Thesis and Dissertation Announcements

Thesis Defense

Spatial Variation and Environmental Drivers of Mercury in Caddisflies (Trichoptera) in a Complex River Basin

Major Advisor:   

Dr. Weston Nowlin, Department of Biology, Texas State University

Committee Members:

• Dr. Matt Chumchal, Department of Biology, Texas Christian University
• Dr. Jess Dutton, Department of Biology, Texas State University
• Dr. Todd Steissberg, U.S. Army Engineer Research and Development Center
• Dr. Sarah Fritts, Department of Biology, Texas State University

Zoom Meeting: https://txstate.zoom.us/j/81745736712pwd=VWVXfSdxkrPzcYOyIcjkrAJRjj7mUZ.1

Abstract: Mercury (Hg) is a global contaminant. In its toxic organic form (methylmercury; MeHg), it biomagnifies in aquatic food webs. Ecotoxicologists have identified a diversity of environmental factors that influence MeHg biomagnification in food webs. However, the relative strength of factors in determining river food web Hg contamination across spatial scales remains relatively unknown. I assessed spatial variation and environmental factors driving Hg concentrations in net-spinning Hydropsychid caddisflies (Hydropsyche and Cheumotopsyche) across the Colorado River basin (Texas, USA) which exhibits pronounced spatial gradients in land use and land cover and water chemistry. I collected caddisflies and water chemistry from 20 reaches from five rivers in the basin, and LULC composition was determined at riparian and watershed scales. Caddisfly larvae were analyzed for total Hg (THg), MeHg, and stable isotopes of carbon and nitrogen. Water chemistry and patterns in LULC varied substantially across the basin. Caddisfly THg differed among rivers, whereas MeHg in caddisfly larvae varied with watershed position (upstream versus downstream position). The ratio of MeHg:THg in caddisfly larvae varied between 0.3 and 0.5, which is consistent with the literature. Variation in caddisfly THg was best explained by factors at multiple spatial scales, including local in-stream percent canopy cover, deciduous and evergreen riparian coverage in the riparian zone, and deciduous and evergreen coverage at the watershed scale. In contrast, MeHg variation in caddisfly larvae was best explained by local environmental factors, including sulfate concentration in water, local canopy cover, and dissolved oxygen concentration. Trophic position estimation of caddisfly larvae using stable isotopes indicated that the upper positions of the San Saba, Llano, and Pedernales rivers were slightly greater than other rivers and positions. These results suggest that forest coverage at local and watershed scales are a strong contributor to Hg exposure risk in stream invertebrates and provides a better understanding of the relative strength of local, riparian, and watershed-scale factors influencing Hg contamination of food webs.

Bio: Waverly Wadsworth graduated from Sewanee: The University of the South with a B.S. in Biology: Ecology and Biodiversity and a double minor in Chemistry and Environmental Studies. She started her Wildlife Ecology M.S. in Dr. Weston Nowlin’s aquatic ecology lab in the Fall of 2022. She will continue her academic career as a PhD student in environmental engineering at the University of Georgia.

Dissertation Proposal Defense

Glucocorticoids, microbiomes, and immune interactions in amphibians across life stages

Major Advisor: Dr. Caitlin Gabor

Committee Members: 

• Dr. Andrea Aspbury
• Dr. Lauren Fuess
• Dr. Douglas Woodhams
• Dr. Tom Luhring

Zoom: https://txstate.zoom.us/j/84436249800pwd=KCB4akdQZ7KMd6ZZI1rRBJYB62yObH.1

Abstract: Environmental stressors significantly influence the physiology, development, and survival of organisms. In amphibians that undergo distinct developmental stages, stressors can exert varying physiological effects across life cycles. Glucocorticoids, primarily corticosterone in amphibians, are essential hormones in the vertebrate stress response, enabling organisms to cope with environmental challenges and maintain homeostasis. Measuring glucocorticoid profile of baseline, stress-induced, and recovery levels provides insight into coping capacity, the ability to contend with and recover from stressors. Glucocorticoids also modulate immune function, where moderate, short-term elevations can enhance immunity, while chronic elevation can suppress immune defenses. Additionally, amphibians rely heavily on their dermal microbiomes for immune protection, and glucocorticoid activity can disrupt microbiome stability, creating an intricate relationship between stress physiology, microbial communities, and immune performance. Specifically, I will (1) measure glucocorticoid profiles to assess coping capacity across life stages in lesser sirens, Siren intermedia, across spatial and temporal gradients, (2) characterize changes in skin microbiome composition and diversity at different developmental stages in S. intermedia, and (3) evaluate how larval environments influence coping capacity and immune competence in leopard frogs, Rana berlandieri, from larval to adult stages. I hypothesize that stressors encountered during larval stages will have lasting consequences on glucocorticoid profiles, microbiome composition, and immune function later in life, and that intermediate exposure to stressors will prime and optimize physiological and immune responses compared to chronic exposure or absence of stressors. I also hypothesize that abiotic factors will influence coping and microbial regulation, and that younger individuals will exhibit greater sensitivity to these environmental conditions due to changes in glucocorticoid regulation and immune structures across development. This work will integrate field-based and laboratory approaches to identify periods of heightened vulnerability and resilience in amphibians. I aim to identify periods across amphibian development when coping and immune function may be limited.

Bio: Meg grew up in Las Vegas, Nevada and was awarded her B.S. in Zoology from Kentucky Wesleyan College in 2020. She then got her M.S. from Texas State in Population Biology and Conservation in 2023. Megan currently lives in San Marcos, TX with her fiance, 2 dogs, a cat and some guppies.

Thesis Defense

Effects of supraseasonal drought on karst aquatic communities of the Edwards Plateau of Texas

Major Advisor: Dr. Timothy H. Bonner

Committee Members: 

• Dr. Caitlin Gabor
• Dr. Jessica Dutton

Zoom link: https://txstate.zoom.us/j/84752229981pwd=qdbMEsR1xDxk7ML1bHb5Pdu39QxX0D.1    

Meeting ID: 847 5222 9981// Passcode: 769022

Abstract: Supraseasonal droughts refer to an unpredictable period of below average precipitation occurring over multiple seasons and are predicted to become more frequent in central Texas under future climate scenarios.  The purpose of this study was to opportunistically assess the effects of a supraseasonal drought (2022 – 2024) on aquatic habitats, mussel assemblage, and fish assemblage within headwater (N = 6 sites), mainstem (N = 10), and tributary (N = 4) reaches of the upper Guadalupe River.  At the start of an exceptional drought in 2022 and through 2024, streamflow from spring outflows of karst aquifers were sufficient to provide flowing water habitats in the headwater reaches, upper mainstem, and one of the tributaries.  Farther downstream in the mainstem, stream flows became subsurface and reemerged periodically to provide surface waters. All reaches, including the downstream reach with fragmented flows, supported mussels, including federally-listed Guadalupe Orb Cyclonaias necki and Guadalupe Fatmucket Lampsilis bergmanni.  Likewise, all reaches supported spring-associated fishes and riverine fishes, including several imperiled species, with spring-associated fishes persisting in the headwater reaches between 2022 and 2024.  Although exceptional and supraseasonal droughts are typically linked to substantial changes in aquatic communities in more humid regions, lack of detectable changes in aquatic habitats and fish assemblages within a semi-arid region (this study) were attributed to continuous flow of water from karst aquifers and to an aquatic community that has been filtered (e.g., retreating edge hypothesis) via a shift towards a semi-arid climate during Holocene warming.

Bio: Ayden grew up in Rock Port, Missouri and graduated with his B.S. of Biology – Animal Biology from Kansas State University in 2023. While attending Kansas State University, he studied the behavior of guppies when exposed to a perceived goal and endurance trials on surface and cave morphs of Astyanax argentatus. He then joined Dr. Timothy Bonner’s lab pursuing a M.S. in Biology. He has contributed to various studies across the state of Texas looking at fish and mussel communities. He is hoping to continue his academic career with a PhD and work with live-bearing fish taxa, eventually with the goal of becoming a professor and teach the next generation of scientists. Outside of his work in the lab, he spends his time bass fishing, diving, cooking, playing games, and spending time with his friends.

Thesis Defense

Examining Motivation and Retention Factors Among Texas Master Naturalist Volunteers in Science-Based Projects

Major Advisor: Dr. Kristy L. Daniel

Committee Members:

• Dr. Carrie Jo Bucklin
• Dr. Sunni Taylor

Abstract: In many previous studies regarding the types of motivation responsible for volunteering, only the initial motivation of individuals is analyzed. Although recognizing initial volunteer motivation is important, research should also focus on exploring the types of motivation driving continued volunteerism. This study aimed to understand what motivates Texas Master Naturalist participants to volunteer in science-based activities and their sustained involvement in science-based projects. The participants of this study were certified Texas Master Naturalist members or trainees in attendance at the 2024 annual Texas Master Naturalist conference. This qualitative study incorporated four different modes of data collection: Qualtrics questionnaire (n=178), focus group interviews (n=45), voting (n=231), and prompted graffiti walls (n=66), to provide a thorough understanding of the motivation driving initial and prolonged volunteerism. The collected data were coded using NVivo coding software, in which three rounds of coding were performed to analyze the participants' associated motivations. An inductive approach was used for the initial coding, and a deductive approach was used to organize the codes. Motivations were classified as intrinsic or extrinsic and further divided into the pillars of the self-determination theory, as well as the categories of the functional volunteer inventory. The motivations for volunteering reflected high intrinsic or self-motivated themes. Some participants were externally motivated; however, this motivating factor was only present in some categories and often in a minuscule amount. These findings provide insight into what motivates individuals to volunteer and how this motivation can mitigate challenges associated with sustained involvement and program longevity.

Bio: Kristi began her undergraduate career at Temple College and transferred into Texas State, where she obtained her B.S. in Biology in 2022. After graduation, she took a year off before beginning her graduate studies. In the spring of 2025, Kristi joined the Daniel Education Research Lab to explore the motivations responsible for initial and prolonged volunteerism in the Texas Master Naturalist Program. During her time as a graduate student, Kristi has helped create the Research Rangers Feeding Fungi activity booklet and attended Seasons of Science events to lead guided nature explorations.

Dissertation Proposal Defense

Cognitive Ecology of Gambusia affinis: Exploring habitat complexity, shoaling, and predation as drivers of variation in cognition and behavior

Major Advisor: Dr. Caitlin Gabor

Committee Members: 

• Dr. Andrea Aspbury
• Dr. Timothy Bonner
• Dr. Levi Storks
• Dr. Tyrone Lucon-Xiccato

Zoom Link: https://txstate.zoom.us/j/87227847101

Abstract: Environmental heterogeneity plays a critical role in shaping cognitive and behavioral traits in wildlife, yet few studies have experimentally linked specific ecological features to inhibitory control. Inhibitory control, a cognitive function enabling animals to override impulsive actions in favor of goal-directed behavior, is essential for survival in unpredictable environments, and its development may be shaped by both genetic and environmental factors. This study aims to test how habitat complexity, predator exposure, and shoaling interact to influence inhibitory control and risk-taking behavior in The Western Mosquitofish (Gambusia affinis). Using detour maze assays and optical habitat analysis, I evaluate behavioral responses and cognitive performance across three experimental chapters. First, I compare wild- and captive-reared fish to test whether rearing environment affects inhibitory control, and quantify neuron density in brain regions linked to spatial navigation (e.g., telencephalon). I predict wild fish from complex environments will show superior performance and higher neuron density, suggesting experience-dependent plasticity. Second, I assess how shoaling influences cognition by testing G. affinis in both solitary and group (n = 3) detour trials across nine natural populations from varying degrees of habitat complexity. I hypothesize that shoaling enhances cognitive performance, especially in fish from low complexity environments where structural refuge is limited and social coordination is vital for predator evasion. Third, I investigate how predator cue exposure (visual and olfactory from Lepomis cyanellus) interacts with habitat complexity to influence cognition and behavior in lab-reared, naïve fish. Fish are reared in low- or high complexity tanks and exposed to predator cues for 14 days prior to testing. I predict that fish in low-complexity, predator-exposed environments will exhibit faster exit times and greater inhibitory control, indicating that cognitive traits are shaped by perceived predation risk. Behavioral and cognitive metrics—exit time, motivation, and solution speed—are quantified using Cox proportional hazards models. Neuron densities are analyzed through isotropic fractionation and DAPI staining. This research integrates behavioral assays, neuroanatomy, and ecological context to explore how environmental complexity, shoaling and predation shape cognitive traits and behavioral responses. Findings will inform theories of cognitive and behavioral plasticity and contribute to a broader understanding of cognitive ecology in aquatic systems.

Bio: Kyndal Irwin earned her M.S. in Population and Conservation Biology from Texas State University in 2023, where she conducted research on fish behavior and physiology under the mentorship of Dr. Caitlin Gabor. Motivated by that experience, she accepted the competitive R2-R1 Fellowship to continue her work as a Ph.D. student at Texas State. Outside of research, Kyndal has a long-standing commitment to wildlife rehabilitation- she was the first volunteer with Austin Bat Refuge in 2015 and has since helped release hundreds of rehabilitated bats back into the wild. Following her Ph.D., she plans to pursue an international postdoctoral position to expand her research in cognitive ecology across diverse ecosystems.

Thesis Defense

Investigation of Environmental Impacts on Cnidarian Immunity Using the Model Exaiptasia diaphana

Major Advisor: Dr. Lauren Fuess

Committee Members:

• Dr. Tim Bonner
• Dr. Jim Ott

Zoom link: https://txstate.zoom.us/j/9781581599

Passcode: 239847

Abstract: Scleractinian corals have faced multiple mass mortality events due to coral bleaching and disease outbreaks stemming from a range of climate-related stressors. Patterns of disease infection following a bleaching event have been frequently observed, but the underlying mechanisms are poorly understood. I conducted a time-series experiment using the tractable model Exaiptasia diaphana (Aiptasia) to characterize the impacts of changes in symbiont density on host immunity and energetic reserves through heat-stress and recovery. I compared responses of symbiotic and aposymbiotic Aiptasia to disentangle the effects of temperature from symbiont density. I found that immune activity was differentially expressed depending on symbiont density, symbiont status, and energetic availability of the host, but not temperature stress. This study provides insight regarding the impacts of symbiosis on energy allocation and immune activity.

Bio: Originally from Indonesia, Noah came to pursue higher education in the U.S. He completed his bachelor’s in marine biology at Oregon State University in 2023 where he discovered his passion for coral reefs. Later that year, he joined the Symbiommunity lab as a master’s student studying corals using an anemone as a model species. After graduating, he hopes to continue doing marine research at a non-profit or state agency. Outside of the lab, he is part of the Indonesian Gamelan Orchestra at Texas State.

Thesis Defense

Quantitative Analysis of A Polymicrobial Population from the International Space Station

Major Advisor: Dr. RJC (Bob) McLean

Committee Members:

• Dr. Kelly Woytek
• Dr. Lauren Fuess

Zoom: https://txstate.zoom.us/j/83223577290pwd=OlBQlE2ebna7aRCklfvQvGhmBbdC5F.1

Meeting ID: 832 2357 7290

Abstract: The success of prolonged human space travel depends on critical life support systems. Onboard the International Space Station (ISS) the clean water supply is maintained by recycling urine, shower runoff, and humidity condensate through the Water Recovery System (WRS). The WRS provides potable water for both consumption and for use in the Oxygen Generator Assembly (OGA). A resident mixed-species bacterial population has persisted in the WRS despite various microbial control methods. The bacteria identified grow together in mixed-species communities and have a propensity to form biofilms, which can alter microbial virulence and susceptibility to antimicrobial substances. In addition to maintaining astronaut health, these polymicrobial communities should be monitored for their role in malfunctioning spacecraft equipment such as surface corrosion and clogging of WRS filtration units.

Currently, microbial monitoring on the ISS requires samples to be collected and sent back to Earth for processing. This is costly, time consuming, and has many limitations as several months can elapse between sampling and microbial identification. Onboard molecular testing providing microbial information in 1-2 hours, could be used to mitigate illness and damage to critical life support systems caused by opportunistic microorganisms. This study developed and validated a multiplex quantitative Polymerase Chain Reaction (qPCR) method to identify and quantify members of a five species model biofilm community acquired from the ISS. This qPCR protocol will assist in the rapid identification and monitoring of these polymicrobial communities and can aid in the timely and optimized treatment of life support systems to reduce incidents of disease or damage in the future.

Bio:  Amber received her B. S. in Molecular Cell Biology from California State University San Marcos in 2005. She then joined the Lai lab in the Neuropharmacology Department at The Scripps Research Institute, La Jolla, CA., where she worked as a research assistant creating bacterial artificial chromosomes for transgenic mouse studies. After returning to Texas to be near family, she joined Rigaku Americas Corporation in The Woodlands as a senior lab technician where she worked in protein crystallography and X-ray diffraction. She moved to Wimberley to raise her children in the beautiful Texas hill country in 2013 and then in 2023 she began attending Texas State University in pursuit of her master’s in biology and joined the McLean lab. Outside of school she is a band mom, hockey wife, and lavender farmer.

Thesis Defense

A CURE for Science Teaching Self-Efficacy in Pre-Service Teachers

Major Advisor: Dr. Carrie Jo Bucklin

Committee Members:

• Dr. Sunni Taylor
• Dr. Michelle Forsythe

Zoom: https://tinyurl.com/CarletonDefense

Meeting ID: 827 2137 1713

Abstract: A basic understanding of science is vital to developing a scientifically informed society. Well prepared teachers are crucial for quality science education. However, only about 30% of elementary teachers in the U.S. feel confident teaching science. Teachers with high science teaching self-efficacy have better student learning outcomes than those with lower science teaching self-efficacy. To increase science teaching self efficacy, pre-service teachers (PSETs) must have positive, constructive experiences with science. A practical science instructional method is Course-based Undergraduate Research Experiences (CUREs). CUREs are a course structure where students are expected to complete scientific research projects. CUREs have five defining features: collaboration, relevance, discovery, iteration, and scientific practices. Students participating in a CURE gain content knowledge, scientific and collaboration skills, and improved science self-efficacy. My project is one of the first to examine the influence of participation in a CURE on PSETs' science teaching self efficacy. The course implemented a water quality CURE with the PSETs completing a collaborative research project. PSETs collected water quality data using Texas Stream Team protocols, analyzed their data, and presented their findings to their peers. I collected questionnaire responses to measure PSET perceptions of the CURE experience and changes in PSETs perceived science teaching self-efficacy. PSETs who participated in the CURE reported a significant increase in science teaching self-efficacy and perceived the lab aligning with CURE essential elements. CUREs could be part of future effective PSET education to produce confident elementary science educators.

Bio: DeeDee first started in the educational field as a Supplemental Instruction Leader at Austin Community College. She then transferred to Texas State to join her two passions, science and education. DeeDee received her B.S. In Biology from Texas State University in 2023 with a certification to teach life sciences in grades 7-12. The following semester, Spring 2024, she joined the Bucklin Biology Education Research Lab to investigate teacher preparation through CUREs. During her time as a graduate student, DeeDee participated in science outreach events and was the secretary of the Knitting and Crochet Club at Texas State. DeeDee plans to take her education and experience in science education research to work as an educator.

Dissertation Proposal Defense

Characterizing the Mechanisms of Sequential Bleaching and Disease in Cnidaria

Major Advisor: Dr. Lauren Fuess

Committee Members:

• Dr. Chris Nice
• Dr. Caitlin Gabor
• Dr. Michael Studivan
• Dr. Dustin Kemp

Zoom: https://txstate.zoom.us/j/4273471297

Abstract: Coral reef ecosystems, which are formed by scleractinian corals, face widespread declines in ecosystem health and function due to co-occurring environmental stressors. In recent decades, hyperthermic bleaching events and disease outbreaks have been prominent stressors on reefs. Disease outbreaks often follow hyperthermic bleaching events, yet the mechanisms driving the sequential associations between bleaching and disease are poorly understood. This dissertation aims to characterize the cellular mechanisms linking bleaching and disease across cnidarians. The first chapter investigates the mechanisms contributing to differential pathogen susceptibility following experimental heat stress using the model cnidarian Exaiptasia diaphana. I examined the transcriptomic responses of anemones to immune challenge during acute recovery from prior heat stress. I observed opposite regulation of apoptotic and autophagic pathways in anemones exposed to elevated and ambient temperatures. Furthermore, network analyses suggest that disruption of host-Symbiodiniaceae nutrient exchange during bleaching recovery of previously heat-stressed anemones may contribute to observed immune suppression following heat stress. To identify whether similar patterns of symbiotic immunosuppression are occurring in scleractinian corals following hyperthermic bleaching, chapters 3 and 4 leverage a unique long-term sampling dataset which includes physiological and ecological data from scleractinian corals in Carrie Bow Cay (CBC), Belize from 2019 to 2024, a period which encompasses both major bleaching and disease (SCTLD) events. I will characterize host physiological responses during bleaching and recovery across five species of scleractinian corals with varying degrees of SCTLD susceptibility. I will also compare host transcriptomic responses between of two scleractinian corals with contrasting bleaching phenotypes. Furthermore, I will use network analyses to correlate physiological and transcriptomic responses for these two species. Altogether, this work will provide insight into the cellular mechanisms facilitating increased disease susceptibility during recovery from heat stress, highlighting the roles of immunological regulation and nutrient availability in these processes.

Bio: Sofia is originally from Miami, Florida and was inspired to pursue a science degree by her high school environmental science teacher. She graduated with two B.As in Biological Science and Environmental Studies from Wellesley College after which she returned to Miami to tutor and volunteer in the Coral Reef Futures Lab. She completed her M.S. under the supervision of Dr. Lauren Fuess at Texas State University and hopes to combine her love for education and outreach with her research.

Dissertation Defense

Host-Pathogen Dynamics of the Amphibian Killing Fungus in Mainland Ecuador

Major Advisor: Dr. David Rodriguez  

Committee Members: 

• Dr. Chris Nice
• Dr. Ana Longo
• Dr. Dittmar Hahn
• Dr. Shawn McCracken

 Zoom link: https://txstate.zoom.us/j/8421319915

 Meeting ID: 842 131 9915   Passcode: NA

Abstract: Amphibian populations are experiencing alarming declines worldwide, only comparable to mass extinction events. These declines are driven in part by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), which causes the emerging infectious disease chytridiomycosis. Ecuador, a megadiverse country with high amphibian diversity and endemism, has documented widespread Bd presence across high elevation landscapes—yet the ecological and environmental drivers of Bd persistence across the three mainland regions remain poorly understood. This dissertation investigates Bd infection dynamics through a multifaceted approach: (1) evaluating Bd prevalence in phytotelmata across vertical forest strata and assessing the drivers of Bd across landscapes; (2) evaluating seasonal infection patterns in fragmented urban forests on the coast of Ecuador and the implications of the size of urban forests on infection prevalence; (3) modeling Bd distribution using bioclimatic and topographic variables to predict the occurrence of Bd in poorly explored landscapes; and (4) documenting amphibian diversity and abundance in Andean canopy habitats. Results highlight the critical role of precipitation over temperature in shaping Bd suitability, the importance of microhabitats such as bromeliads in pathogen persistence across landscapes, and the overlooked risk of Bd in lowland coastal and amazonian forests. These findings underscore the need for more widespread Bd surveillance and the implementation of conservation strategies, particularly in ecologically vulnerable and understudied habitats.

Bio: Mar Moretta is a biologist from Guayaquil, Ecuador. She earned her undergraduate degree in biology in ESPOL University and later moved to the United States to pursue her Ph.D. at Texas State University. Her research focuses on the ecology of amphibian diseases in tropical environments. Mar is passionate about bridging science, conservation, and community engagement, especially in underserved regions of Latin America. In her free time, she looks for opportunities to serve—particularly by supporting girls who dream of pursuing careers in STEM. Her long-term goal is to create an NGO that empowers girls from underprivileged backgrounds to complete high school and access higher education in Ecuador and beyond.

Dissertation Proposal Defense

Genomics of a Continental Adaptive Radiation

Major Advisor: Sam Borstein  

Committee Members:

• Chris Nice
• Noland Martin
• Jeremy Beaulieu  
• Matthew McGee

Zoom: https://txstate.zoom.us/j/3838751488pwd=bMFuIhFOHoJTJIAZ2r5XJ37Op30jLK.1&omn=88392864926

Meeting ID: 3838751488        Passcode: hybridfish

Abstract: Understanding the generators of biodiversity has been a central theme in biological studies. One major generator of biodiversity is adaptive radiation, a process by which organisms diverge from a common ancestor with coinciding ecological diversification. Because adaptive radiation incorporates both ecology and evolution, it provides a framework for understanding the mechanisms of adaptive diversification. Recent genomic studies have shown that hybridization may promote adaptive radiation by facilitating the movement of genetic material across species boundaries which may generate variation in functional traits. Investigations of trait evolution rely on ‘fully resolved’ species trees to describe the history of traits. This assumes that the genes associated with a trait follow the same history as the species tree. However, this may not always be the case due to evolutionary processes like hybridization and incomplete lineage sorting. Cichlid fishes (Family: Cichlidae) are a model system for investigating adaptive radiation. However, much of the literature has focused on the geographically isolated and relatively young radiations in East Africa, where hybridization has been shown to play an important role. Cichlids are also a key faunistic component in the Neotropics. Heroine cichlids (Tribe: Heroini) are one of the most speciose and ecologically diverse clades of Neotropical cichlids and likely radiated in the presence ecological opportunity as they invaded Central America from South America. The heroine adaptive radiation is substantially older than the African cichlid radiations, making it a valuable system to study adaptive radiation over deeper evolutionary timescales and broader spatial scales. Here, I investigate the genomic mechanisms underlying adaptive radiation in Heroini cichlids. First, I identify instances of hybridization in heroine cichlids using a publicly available dataset. I then discuss generating whole genome-sequences to determine if taxa that have similar ecologies are more likely to hybridize. Finally, I discuss investigating the genomic basis of ecologically relevant traits to determine if hybridization is facilitating the movement of these traits across the heroine cichlid radiation. By focusing on an older adaptive radiation, this work will deepen our understanding of how historical hybridization plays a role in generating biodiversity.

Bio:  Shannon was born and raised in San José, Costa Rica. In 2015, he moved to the United States to pursue a bachelor’s degree in biology at Berry College in Georgia. After graduating, Shannon attended Kennesaw State University in Georgia, where he earned a master’s degree in integrative biology. In his free time, he enjoys fly fishing, hiking, hanging out with friends and family, and playing with his three cats: Kiwi, Cherry, and Coconut.

Thesis Defense

Development of a Transgenic System for Overexpressing tRNA-Derived Small RNAs to Enhance Resistance in Plants

Major Advisor: Dr. Hong Gu Kang

Committee Members: 

• Dr. Nihal Dharmasiri
• Dr. Sunethra Dharmasiri 

Abstract: In our recent investigation, we identified small RNAs originating from tRNA as important regulatory molecules that induce the transcription of stress-responsive genes in Arabidopsis. These small RNAs, known as tRNA fragments (tRFs), demonstrate sequence-specific binding to their target genes, leading to the induction of transcription. However, a system for effectively expressing these intriguing small RNAs in plants has yet to be established. To address this, I explored two transgenic approaches for tRF expression, evaluating two distinct promoters: (i) an estradiol-inducible promoter, which utilizes RNA polymerase II, and (ii) a U6 promoter, which employs RNA polymerase III. The efficacy of these expression systems is currently being assessed through transient expression in Nicotiana benthamiana. 

Interestingly, the U6-1 promoter, commonly used for guide RNA overexpression in CRISPR/Cas9 systems, induced programmed cell death when driving the overexpression of tRF^31Asp2—an immunity-activating tRF identified in our studies. This suggests that the U6 promoter-based system may provide a promising platform for tRF expression. I have characterized these overexpression systems at the molecular level and generated transgenic Arabidopsis plants to evaluate their efficiency in driving tRF expression. Additionally, the potential utility of this system for expressing tRFs will be explored to develop valuable crop traits, offering a new approach for plant breeding and biotechnology.

Bio: Tanzila, an international student from Bangladesh, holds a B.Sc and M.Sc in Botany from the National University of Bangladesh. She joined Dr. Kang’s lab at Texas State University to conduct research on plant immunity. Currently preparing to defend her thesis, she will continue her academic journey by pursuing a Ph.D. in Materials Science, Engineering, and Commercialization (MSEC) at Texas State. Outside of her academic work, Tanzila enjoys traveling and spending quality time doing arts and crafts with her daughter.

Thesis Defense

Ascertaining Differential Use of Cave Habitats by Mammal Species Based on Soft Tick Abundance

Major Advisor: Dr. Ivan Castro-Arellano

Committee Members: 

• Dr. Joseph Veech
• Dr. Benjamin Schwartz

Zoom link: https://txstate.zoom.us/j/89231341939pwd=dq4gBy21y5noy0Lh8pEX2jWPEJ09Ik.1

Meeting ID: 892 3134 1939                     Passcode: 074924

Abstract: Ticks are relevant vectors that play a crucial role in zoonotic pathogenic cycles. With a rise in tick-borne diseases in North America, it is imperative to identify reservoir hosts where certain TBDs are endemic. While the soft tick, Ornithodoros turicata, is recognized as one of the primary vector species for Borrelia turicatae, the agent of tick borne relapsing fever (TBRF) in the United States, potential vertebrate reservoirs that are relevant for the sylvan cycle of this pathogen remains largely unknown. This study quantified the risk of exposure of different mammal species to O. turicata in cave habitats in central Texas and examined the relationship between mammal cave use and soft tick abundance. Camera trap data recorded 1,901 individual vertebrate visits across ten caves, with mammals comprising 54.1% of total visits. Species-specific patterns of cave use varied, but northern raccoons (Procyon lotor), Virginia opossums (Didelphis virginiana), and nine-banded armadillos (Dasypus novemcinctus) were the most frequent mammal visitors with the highest exposure indices. A generalized linear mixed model (GLMM) indicated that species that visited caves most frequently also tended to stay longer, and this relationship was confirmed by linear regression, which showed a significant positive correlation between visit frequency and average duration per visit. This pattern suggests that species with high cave usage may have an increased potential for exposure to O. turicata. However, there was no significant avoidance of high tick abundance caves, or no preference for caves with low tick abundance. Additionally, temperature was a significant predictor of soft tick abundance, whereas humidity and physical cave characteristics were not. These findings provide new insights into soft tick-host interactions and environmental factors influencing O. turicata populations. By examining ecological patterns of vector-host interactions at fine spatial scales, these findings contribute to identifying key reservoir hosts that may sustain pathogen transmission. Understanding the distribution of reservoir hosts for a pathogen within a wildlife community is crucial to understanding the potential risks of human zoonotic infections.

Bio: Brianna was born and raised in El Paso, Texas. She earned her B.S. in Wildlife and Fisheries Science with a concentration in Vertebrate Zoology from Texas A&M University in 2019. In Fall 2022, she returned to graduate school to pursue an M.S. in Wildlife Ecology, joining Dr. Castro's lab to study soft-tick host interactions in cave habitats. She's always had a deep love for the outdoors, animals, and bugs, which made field-based research a natural fit. Outside of school and research, she enjoys going out on hikes, thrifting, and exploring new coffee shops.

Thesis Defense

Spaceflight-Induced Changes in Polymicrobial Biofilm Structure and Silver Susceptibility

Major Advisor: RJC (Bob) McLean

Committee Members:

• David Rodriguez
• Starla Thornhill

Zoom: https://txstate.zoom.us/j/86029167056

Abstract: Biofilms, surface-adherent microbial populations, represent a common mode of bacterial growth in nature, including the water recovery system (WRS) in spacecraft. Several factors have been associated with biofilm structure, including shear forces associated with turbulent flow, microbial community composition, and available nutrients and other culture conditions. Here we investigated biofilm formation of a mixed Escherichia coli-mCherry - Pseudomonas aeruginosa-PAO1-gfp culture during microgravity in spaceflight, and full gravity (ground control), in BioCellTM flight hardware with an artificial urine medium that replicates conditions in the International Space Station (ISS)-WRS. At the early 4-d time point in spaceflight samples, the gas-permeable Teflon membrane on the BioCell hardware surface, was heavily colonized by green-fluorescing P. aeruginosa, whereas the underlying 316L stainless steel coupon had a notable red-fluorescing E. coli population. The 4-d spaceflight P. aeruginosa Teflon biofilm had a clumped appearance with regions of higher cell density (microcolonies) and low cell density (water channels). Interestingly, the overall structure resembles Van Gogh’s Starry Night. In contrast, the corresponding 4-d ground control P. aeruginosa-dominated Teflon biofilm was completely uniform with no obvious clumping. At later time points (14-d and 117-d), P. aeruginosa became much more prominent on both Teflon and stainless steel surfaces, the unique spaceflight biofilm structures were no longer observed and the overall populations decreased. Based on our results and similar findings of other investigators, we propose that microgravity conditions during spaceflight represent a factor that can influence biofilm structure in some culture conditions.

Bio: Taylor received her B.S. in Microbiology from Texas State University in Fall 2022 and continued as an M.S. student with Dr. Bob McLean in the Microbiology of Biofilms and Polymicrobial Communities lab. Her main research focus has been studying spaceflight-induced changes of polymicrobial biofilm structure and susceptibility to silver disinfection. Outside of school and research, she enjoys being outdoors, reading, and beating her kids at video games.

Thesis Defense

Towards a Temporal Theory of Ecology: Body Mass Role for Activity Patterns of North American Artiodactyls

Major Advisor: Dr. Ivan Castro-Arellano

Committee Members:

• Dr. M. Clay Green
• Dr. Floyd Weckerly

Zoom Link: https://us05web.zoom.us/j/87108321224pwd=gNwtgGQZdZYzYpT6fwnaj53t3NateC.1

Meeting ID: 87108321224 Passcode: 3KXLNZ

Abstract: Energy dynamics can shape ecological patterns and impact the evolutionary trajectory of a species. The metabolic theory of ecology links body mass to multiple ecological traits. This study seeks to extend these insights to activity patterns at a macroecological scale, using the large repository of camera trap dataset to explore the relationship between body mass and diel patterns of activity of North American artiodactyls. Artiodactyla, a diverse mammalian order, reflects episodes of rapid evolution driven by climate volatility, resulting in a wide range of body sizes and morphologies. Utilizing a wide range of body masses to investigate its relationship to intraspecific diel temporal niche conservatism (i.e., high coincidence of activity patterns among populations of a species), will help us understand the evolutionary drivers of activity patterns and how energetics may play a role. Activity patterns were classified as homogenous (i.e., low directionality with activity distributed along a 24-hour period), or heterogenous (i.e., high directionality with peaks of activity at different times of the 24-hour period). We found that as the strength of intraspecific diel temporal niche conservatism increases, the directionality of activity decreases in North American artiodactyls. Concurrently, as we saw an increase in body mass of artiodactyl species, we found the directionality of activity increased. Larger species tend to exhibit heterogenous activity, while smaller species will tend exhibit homogenous activity. This supports the hypothesis of a negative relationship between body mass and intraspecific diel temporal niche conservatism. This study contributes to a previously unexplored aspect of macroecology relationships at a continental-scale approach by addressing the relationship between body mass and activity patterns in North American artiodactyls within the context of intraspecific diel temporal niche conservatism.

Bio: Brian was born and raised in Yonkers, New York, and graduated with his B.S. in Biology from Manhattan College in 2019. He then joined the INTECO lab under Dr. Ivan Castro-Arellano’s advisement pursuing a M.S. in Wildlife Ecology. He is hoping to continue his academic journey with a PhD. His love of wildlife pushes him to pursue conservation ecology research as a career. He is supported by his mentors, lab, friends, and family on this academic journey. In his free time, he enjoys exercising, hiking, playing Gaelic Football, and spending time with the people he cares most about.

Dissertation Proposal Defense

Analyzing land use and institutional dynamics in governance of human-elephant conflict in eastern Nepal

Major Advisor: Dr. Christopher Serenari

Committee Member: 

• Dr. Ronald R Hagelman III
• Dr. Leila Siciliano-Martina
• Dr. Jenn Idema, Dr. Elena Rubino

 Zoom link: https://txstate.zoom.us/j/84215064262pwd=4hO0u13ts4Zaposxv8HManF71v12j9.1 

 Meeting ID: 842 1506 4262   Passcode: 675402

Abstract: Human-elephant conflict (HEC) has become an escalating crisis, endangering both the livelihoods of local communities and the survival of elephants around the world. In particular, eastern Nepal has experienced a sharp rise in conflict incidents due to the increasing human-elephant encounters. As negative interactions increase and escalate, they not only inflict severe economic losses and threaten human safety but also drive retaliatory killings, casting doubt on the effectiveness of efforts to conserve and protect endangered Asiatic elephants (Elephas maximus) in Nepal. This documented worsening crisis demands urgent, well-integrated strategies that safeguard both human communities and elephant populations, ensuring cohabitation of the landscape. The proposed study systematically investigates the ecological and institutional drivers of HEC in eastern Nepal via three phases. The first will examine spatial and temporal land use changes from 2002 to 2024 using Landsat imagery and field-verified HEC data to assess how landscape transformations have influenced conflict patterns. The second will employ critical analysis and qualitative interviews to assess governance frameworks, identifying institutional weaknesses and misalignments in HEC management. The final phase will develop an analytical model to assess institutional interactions and governance effectiveness in mitigating HEC. In uniting spatial, critical, and governance perspectives, this study will offer a comprehensive understanding of how landscape changes, governance structures, and community perceptions collectively shape HEC dynamics. In addition, it will inform ways to strengthen HEC governance, enhance institutional coordination, and explore potential for community-driven solutions that align with local livelihoods.

Bio: Kaushal Yadav, a wildlife researcher from Nepal, earned his Master’s in Environmental Science (2016) specializing in biodiversity conservation and wildlife management. With extensive experience leading conservation projects on Asiatic black bears, snow leopards, and biodiversity assessments in the Himalayas, he has developed a strong expertise in wildlife research. His growing interest in human-wildlife conflict led him to Texas State University, where he focuses on the human dimensions of wildlife conservation. Passionate about investigating solutions for conflict resolution in ecological research, Kaushal is committed to advancing conservation strategies that promote human-wildlife coexistence and sustainability.

Thesis  Defense

Ecological and Evolutionary Implications of Diel Temporal Niche Conservatism in Afrotropical Euungulates

Major Advisor: Dr. Ivan Castro-Arellano

Committee Members: 

• Dr. Leila Siciliano-Martina
• Dr. Joseph Veech

Zoom link: https://txstate.zoom.us/j/88551180927pwd=G1dttmSU5X6b6alKc0oYMWtTzkDyVm.1 

Meeting ID: 885 5118 0927 // Passcode: 532469

Abstract: Mammalian activity patterns have been historically understudied due to challenges in collecting and analyzing large-scale temporal data. Advances in trail camera technology, statistical methods, and open-source data platforms have transformed this field, enabling detailed analyses and broader ecological insights. Using open-source trail camera data from diverse African sites, my study examined activity patterns in seven African euungulate species, from small antelopes like blue duikers to larger ungulates like African buffalo, to explore the relationship between activity and body mass. I used R packages ‘Activity,’ ‘Overlap,’ and ‘Circular,’ along with the ROSARIO null model analysis. I predicted larger herbivores with low-nutrition diets would exhibit cathemeral activity with low directionality, while smaller, high-nutrition specialists concentrated activity within shorter periods, showing high directionality. I also tested whether populations within species maintained consistent daily activity patterns (Intraspecific Diel Temporal Niche Conservatism, Intra-DTNC). Results showed a significant negative relationship between body mass and Intra-DTNC, with smaller herbivores demonstrating consistent patterns across sites and larger herbivores showing more variation. In my second chapter, I extended this framework to compare daily activity patterns of the African gemsbok in native and non-native ranges. As predicted by chapter one trends, the gemsbok—a large herbivore—did not maintain consistent activity patterns across sites, highlighting the influence of body size on temporal niche flexibility. These findings underscore the need to identify species constrained by Intra-DTNC and phylogenetic legacies, as their limited adaptability may challenge conservation efforts amid climate change and widespread deleterious anthropogenic effects on ecosystems.

Bio: Brier grew up in Mount Pleasant, Iowa, and spent much of her time outdoors. She graduated with two B.S. in Biology and Animal Ecology at Iowa State University in Ames, Iowa. During her undergraduate studies, she has spent several years studying species such as lichens, wild turkeys, oceanic benthic communities, carnivores, and more. She has contributed trail camera data to the Snapshot USA initiative and has contributed to two publications. Most recently in graduate school she has been able to explore her passions of research and have been fortunate enough to receive awards like Graduate Merit Fellowship as well as the Dan L Duncan Houston Safari Club Scholarship. She aspires to continue to her PhD and continue to work with mammals as she prepares for her future career as a professor. In her free time, she enjoys spending time hiking, playing games with friends, reading, and discovering funky coffee shops.

Thesis Defense

Risky Business: Evaluating the Risk of Catfish-Mediated Zebra Mussel Dispersal in Canyon Lake

Major Advisor: Dr. Astrid Schwalb

Committee Members: 

• Dr. Nate Smith
• Dr. Todd Swannack

Zoom Link: https://txstate.zoom.us/j/82291109533

Abstract: Zebra mussels are a highly invasive species that pose significant ecological and economic threats to freshwater ecosystems. While human-mediated zebra mussel dispersal, especially via boats, has been well studied, dispersal via biological vectors has received less attention. Zebra mussels may be dispersed by catfish that consume zebra mussels, as they can survive their digestive tract at lower temperatures. Yet, in Texas, zebra mussel consumption by catfish has not been studied. The objectives of this study were to examine (1) the number of zebra mussels in the guts of catfish at different times of the year (February, June, October); (2) seasonal variation of zebra mussel densities in Canyon Lake over the past three years using an existing dataset; and (3) evaluate the risk factors for zebra mussel dispersal via catfish. Gut contents of a total of 113 catfish (Ictalurus furcatus and Ictalurus punctatus) were analyzed over the course of three sampling periods: February (n = 65), June (n = 27), and October 2024 (n = 22). Zebra mussels were only found in guts in February, and 23% of 30 randomly selected catfish guts contained at least one living zebra mussel. Overall, 40 of 9,292 zebra mussels were found alive (0.4% of those consumed by catfish). Juvenile mussels between 2 and 10 mm survived with greater frequency. Zebra mussel densities were found to be highest in winter and spring during the recent drought years. The risk for dispersal of zebra mussels via catfish may be highest in early spring, when high availability of juvenile mussels (<10 mm) coincide with higher mobility of catfish, and lower water temperature facilitating the survival of zebra mussels during gut passage.  Future studies should examine this further in order to inform zebra mussel management strategies.  

Bio: Sarah Jenkins Stannard is a Master’s student in Aquatic Resources, under the supervision of Dr. Astrid Schwalb. Sarah has a BS in Wildlife Biology from Texas State University and a background in conservation outreach and science education. She is pursuing a career in watershed management and sustainability. 

Dissertation Defense

Human Dimensions of Recreational Disturbance of Waterbirds

Major Advisor: Dr. Christopher Serenari

Committee Members:

• Dr. Elena Rubino, University of Arkansas at Monticello
• Dr. Clay Green, Texas State University
• Dr. Leila Siciliano-Martina, Texas State University
• Dr. Anthony Deringer, Texas State University

Zoom Link: https://txstate.zoom.us/j/84508174574pwd=KI3aYIyazF3rlX91o23EIyW13wW2ik.1
Meeting ID: 84508174574          Passcode: 721634

Abstract: 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 due to human development and activities, decreasing bird populations. Waterbirds are most sensitive to human disturbance because of the sensitivity of coastal habitats. Texas is home to approximately 139 waterbird species, which are crucial for the environment and primarily nest off the coast on rookery islands. This dissertation employed a social science survey design to address the decline in Texas waterbird populations and efforts to reduce their disturbance while filling knowledge gaps concerning the nexus of recreation and bird activity. A quantitative survey was administered to groups most likely to disturb waterbirds and occurred in person, via push-to-web postcards, and email. Spatial and regression analysis evaluated relationships between potential disturbance sources and proximity to rookery islands, potential compliance and charisma, and potential compliance and self-governance. Spatial hotspot analysis combined participatory mapping and publicly available ArcGIS layers to establish reasonable estimates of the disturbance potential to rookery islands. Findings indicate hotspots of potential disturbances grouped around two metropolitan areas, Corpus Christi, and Galveston, with a cold spot cluster near the Upper Laguna Madre. Findings also revealed that recreationists’ potential to self-govern was high and underpinned by trust in other recreationists, which was positively related to the perceived stated compliance of others. Thus, this research suggests the need to stimulate self-governance among Texas coastal recreationists. Doing so will require activating and engaging social norms and group behavior to improve compliance. Finally, an analysis of how the non-charismatic nature of waterbirds influenced stated compliance demonstrated that birds’ likeability did not significantly impact recreationists’ intention to comply with management actions. The belief that there are enough regulations for waterbirds had a significant negative impact on indicated compliance. From this dissertation we draw least three major implications. One, bird conservation managers such as Texas Parks and Wildlife Department can use findings from chapter one to prioritize areas where disturbance is more likely to occur. Second, self-governance findings provide a pathway to alterations of recreationist’s norms through peer networks. Lastly, the third chapter on charisma revealed the pathway for developing a connection to waterbirds. Overall, this dissertation seeks to provide managers insight into pathways for long-term grassroots waterbird conservation and ensure these birds are around for future generations.

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, led her to focus on human dimensions of wildlife for her master’s and PhD. She is supported by her lab, friends, and family on this academic journey. Her goal is to continue working in conservation research and has been pursuing opportunities to achieve that goal.

Dissertation Proposal Defense

A Comprehensive Study of Breeding Biology and Behavior of the Critically Endangered White-Bellied Heron Ardea insignis to Support Conservation and Population Reinforcement

Major Advisor: Dr. M. Clay Green

Committee Members:

• Dr. Joseph A. Veech
• Dr. Leila Siciliano-Martina
• Dr. Michelle L. Stantial
• Dr. Jonathan Cohen

Zoom Link: https://txstate.zoom.us/j/81178335937pwd=8mTeKbGvsRCzejHChLkMbKTDfbnYYP.1 
Meeting ID: 811 7833 5937
Passcode: 183738

Abstract: The White-bellied Heron (Ardea insignis) is a critically endangered species that poses a significant global conservation concern. Despite ongoing conservation efforts throughout its range, the population continues to decline. Bhutan has made substantial investments in conservation, including the establishment of a captive breeding center, to help protect this species. Previous research indicates a staggering 60% reduction in suitable habitat across its range, which now spans less than 165,000 square kilometers. This continuous population decline is alarming and necessitates more in-depth research. Therefore, I plan to conduct a comprehensive assessment and mapping of the major threats facing the White-bellied Heron and its habitats in Bhutan. By mapping and quantifying these threats, I aim to understand their impact on both population dynamics and the overall survival of the species. Additionally, the breeding population is extremely limited, with only three known active nests in Bhutan representing the only known successful breeding pair in the world. The second phase of my research will focus on the breeding biology and behavior of the species, including how ecological and environmental factors influence breeding behavior and success rates. I plan to employ a mixed-methods approach that includes field observation, remote camera surveillance, and a review of historical breeding data. This will allow me to address knowledge gaps regarding the spatial distribution and severity of threats, and how the herons are responding to these impacts. The findings from my research are expected to not only enhance our understanding of the species but also contribute to refining captive breeding procedures, improving chick rearing in captivity, and informing conservation strategies.

Bio: Indra Acharja is from Bhutan, and his research interests include avian ecology, biology, and freshwater ecosystems. Before joining Texas State, Indra worked at the Royal Society for Protection of Nature (www.rspnbhutan.org), a conservation NGO in Bhutan leading the WBH conservation, captive breeding, and research. Indra holds a Master of Forest Science (2019) from the School of Forestry and Environmental Studies, Yale University, USA, an M. Sc. Forestry (2014) from Forest Research Institute (FRI) University, India, and a bachelor’s degree in Life Science (2012) from Sherubtse College, Royal University of Bhutan. Indra is a member of the WBH IUCN-SSC Working Group and also a National Geographic Explorer and has received several grants and awards, including National Geographic Explorer Grants and the Andrew Sabin International Environmental Fellowship.