Thesis and Dissertation Announcements

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.