducted an experiment to assess how anthropogenic warming affected sperm quality traits and mating behavior in G. affinis. I exposed male G. affinis (n=40) to one of two treatments: control temperature (27C) or experimental temperature (35C). I then performed behavioral trials on the fourth and eighth day of the experimental period. I recorded the number of gonopodial thrusts (copulation attempts) and the latency to thrust toward females. After the final behavioral trial, I assessed sperm quality for each male. Additional measures of sperm quality were assessed, including sperm count, DNA fragmentation, and oxidative status. The number of gonopodial thrusts decreased in response to the elevated heat treatment, whereas thrust latency increased in response to the elevated heat treatment. All metrics of sperm velocity decreased in response to the elevated heat treatment, however no other sperm quality traits were affected by treatment. Thrust latency is significantly negatively correlated with all measures of sperm velocity, suggesting that increased temperatures may modulate these aspects of reproductive behavior and physiology through a shared mechanism. Together, these two studies indicate that sperm quality traits have some degree of independence from each other and different sperm quality traits may be differentially affected by different selective pressures. The disassociated sperm traits indicate that this species has evolutionary potential allowing them to respond to HIREC, further explaining how they have been so effective at tolerating wide variation of environmental conditions and colonizing habitats.
Bio: Skyler is from San Diego, CA. He received his B.A. in Interdisciplinary Studies from San Diego State University, where he studied sociological approaches to conservation of herpetofauna and bats. Skyler has a professional background in zookeeping and currently works as an IVF embryologist. Skyler began his M.S. in Population and Conservation Biology in Spring 2022, advised by Dr. Caitlin Gabor. After graduation, Skyler hopes to return to the zoological field to apply novel artificial reproduction technologies to wildlife conservation.
Thesis Defense: Consequences of BPA induced maternal stress on offspring: cognitive, behavioral, and physiological changes on live bearing fish
Major Advisor: Dr. Caitlin Gabor
Committee Members: Dr. Andrea Aspbury, Dr. Emily Powell
Thursday, November 9, 2023, 2 PM, Norris Room (Supple 376)
Adaptive maternal effects involve mothers enhancing the fitness of their offspring based on reliable environmental cues. This thesis investigates the impact of prenatal stress on offspring in live-bearing fish, focusing on the variation in steroid hormones (reproductive and stress) production across gestation and how maternal stress affects offspring survival, behavior, cognition, and physiology. I studied three species of live-bearing fish (Poeciliidae) that differed in maternal investment (MI) to their embryos. I tested the hypothesis that the relationship between cortisol, estradiol, progesterone release rates would vary with fecundity but that variation would differ depending on their MI index. For Heterandria formosa (MI = 14.18), a positive correlation was observed between cortisol (stress hormone) release rates and fecundity, suggesting that as cortisol increase, fecundity is enhanced. However, in Gambusia affinis (MI = 0.62), the correlation was negative. In contrast, there was no significant relationship betwee cortisol release rates and fecundity in Xiphophorus couchianus (MI = 0.61). Furthermore, no significant relationship was found between estradiol and progesterone and fecundity in H. formosa. Whereas G. affinis showed a significant correlation between cortisol, estradiol, progesterone and fecundity. The only significant relationship for X. couchianus was between cortisol and progesterone. These results suggest that the relationship among cortisol, estradiol, progesterone and fecundity vary significantly between different species and reproduction styles indicating different solutions to the costs of matrotrophy. I then asked if prenatal exposure of female Heterandria formosa to environmentally relevant levels of bisphenol- A (BPA 2 μg/L) affects offspring behavior, cognition, and physiology. I predicted that mothers will have higher cortisol, and that offspring will have lower cognitive skills, shoal less, and take more risks. Interestingly, cortisol levels were lower in BPA-exposed mothers, suggesting that mothers may offset stressors of BPA by lowering cortisol. Despite this, offspring may still suffer cognitive costs. BPA exposed offspring showed lower motivation and slower velocity which may result in foraging and predation costs. Increased shoaling proximity of BPA exposed fish may offset predation costs. Overall, these results demonstrate that environmental stressors can have a cost to reproduction in live-bearing fish and this could translate to additional concerns for human health in analogous environmental conditions.
Bio: Saied holds an MS degree in Aquatic Ecology from Isfahan Technical University and is currently studying Population and Conservation Biology at Texas State University. His research focuses on the Conservation Ecology and Biology of endangered fish species, using genetic and morphological approaches to study these species at the population level. Currently, he is concentrating on the behavioral, maternal effect, and genetic responses of fish to stressors and pollutants. These studies guide his future research in the conservation and management of endangered species worldwide.
Thesis Defense: Assessing the soil carbon storage potential of Texas grasslands after 20 years of restoration
Major Advisor: Dr. Jason Martina
Committee Members: Dr. Susan Schwinning, Dr. Joseph Veldman (Texas A&M University)
Monday, November 6, 2023, 9:30 AM, INGR 4102
Grasslands act as carbon sinks, converting CO2 into soil organic carbon (SOC) that can be stored underground for decades to centuries. Habitat management incorporating prescribed fires can theoretically extend the carbon sequestration longevity of grassland soils to millennia through the formation of highly recalcitrant pyrogenic carbon (PyC). To evaluate the effects of management on SOC and PyC, we collected 30cm depth soil cores, partitioned into 10cm segments, from seasonal burn, frequent mow, control, and old-growth plots, and before and immediately following a summer prescribed fire (n=6 per treatment) on restored grasslands at the LBJ Wildflower Center and City of Austin WQPL properties in Central Texas. Six cores were taken along established transects from 36, one-half hectare plots, totaling 216 cores. Soils were separated by depth, pooled at the plot level, and analyzed for SOC, PyC, nitrate, ammonium, macronutrients, and carbon mineralization rates. PyC and SOC increased significantly (P<0.05) between pre and post summer fire treatments producing an average of 3.8x10-4 g/cm3 of PyC, a 7.29% increase, in a single burn. Soil incubation tests confirmed that PyC was associated with lower CO2 emission rates. While we found higher concentrations of PyC in burned plots, relative to unburned plots, PyC was detected in all treatments, indicating a potential susceptibility to distribution via wind and water erosion after formation. Additionally, we observed positive correlations (P<0.05) between PyC with percent organic matter (OM) and with woody cover. Our findings indicate that management history has a significant effect on the generation, redistribution, and catchment of PyC and the enhancement of long-term C storage via the introduction and incorporation of highly recalcitrant PyC.
Bio: Central Texas has been home to Traci for much of her life. She received a B.A. in Geography from the University of Texas and spent the following decade working or interning for non-profit organizations, private business, and the U.S. government all while raising a family. She joined the Martina lab in 2020 to pursue an M.S. in Population and Conservation Biology. Traci recently accepted a job with the U.S. Forest Service as a Natural Resources Specialist and will begin her new position in Durham, New Hampshire after graduation.
Thesis Defense: The use of biomonitoring data to inform species distributions, habitat associations, and threats
Melissa L. Wolter
Major Advisor: Dr. Timothy Bonner
Committee Members: Dr. Caitlin Gabor, Dr. Al Groeger
Friday, November 3, 2023, 3:30 PM, FAB 102
Biomonitoring is a periodic and systematic quantification of species numbers, abundances, or densities and the species associated environments. As a stipulation of U.S. Fish and Wildlife Service (USFWS) incidental take permit, a biomonitoring program was established in the upper reaches of the San Marcos and Comal rivers (TX) in 2013 to monitor incidental take of the federally endangered Fountain Darter E. fonticola. The purpose of this study was to evaluate the biomonitoring program over a 9-year period (2014 – 2022) for the benefit of discovering new insights into Fountain Darter ecological relationships and potentially for refining the program for the upcoming incidental take permit renewal. Study objectives were to quantity spatial and temporal patterns in Fountain Darter densities, flow-density relationships, recreation-density relationships, and habitat associations of the Fountain Darter among three reaches of the San Marcos River and four reaches of Comal River in wadeable habitats and in non-wadeable habitats with each reach and habitat type representing a semi-independent observation. Among some of the more significant findings, Fountain Darter densities were greater in the upper most reaches of each river than in the lower reaches, densities varied through time with some reaches indicating increasing and decreasing population trends, and densities were largely unaffected by flows, which ranged from low flow events during an extreme drought to small flood events during wet years. Non-wadeable reaches with high amounts of instream recreation had lower densities of Fountain Darters than non-wadeable reaches with low amounts of instream recreation. Density distributions were used to establish density thresholds (low, moderate, and high condition) for qualitatively communicating the health of Fountain Darter populations, which represents an example of using biomonitoring data as a context to interpret future biomonitoring data. With more species being listed by USFWS, the number of incidental take permits will undoubtedly increase; therefore, evaluation of existing biomonitoring programs can lead to improved designs in biomonitoring protocols.
Bio: Melissa Wolter graduated from Texas State University with a B.S. in Biology and a minor in Secondary Education. She finds joy in spending time with her children, Abel and Amelia, as well as her friends and family, fishing, camping, and exploring Texas rivers and beyond. She is currently working as a secondary educator, teaching Aquatic Science.
Thesis Defense: Post-delisting monitoring and disease dynamics in the Concho water snake (Nerodia harteri paucimaculata)
Major Advisor: Dr. David Rodriguez
Committee Members: Dr. Sarah Fritts, Dr. Paul Crump (TPWD)
Friday, November 3, 2023, 10 AM, Norris Conference Room
Abstract: The Concho water snake (Nerodia harteri paucimaculata) is a range-restricted species endemic to the Colorado and Concho Rivers in Central Texas. The Concho water snake (CWS) was federally protected in 1986 but was recently delisted from the Endangered Species Act in 2011 due to the abundance and successful reproduction of the species throughout its range. Post-delisting monitoring has been ongoing since 2013. As part of these efforts, our study examines three primary components: 1) presence and abundance of CWS throughout its range, 2) host-pathogen disease dynamics of the newly emerged snake fungal disease, and 3) population genomics of CWS using next generation sequencing. To accomplish this, we used a model system to compare the CWS (a specialist species) to two generalist sympatric congeners (Nerodia rhombifer and Nerodia erythrogaster transversa). This model allowed us to compare the impacts of snake fungal disease on each species and assess whether gene flow and population structure are influenced by landscape and life-history traits. Compared to previous reports, we found CWS to be in lower abundance and to be present at far fewer historical sites. We were able to successfully locate a population of CWS occupying the Concho River for the first time since 2011 and found that capture rates at specific sites varied between seasons and previous studies. Prevalence estimates for the pathogenic fungi (Ophidiomyces ophidiicola) were similar across all three species of Nerodia but were much higher than semi-aquatic (Thamnophis proximus rubrilineatus) and arboreal (Opheodrys aestivus) species of snake. We found neonate snakes to have significantly lower prevalence estimates which is in line with other research indicating over-wintering den sites are a primary area for coming into contact with the pathogen. We found evidence that landscape could be influencing pathogen prevalence with river habitats having greater prevalence than reservoir habitats. Population genetic analysis of the CWS indicated greater degrees of gene flow than previously reported. Interestingly, we found continued evidence of individuals occupying O. H. Ivie Reservoir to genetically cluster separate to individuals found in river habitats across all three species of Nerodia. The higher prevalence of Ophidiomyces ophidiicola found on Nerodia in the Colorado River watershed is a cause for concern and highlights the need to better understand the pathogenesis of this disease. Not only does this disease pose a threat to the species but climate change and the associated increase in frequency and duration of drought periods may lead to the extirpation of populations and potentially the extinction of the species. As it currently stands, the CWS has not met all of the post-delisting monitoring criteria set forth by the U.S. Fish and Wildlife Service and would benefit from federal protections and a multifaceted conservation approach.
Bio: Bio: Tristan Vratil is from Olathe, Kansas. He received his B.S. from Florida State University in 2017. He worked a variety of wildlife research-based jobs ranging from the jungles of Thailand to the deserts of Nevada. In the fall of 2021, he joined the Dr. Rodriguez lab to pursue his M.S. in Biology. After graduation, Tristan plans to continue working in the field of wildlife ecology and conservation.
Thesis Defense: Optimizing chitosan-functionalized hollow silica microspheres for speedy capture of RNA from wastewater
Major Advisor: Dr. Shannon Weigum
Committee Members: Dr. Dana Garcia, Dr. Manish Kumar
Monday, October 30, 2023, 1PM, Norris Conference Room (Supple 376)
Sheltering in place is an important strategy for controlling infectious disease outbreaks like the coronavirus disease 2019 (COVID-19) pandemic, but it carries significant social and economic burdens. These burdens could be relieved by using community-level data on disease presence to focus quarantines on areas with emerging outbreaks, allowing people outside of those areas more freedom. One way to track the prevalence of a disease within a community is by using wastewater-based epidemiology (WBE). In the case of COVID-19, WBE involves concentrating ribonucleic acid (RNA) from the wastewater and testing it for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19. Several RNA concentration methods exist, but they tend to be time-consuming or require equipment that may not be available in low-resource settings. Equipment requirements also prevent RNA concentration from being performed in the field. Here, chitosan-functionalized hollow silica microspheres were used to capture an oligonucleotide from a dilute solution in as little as 10-30 minutes. The supplies for chitosan-functionalized microspheres are commercially available and relatively inexpensive, and this technique does not require a centrifuge, so it could be useful in low-resource settings.
Bio: Shannon is from Round Rock, TX, where she grew up loving science and soaking up information. She is a cat mom and dog sister. When she’s not working, she’s into American Ninja Warrior, trivia, comedy, working out, staying up to date on current events, and hanging out with family and friends.
Thesis Defense: Selenium:Mercury Molar Ratios in Muscle and Organs of Immature Sharks in Texas Bays
Major Advisor: Dr. Jessica Dutton
Committee Members: Dr. Weston Nowlin, Dr. Aaron Roberts (Univ. North Texas)
Friday, October 27, 2023, 12:30 PM, FAB 136
Abstract: Mercury (Hg) is a nonessential trace element that bioaccumulates in marine organisms and biomagnifies in marine food webs, so top predators, including sharks have the greatest Hg concentrations. Most studies investigate Hg concentrations in adult sharks, with little research on immature (young-of-the-year and juvenile) sharks, even though high Hg concentrations could result in adverse health effects that impact growth and development. Selenium (Se) has an antagonistic relationship with Hg and may have a protective effect against Hg toxicity if the Se:Hg molar ratio is >1:1. There are no studies examining Se:Hg molar ratios in tissues of immature sharks due, in part, to the difficulty acquiring samples. Texas Bays are essential habitat that provide nursery areas for shark species that utilize the bays for protection and growth, but industrial pollution may threaten these habitats. I investigated the Hg and Se concentrations, and calculated the Se:Hg molar ratios in dorsal muscle, heart, brain, kidney, and liver of immature bull sharks (Carcharhinus leucas), blacktip sharks (Carcharhinus limbatus), and bonnethead sharks (Sphyrna tiburo), in four bays (Sabine Lake, Aransas Bay, Corpus Christi Bay, and Lower Laguna Madre) along the Texas coast. Sharks were collected during the Texas Parks and Wildlife Department 2020-2022 fall and spring gill net seasons (n = 20-30 per species per bay). Mercury concentrations were determined using a direct mercury analyzer (DMA-80) and Se concentrations measured using microwave acid digestion and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis. Overall, Hg concentrations were greatest in muscle and heart and lowest in brain and liver in all species and bays. In comparison, Se concentrations were greatest in kidney and lowest in muscle for all species and bays. There were inconsistent trends within and among bays when examining the relationship between Hg concentration and fork length, Se concentration and fork length, and Se:Hg molar ratios and fork length for each tissue, most likely due to the variability in Hg and Se availability and factors affecting uptake. For all bays combined, 38.3% of bull sharks, 6.0% of blacktip sharks, and 1.7% of bonnethead sharks had a muscle Hg concentration that exceeded the Hg adverse biological effects threshold level (0.5 µg/g Hg wet weight). Se:Hg molar ratios were >1:1 in all tissues, indicating that Se may have a protective effect against Hg toxicity in immature sharks. High tissue Se:Hg molar ratios in immature sharks (e.g., 155:1 in heart, 654:1 in kidney, and 367:1 in the brain of bonnethead sharks) could reduce the adverse effects of Hg on growth and development, however, the Se:Hg molar ratio at which Se is protective against Hg toxicity (e.g., 1:1, 5:1, or greater) is not known, highlighting the need for further research in taxa that have higher Hg concentrations due to their reproductive strategy, long-life span, and high trophic position.
Bio: Natalie is from Marion, MA. She received her B.S. in Biology with a minor in Chemistry from Gettysburg College, where she worked with zebrafish behavior in response to copper exposure. She has always had a passion for marine science since she was a child, and her love of sharks has only grown since moving near Cape Cod with her family. Natalie started her M.S. in Aquatic Resources in Spring 2021, where she was advised by Dr. Jessica Dutton. Natalie’s interests include fishing on the local docks and sunbathing with her elderly cat, Tiger. After graduation, Natalie hopes to continue to pursue her interest in marine research and environmental issues.
Thesis Defense: The Effects of Chronic Nitrite Exposure on Tissue Morphology and Physiology in Xiphophorus couchianus
Hannah M. Hughes
Major Advisor: Dr. Mar Huertas, Dr. Lauren Fuess, Co-chair
Committee Members: Dr. Caitlin Gabor
Wednesday, October 18, 2023, 2 PM CDT, Norris room - Supple 376
Abstract: The increase of agriculture production to sustain growing populations is associated to an increase of fertilizer-derived nitrogenous compounds in aquatic ecosystems. One of the nitrogenous derivates, nitrite, has been known to cause physiological and morphological damage in aquatic species in acute short-term exposures. However, there is a lack of current knowledge on how nitrites effect maternal health and, consequently, embryo health and development. Moreover, it is unknown how chronic exposure to contemporary water nitrite concentrations can affect fish physiology. Therefore, we proposed the live-bearing fish species Xiphophorus couchianus as a model organism to better understand the effects of chronic nitrite exposure on tissue physiology, morphology and oxidative stress in maternal subjects. Thus, we hypothesized that chronic nitrite exposure would lead to elevated levels of accumulated nitrite in tissues, altered morphology of tissues, and affect oxidative stress (relating to maternal immunity). Our primary objective was to characterize the effects of sublethal and contemporary environmental nitrite exposure on morphology and physiology in X. couchianus pregnant mothers. To test our hypotheses, three experiments were conducted: acute nitrite exposure (to determine chronic concentrations) and two chronic exposures. Our acute exposure lasted for a period of 48 hours and fish were exposed to two nitrite concentrations (0 mM and 0.44 mM). Our first chronic exposure lasted for 28 days, and fish were exposed to two nitrite concentrations (0 mM and 0.3 mM). Our second exposure exposed fish to contemporary environmental (or sub sublethal) and sublethal concentrations of nitrite for 28 days (0 mM, 0.05 mM, and 0.5 mM). Preliminary results from the acute exposure showed impairment of typical olfactory functioning and morphology. Preliminary results from the first chronic exposure showed accumulation of nitrite in tissues and changes to reproductive organs. Results from the last chronic exposure showed significant accumulation of nitrite in tissues, altered morphology in tissues, and changes in oxidative stress parameters in response to chronic exposure to sublethal nitrite concentrations. Our study provides a baseline for future chronic experiments related to pregnancies using X. couchianus as the model organism.
Bio: Hannah Hughes is from League City, TX and graduated from Texas State University with a B.S. in Biology in 2021. In the fall of 2021, she joined the Huertas lab to pursue her M.S. in Aquatic Biology. In her free time, she enjoys camping, hiking, fishing, and spending time with friends.
Thesis Defense: Trophic Ecology and Environmental Conditions Affect Mercury Concentrations in Immature Sharks in Texas Bays
Major Advisor: Dr. Weston Nowlin and Dr. Jessica Dutton
Committee Members: Dr. Matthew Chumchal, Texas Christian University
Wednesday, October 18, 2023, 8:00 AM CDT, FAB 136
Abstract: Sharks are ecologically important predators and are among the most threatened marine fishes due to over-fishing, climate change, and exposure to contaminants. Because many shark species are higher trophic-level consumers, they are prone to exposure to bioaccumlative and biomagnifying contaminants such mercury (Hg) through their diet. However, there is limited data on Hg concentrations in young-of-the-year and juvenile sharks (hereafter, immature) occupying coastal habitats and how immature shark Hg along coastlines are affected by spatial variation in diet and environmental conditions. I measured Hg concentrations in immature individuals of three shark species [blacktip (Carcharhinus limbatus), bull (Carcharhinus leucas), and bonnethead (Sphyrna tiburo)] in four Texas bays: Lower Laguna Madre, Corpus Christi Bay, Aransas Bay, and Sabine Lake, which represent a range of abiotic conditions and environmental setting. Shark dorsal muscle tissue and putative prey were assessed for Hg and stable isotopes (δ13C, δ15N, and δ34S) to determine how inter- and intraspecies variation in trophic ecology influenced Hg exposure risk. I also additionally assessed how spatial variation (inter-bay differences) in environmental conditions (salinity, water temperature, and dissolved oxygen) may influence overall Hg concentrations in sharks and their prey. There were interspecies differences in immature shark Hg, with bull sharks generally having higher Hg across sites. Dietary mixing models and estimates of niche overlap derived from stable isotopes indicated that bull sharks across sites derived a greater proportion of their diet from sciaenid fishes, which generally had greater Hg than other potential prey items. In contrast, bonnetheads showed a greater dietary contribution of crustaceans and blacktips had a greater contribution of menhaden and squid. These results indicate that trophic ecology of immature sharks can exhibit substantial interspecies variation, which influences Hg exposure risk. In addition, I found that Sabine Lake and Aransas Bay had greater Hg concentrations in immature sharks than other bays, but estimates of Hg trophic magnification slopes (i.e., the rate of Hg accumulation with trophic position) did not differ among bays. However, Hg concentrations in a baseline organism found in all bays [eastern oyster (Crassotrea virginica)] exhibited greater Hg concentrations in Sabine Lake and Aransas Bay. I hypothesize that spatial differences in conditions which influence microbial Hg methylation, bioavailability, and inputs (i.e., salinity and dominant watershed vegetation type) contributed to the observed biota Hg differences among bays. This study is one of the first to examine the relationship between diet, environmental conditions, and Hg in immature sharks in Texas bays and makes a substantial contribution to understanding the ecotoxicology of Hg in elasmobranchs.
Bio: Jasmine is from Chandler, AZ. She received her B.S. in Biology with a Marine emphasis from Texas A&M University – Corpus Christi, where she worked with marine sportfish. Her fascination with sharks began at a very young age from watching nature documentaries with her family. Jasmine started her M.S. in Aquatic Resources in Spring 2021, where she was advised by Dr. Weston Nowlin and Dr. Jessica Dutton. Jasmine loves spending her free time with her beloved pets, Chief and Chaos. After graduation, Jasmine hopes to continue to pursue her interest in ecotoxicology as a PhD student under Dr. Weston Nowlin.
An Analysis of Canopy Cover within the Home Ranges of Mexican Wolves (Canis lupus baileyi) Reintroduced into New Mexico and Arizona
Major Advisor: Dr. Joseph Veech
Committee Members: Dr. Ivan Castro-Arellano, Dr. Chris Serenari
Thursday, May 11, 10 AM
Identifying the most important characteristics of a species’ habitat is vital in understanding its basic ecology and conservation needs. For predators such as the Mexican wolf, woody vegetation in the form of canopy cover is a habitat characteristic that may play a pivotal role in helping to facilitate many basic needs, such as shelter, hunting, and rearing pups. The Mexican wolf is listed as endangered; it is the most genetically distinct subspecies of gray wolf in North America. The United States Fish and Wildlife Service (USFWS) has been managing a wolf reintroduction program since 1998. I utilized locational data points of GPS-collared wolves within the Mexican Wolf Experimental Population Area (MWEPA) of Arizona and New Mexico, and canopy cover data from the National Land Cover Database (NLCD) to determine the extent that Mexican wolves associate with canopy cover. GPS locational data points spanned six years (January 2015 - January 2021). I used ArcGIS to derive three home range types for each of 132 wolves. The home range types consisted of a 95% kernel density estimator (KDE), 60% KDE, and 100-meter buffers (around GPS data points) for each Mexican wolf in my study. For each home range, I used ArcGIS to determine the statistical distribution of canopy cover values (among pixels). In the NLCD, each 30 × 30 m pixel is assigned a canopy cover value in 1% increments. Canopy cover within each home range was compared to two larger reference regions: a minimum convex polygon (MCP) and an 80-km concave polygon, both created in ArcGIS. For each wolf, each of the three types of home range was compared to the two reference regions using a two-sample Kolmogorov-Smirnov (K-S) test to determine if wolves were utilizing a mix of canopy cover that was different from what was available to them in the larger regions. I found that 126 of 132 wolves had at least one of their six K-S tests to be statistically significant (P < 0.05) indicating that these wolves were using or associating with canopy cover in a non-random way. Of those 126 wolves, 65 of them had all six of their K- S tests to be statically significant. Wolf home ranges tended to have much less area in the 0% canopy coverage category and much more in the ≥ 25% canopy coverage category compared to the reference regions. I also found that the home ranges of wolves tended to mostly consist of habitat in the 16 – 30% canopy cover range. These results support the possibility that wolf movement and space use is at least partially influenced by canopy cover wherein wolves tend to avoid areas of little or no canopy cover and spend more time in areas of relatively dense canopy cover. The results of my study may prove to be beneficial to the Mexican wolf recovery program when determining where to provision resources for wolves and what particular areas of a landscape or region to monitor and protect. Furthermore, my study may also aid the USFWS in defining critical habitat for this endangered subspecies and continue the long-term growth and sustainability of the Mexican wolf within the MWEPA.
Bio: Christian received his B.S. from Texas State University in 2017. After completing several wildlife-based internships, he joined the Veech Lab in 2020 to pursue his M.S. in wildlife ecology. Upon graduating he plans to obtain a job as a wildlife biologist.
TWO INVADERS, ONE ECOSYSTEM: EXPLORING INTERACTIONS BETWEEN DREISSENA POLYMORPHA AND HYDRILLA VERTICILLATA
Major Advisor: Dr. Astrid Schwalb, Department of Biology, Texas State University
Monica McGarrity, Texas Parks and Wildlife Department
Dr. Jason Martina, Department of Biology, Texas State University
Friday, April 14th, 2023, 11:00am, CT, Freeman Aquatic Biology Building (FAB) 130
Zoom link: https://txstate.zoom.us/j/95201566004
Invasive species in aquatic ecosystems can alter ecosystem processes, detrimentally affect native species, and facilitate the invasion of other species. One infamous aquatic invader, the zebra mussel (Dreissena polymorpha) is known to cause declines in phytoplankton through their filtering activity and to facilitate the subsequent spread and growth of macrophytes by increasing water clarity. In turn, submerged macrophytes may provide substrate for settlement of zebra mussels, which require a firm substrate to settle on (i.e., not mud or sand). The invasion of Canyon Lake, TX by zebra mussels has occurred relatively recently, and since then, the spread of an invasive submerged macrophyte, Hydrilla verticillata, has also been observed. The goal of this study was to examine variation in the distribution of both zebra mussels and Hydrilla in relation to sediment composition, to each other, and over time (summer vs. fall), and potential facilitation between the species in laboratory and field experiments. To investigate the distribution of each species, dive surveys were conducted in June 2022 and September 2022 using sampling quadrats along a transect at eight sites at Canyon Lake, TX. Field and lab experiments used a fully crossed experimental design to examine the impact of Hydrilla on zebra mussels and vice versa with controls (Hydrilla only and zebra mussels only), and treatment (Hydrilla + zebra mussels). For the surveys, Hydrilla densities tended to be higher in muddy compared to rocky sediment. In contrast, zebra mussel densities tended to be higher in rocky (on Hydrilla and rocks) compared to muddy habitat (only on Hydrilla). Within the rocky habitat, zebra mussels attached to Hydrilla had significantly higher densities and a smaller size than those attached to rocks. However, only a small fraction of zebra mussels remained on Hydrilla in September, almost exclusively representing a new settlement cohort based on their size distribution. Hydrilla biomass did not change significantly between summer and fall. The experiments did not detect any significant impact of zebra mussels on growth and condition of Hydrilla and positive effects of Hydrilla on zebra mussels was limited to Hydrilla presence in low densities. Nevertheless, Hydrilla may directly facilitate zebra mussel dispersal, especially in spring, as mussels attached to plant fragments can be transported by currents downstream or by human activities, such as entanglement in boat propellers or trailer bunks.
Bio: Emily Lorkovic is originally from Nebraska but settled in Texas with her husband in 2016. She earned a B.S. in Aquatic Biology from Texas State University in 2021. She has a passion for all things water related and enjoys kayaking and scuba diving in her spare time. After graduation, Emily will pursue a career in the field of aquatic ecology and wetlands conservation.
EFFECTS OF AGE, GUT FILL, AND SEX ON DRESSED MASS – WHOLE MASS RELATIONSHIPS OF WHITE – TAILED DEER
Major Advisor: Dr. Floyd Weckerly, Department of Biology, Texas State University
Dr. Clay Green, Department of Biology, Texas State University
Dr. Mark Ricca, Supervisory Biologist, USGS – Forest and Rangeland Ecosystem Science Center
Friday, April 14, 2023, 9AM-11AM, Ingram 3204
Zoom link: https://txstate.zoom.us/j/93560752445?pwd=Z29hTmFtOXA4RGp3MG5tSU80dU9Jdz09
Hunters are often interested in whole mass of harvested white-tailed deer (Odocoileus virginianus) but measuring whole mass in the field is challenging, which is why hunters often dress deer. Dressed mass consists of the carcass mass minus organs in the abdominal, thoracic, pelvic cavities as well as any blood loss. Dressed mass is strongly related to whole mass but covariates of site where deer was harvested, age, sex, body fat, and lactation state of females might also improve predicting whole mass. Also, gut fill variation should help explain why some covariates are influential. Using data from three different sites, which contained deer of various ages, sexes, and lactation states of females, I analyzed the effects of site, age, sex, body fat, lactation state of females, and gut fill on relationships between dressed mass and whole mass (n = 432). Rumen-reticulum fill served as my surrogate of gut fill because these compartments comprise 50 – 70 percent of gut capacity. I analyzed linear regression models and compared them for fit and parsimony with a Bayesian Information Criterion model selection analysis. The selected model had statistically significant predictors of dressed mass, age, sex, lactation status of females, and site. Gut fill also influenced dressed mass – whole mass relationships. Variation in gut fill across sites and due to age, sex, and lactation status of females was consistent with effects of these covariates on dressed mass – whole mass relationships. Lastly, I standardized variables in the selected model to have a mean of zero and standard deviation of one to assess the extent of influence of dressed mass and covariates on whole mass. Dressed mass had a much larger influence on whole mass than covariates. Although site, age, sex, and lactation status of females are influential, the improvement in predicting whole mass is slight. First and foremost, to accurately predict whole mass of small to large deer requires measuring animals that range widely in dressed body mass.
Bio: Jorge is from San Antonio, TX. He received his B.S. in Wildlife and Fisheries Sciences from Texas A&M University. After multiple visits to Guatemala, where his family is from, and growing up watching Animal Planet, he decided to pursue a career in biology and animal research. Jorge started his M.S. in Biology in Dr. Weckerly’s lab. Outside of school, Jorge enjoys spending time with his friends and family, volleyball, attending mass and volunteering at his church, and playing games.
Effects of extreme flow events on community composition and habitat complexity in groundwater dominated systems
Joshua D. Tivin
Major Advisor: Dr. Timothy H. Bonner, Department of Biology, Texas State University
Dr. Butch Weckerly, Department of Biology, Texas State University
Dr. Al Groeger, Department of Biology, Texas State University
Thursday, April 13th, 2023, 2:00PM, Freeman Aquatic Biology Building (FAB) 130
Extreme flow events in the form of major floods and droughts are primary drivers in structuring aquatic habitats and communities. While floods and droughts can directly alter aquatic biota by displacement or by increased mortalities, extreme flow events can have an indirect and prolonged effect on biota by altering habitat complexity, which in turn delays the recovery of the aquatic biota. Interrelationships among extreme flow events, habitat complexity, and fish communities are established in hydrologically variable rivers. Less known are the interrelationships among stream flow extremes, habitat complexity, and fish communities in hydrologically stable rivers. The purpose of this study was to assess how extreme flow events effect habitat complexity and the fish community within two hydrologically stable rivers in Texas (San Marcos and Comal rivers) using a 9-year dataset. Habitats (N = 4,863) within 12 reaches of the rivers were categorized as high, moderate, or low complexity along a depth, vegetation, substrate, and current velocity gradient. Following or during extreme flow events, shifts in habitat complexity were not evident except in low complexity habitats that shifted towards greater complexity during drought. Among a total of 43 fish species and 135,199 individuals observed, densities of surface water fishes (Gambusia), pelagic generalist fishes (Lepomis, Micropterus, Herichthys), pelagic fluvial fishes (Dionda, Notropis, and Astyanax), and benthic fishes (Etheostoma) generally were greater in high and moderate habitat complexity reaches than in lower habitat complexity reaches and generally unaffected by extreme flow events with few exceptions. These results indicated that habitat complexity in hydrologically stable rivers support greater densities and diversity of fishes similar to hydrologically variable rivers, but habitat complexity and fish community were more resistant and resilience in hydrologically stable rivers than in hydrologically variable rivers.
Bio: Joshua Tivin was born in Cincinnati, Ohio where he graduated from Miami University of Ohio with a B.S in Biology in 2020. He enjoys saltwater fishing and duck hunting on the Texas coast, spending time with friends and fitness. Josh will begin a new job as a fish taxonomist with Amnis Opes Institue conducting river and stream surveys in the Pacific Northwest in May 2023.
Prior heat stress affects disease susceptibility in the cnidarian model Exaiptasia diaphana
Name: Sofia Cristina Diaz de Villegas
Major Advisor: Dr. Lauren Fuess
Committee Members: Dr. Robert McLean
Dr. Mar Huertas
Thursday, April 13th at 1:00pm CDT; Supple Norris Conference Room (Rm. 376)
Zoom Link: https://txstate.zoom.us/j/94118774632
Corals reefs form the foundation for essential marine habitats and ecosystem services. However, these ecosystems have undergone dramatic declines due to the effects of climate-related stressors. In particular, increasing sea surface temperatures (SSTs) have had disproportionate effect on reefs, both triggering breakdown of cnidarian symbioses (“bleaching”) and exacerbating the prevalence and severity of disease outbreaks. Notably, both bleaching and disease have been observed in close spatial and temporal association, yet few studies have examined the connections between the two. I used a model cnidarian to test whether prior heat stress impacts subsequent pathogen susceptibility. Two genotypes of the anemone Exaiptasia diaphana were exposed to a thermal stress event and allowed to recover for two weeks, at which point they underwent pathogenic challenge. Mortality was tracked, and a subset of anemones were sampled for immunological and physiological assays which measured symbiont density, host immune parameters, and host energetic budget. Prior heat stress significantly increased disease susceptibility: heat stressed anemones had increased mortality and decreased activity of several established immune parameters at two weeks post-bleaching. These reductions may be partially explained by observed changes in energetic and immunological associations. Furthermore, I observed context-specific changes in the relationship between symbiont density and energetic reserves which may also contribute to overarching patterns of disease susceptibility. My results are among the first to provide insight into the mechanistic causes linking bleaching and disease, suggesting that changes in energetic reserves and their variation with symbiosis contribute to increased disease susceptibility following bleaching. This work provides an important starting framework for further disentangling the complex mechanisms linking dysbiosis with increased disease susceptibility in cnidarians.
Bio: Sofia is from Miami, Florida and received a B.A. in Biological Sciences and Environmental Studies from Wellesley College. She discovered her love for coral reef ecology during her work in the Coral Reef Futures lab at the Rosenstiel School. She plans to continue her research in cnidarian symbiosis and immunology as a PhD student in the Fuess lab.
EFFECTS OF TRAFFIC NOISE ON GLUCOCORTICOID RESPONSE, GROWTH, BEHAVIOR AND COGNITION ON LARVAL AND ADULT FROGS
Name: Megan Flanagan
Major Advisor: Dr. Caitlin Gabor
Committee Members: Dr. Andrea Aspbury
Dr. Christopher Serenari
Thursday, April 13th at 9:00am in Supple 376 (Norris Room)
Zoom Link: https://txstate.zoom.us/j/95309646119?pwd=QVFudE1mM1BVUmNjTjU0Wkk5UVBWZz09
With increased urbanization, traffic noise has responded in tandem. Increased noise is associated with glucocorticoid (GC) dysregulation and behavioral changes in amphibians. GCs are hypothesized to be adaptive and maintain homeostasis while balancing energetic tradeoffs between immune response, growth, reproduction, and activity. We measured growth, activity and GCs of two tadpole species; Acris crepitans (Ac) and Rana berlandieri (Rb) in response to high levels of traffic noise. We hypothesize that tadpoles would show flexible stress responses when exposed earlier in life to cope with negative consequences associated noise perturbations. Tadpoles were exposed to a white noise control (30dB) or traffic noise (75dB) first for 8 days (early), then the opposite treatment second (later). We tracked activity levels and growth throughout the experiment. Ac and Rb utilized different strategies when exposed to noise earlier in life. The timing of exposure to noise during development significantly impacted GCs, with tadpoles exposed to noise earlier having higher corticosterone release rates across both species. Species of tadpoles differentially modulate their energetic resources in response to early exposure to traffic noise. Rb allocated more energy to activity compared to Ac, while Ac allocated more energy towards growth. These different strategies between our tadpole species may potentially be due to life history differences. We also tested if exposure to noise intermittently (2 weeks) affected cognitive performance and behavior of frogs. Subjects were repeatedly tested (baseline, in the presence of noise and recovery) using a detour test design with fruit flies as the motivation. Frogs showed significant differences in exit time and motivation between detour tests. Frogs had the highest motivation in the presence of noise, which could potentially impact foraging success and movement patterns. Our results indicate that traffic noise alters GCs, behavior, and growth in frogs more so earlier in life but also to a less extent later. While noise comes with costs, the two species we tested show flexible response that may aid in diminishing the costs of traffic noise.
Bio: Megan was born in Tampa, Florida and grew up in Las Vegas, Nevada. She was awarded her B.S. in Zoology from Kentucky Wesleyan College in 2020. Megan currently lives in San Marcos, TX with her boyfriend and 2 dogs. After completing her M.S., Megan will be remaining in GASP lab to complete her PhD where she will compare the glucocorticoid response between populations of wild lesser sirens, Siren intermedia over 2 years.
Hydrology and geology as structuring mechanisms of semi-arid fish communities
Lauren E. Chappell
Major Advisor: Dr. Timothy H. Bonner, Department of Biology, Texas State University
Dr. Noland Martin Department of Biology, Texas State University Dr. Benjamin Schwartz, Department of Biology, Texas State University
Thursday, April 13th, 2023, 8:00AM, Freeman Aquatic Biology Building (FAB) 130
In the semi-arid regions of the Edwards Plateau in southwest USA, spring-associated fishes, including several federally and state listed species, are closely linked to spring outflows of karst aquifers. However, not all spring outflows are of sufficient enough volume to provide surface flows far distances downstream. Stream disconnectivity can occur during dry periods, especially in systems where the surficial geology transitions from water gaining reaches (i.e., spring outflows) to water losing reaches (i.e., surface waters lost to alluvium or recharging another karst aquifer). The purpose of this study was to describe habitats and fish community distributions, with an emphasis on spring-associated fishes, along a longitudinal gradient consisting of different geologies and gaining/losing reaches between a wet hydrological period (2015 – 2016) and dry hydrological period (2021 – 2022) in three independent river systems. During five collection events, collective fish communities consisted of 26 species (6 spring-associated fish species) and 21,297 individuals (10,317 spring associated fishes). Among 366 habitats quantified, reaches consisted primarily of riffles and runs with gravel and cobble substrates, moderately swift current velocities (mean ± 1 SE; 0.33 ± 0.29 cm/s) and shallow depths (0.38 ± 0.27 m) during the wet hydrological period, although two rivers were dry or surface waters were restricted to isolated pools in the Quaternary Losing Reach. During the dry hydrological period, habitats were similar in the Cretaceous Gaining reaches, isolated pools formed in the Cretaceous Losing reaches, and streambeds were completely dry in the Quaternary Losing reaches. Correspondingly, species richness, diversity, and evenness were generally greater in the Cretaceous Gaining and Losing reaches compared to the Quaternary Losing reaches during wet and dry hydrological periods. Surprisingly, spring-associated relative abundances were similar in the Cretaceous Gaining and Losing reaches, despite the formation of isolated habitats in the Cretaceous Losing Reach. In the past, losing reaches of Edwards Plateau streams were interpreted as sinks for spring-associated fishes, yet this study demonstrated that losing reaches can serve as aquatic refugia for sources of spring-associated fish populations and therefore have conservation value for a number of the Edwards Plateau endemic fauna.
Bio: Lauren is from San Antonio, TX and received her B.S. in Wildlife Biology from Texas State University. She enjoys spending time recreationally on Texas rivers, camping, reading and volunteering in her community. She is hoping to continue her career in academia by pursuing a doctoral degree.
Investigating the effectiveness of mindfulness and nudging on coastal recreationist to mitigate shorebird disturbance
Name: Brooke A. Laycock Major Advisor: Dr. Christopher Serenari, Department of Biology, Texas State University
Dr. Clay Green, Department of Biology, Texas State University
Dr. Kristy Daniel, Department of Biology, Texas State University
Zoom Link: https://txstate.zoom.us/j/97311205472?pwd=UmFoREJ5N2xIRzQ3MGJtVi9XRisvUT09
April 12th 2:00pm-4:00pm, Undergraduate Academic Center (UAC) Room 208
Growing coastal recreation across the globe is leading to more intense disturbances to wildlife. In particular, waterbirds, such as the Black Skimmer, are critical indicators of coastal ecosystem health but experiencing population declines. Thus far, research on mitigation of recreational disturbance to coastal bird species has mainly focused on ecological changes associated with the shorebird and waterbird populations, and implementation of education and enforcement mechanisms to influence human behavior. These popular approaches may be effective in some contexts but perhaps less effectual in remote environments that lack rules and regulations, law enforcement patrols, or the gaze of other recreationists. Purposes of this study included a) exploring the efficacy of contemplative pedagogy (i.e., mindfulness, focused on attention, reflection, and heightened awareness) and b) investigating the capability of recreationists to be either nudged versus shoved to comply with waterbird guidelines and rules. Both contemplative and nudging approaches may create novel pathways to help recreationists manage their own behavior occurring in more remote waterbird habitats but remains understudied in wildlife conservation. Findings from interviews with 21 recreationists and officials with extensive knowledge about recreation and tourism visitation to or near rookery islands on the Texas coast revealed that recreationists who were more aware about the consequences of their intentions, attention, and attitudes towards waterbird populations emerged more likely to conserve waterbirds. Additionally, results revealed that coastal waterbird managers who design their education and outreach programming to target mindfulness while prioritize nudging, may achieve higher rates of compliance with pro-waterbird guidelines and policies, thereby, decreasing recreational disturbance to waterbirds. Informants revealed that waterbird officials are using low-touch nudge mechanisms (e.g., signs, handouts, emails, etc.) but seeing very minimal results in their conservation efforts. Hence, shoving via active coast enforcement is also critical for influencing behavior. Findings suggest that by utilizing a mindful holistic approach and incorporating acts of shoving in the form of low-touch shove and high-touch shove, waterbird populations would stand a better chance at thriving along the Texas coast.
Bio: Brooke graduated from The University of South Florida with her bachelor's of science in Integrative Animal Biology in 2020. In her spare time Brooke likes to read, spend time in the sun at Sewell Park with friends, and checking out new restaurants!
Characterizing the Metal Stress Response in Pseudogymnoascus destructans
Name: Saika Anne
Major Advisors: Dr. Ryan L. Peterson, Dept. of Chemistry and Biochemistry, Texas State University
Committee Members: Dr. Robert JC McLean, Department of Biology, Texas State University
Dr. Mar Huertas, Department of Biology, Texas State University
Wednesday, April 12, 2023, 10:00 am. CST, Location: CHEM 304
White nose syndrome (WNS) is a highly contagious fungal disease that affects bats during hibernation. The disease is caused by a pathogenic psychrophilic fungus called Pseudogymnoascus destructans (Pd), which grows on the skin of bats and causes them to wake up frequently during hibernation, leading to depletion of energy stores and eventual death. Some North American bat species are experiencing > 90% population declines. Copper is vital to the growth of both pathogens and animals they infect. A new idea that is gaining ground in the field of innate immunity is that animal hosts intentionally restrict labile metal pool to starve and weaken the invading microbial pathogens. However, copper can also be harmful to cells at high levels because of its redox properties and its potential to interfere with metalloprotein function. As a result of these toxic effects, copper can act as a potent antimicrobial agent and is imported into microphage phagolysosomes to kill invading pathogens. Thus, strictly regulating cellular copper levels is important for fungal survival in their animal host niche. There are no approved methods for treating WNS positive bats. Efforts are underway to research the disease and develop strategies to mitigate its spread and impact on bat populations. It is our hypothesis that altering the ability of Pd to harvest copper from their bat hosts will reduce Pd propagation, which will lead to reduced fungal loads on bats and lead to increased bat survivorship. In our efforts to characterize the basic Cu cell biology of Pd, we are working on generating two Pd knockout strains of the putative copper sensing transcription factors VC83_00821 and VC83_01625. Our preliminary results suggest that both Pd mutant strains exhibit normal growth behavior across a wide range of copper growth conditions. As an alternative method to characterizing the Pd copper stress response, we have executed a transcriptomic study looking into Pd genes regulated by high and low copper levels. At sites of active WNS infection, the fungal pathogen Pd, produced a variety of unusual metabolites, including iron, siderophores and riboflavin. The latter has been shown to be essential for fungal virulence. The presence of these metabolites at sites of active WNS infection highlights the complex interactions between Pd and its bat hosts. We hypothesize that riboflavin secretion is a response growth under metal restrictive conditions to mobilize biologically inert metal ion pools. To test this hypothesis, we developed an assay using synthetic media SD and LoFloglu media to monitor riboflavin secretion in Pd growth media. We quantify riboflavin secretion spectrophotometrically in the growth media by monitoring emitted light at 528/530 nm after 495 nm excitation. Our results indicate that riboflavin secretion by Pd may be independent of exogenous metal ions and chelator levels. This behavior is different than observed for other pathogenic fungi, such as Candida albicans and Aspergillus fumigatus. Further studies will investigate other stress conditions that alter Pd riboflavin secretion.
Bio: Saika was born and raised in Bangladesh. She earned a BS in Agriculture in 2016 and an MS in Genetics and Plant Biology in 2017. She joined Texas State University to pursue her second master’s degree in Biology. Afterwards, she will be pursuing her Ph.D. in MSEC program at Texas State University. In addition to her research, she enjoys traveling, exploring different cuisines, as well as connecting with people who have a positive attitude.
Assessing the current direction of hybridization between the federally endangered Houston toad (Bufo houstonensis) with the sympatric Gulf Coast toad (Bufo nebulifer) on the main recovery site within its designated critical habitat
Name: Ferris Zughaiyir
Major Advisors: Dr. Michael R.J. Forstner, Department of Biology, Texas State University
Committee Members: Dr. David Rodriguez, Department of Biology, Texas State University
Dr. Chris Nice, Department of Biology, Texas State University
Tuesday, April 11, 2023, 8:00 am CST, Supple Norris Conference Room
Understanding the influence of demographic change on introgression rates between two sympatric species is particularly important when one of the species is rare and threatened with extinction. I assessed the level and direction of interspecific gene flow between the federally endangered Houston toad (Bufo [=Anaxyrus] houstonensis) with the sympatric Gulf Coast toad (Bufo [=Incilius] nebulifer) on a primary recovery site for Houston toads at the Griffith League Ranch (GLR) in Bastrop, Texas. Previously (2000-2008), a higher amount of admixture among Houston toad populations was observed indicating that the level of geneflow was from the more abundant Gulf Coast toad into Houston toads which were at critically low numbers at that point of time. The rarity of Houston toads was hypothesized to be driving the higher amount of unidirectional geneflow from Gulf Coast toads into the rare Houston toads. Since 2014, Houston toad supplementation efforts on GLR have increased, and numbers of Houston toads detected on GLR have concomitantly risen. Given these demographic changes, I investigated whether a potential increase in abundance of Houston toads supported the prior hypothesis. Specifically, whether an increase in abundance of B. houstonensis would change the direction of introgression. I used polymorphic microsatellite loci from nuclear DNA to evaluate levels of interspecific admixture among a contemporary population (2020-2021) of sympatric toads and compared it to levels of interspecific admixture observed previously (2000-2008). Mitochondrial sequence data was used to infer parentage of admixed individuals. Coalescent based models were used to infer potential patterns of interspecific gene flow. Comparable rates of introgression between both time periods and a slight increase in admixed individuals on GLR were observed, indicating no decrease in the level of interspecific admixture among B. houstonensis thus far.
Bio: Ferris was born in San Francisco, California. He completed his B.S. in Biology (concentration: zoology) from San Francisco State University in 2017. He is interested in herpetology and hopes to pursue a career in conservation with a focus on maintaining biodiversity among herpetofauna.
Wintering Reddish Egret (Egretta Rufescens) Foraging Response to Environmental Variability on The Southern Texas Gulf Coast
Major Advisor: Dr. Clay Green, Department of Biology, Texas State University
Dr. Floyd Weckerly, Department of Biology, Texas State University
Dr. Andrea Aspbury, Department of Biology, Texas State University
Monday, April 10 from 2-4pm CT via Zoom
Zoom Link: https://txstate.zoom.us/j/97559610146?pwd=NEZ6VkJSZkRjMnFid2pEQitiVk50Zz09
The Reddish Egret (Egretta rufescens) is a rare species of heron due to its limited geographic range as well as its narrow habitat requirement, relying exclusively on coastal tidal flats throughout its yearly cycle. It is therefore vulnerable to stressors ranging from human coastal development to sea level rise due to climate change. While Reddish Egret breeding ecology has been well studied, little information is known about the wintering ecology of the species. With the goal of gaining more knowledge of its winter foraging habitat requirements, I conducted line transect surveys via boat of foraging Reddish Egrets from November 2019 to March 2021 in the Laguna Madre land cut of the Gulf Intracoastal Waterway, an area with a large portion of tidal flat habitat. Using negative binomial and logistic generalized linear mixed effect models of our count data and multiple environmental variables, I found increasing wind speed and an easterly wind direction had negative effect on the presence of foraging Reddish Egrets in the study area, while a westerly wind direction had a positive effect, suggesting that wind patterns influence the distribution of foraging individuals on the Texas coast. In comparison of light and dark plumage morph Reddish Egrets, higher air temperature and an increasing cloud cover was associated with a higher proportion of light morph to dark morph Reddish Egrets in the flats, indicating support for difference in foraging behavior between the two color morphs. This study will help in furthering knowledge of Reddish Egret winter foraging preferences and may help inform conservation actions including suitable habitat identification and protection in the future.
Bio: Robert Finer is from Petaluma, CA. He received his B.S. in biology from University of California Santa Cruz. After working with threatened and endangered birds in Nebraska, Massachusetts, Texas, and North Carolina he started his M.S. in wildlife ecology in Dr. Green’s lab. Robert enjoys hiking, cycling, and photography in his spare time.
Interplay Between Microbiome and Temperature in Tenebrio molitor
Major Advisor: Camila Carlos-Shanley
Committee Members: Chris Nice, Dittmar Hahn
Day, Date, Time, Building and Room
Friday, April 7th, 9:00am, Ingram 4101
Zoom Link: https://txstate.zoom.us/j/95702914934
Abstract: Arthropods are the most diverse Phylum of animals on the planet, but they are currently facing a massive loss of diversity and biomass worldwide. They are poikilothermic organisms that serve important niches in many different ecosystems, and their decline is becoming increasingly noticeable. Using the common yellow mealworm, Tenebrio molitor, as a model arthropod organism, an experiment was designed to elucidate the impact of temperature and a disrupted microbiome in arthropods. The purpose of this project was to bridge the gap in understanding between temperature, and gut microbiome of T. molitor, and to further establish T. molitor as a model insect organism. Results from this experiment suggest that there is a compounding effect by temperature and microbiome on T. molitor lifespan. Future directions with T. molitor not only include studying the individual and compounding effects of temperature and microbiome on insect lifecycles, but also to explore its untapped potential as a human or agricultural source of protein. The full utility of T. molitor extends far beyond the scope of this work.
Bio: Sam is from Wimberley, Texas and has attended Texas State University for 9 years now. He graduated with a B.S. in Microbiology from Texas State University in 2019. Outside of the lab, he enjoys video games, weightlifting, and boxing. After graduation, he will seek a job to survive.
THE EFFECTS OF ANAEROBIC GROWTH ON QUORUM SENSING, COBALT INHIBITION, AND BIOFILM FORMATION IN CHROMOBACTERIUM VIOLACEUM
Name: Charlotte Packard
Major Advisor: Dr. Robert J.C. McLean
Committee Members: Dr. Manish Kumar
Dr. Karen Lewis
Thursday, April 6th, at 3:00pm in Supple 257
Zoom Link: https://txstate.zoom.us/j/97423487450?pwd=cjlacjZBQk5iTGFpOHg1bHNMdmdlUT09 Meeting ID: 974 2348 7450 Passcode: 984560
Bacteria are able to act as a community and alter gene expression and phenotypes by reacting to population density via quorum signaling. Chromobacterium violaceum utilizes quorum sensing to control motility; planktonic and biofilm growth; and violacein pigment and chitinase production. Many bacteria that possess quorum sensing are facultative anaerobes; however, most quorum-related investigations are performed using aerobic culture. Here, we measured planktonic and biofilm growth, violacein (pigmentation), chitinase, and motility under aerobic and anaerobic conditions. We aimed to broaden the understanding of bacterial quorum sensing and employed a variety of experiments to do so. We tested the effects of cobalt (Co2+) on C. violaceum in both aerobic and anaerobic conditions by way of culture growth in both suspended (planktonic) and attached (biofilm) environments through the measurement of colony forming units (CFUs); the quorum- controlled phenotypes (pigmentation and chitinase) by way of a microtiter and dye-release assay; quorum inhibition by Co2+ through the utilization of differing concentrations of Co2+; and the effects of anaerobic growth and Co2+ inhibition by way of a motility assay. While C. violaceum planktonic growth was reduced during anaerobic growth, biofilm growth was enhanced. Violacein production was not evident under anaerobic growth, which is in accordance with previous work by other investigators showing an oxygen (O2) requirement for synthesis. Chitinase was more prevalent during aerobic growth. Co2+ inhibition of motility was evident, particularly under anaerobic conditions in a dose response manner. In summary, anaerobic growth enhances biofilm formation and influences some but not all phenotypes of C. violaceum, including its response to Co2+.
Bio: Charlotte is from San Antonio, TX. She received her B.S. in Biology from Texas State University in 2021. With a fascination of all things microbial, she joined The Slime Gang in 2021 to pursue her M.S. in Biology. After graduating with her M.S., Charlotte hopes to pursue her Master of Physician Assistant Studies (M.P.A.S.) degree. In her spare time, Charlotte enjoys spending time with her family and friends, being outside in nature, playing video games, watching anime, and reading manga.
An integrated view of how environment shapes physiological stress markers in a widespread toad
Dillon J. Monroe
Major Advisor: Dr. Caitlin Gabor
Committee Members: Dr. Joseph Veech, Texas State University
Dr. Andrea Aspbury, Texas State University
Dr. Veronika Bókony, "Lendület" Evolutionary Ecology Research Group,
Plant Protection Institute (NÖVI)
Dr. Susannah French, Utah State University
Thursday, April 6th at 10:30 AM in Supple 376 (Norris Room)
A species distribution is best understood by examining the organism-environment interaction making physiological stress markers central to understanding species distributions. Glucocorticoids are steroid hormones important to maintaining homeostasis and responding to unpredictable stressors through modulating behavior and energy allocation. Amphibians are ectotherms with highly permeable skin, making them particularly sensitive to environmental changes. Studies of the glucocorticoid stress response are commonly used to understand how species physiologically and behaviorally cope with environmental stressors. The inclusion of downstream changes can help determine whether responses are adaptive or pathological. The Gulf Coast toad (Incilius nebulifer) is native to Texas and Mexico and in a time of global amphibian decline is increasing its distribution and abundance. We studied the physiological and behavioral responses of the Gulf Coast toad to environmental stressors in lab and field studies and examined changes in the northern extent of their distribution using ecological niche modeling. We found that the Gulf Coast toad employs a unique stress response to temperature and urbanization that is associated with increased energy storage at the cost of hop endurance. We also found that higher temperatures and increased urbanization are important factors in explaining the northern distribution. From 2013 to 2023 the Gulf Coast toad has expanded north and east significantly and even under conservative predictions of future climate the range will continue to expand north and east. Exploring glucocorticoid stress response at the range edges may aid in further understanding how tolerant species persist in changing environments.
Bio: Dillon was born and raised in Monroe, Utah. He received his B.S. in Biology from Southern Utah University in 2013. After working a few years with various state and federal agencies he decided to continue his formal education at California State University, Northridge. He graduated with his M.Sc. in Biology in 2019. He is married to Laura Monroe, and they have two kids. After graduation, Dillon will be returning to Southern Utah University as an Assistant Professor teaching anatomy and physiology.
Presence of Plastics in the Gastrointestinal Tract of Sharks in Texas Bays
Dillan Jerod Wulf
Major Advisor: Dr. Jessica Dutton
Committee Members: Dr. Weston Nowlin & Dr. Jeremy Conkle
Thursday, April 6th, 2023, 9:00 AM CDT, Undergraduate Academic Center (UAC) 310
Zoom Link: https://txstate.zoom.us/j/3083957884?pwd=K21aRHVYbmJ1NnJBQTRaRllKM0hWdz09
Meeting ID: 308 395 7884
The issue of plastics in the marine environment has become an important topic in the recent decade due to its ubiquitous presence, long lasting impacts, and detrimental health effects. Plastics have been observed affecting marine organisms by causing gastrointestinal or respiratory blockages or tears. Other consequences of plastic ingestion include exposure to endocrine disrupting compounds, persistent organic pollutants, and toxic trace metals. Few studies have investigated the presence of plastics in shark gastrointestinal tracts, and nothing is known for sharks in Texas bays. This study assessed the presence, abundance, and type of plastics present in the gastrointestinal tracts of three shark species [blacktip shark (Carcharhinus limbatus), bonnethead shark (Sphyrna tiburo) and bull shark (Carcharhinus leucas)] in four bays (Sabine Lake, Aransas Bay, Corpus Christi Bay, and Lower Laguna Madre) along the Texas coast utilizing microscopy and Fourier transform infrared spectroscopy (FTIR). Of the total number of sharks examined (n = 240), only eight individuals were found to contain plastic in their gastrointestinal tract, and a total of nine pieces of plastic was found. Suspected plastics were extracted, photographed, and categorized by type (fragment, fiber, film, or pellet), size, clarity (opaque, translucent, or transparent), and color during visual inspection under a stereomicroscope. The polymer type of each plastic was identified using FTIR. Fibers were the most common plastic item, colorless (clear) plastic was found the most, and translucent was the dominant clarity type. The most frequently found polymers were polyethylene (PE) and nylon 6. Monofilament fishing line and hooks were predominantly found, meaning that plastic ingestion through the diet is not the main problem and fishing practices are a bigger issue. Due to the low number of plastics found in these sharks, apart from monofilament fishing line, plastics do not appear to pose a threat to the health of these species in Texas bays.
Bio: Dillan is from San Marcos, TX and earned his B.S in Recreational Administration from Texas State University in 2020. His passion for aquatic and marine ecology stemmed from a young age as he has always enjoyed spending his time outdoors. He is currently working at Inks Dam National Fish Hatchery in Burnet, TX and has accepted a seasonal position with the U.S. Fish and Wildlife Service in Alaska beginning this fall.
Examining the potential influence of land-use change on a population of timber rattlesnakes (Crotalus horridus) in East Texas
Name: Stephen Witkowski
Major Advisors: Dr. Michael R.J. Forstner, Department of Biology, Texas State University
Committee Members: Dr. Chris Nice, Department of Biology, Texas State University
Dr. Rulon Clark, Department of Biology, San Diego State University
Wednesday, April 5th, 2023, 12:00 pm CST, Supple 112
Timber rattlesnakes (Crotalus horridus) are considered a well-studied organism, but this is only true for specific portions of their distribution. In Texas, the most southeastern part of their distribution, data for this organism seems to be lacking. I used microsatellite loci to understand the current population genetic structure from a remanent fragment of a once continuous population of Crotalus horridus in southeast Texas. The microsatellites reveal low levels of gene flow among populations in Texas, likely due to a dramatic reduction in allelic richness. Significant genetic differentiation seen between the populations are due most likely to genetic drift and could possibly be explained by a local breeding aggregation. This aggregation behavior is not known to occur in Texas and would be a novel aspect of the behavior of these snakes.
Bio: Stephen was born in Honolulu, Hawaii. He completed his B.S. in Biology (concentration: ecology) from San Diego State University in 2017. He is interested in herpetology and will continue his career in conservation with the Lost Pines Habitat Conservation Plan (LPHCP) in Bastrop County, Texas.
USING ACOUSTICS AND IMAGING TO ASSESS BAT BEHAVIOR AND ACTIVITY AT TOWERS: IMPLICATIONS FOR WIND ENERGY
Name: Robert Tyler
Major Advisor: Dr. Sarah Fritts
Committee Members: Dr. Sara Weaver (Bowman), Dr. David Rodriguez
Monday, April 3rd, 2023, 02:00 PM. Ingram 3023
Zoom: https://txstate.zoom.us/j/93912161172 Meeting ID: 939 1216 1172
Wind turbines have been identified as one of the leading causes of bat fatalities in the USA. To reduce the impacts of wind farms on bat populations, risk assessments are performed before construction by monitoring bat activity in the proposed area. However, pre-construction bat activity often does not correlate with bat fatalities reported after a wind farm is constructed. This may be due to bats being attracted to turbines or from limitations of the methods used during risk assessments, which typically use acoustic monitoring of bat echolocation calls. To investigate this discrepancy, we supplemented acoustic monitoring with thermal cameras during bat risk assessments at meteorological towers in south Texas. My hypotheses were 1) activity rates from thermal videos and acoustic monitoring will differ, 2) thermal detections can be predicted from acoustic detections, and 3) temporal and weather patterns will correlate with activity from both acoustic and thermal recordings. We monitored bat activity at 2 meteorological towers in the south Texas plains from September 2020 – November 2020 and April – December 2021. We used machine learning to classify thermal detections as bats or other objects and only used detections scored with greater than 95% confidence and an area greater than 10 pixels as bats in subsequent analyses. We recorded 1,236,834 total thermal detections and 141,448 total acoustic detections, with a total of 15 species and a up to 9 bats around the tower at once. The month, time, absolute humidity, windspeed, and lunar illumination were predictors of both thermal and acoustic bat activity, and temperature was a predictor of acoustic activity. Results supported our hypothesis that thermal and acoustic activity rates differed, both by the time of night and by season, and that thermal activity could be predicted from acoustic activity. Differences between acoustic and thermal results indicate that bat activity may be underestimated during pre-construction risk assessments, which may result in greater bat fatalities at wind farms. Footage of bats at the tower also indicates interactions between bats and large structures and potentially new insights into bat attraction to wind turbines involving pheromonal marking and olfactory cues. Overall our study highlights the strength of supplementing acoustic monitoring with thermal cameras and including thermography in bat risk assessments could help save bats before wind farm construction begins.
Bio: Robert Tyler hails from Austin, Texas where he grew up fascinated with science and the local wildlife, especially bats. He graduated from Texas State University in 2018 with a B.S. in Wildlife Biology. After working on field projects from Ecuador to Tennessee, he returned to his alma mater, and the lab of Dr. Sarah Fritts, to pursue an M.S. in Wildlife Ecology in the Fall of 2020. His research interests include habitat ecology, fire ecology, forestry, conservation, and most prominently: bats.
Differences in gene expression responses to heat shock between warm- and cool-adapted isolates of Batrachochytrium dendrobatidis
Name: Chloe Troupe
Major Advisors: Dr. David Rodriguez, Department of Biology, Texas State University
Dr. Camila Carlos-Shanley, Department of Biology, Texas State University
Committee Members: Dr. Lauren Fuess, Department of Biology, Texas State University
Monday, April 3, 2023, 9:00 am CST, IGRM 3203
Batrachochytrium dendrobatidis (Bd) is one of the most destructive emerging infectious diseases to impact wildlife populations in modern history. Bd displays drastically different patterns of infection, both between distinct amphibian species and between different climates; this has resulted in inconsistent data on its virulence and pathogenicity. In regions within Bd’s known thermal optimum, amphibian declines are extensive and have resulted in entire species going extinct. Yet, in regions that are suboptimal and/or variable in terms of temperature, Bd persists enzootically in local populations with little to no infection and declines associated with the presence of Bd. In this study, we heat shocked six Bd isolates, and their gene expression profiles were compared to a control treatment within the accepted thermal optimum. Two cool-adapted and four warm-adapted isolates were used to compare expression levels between groups to examine differences in their reactions to heat shock. Our results showed that in response to heat shock, cool-adapted isolates upregulated the expression of genes associated with cellular and transmembrane transport activities. Cool-adapted isolates also downregulated the expression of genes relating to peptidase production, a known virulence factor of Bd. This variation in gene expression broadly supports the hypothesis that Bd’s persistence in warm climates comes at the cost of its pathogenicity as it prioritizes maintaining metabolic homeostasis over infectivity. These findings provide more context surrounding species extinctions by investigating the adaptive potential of Bd and its ability to spread across varying environments.
Bio: Chloe was born in England and moved around the United States until her family settled in Texas in 2011. She completed her B.S. in Microbiology from Texas State University in Fall 2019. Chloe enjoys spending time with her two cats, cross stitching, and watching hockey.
Choosing sides: freshwater mussels vary along a gradient of substrate preference and mobility in a behavioral choice experiment.
Meghan E. Martinski
Major Advisor: Dr. Astrid Schwalb, Department of Biology, Texas State University
Dr. Andrea Aspbury, Department of Biology, Texas State University
Clint Robertson, Texas Parks and Wildlife Department
Darixa Hernandez-Abrams, U.S. Army Corps of Engineers
Tuesday, March 28th, 12:00PM CT, Freeman Aquatic Biology Building (FAB) 102
Zoom link: https://txstate.zoom.us/j/97085761701
Unionid mussels, a highly imperiled group of freshwater organisms, are generally considered to have broad sediment tolerances, although at least some species are considered micro-habitat specialists. Mussel mobility can vary between mussel species, but few studies have tested this consistently under controlled conditions. The objective of this study was to use pair-wise substrate choice experiments to examine whether freshwater mussel substrate preference and mobility (horizontal and vertical) would vary between 10 unionid mussels species from Central and East Texas. Our goal was to test various hypotheses in relation to previously proposed habitat preferences based on phylogenetic patterns, life history strategies, and mussel size. Behavioral responses were measured in Mud-Sand and Sand-Gravel tanks over 72 hours, using approximately 50 individuals per species (range of 10 to 54 individuals). Behavioral responses varied widely between species. Four of the ten species (Lampsilis teres, Lampsilis hydiana, Fusconaia askewi, and Obliquaria reflexa) showed a strong substrate preference, while two showed no preference (Potamilus purpatus and Plectomerus dombeyanus). Mussels moved an average of 3.9 cm/day horizontally, with some species (L. teres) moving ~22 times their body length. Most species burrowed either partially or fully > 80% of the time, but some immobile species (P. dombeyanus) neither burrowed nor moved. Detected substrate preferences were consistent with previously proposed habitat preferences for 6 of 10 species. Life history strategy was better able to predict differences in horizontal movements than phylogenetic patterns or mussel size, although smaller widths tended to prefer finer substrate and burrow deeper. The results suggest that species can be classified along a gradient from broad substrate tolerance (i.e., generalists) to strong substrate preference (i.e., specialists) for different sediment types. The species with the lowest mobility showed no substrate preference and the species with the highest mobility showed a strong substrate preference, but these patterns weren’t consistent for all species. This study provides insights into species specific differences in substrate preference and mobility of adult unionid mussels, which is needed for conservation efforts such as relocation and re-introductions.
Bio: Meghan Martinski was born in Midland, Michigan and obtained her B.S. at Central Michigan University. After graduation she will continue working with mussels and other wildlife at a consulting company in MI.
Mussel community and changes in water quality within a southcentral river basin of North America with emphasis on two federal candidate species
Caitlin N. Schoeck
Major Advisor: Dr. Timothy H. Bonner, Department of Biology, Texas State University
Dr. Sarah Fritts, Department of Biology, Texas State University
Dr. Al Groeger, Department of Biology, Texas State University
Thursday, March 9th, 2023, 3:00PM, Freeman Aquatic Biology Building (FAB) 130
Zoom link: https://txstate.zoom.us/j/98414371148
Louisiana Pigtoe Pleurobema riddellii and Texas Heelsplitter Potamilus amphichaenus are candidates for listing by the USFWS under the Endangered Species Act and recognized as functionally extirpated within the Sabine River basin of Texas and Louisiana. Threats to range-wide population viability include changes in water quality. Purposes of this study were to update current knowledge of Louisiana Pigtoe and Texas Heelsplitter occurrences, catch-per-unit effort (CPUE), and habitat associations and to assess changes in Sabine River basin water quality over a 50-year period. A total of 9,244 individuals, representing 28 species, was identified and enumerated among five reaches (two mainstem reaches, three tributary reaches) and 46 samples. Mean CPUE (± 1 SD) per species among all reaches ranged from 0.01 (0.04) mussels/person hour (p-hr) to 10.4 (21.1) mussels/p-hr. Louisiana Pigtoe (N = 57) and Texas Heelsplitter (N = 7) were only observed in the upper Sabine River with a mean CPUE of 0.51 (± 1.68) mussels/p-hr for Louisiana Pigtoe and 0.06 (± 0.20) mussels/p-hr for Texas Heelsplitter. Louisiana Pigtoe was associated with mid-channel, riffle and run habitats with swift current velocities, shallow depths, and gravel substrates. Texas Heelsplitter, based on a small sample size, was associated with mid-channel, riffle habitats with swift current velocities and shallow depths and sand and gravel substrates. Between 1960/1970s and 2020s, water quality variables generally improved when comparing to water quality standards deemed suitable for aquatic life use within the Sabine River basin. One exception was noted in two reaches with recent elevation in sulfides. Between 1960/1970s and 2020s, information on mussel occurrences and CPUE are lacking to assess trends in mussel communities. Nevertheless, mussel community and water quality data provided herein will provide baselines for future monitoring of the mussel community.
Bio: Caitlin Schoeck graduated from Emporia State University with a B.S. in Ecology and Biodiversity in 2018. She enjoys hiking with her dog Donte, adding new fish to her life list, and reading. Caite will begin a new job as a fish taxonomist with Kansas Department of Health and Environment in March 2023.
THE INFLUENCE OF NEST SITE CHARACTERISTICS ON NEST SUCCESS AND PARASITISM OF BLACK-CAPPED VIREOS (VIREO ATRICAPILLA) IN THE SOUTHWESTERN EDWARDS PLATEAU
Major Advisor: Dr. Clay Green, Department of Biology, Texas State University
Dr. Jim Giocomo, American Bird Conservancy
Dr. David Lemke, Department of Biology, Texas State University
Thursday, March 9, 2023, 10:00AM, Norris Room
Zoom link: https://txstate.zoom.us/j/98464479846?pwd=cU9PakQ2TEFhK0tMeFN5WUZ5K2Vmdz09
The Black-capped Vireo (Vireo atricapilla) was delisted from the U.S. Endangered Species List by the United States Fish and Wildlife Service (USFWS) in 2018. As part of the USFWS Post-Delisting Monitoring Plan, nest searching and monitoring of vireo nests were completed in 2021 and 2022 to provide an estimate on parasitism and nest success in the region. Field work for this study took place in Kickapoo Cavern State Park in the western Edwards Plateau of Texas. The two field seasons were characterized by mild drought conditions in 2021 and exceptional drought conditions in 2022. The logistic exposure method was used to quantify the relative success vireo nests had in each year. Nests found in 2021(n = 18) had a daily survival rate (DSR) of 0.96 and an overall chance of survival from nest building to fledging of 0.40. Nests found in 2022 (n = 15) had a DSR of 0.88 and an annual survival rate of 0.04. Additionally, in 2021 vireos only nested in Ashe Juniper (Juniperus ashei) 16% (n = 3) of the time while in 2022 juniper was utilized in 46% (n = 7) of nests. This is of particular importance because juniper removal is one method used to help enhance potential Black-capped Vireo habitat. Black-capped Vireo nests were parasitized by Brown-headed Cowbirds 33% (n = 6) and 47% (n = 7) of the time in 2021 and 2022, respectively. The results of this study will help inform management decisions for Black-capped Vireo populations as historic drought conditions likely become more common under changing global climates.
Bio: Brendan Mulhall graduated from the University of New Hampshire with a B.S. in Zoology in 2019. After completing field work in Minnesota, he pursued a graduate degree in Dr. Green’s lab. Brendan enjoys birding, hiking, and cheering on New England sports teams in his free time. After graduation, he will return to the northeast to pursue a career in natural resources conservation.
Investigating potential trade-offs associated with immunity and reproduction in the northern star coral, Astrangia poculata
Major Advisor: Dr. Lauren Fuess, Department of Biology, Texas State University
Dr. Jason Martina, Department of Biology, Texas State University
Dr. Camila Carlos-Shanley, Department of Biology, Texas State University
Thursday, March 6, 2023, 11:00 am CST, Supple Norris Conference Room
Zoom link: https://txstate.zoom.us/j/7454450890
Most living organisms face ubiquitous pathogenic threats, and have consequently evolved immune systems to protect against potential invaders. However, many components of the immune system are physiologically costly to maintain and engage, often drawing resources away from other organismal processes such as growth and reproduction. These trade-offs have been studied in a wide diversity of systems in order to better understand how organisms respond to competing needs and optimize fitness. Research on these topics in cnidarians, which include ecologically important organisms like hard corals, is critical for understanding future ecological dynamics in the face of rapid environmental change. Here, we characterize trade-offs between constitutive immunity and reproduction in the facultatively symbiotic coral Astrangia poculata. We hypothesized that trade-offs would exist between constitutive immunity and reproduction. Further, we expected that corals with higher symbiont density would have proportionally higher energetic budgets, and thus more energy to allocate towards immunity or reproduction. Male colonies underwent ex situ spawning and sperm output was quantified. We then tested for correlations between reproductive output and common metrics of coral immunity including melanin synthesis, antioxidant production, and antibacterial activity. Finally, we tested for correlations between lipid and carbohydrate levels (as a proxy for energetic budget) and immune phenotype activity. We found no significant associations between reproductive output and immunity phenotype activities, and no differences in energetic metrics between symbiotic states. However, we did find a significant positive association between melanin production and lipid and carbohydrate concentration. The lack of observed trade-offs highlights complexities in energetic budgets, the importance of characterizing multiple traits when considering these questions, and the potential nuances associated with laboratory-based approaches. Our results provide a preliminary framework for future studies to understand immune trade-offs in cnidarians which will further improve knowledge on how corals allocate resources in response to disease.
Bio: Natalie Villafranca graduated from the University of Dallas with a B.S. in Biology in 2021. She enjoys baking gluten free goods, and learning about energy policy. Following the completion of her M.S., she will join a Ph.D. program at a new institution to study coral restoration.