Thesis and Dissertation Announcements

Dissertation Proposal Defense

An Investigation of Undergraduate Students' Cognitive Understanding in Interpreting Biological Representations Using Eye Movement

Major Advisor: Dr. Kristy L. Daniel

Committee Members:

• Dr. Carrie Jo Bucklin
• Dr. Noland Martin
• Dr. Katherine R. Warnell
• Dr. Anita Schuchardt

Zoom: https://txstate.zoom.us/j/87472486673pwd=TrdzLzbVKdXJcJihPfEvJnPfyBHrec.1

Abstract: Diagrams and other forms of representation play a critical role in helping students understand scientific concepts. In science education, complex phenomena, such as evolutionary relationships or genetic mutations, are often conveyed through models, diagrams, or equations. These visual representations serve as tools for organizing and illustrating complex scientific processes, facilitating the communication of these concepts in a clear, accessible manner. The ability to interpret, apply, and reflect on understanding the meanings of these representations is known as representational competence, a skill that is increasingly important in biology education as the use of visual and symbolic representations continues to grow. Despite their importance in learning biology, many students struggle to fully understand the scientific concepts being represented and use scientific representations effectively when learning and communicating biology. These struggles highlight the need to examine the cognitive processes involved with representational competence, particularly in how students perceive, interpret, and mentally transform different forms of information being represented when learning biology. Gaining insight into cognition is essential for identifying potential disconnects in visual processing and conceptual understanding to begin offering implications for how instructors can better support the development of scientific representational competence. My study explores how undergraduate students make sense of biological concepts represented through formulaic equations and diagrams. I am specifically interested in investigating different visual and cognitive processes involved in genetic mutation sense-making when interpreting the concepts presented as mathematical equations, and evolutionary relationships represented as phylogenetic trees, with and without example taxa. By integrating eye-tracking technology with verbal data collection methods, my research will capture the underlying mechanisms that shape students' cognitive behavior impacting representational competence, ultimately informing how to develop more effective teaching strategies to develop related skills.

Bio: Mallika Saha has completed her BSc and MSc in Zoology from Jagannath University, Bangladesh. After graduation, she worked as a Research Assistant at the Department of Biology at Jagannath University. Later, she joined a developmental organization as a Liaison and Monitoring officer of a British Council project. The project was focused on food safety and the empowerment of rural women. Mallika completed her second Master's degree in Biology at Texas State University and is currently pursuing her doctoral studies, continuing her work with Dr. Kristy Daniel. In her time at TXST, she has had the opportunity to teach introductory biology to undergraduate students. In the future, she wants to pursue a teaching career or academic position.

Dissertation Proposal Defense

Conservation of Kangaroo Rats: Field and Zoo Investigations

Major Advisor: Dr. Joseph Veech

Committee Members: 

• Dr. Chris Serenari
• Dr. Leila Siciliano-Martina
• Dr. David Germano (California State University - Bakersfield)
• Dr. Allison Julien (Fort Worth Zoo)

Zoom: https://txstate.zoom.us/j/84512802384

Abstract: Anthropogenic disturbance to the environment through climate change, pollution, introduction of invasive species and diseases, and habitat loss continues to threaten biodiversity in general and in particularly vulnerable species. Populations become smaller, more fragmented, and isolated thus increasing the chance of extinction. To address declining populations and prevent small populations from succumbing to extinction, conservation interventions are often necessary. Habitat management and species management (translocation and captive breeding) are two of the tools at the disposal of conservationists. Given certain aspects of their biology and ecology, kangaroo rats (Dipodomys) might be particularly prone to habitat loss, small population sizes, and extinction vortices. Many Dipodomys are under threat from habitat loss and fragmentation, leading to declines at the population and species level. Additionally, Dipodomys typically have low reproductive rates, due to small litter sizes and a low number of litters per breeding season. Much of my dissertation research will focus on the Texas kangaroo rat (Dipodomys elator, TKR). This is a rapidly declining species proposed for the endangered species list of the USFWS. It currently exists in very small and isolated populations in a limited area of north Texas. Given the conservation status of this species, and other Dipodomys, my dissertation will aim to address four areas of research, described below. Chapter 1 of my dissertation will be a review of conservation efforts undertaken for various species and subspecies of Dipodomys. I will review past Dipodomys translocations with particular emphasis on factors influencing success and failure. For Chapter 2 I will measure stress levels (via faecal glucocorticoids concentration) throughout each phase from capture to captivity in order to ascertain if wild-caught TKR are experiencing chronic stress throughout capture, transport, quarantine, and captivity at the Fort Worth Zoo. For Chapter 3 of my dissertation, I will use camera traps and video recordings to investigate the co-occurrence of TKR and other nocturnal rodents at shared resources: natural and artificial burrows, in the field. This knowledge could aid in mitigating competition or displacement of TKR individuals by other rodent species when TKR are reintroduced as part of future conservation efforts. Finally, Chapter 4 of my dissertation will examine the rates of female selectivity and male acceptability in TKR mating behaviour. I will use behavioural observations to parameterise a probabilistic model with empirical estimates of female selectivity and male acceptability obtained from these behavioural observations. This will allow for the modelling of the captive population size and male:female ratio required to produce a given number of impregnated females. Collectively, the research described in these dissertation chapters will inform TKR conservation decisions, primarily reintroduction efforts and captive breeding, two management interventions that have or will be taken to improve upon the species' vulnerable status.

Bio: Maya is from the UK, where she earned a BSc in Zoology at the University of Exeter, and an MSc in Wild Animal Biology from the Royal Veterinary College. She joined the Veech Lab in Fall 2024 to pursue her PhD studying kangaroo rats. Outside of this, she enjoys going for walks, looking for birds and wildlife, and drinking tea.

Dissertation Proposal Defense

Molecular Responses of Brackish Diatoms to Environmental Stress During Photobiological Treatment of Reverse Osmosis Concentrate

Major Advisor: Dr. Keisuke Ikehata

Committee Members: 

• Dr. Hong-Gu Kang (Co-chair), 
• Dr. Shinya Sato
• Dr. Nihal Dharmasiri
• Dr. Benjamin Schwartz

Zoom: https://txstate.zoom.us/j/88351529180

Abstract: The recovery of freshwater by reverse osmosis (RO) is often limited by membrane scaling from inorganic constituents such as silica and calcium, and the process also generates a waste stream, the RO concentrate, which presents environmental and operational challenges. A photobiological process using diatoms was developed to offer a sustainable solution, utilizing diatom's natural ability to absorb silica and nutrients from RO concentrate to enable additional water recovery and reduce RO concentrate generation. This dissertation aims to investigate the molecular and physiological responses of diatoms to environmental conditions encountered during photobiological treatment of RO concentrate. It focuses on mixed diatom cultures and a non-model brackish diatom, Nanofrustulum trainorii, a species that remains molecularly uncharacterized under the high-silica, nutrient-variable conditions of RO concentrate. The dissertation aims to (1) understand the adaptive responses of N. trainorii offering molecular insights to silica and nutrient limitations in RO concentrate; (2) evaluate the effects of environmental stressors, including temperature, ultraviolet (UV) radiation, and high ammonia, on silica uptake and growth of unialgal and mixed diatom cultures; and (3) transcriptomic analysis to understand the molecular mechanisms underlying response to temperature and UV stress in N. trainorii. In chapter 1, De novo transcriptome profiling of N. trainorii was performed on samples collected at three time points during the photobiological treatment, corresponding to high, medium, and low silica, to understand the adaptive response to silica and nutrient depletion. The result showed transcriptional reprogramming with declines in silica and nutrient concentrations, and enrichment of processes related to photosynthesis and ribosomes. Chapter 2 evaluates the performance and resilience of both N. trainorii and mixed diatom culture under environmental stressors, including temperature, ultraviolet (UV) radiation, ammonia, and variable light availability. Mixed cultures demonstrated enhanced silica uptake compared to N. trainorii; however, similar tolerance to high temperatures and high UV exposure was seen, indicating that these stresses can impose fundamental physiological constraints. Building on the findings from Chapter 2, Chapter 3 will investigate the transcriptome effects of temperature and UV radiation on N. trainorii, focusing on genes and pathways associated with stress responses, photosynthesis, and silica biomineralization. This dissertation integrates biological processes, such as silica biomineralization and photosynthesis, with environmental stressors and constraints, including silica limitation, temperature, and UV radiation, to elucidate the mechanisms governing diatom responses under RO concentrate conditions. These insights are expected to provide a framework for the rational optimization of photobiological treatment systems and advance understanding of diatom adaptation to variable conditions of RO concentrate, which differ markedly from those found in natural aquatic environments.

Bio: Lokendra was born and raised in Nepal. He completed his BS in Microbiology from Tribhuvan University (TU) and his MS in Physiology from Kathmandu University (KU) in Nepal. Prior to his PhD, he worked as a lecturer at KU, Kathmandu, Nepal. His research focuses on diatom transcriptomics, with an emphasis on silica uptake and environmental stress.

Thesis Defense

An Assessment of Reservoir Embankments in Providing Habitat for Grassland Birds

Major Advisor: Dr. Joseph Veech

Committee members: 

• Dr. Leila Siciliano-Martina
• Dr. Craig Farquhar

Zoom link: 

https://txstate.zoom.us/i/82335480561pwd=OcxPhdhR6eYJpBebKDipDI4etLJJ22.1

Meeting ID: 823 3548 0561

Passcode: 323245

Abstract: Grassland ecosystems have experienced extensive loss and fragmentation across North America, contributing to long-term declines in many grassland bird species. As large, contiguous grasslands become increasingly scarce, anthropogenic habitats may play a growing role in supporting grassland avifauna. Reservoir embankment grasslands are linear, managed grasslands found on dams and reservoir structures, but their potential as habitat for grassland birds has received little attention. I evaluated whether reservoir embankment grasslands support grassland bird richness and tested whether embankment richness was influenced by regional richness, embankment area, surrounding grassland cover within the region, geographic location, and season. Using eBird data for 46 grassland species observed from 2018 to 2024 across 52 embankment sites within Bird Conservation Regions 19, 20, 21, 22, 23, and 36, I quantified embankment and regional richness at 20, 40, and 60 km spatial extents. On average, embankments supported 15 grassland bird species with a maximum of 31 species. Regional richness positively predicted embankment richness at all spatial extents, with the strongest relationship observed at 20 km. Proportional richness was not significantly related to regional richness at any spatial extent, averaging 45–53% across buffer scales but varying widely across sites. Embankment area had a positive but weak effect on richness, while surrounding grassland cover and geographic location were not significant predictors. Richness varied significantly among sites and seasons, with most embankments recording peak richness during spring or winter and lowest richness during summer. These findings suggest that reservoir embankment grasslands function as habitat patches that track regional species pools rather than being strongly structured by local landscape composition. While unlikely to replace large native grasslands, embankments may contribute meaningfully to regional grassland bird diversity, particularly during migration and winter.

Bio: Sarah grew up in San Antonio, Texas. She earned her B.S. in Environmental Science with a concentration in Conservation and Restoration Ecology from the University of Texas in San Antonio in Spring 2022. In Fall 2022, she joined the Veech lab at Texas State University to pursue her M.S. in Wildlife Ecology, studying grassland bird associations with anthropogenic grasslands. Her lifelong passion for the environment and wildlife is what inspired her to pursue a career in conservation. In her free time, she enjoys bird watching, kayaking, live music, and coffee shops. 

Dissertation Defense

An Exploration of Population Genetic and Reproductive Patterns in a Freshwater Mussel and Hybridization in a Wetland Flowering Plant System

Major Advisor: Dr. Timothy H. Bonner, Department of Biology, Texas State University

Co-chair: Dr. Noland H. Martin, Department of Biology, Texas State University

Committee Members: 

• Dr. Sam Borstein, Department of Biology, Texas State University
• Dr. Charles Randklev, Department of Rangeland, Wildlife, and Fisheries Management, Texas A&M University
• Dr. Michael Arnold, Department of Genetics, University of Georga

Zoom link: https://txstate.zoom.us/j/88398159607

Abstract: Understanding the processes that generate and maintain biodiversity requires integrating patterns of genetic variation, life history timing, and hybridization dynamics across diverse systems. The three chapters of this dissertation examine how population genomic structure, reproductive periodicity, and introgressive hybridization contribute to patterns of diversity in aquatic and wetland organisms. In Chapter 1, I investigated range-wide population genomic structure in the rare freshwater mussel, Pleurobema riddellii, across seven river basins in the Gulf Coastal Plains region of the USA. Using genome-wide single nucleotide polymorphism (SNP) data, I identified strong spatial structuring consistent with a central-marginal pattern, where centrally distributed populations exhibited higher genetic diversity and lower differentiation relative to more isolated marginal populations. These results suggest that historical hydrological connectivity and contemporary basin isolation have interacted to shape the standing patterns of genomic variation in this species. In Chapter 2, I characterized the reproductive periodicity of P. riddellii using annualized measures of gametogenesis and brooding activity. Measures of gametogenesis revealed continuous production of gametes across much of the year, with overlapping developmental stages indicating prolonged reproductive activity rather than discrete seasonal events. These findings highlight the importance of life-history timing in understanding reproductive strategies and informing management efforts for imperiled mussel species. In Chapter 3, I examined genomic divergence and introgression across a hybrid zone between two species of wetland flowering plants in a coastal Texas marsh, Iris brevicaulis and I. hexagona. Genomic analyses revealed low overall divergence with a small subset of highly differentiated loci, alongside widespread but asymmetric excess introgression biased toward I. brevicaulis ancestry. Loci with elevated divergence were disproportionately associated with extreme introgression, indicating a non-random relationship between genomic differentiation and unusual patterns of introgression. This dissertation demonstrates that biodiversity patterns in wetland and freshwater systems are molded by the interaction of historical hydrological connectivity, contemporary isolation, reproductive timing, and hybridization. By integrating population genomics with life-history and hybrid zone analyses, this dissertation provides a comprehensive approach for understanding the processes that structure genetic variation and species boundaries in natural systems.

Bio: Alex Zalmat is a Texas native, born in Dallas, with a passion for hiking, fishing, rock climbing, and biology. His research focuses on hybridization and speciation, with an emphasis on understanding how genetic variation is partitioned during divergence. He has applied these interests across a diverse range of study systems, including freshwater mussels and flowering plants. When he is not conducting research, Alex can be found outdoors or spending time with his wife and family, often enjoying a friendly game of poker.

Thesis Defense

Analytical Characterization of Molecular Bouys Method for SARS-CoV-2 RNA Isolation and RT- qPCR Detection in Wastewater

Major Advisor: Dr. Shannon Weigum, Department of Biology, Texas State University

Committee Members:

• Dr. Mari Salmi, Core Research Operations, Texas State University
• Dr. Joel Bergh, Department of Biology, Texas State University

Abstract: Wastewater-based epidemiology (WBE) is a tool that has gained popularity in the surveillance of various diseases and drug biomarkers in communities. This tool has been used to identify warning signs of disease outbreaks in local communities before the emergence of clinical signs. In recent years, WBE has received a lot of attention in the surveillance of SARS-CoV-2, serving as a complement to clinical diagnostic testing of an individual. The target analyte isolation method is a crucial step in WBE, as the reliability of results generated from WBE experiments is dependent on it. Research has explored the use of hollow silica microspheres (molecular buoys) to isolate target analytes of disease pathogens from wastewater, and this method has proven to be reliable and swift in generating results while using inexpensive materials. The current study characterizes the analytical performance of hollow silica microspheres for the isolation of SARS-CoV-2 RNA from wastewater. Hollow silica microspheres were functionalized by allowing chitosan (a nucleic-acid-binding polymer) to bind to the epoxide rings expressed on the surface of the silica microsphere. Using a fluorescently tagged DNA aptamer diluted in Phosphate Buffer Saline (PBS), the nucleic acid binding capacity of the functionalized silica microspheres was examined. Observation under a fluorescent microscope showed that Hollow silica microspheres reached optimum functionalization at 24-hour incubation in buffer chitosan solution. Functionalized beads were incubated in SARS-CoV-2 RNA-inoculated pseudo-wastewater (diluted human stool). The speed and efficiency of hollow microspheres in isolating SARS-CoV-2 viral RNA from wastewater were analyzed using RT-qPCR; the procedure was done immediately after microsphere incubation in pseudo-wastewater. This study aims to validate time optimization for the functionalization of hollow silica microspheres as well as establish a SARS-CoV-2 viral RNA limit detection (LoD) for molecular buoys following established requirements by the Centers for Disease Control (CDC).

Bio: Ololade is from Nigeria, where she earned a Bachelor of Technology in Animal Science. She later expanded her academic foundation with a Master of Arts in Communication Studies, specializing in health communication, in 2024. That same year, she joined the Weigum Nanomaterials and Biosensor Lab to pursue her M.S in Biology. With a strong passion for cellular and molecular sciences, she aims to gain hands-on experience in clinical research after graduation, ultimately working towards a Ph.D. in Cell and Molecular Biology.

Thesis Defense

A Novel Device Based on Counter-Flow Heat Exchange for Simultaneously Studying Factors Affecting the Thermal Preference, C_Tmin and C_Tmax of Small Aquatic Organisms

Major Advisor: Dr. David Huffman, Department of Biology, Texas State University

Committee Members:

Co Chair: Dr. Timothy Bonner, Department of Biology, Texas State University

• Dr. Shannon Weigum, Department of Biology, Texas State University
• Dr. Katherine Bockrath, US Fish and Wildlife
• Randy Gibson, US Fish and Wildlife

Zoom Link: https://txstate.zoom.us/j/87546158267pwd=sSlnD99Y8svSVmOJNiJjByea8EIxLx.1

Meeting ID: 875 4615 8267 Passcode: TBAD

Abstract: A novel Thermal Biology Assessment Device (TBAD) employing Counter-Flow Heat Exchange principles was developed to generate and robustly maintain & manipulate a stable, linear temperature gradient for studying the thermal biology of small aquatic organisms. The TBAD trough and all associated equipment are mounted on a mobile cart with precise levelling control. The 2.6 m acrylic trough integrates two multiplexed CFHE conduit assemblies, and reconfigurable modular testing arenas with removable cages to allow for simultaneous assessment of thermal preference and critical thermal limits (C_Tmin and C_Tmax) in the same environmental water. This report focuses on the design, construction, testing and potential applications of the TBAD as an experimental platform, emphasizing design and control issues that enable precise temperature control while preserving behavioral realism for thermally sensitive taxa. Particular attention was given to how the trough geometry, convection paths, and bubbler-driven mixing interact to generate a linear temperature gradient that organisms can freely explore. The TBAD testing arena is reconfigurable to accommodate mobility, substrate, lighting and cover requirements of small aquatic organisms characterized as pelagic, benthic, interstitial, infaunal, and subterranean. It is intended for short- or long-term studies of how specific traits and status (sex, ecology, age, disease & nutritional status, etc.) interact with various thermal regimens in freshwater and marine ecosystems. Potential conservation applications include improving temperature management in captive assurance populations, informing timing, weather and locality of restocking strategies, and supporting conservation decisions for imperiled aquatic communities under ongoing flow and climate stressors.

Bio: Enzo grew up in Dallas, Texas, where he made a habit of finding nature where ever he could in the big city. This drive to find nature turned into a passion for wildlife and conservation at an early age. When he was not outside, he was in the garage with his father, working on cars and engines and developing a mechanical and engineering mindset. Little did he know that both of his favorite past times would converge to result in the development of novel lab equipment. Enzo graduated from Texas State University in May of 2023 with a BS in Wildlife Biology and a minor in Geography, and immediately returned for a Master of Science in Population and Conservation Biology at Texas State in fall of 2023.

Thesis Defense

Mussel and Fish Assemblages Within Off-Channel Water Bodies of the Sabine and Neches Rivers

Major Advisor: Dr. Timothy H. Bonner, Department of Biology and The Meadows Center for Water and the Environment, Texas State University

Committee Members:

• Dr. Benjamin Schwartz, Department of Biology, Texas State University
• Dr. Charles Randklev, Texas A&M Natural Resources Institute, Texas A&M University

Abstract: Off-channel water bodies are predominantly lentic areas within the floodplain of riverine systems including adventitious streams and oxbow lakes. In the past, off-channel water bodies were largely ignored as habitats for riverine mussels and fishes based on the general perception of off-channel water bodies having poor water quality (e.g., low dissolved oxygen) and supporting only tolerant species. With increasing efforts by federal, state, and private organizations to assess population status of imperiled riverine species, there is a need to document all available habitats for more complete assessments of species occurrences and abundances within riverine systems. Objectives of this study were to quantify occurrences and abundances of mussels and fishes, to describe water quality and environmental variables, and to relate aquatic biota occurrences and abundances to reach effects (i.e., upper basin, lower basin) and system type effects (i.e., lotic, lentic) among 20 off-channel water bodies located within the Neches River and Sabine River basin of Texas between 2022 and 2025. Twenty seven species of mussels (N = 3,812) and 71 species of fishes (N = 25,480) were recorded from the 20 off channel water bodies. Most abundant mussel species were Glebula rotundata (26% in relative abundance), Quadrula quadrula (17%), and Quadrula nobilis (17%). Most abundant fish species were Dorosoma petenense (22%), Alburnops texanus (8.4%), Lepomis macrochirus (6.8%), Labidesthes (6.2%), and Pimephales vigilax (5.1%). Mussel assemblages and fish assemblages differed by reach with greater proportions of mussels with opportunistic life history strategies and lentic fishes found in upper reaches. Greater proportions of mussels with equilibrium life history strategies and lotic fishes were found in the lower reaches. In addition, off-channel water bodies classified as lotic systems (e.g., adventitious streams, oxbows running parallel to river mainstem) consisted of greater proportions of mussels with equilibrium life history strategies and lotic fishes than in off channel water bodies classified as lentic systems. Water quality variables indicated moderate levels of water quality (e.g., dissolved oxygen: 4.1-6.3 mg/l), although one time sampling during summer months was not sufficient seasonal variability in water quality. Overall, off-channel water bodies within the Neches and Sabine rivers of Texas supported a diverse community of aquatic organisms, similar to those (e.g., billabongs, fadamas, resacas) reported globally, and contributed to the biodiversity within river mainstems.

Bio: Caleb's appreciation for the outdoors began with hunting and fishing the woods and river bottoms of Northeast Texas. After earning an A.S. degree at Tyler Junior College, he transferred to Texas State University earning a B.S. degree in Wildlife Biology where his interest in the field of aquatic resources grew under the mentorship of Dr. Timothy Bonner. After graduating, Caleb hopes to continue learning and working in various freshwater rivers and streams.

Dissertation Proposal Defense

Shifting Environmental Community Behaviors Through the Use of an Education Intervention

Major Advisor: Kristy Daniel

Committee Members: 

• Leila Siciliano-Martina
• Derrick Taff
• Carrie-Jo Bucklin
• Merritt Drewery

Zoom Link: https://txstate.zoom.us/j/84149149772

Abstract: Interactive environmental education opportunities can boost one's interest in science. Engaging in meaningful outdoor activities can also promote pro-environmental behaviors among outdoor recreationists and science learners of all ages. As anthropogenic forces create strains on natural spaces, opportunities that allow visitors to connect with and learn about nature are crucial in maintaining the longevity of natural areas for communities to enjoy. A notable increase in people's investment in outdoor activities has resulted in an influx of visitors to outdoor spaces and recreational areas. Engaging with nature is crucial for human development, thus the trend of increased visitation is highly encouraging for community well-being. While spending time in nature can have positive cognitive, educational, and health benefits, increased outdoor traffic can create a negative impact on green spaces and the species that inhabit them. Common acts of trail degradation that contribute to this impact include the loss of soils and flora due to visitors venturing off-trail, water contamination due to fecal matter introduction, and wildlife disturbances. Further, when an outdoor area is visibly degraded, visitors may be less inclined to utilize the space, viewing these negative recreational impacts as intolerable. A balance must be struck between public usage and intentional conservation of natural resources. If stakeholders, such as land managers, day hikers, and other community members, treat outdoor green spaces mindfully through practices like those of Leave No Trace, degradation of the resources may be reduced. To encourage one to care for the natural world, we must first understand the factors that might motivate pro-environmental behaviors, such as environmental awareness, appreciation of nature, connectedness to place, and stewardship mindsets. Informal science experiences can engage learners by providing meaningful and relevant lessons in a hands-on, low-stakes environment. Immersive, place-based environmental education that connects content with participants' lived experiences may be key in shifting environmental attitudes and changing environmentally damaging community behaviors. Integrating authentic opportunities for scientific inquiry and data collection encourages participants to engage with nature while practicing pro-environmental behaviors.

Bio: Carolyn Jess holds her B.S. in environmental science from Sam Houston State University and a M.S. in Biology from Texas State University in 2024. While in the Daniel Biology Education Research Group and Texas Master Naturalist Program, she has had the opportunity to teach local families about nature and science topics through the Research Rangers program. Carolyn has a passion for wildlife conservation and hopes that through her work, she may teach others about San Marcos' natural spaces and inspire responsible treatment of these places.

Thesis Defense

Ribbiting stuff: Effects of environmental conditions on coping capacity, growth, and behavior in larval anurans

Major Advisor: Dr. Caitlin Gabor, Department of Biology, Texas State University

Committee Members:

• Dr. Andrea Aspbury, Department of Biology, Texas State University
• Dr. Emily Powell, Department of Biology, Texas State University

Zoom Link: https://txstate.zoom.us/j/87879723582pwd=fqXhj5sLg9scbhVsmfb071F9kTEcXa.1

Meeting ID: 878 7972 3582 Passcode: tadpoles

Abstract: Amphibians have biphasic life cycles and permeable skin that render them particularly vulnerable to shifts in both terrestrial and aquatic environments. Therefore, evaluating their fitness can determine habitat quality and provide early warnings of ecosystem stress. Amphibians exhibit plasticity and adjust their life-history traits, behavior, and morphology to cope with dynamic environmental conditions, but the anthropogenic increase in unpredictable events such as extreme weather and habitat loss/modification may exceed their coping capacity. I conducted two studies to determine effects of anthropogenically-driven environmental stressors on growth, development, activity, and coping capacity in two native Texas anurans. I tested the hypothesis that chronic exposure to environmental stressors disrupts larval development and reduces coping capacity by collecting urban-tolerant Gulf coast toad (Incilius nebulifer) tadpoles and randomly assigning each to one of five treatment groups: (1) cool/wet (control), (2) cool/dry, (3) hot/wet, (4) hot/dry, or (5) unpredictable variation of these conditions. I collected baseline waterborne corticosterone (CORT) samples on day 8, and baseline-stress recovery CORT samples on day 14 from both tadpoles and metamorphs. Baseline corticosterone in the unpredictable group was marginally elevated on day 8, suggesting unpredictability may serve as its own stressor, but by day 14 there were no significant differences in tadpole CORT. Metamorphs from both heat treatments (hot/wet and hot/dry), however, showed significantly higher CORT release rates compared to the control group, suggesting that negative latent effects on coping capacity carry over from the larval environment, even in an urban-tolerant species. I tested the hypothesis that watershed urbanization disrupts natural behaviors and reduces organism fitness by collecting urban-tolerant Gulf coast toad (I. nebulifer) tadpoles as well as Leopard frog (Rana berlandieri) tadpoles from seven sites that varied in urbanization, habitat complexity, and water quality, and recorded their time spent moving and hiding before and after exposure to a chemical predator cue. I found that habitat complexity and water quality were significantly negatively correlated with watershed urbanization, and R. berlandieri tadpoles from urban sites moved significantly less and were significantly smaller than those from rural sites, suggesting that urbanization may affect foraging success and overall fitness in R. berlandieri. I found no significant effect of urbanization on I. nebulifer tadpole behavior or size. Overall, my findings show that exposure to heat in the larval environment reduces coping capacity after metamorphosis in an urban-tolerant toad and suggests that urbanization degrades aquatic habitat quality and affects the natural behavior and fitness of R. berlandieri.

Bio: Jessie grew up in Austin, Texas, where she developed a passion for animals and conservation at an early age. She has always been especially drawn to the water, with a deep love for rivers, oceans, and other aquatic ecosystems that inspires both her work and hobbies. She graduated from Texas State University in 2022 with a BS in Geography/Environmental Studies and a BA in Spanish before returning to Texas State in 2024 to pursue her master's degree.

Thesis Defense

Establishment, mortality, and growth of recruits in an experimentally disturbed Piñon juniper woodland

Major Advisor: Dr. Susan Schwinning

Committee Members:

• Dr. Noland Martin
• Dr. Marcy Litvak

Zoom: https://txstate.zoom.us/j/82040471421pwd=1Q2HZV4RECHHsydOamgozgPbL7INbk.1

Meeting ID: 82040471421 Passcode: 918489

Abstract: Piñon-juniper woodlands across the American Southwest are experiencing widespread overstory mortality due to prolonged extreme drought. There is a question whether forests can fully recover from these events to their previous state, or whether they are succeeded by more arid woodlands, such as juniper savanna. To better understand the process of vegetation recovery from disturbance, we imposed an experimental disturbance regime by girdling all mature juniper or Piñon trees at a plot scale with replication (N=3). Together with three undisturbed control plots, I monitored over three years sapling survival and growth, newly emerged seedling numbers, and their development and survival by tagging nearly 4000 individuals. My hypothesis was that tree death should enhance survival and growth in wet years but potentially reduce growth and survival in dry years. In addition, I hypothesized that the positive effects of intraspecific girdling would be stronger than those of interspecific girdling, indicating niche dynamics, and setting a strong signal for recovery to the mixed forest state. The girdling treatment increased soil moisture, which was most clearly observed at a depth of 40-60 cm. Sapling survival was generally high and depended on sapling size but was independent of treatment. Sapling growth was enhanced in girdle treatments relative to the control but was not observed until the second year after girdling. Though there were subtle signs of niche dynamics overall, the death of juniper and Piñon trees had similar effects on saplings growth. The number of new Piñon seedlings decreased sharply after girdling Piñon trees, but this effect was not significant for juniper. These findings underscore the importance of advance-regeneration through saplings that passed their most vulnerable life stages. Contrary to expectations, sapling growth benefitted from overstory tree death of either species, including in dry years. However, the two species exhibited distinct recruitment dynamics with lower rates of juniper establishment, but higher survival, and in the juniper-girdle treatment signs of recruiting from a stable seedbank. By contrast, Piñon seedlings emerged in higher numbers but had higher first-year mortality with little buffering from a persistent seedbank. Larger and presumably older saplings were more often found under the cover of heterospecific trees, compared to smaller saplings, which were more often associated with conspecific trees. Indirectly, this indicates that proximity to heterospecific overstory trees is a relatively safer site. Though I did not find direct evidence of stabilizing niche dynamics in the immediate aftermath of disturbance, sapling distribution patterns appear to indicate reduced levels of negative density dependence between juniper and Piñon.

Bio: Aarin is from Washington State. He earned is undergraduate degree at the University of Washington in Forestry and environmental science resource management. He has worked extensively in field research with several federal agencies such as U.S. Forest Service, Bureau of Land Management, Alaska Department of Fish and Game, National Park Service, and recently with the U.S, Geological Survey. His interest are dryland ecology and dryland systems. He hopes to continue working in dryland systems with an emphasis on drought monitoring.

Thesis Defense

Assessing Fall Bat Activity in Texas: Implications of Wind Energy, White-Nose Syndrome, and Ultrasonic Deterrent Strategies

Major Advisor: Dr. Sarah Fritts

Committee Members:

• Dr. Shilo Felton
• Dr. Clay Green
• Dr. Anica Lee

Zoom Link: https://txstate.zoom.us/j/88591844610pwd=MwwaMBMLhKpedXLaoxJRF9xA4mfH38.1

Meeting ID: 974 485 6261 Passcode: 792006

Abstract: Bats serve as keystone species within ecosystems, fulfilling essential ecological functions including insect predation, plant pollination, and seed dispersal. Migratory tree bats: hoary (Lasiurus cinereus; LACI), eastern red (L. borealis; LABO), and silver-haired (Lasionycteris noctivagans; LANO), face significant threats during migration, resulting in substantial fatalities at North American wind energy facilities. Hibernating species, including cave myotis (Myotis velifer; MYVE) and tricolored bat (Perimyotis subflavus; PESU), while less impacted by wind energy, remain threatened by the westward spread of white-nose syndrome. To better understand environmental drivers of activity for these species and inform mitigation strategies, I conducted two studies. My first study assessed multiple environmental predictors of acoustic bat activity during fall across 48 sites in Texas, sampled over six four-day periods across three years using SM4BAT-FS detectors. The strongest predictor across most species was minimum daily temperature (TMIN), except for REDS. Land cover associations and effect sizes varied by species and spatial scale. For REDS, I pooled acoustic detections of LABO, western red (L. blossevillii; LABL), and Seminole bats (L. seminolus; LASE), and temperature effects remained competitive, while longitude exhibited the largest effect size among all top-performing models. My second study assessed the effectiveness of the MIDÉ ultrasonic deterrent at three pond sites in Hays County, Texas, across nine deterrent trials in September 2024. Using two SM4BAT-FS detectors and an AXIS 1942-E thermal camera, I assessed bat occupancy (via video detections and acoustic passes) within the treatment space for six control and treatment periods. Overall, the deterrent did not result in a significant reduction in bat activity, though effectiveness varied considerably across pond sites. Overall, my findings highlight the need for species-specific mitigation strategies that integrate temperature, land cover, and temporal variables to aid in the conservation of bat populations affected by wind energy operations and white-nose syndrome.

Bio: Cerise is a Georgia native with a strong passion for wildlife conservation and endangered species protection. She earned her bachelor' s degree in Wildlife, Fisheries, and Aquaculture with a concentration in Conservation Biology from Mississippi State University. Her experience includes wildlife research using drone-based survey methods, aquaculture management work on Double-crested cormorants (Nannopterum auritum) with the United States Department of Agriculture, and surveying species of concern such as northern long-eared bats (Myotis septentrionalis), oldfield mice (Peromyscus polionotus), and eastern spotted skunks (Spilogale putorius) as a Natural Resource Specialist with the Mississippi Department of Wildlife, Fisheries, and Parks. Outside of research, you can find her hiking, reading, thrifting, crafting, or binging the latest Netflix series. She looks forward to continuing her career in wildlife conservation and research and hopes to inspire more underrepresented students to pursue careers in the field.

Dissertation Proposal Defense

Identifying Novel Oncogenic Differentiation-blocking Genes from Human Druggable Receptome in Neuroblastoma Cells

Major Advisor: Liqin Du

Committee Members:

• Mar Huertas
• Peggy Biga
• Snezna Rogelj
• Tamer Saad Kaoud

Zoom: https://txstate.zoom.us/j/85862773868pwd=PylaPsOdiybiCdBwfQr0tqtnBHxAEN.1

Meeting ID: 858 6277 3868, Passcode: 961195

Abstract: Neuroblastoma is the most common extracranial solid tumor in children and a major cause of pediatric cancer related deaths. High-risk neuroblastoma is often characterized by poor differentiation, resistance to therapy, and unfavorable clinical outcomes. Differentiation therapy, such as retinoic acid treatment, has shown clinical benefit by promoting tumor cell maturation, but the molecular mechanisms that block differentiation remain poorly understood, limiting the development of more effective targeted therapies. This research project aims to identify key receptor proteins that act as molecular barriers to neuroblastoma cell differentiation and to determine whether pharmacological inhibition of these receptors can restore differentiation and suppress tumor growth. By focusing on receptor-driven signaling pathways within the human druggable receptome, the study seeks to uncover critical regulators that maintain neuroblastoma cells in an undifferentiated and proliferative state. The project integrates high-throughput functional screening with system-level network analysis to identify candidate receptor genes involved in neuronal differentiation and cell proliferation. These candidates are further explored through signaling pathway and interaction network analyses, along with microRNA-based regulatory studies, to reveal mechanisms underlying differentiation control in neuroblastoma. A key translational component of this research involves evaluating FDA-approved and clinically advanced small-molecule inhibitors targeting the identified receptors. By assessing both differentiation induction and cell viability, the study aims to prioritize compounds that promote differentiation at non-toxic concentrations. This drug repurposing strategy offers a rapid and cost-effective pathway to identify promising therapeutic candidates. Overall, this research has the potential to advance understanding of neuroblastoma biology and contribute to the development of safer, more effective differentiation-based therapies for children with high-risk neuroblastoma

Bio: Saika Anne is a PhD researcher in Aquatic Resources and Integrative Biology at Texas State University, USA. Her interdisciplinary background in agriculture, genetics, and biology has shaped her interest in understanding complex biological processes. Her research interests include molecular biology, environmental stress responses, and integrative biological systems. She aims to pursue a career in academia and foster interdisciplinary collaboration to address biological and environmental challenges.

Dissertation Proposal Defense

Spatio-temporal dynamics of tropical mammalian carnivores: functional traits, niche conservatism and human impacts

Major Advisor:  Dr. Iván Castro-Arellano

Committee Members:

• Dr. Leila Siciliano-Martina
• Dr. Michael Clay Green
• Dr. Juliana Bedoya-Durán
• Dr. José F. González-Maya

Zoom: https://txstate.zoom.us/j/85151169049pwd=eK2TaYbopMOGsAwyYdgM6gBBm35Bca.1

Meeting ID: 851 5116 9049; Passcode: 843133 

Abstract: The mechanisms structuring mammalian carnivore assemblages (order Carnivora) remain incompletely understood, limiting biodiversity conservation efforts. Resource utilization, constrained by biomechanical and physiological factors, is central to these dynamics and linked to niche dimensions such as microhabitat, diet, and time. Among these, time represents a critical axis that can be partitioned to reduce resource overlap and competition. Functional traits, including body size and dental morphology, influence energetic requirements, prey size limits, and degrees of carnivory specialization, thereby facilitating trophic niche differentiation. Coexistence is further promoted through variation in hunting strategies, activity patterns, and habitat use. Analytical tools such as the Rosario algorithm enhance assessments of temporal overlap, yet applications remain limited. Comparative evidence indicates that activity patterns differ between island and continental species, reflecting adaptive responses to distinct ecological pressures. Anthropogenic disturbances, including fragmentation, urbanization, and apex predator loss disrupt temporal partitioning, intensify competition, and destabilize communities. My dissertation addresses critical gaps in understanding how mammalian carnivores use time as a niche axis across continental and island ecosystems under natural and human-modified conditions. Specifically, it aims to: (1) test whether diel activity patterns exhibit temporal niche conservatism between islands and continents; (2) examine interactions between spatio-temporal overlap and functional traits such as body size and dentition; and (3) evaluate how habitat fragmentation reshapes temporal partitioning and coexistence strategies. Chapter 1 updates the Rosario algorithm for cyclical pattern analysis using R. Chapter 2 investigates spatio-temporal partitioning among carnivore species, the influence of functional traits on activity patterns, and the role of temporal niche conservatism across continental and island ecosystems. Chapter 3 evaluates the effects of habitat fragmentation on carnivore activity patterns in Colombia, comparing large-scale patterns (continent vs. island) with local-scale dynamics (forest remnants functioning as islands within a transformed matrix). By integrating ecological theory, functional morphology, landscape ecology, and advanced analytical tools, my research aims to elucidate mechanisms driving mammalian carnivore assemblages’ structure and providing insights for biodiversity conservation in increasingly human-modified landscapes.

Bio: Tatiana is a wildlife biologist from Colombia. Growing up in a charming small town in the middle of the Colombian Andean mountains has fueled her interest in wildlife studies. She holds a bachelor’s degree in biology from Universidad del Quindío (2016) and a master's degree from Universidad del Valle (2024). Her research focuses on the ecology, taxonomy and conservation of tropical mammals. After completing her degree, she wants to remain in academia and will encourage collaboration between NGOs, local communities, and universities in Colombia with the goal of developing targeted conservation strategies for tropical ecosystems.