Thesis and Dissertation Announcements

Understanding Grassland Ecosystem Stability Under Global Change: Interactions of Nutrient Addition, Soil Disturbance, and Drought Events

Major Advisor: Dr. Jason P. Martina

Committee Members: 

1. Dr. Susan Schwinning 
2. Dr. Nowlin H. Weston
3. Dr. Joesph W. Veldman (Texas A&M College Station) 
4. Dr. Jenifer L. Yost (USDA-ARS Temple, TX)

Zoom Link: https://txstate.zoom.us/j/83133806603pwd=LcbqibdEfVodZIMBuSEHrrNLFYSuhR.1

Grasslands, covering 40% of Earth's ice-free land surface, are among the most dominant terrestrial ecosystems. They provide crucial ecosystem services for human well-being, including biomass production, carbon sequestration and storage, nutrient cycling, and biodiversity conservation. Historically, disturbances like fire, grazing, and drought have shaped grasslands, but anthropogenic global change such as nutrient deposition, land use change, and increased severity and frequency of drought are altering grassland structure and function, thereby impairing the ecosystem services they provide. Understanding grassland stability is essential to determine whether grassland ecosystems can sustainably provide their crucial services and functions. Therefore, the primary objective of this dissertation is to investigate the impacts of global change drivers and their interactions on grassland ecosystem stability. The first chapter examines the effects of nutrient addition and soil disturbance on the temporal stability of overall grassland biomass production, while assessing the relative importance of aboveground and belowground biomass stability. The second chapter investigates the short- and long-term effects of nutrient addition and soil disturbance on soil organic carbon dynamics in grasslands, focusing on carbon inputs and losses and the factors influencing these processes. Finally, the third chapter explores how prolonged fertilization affects the long-term stability of grasslands and the trade-offs between drought resistance and recovery, referred to as the resilience trade-off. Overall, this study will elucidate the individual and interaction effect of different global change drivers on grassland ecosystem, thereby offering insights for sustainable grassland management.

Bio: Tilak, originally from Nepal, holds a B.Sc. in Forestry from Tribhuvan University (2010), a master's in Forest Sciences and Forest Ecology from the University of Göttingen (2015), and a second master’s in biology from Texas A&M University–Kingsville (2021). He is a member of the Ecological Society of America and Nepal's Foresters Association. With seven years of professional experience in forestry, wildlife conservation, and ecology, he has worked with national and international organizations. His research focus shifted from forest to grassland ecosystems when he joined Dr. Martina's lab in Spring 2022. He is happily married with two kids and enjoys playing soccer, exploring nature, hiking, and watching movies.

Exploring the Effectiveness of Course-Based Undergraduate Research Experiences (CURES) on Pre- Service Elementary Teachers (PSETS)

Major Advisors: 

1. Dr. Carrie Jo Bucklin (Chair), Department of Biology, Texas State University
2. Dr. Kristy Daniel (Co-Chair), Department of Biology, Texas State University

Committee Members: 

1. Dr. Christopher Serenari, Department of Biology, Texas State University 
2. Dr. Carlton Fong, Department of Curriculum and Instruction, Texas State University
3. Dr. Anita Schuchardt, Biology Teaching and Learning Department, University of
   Minnesota

Zoom Link: https://txstate.zoom.us/j/86149295445pwd=SLBX2Y522FHBnHwb3f1ifSe7IswTJ9.1&from=addon

Teacher preparation programs often lack sufficient emphasis on science training. As a result, teachers who have had negative experiences with science during their schooling and harbor certain misconceptions about the subject may feel uncomfortable, unmotivated, and unconfident about teaching science at the start of their careers. There is a pressing need to address this issue by implementing interventions in teacher preparation programs that not only increase prospective teachers' interest in science but also enhance their understanding of its broader implications. This understanding could then motivate them to inspire their future students. Research experiences have shown promising results in boosting undergraduate students’ interest in and commitment to continuing in science. Among these, Course-based Undergraduate Research Experiences (CUREs) have proven particularly effective due to their accessibility to a diverse audience and seamless integration into curricula. While much of the literature highlights the benefits of CUREs for science majors, there is limited research focusing on non- science majors in general, and Pre-Service Elementary Teachers (PSETs) in particular. My study aims to address this gap by exploring the impact of CUREs on this specific group of participants, with a particular focus on their science affinity, future intentions to teach science, motivation to learn, and the quality of instruction and support from Student Instructional Assistants (SIAs). This study will be conducted in a general science class that will be converted into a CURE laboratory. It will involve two groups of participants: Pre-Service Elementary Teachers (PSETs) and Student Instructional Assistants (SIAs), who are predominantly sophomores and senior undergraduates majoring in education, respectively. The study employs both quantitative and qualitative methods to address the research questions, including self-reported surveys for all questions, open-ended reflection questions for the first two research questions, and observations of instructors for the third question. It is anticipated that the integration of this educational intervention will address the concerns related to science preparation in PSETs and hold potential if integrated into their educational curriculum.

Bio: Born and raised in India, I completed my undergraduate and master's degrees in Biotechnology before transitioning to Biology Education Research. I recognized a need in my country's education system for young students to contribute to the formulation and revision of curricula and policies. This realization motivated me to pursue education research within the realm of Biology, aiming to bring these insights back to my country. I am particularly interested in teacher preparation programs, as I believe teachers can ignite a curiosity for science in young minds. My PhD research is aligned with this goal, focusing on preparing Pre-Service Elementary Teachers (PSETs) through an educational intervention known as Course-based Undergraduate Research Experiences (CUREs). In my free time, I love connecting with other people to learn their culture and perspectives about life.

The Tortoise and the Landscape: Examining The Habitat, Daily Movement, Space Use, and Thermal Ecology of the Texas Tortoise (Gopherus berlandieri)

Major Advisor: Dr. Joseph Veech      

Committee Members:

1. Dr. Todd Esque (USGS – Nevada)
2. Dr. Drew Davis (Eastern New Mexico University)
3. Dr. Lee Fitzgerald (Texas A&M University)
4. Dr. Caitlin Gabor
5. Dr. Ivan Castro-Arellano

Zoom: https://txstate.zoom.us/j/86937647505

The Texas Tortoise (Gopherus berlandieri) inhabits Tamaulipan thornscrub and savannah-like prairies throughout south Texas and has been identified as a species of greatest conservation need. While the need for conservation has been recognized, we lack detailed knowledge of some aspects of the species' ecology. G. berlandieri is a habitat generalist, and adopting an exclusionary perspective on habitat could be appropriate for modeling and mapping its habitat. The exclusionary perspective typically requires the use of only a few habitat (environmental) variables to map where a species cannot be found and thus by default, identify areas that might be suitable habitat. I modeled tortoise habitat across south Texas, with particular focus on protected natural areas. At least a fifth of all potential G. berlandieri habitat is already protected; six land-holding entities control the majority of these areas. In a separate study, I obtained locational data through GPS tracking of tortoises at three sites to better understand tortoise movement and space use. I applied path analysis to analyze the relationship between daily weather and movement and found that weather did not significantly affect tortoise movement. However, movement did affect the size of tortoise home ranges (space use). In another related study, I investigated whether invasive Guinea grass negatively affects the thermal environment of tortoises. To examine the thermal ecology of G. berlandieri more broadly, I used thermal loggers to record body temperatures of free-ranging tortoises and environmental temperatures through operative temperature models. Texas tortoises are more tolerant of cold weather than their congenerics but are also most stressed during the coldest season. Invasive Guinea grass does not negatively impact the thermal environment for G. berlandieri but it is not necessarily a neutral invader. It may have negative effects on tortoises that remain to be examined. Gopherus tortoise species throughout the southwestern USA and northern Mexico are increasingly endangered by habitat loss and fragmentation, anthropogenic mortality, and removal from the wild. My research provides foundational knowledge on the movement behavior, habitat use, and thermal ecology of the Texas tortoise and explicitly identifies potential habitat within south Texas. This knowledge will be useful in designing and implementing conservation strategies for the Texas tortoise.

Bio: Daniel was born and raised in San Antonio, Texas, and graduated with his bachelor’s degree from Texas A&M University-San Antonio in 2018. He then joined Dr. Veech’s lab pursuing a master’s degree in Population and Conservation Biology; he finished this degree in Fall 2020. His research on G. berlandieri has spanned both his thesis and dissertation. He will remain at Texas State as a postdoctoral researcher modeling the habitat of Reddish Egrets. While tortoises are his first love, Daniel hopes to contribute to conserving various taxa, especially other reptiles and birds. 

Bridging the Gap: Exploring the Challenges and Opportunities to Creating Wildlife Corridors in the Great Plains

Major Advisor: Dr. Chris Serenari, Department of Biology, Texas State University

Committee Members: 

1. Dr. Matthew Wagner, Department of Biology, Texas State University
2. Dr. Leila Siciliano-Martina, Department of Biology, Texas State University    

Zoom Link: https://txstate.zoom.us/j/84870030508

Habitat fragmentation occurs when a large area of natural habitat is broken up into smaller patches and isolated from one another, degrading ecosystems and leading to significant biodiversity loss. This issue is projected to worsen as climate change progresses, forcing wildlife to relocate to more suitable habitats. Agricultural lands, especially within the Great Plains region of the U.S., are a major contributor to fragmentation. Wildlife corridor creation, linkages that reconnect pieces of habitat, is a promising and effective policy tool to mitigate the negative effects of fragmentation. However, for various understudied reasons, formulation and implementation of wildlife corridor policies has been slow or non-existent in most states. The goal of this research is to aid the development of wildlife corridor policy in the U.S. by identifying the primary policy barriers that prevent creation of wildlife corridors in the Great Plains. We surveyed professionals in 12 states with experience working on a wildlife corridor project within this region to identify factors that hinder the various stages of the policy process. Findings revealed that insufficient funding, regulatory obstacles, and coordinating with government agencies are the primary barriers to wildlife corridor implementation. Alignment with the political climate and evidence-based data were identified as important facilitators for the creation of corridors on private agricultural lands. A review of policy diffusion theory in the context of wildlife corridor creation revealed that learning is the most important mechanism that influences the adoption of corridor policies. This research contributes to understanding how policymakers can best initiate, create, and monitor effective wildlife corridors, particularly in fragmented agricultural landscapes.

Bio: Born and raised in South Dakota, Shelby first developed her love for wildlife and conservation from spending her childhood surrounded by natural spaces on her family’s ranch. After receiving her B.S. in Biology from the University of South Dakota, she took some time off from school and worked various field tech jobs. Her interest in human-wildlife conflict influenced her to join Dr. Chris Serenari’s Human Dimensions of Wildlife lab under the M.S. Wildlife Ecology program at TXST in 2022. Following graduation, she hopes to work in wildlife conservation policy.

Investigating Mitogenomic Rearrangements and Their Phylogenetic Consequences in the Pristimantis Conspicillatus Species Group

Major Advisor:  Dr. David Rodriguez

Committee Members: 

1. Dr. Chris Nice
2. Dr. Shawn McCracken (Texas A&M Corpus Christi)

Until recently, species identity and phylogeny have been established primarily on morphology, which has presented challenges due to instances of cryptic speciation. The use of molecular data for species identification (i.e., barcoding) and phylogenetics can help circumvent these issues. In this context, the mitochondrial genome (mitogenome) has been the workhorse, given its rapid rate of evolution (relative to the nuclear genome), lack of recombination, and conservative gene order. However, several studies have revealed deviations in the typical vertebrate gene order within the mitogenome across a multitude of taxa. These rearrangements can make sequencing mitochondrial loci challenging, as Sanger and most short-read technologies are unable to recognize structural variants (SVs). These challenges can be overcome by using long-read sequencing. In this study, we used Oxford Nanopore Technologies (MinION) long-read sequencing to characterize the mitogenome of Pristimantis achatinus. Previous attempts to sequence informative mitochondrial loci for this species have been unsuccessful due to suspected SVs. Additionally, we sequenced close relatives of P. achatinus in the P. conspicillatus species group in an attempt to trace the evolutionary history of the SVs to their most recent common ancestor. We uncovered novel SVs unique to P. achatinus, as well as different SVs present in its close relatives. By incorporating these SVs into phylogenetic analysis, we found that their presence indicates greater divergence between taxa than otherwise suggested by single mitochondrial gene phylogenies. Our discovery of SVs implies that phylogenies and species delimitation need to be revisited in Pristimantis, the most speciose terrestrial vertebrate genus in the world.

Bio: Raised in Texas, Tori spent her free time as a kid catching frogs and lizards. In 2020, she turned that love for herpetofauna into a job and took her first dive into genomics when she began working in Dr. Rodriguez’s lab. In 2022, she completed an honors thesis and graduated with dual bachelor’s in microbiology and English. During her master’s, Tori has had the privilege to continue working for Dr. Rodriguez, has traveled to Ecuador multiple times, and has gotten to help on several projects relating to snakes, frogs, and several parasites in between. Four months ago, she also had the great fortune to marry the love of her life, Joshua Rogalski.

Mercury and Selenium Concentrations in Offshore Fishes in the Northwestern Gulf of Mexico

Major Advisor: Dr. Jessica Dutton

Committee Members: 

1. Dr. Timothy Bonner
2. Dr. Kesley Banks (Harte Research Institute for Gulf of Mexico Studies, TAMU-CC)

Join Zoom Meeting
https://txstate.zoom.us/j/8525821253pwd=hDJ5TEwhqOgQbbj5GtImaac5kyOS9K.1&omn=85644668662

Meeting ID:    852 582 1253    Password: fish

Mercury (Hg) bioaccumulates in organisms and biomagnifies in marine food webs, resulting in concentrations that can be great enough to cause deleterious health effects in fishes and humans. Selenium (Se) has an antagonistic relationship with Hg forming a mercury-selenide (HgSe) complex that is toxicologically inert. Fish consumption advisories are issued based on the Hg concentration in muscle tissue, however, the Se:Hg molar ratio and selenium health benefit value (HBVSe) have been proposed as additional seafood safety criteria in risk assessment. There are several important commercial and recreational offshore fisheries in the northwestern Gulf of Mexico; while Hg concentrations have been investigated for several species (e.g., dolphinfish, king mackerel, and red snapper), many species have not been investigated, and nothing is known about Se concentrations, Se:Hg molar ratios, and HBVSes in any species. This study investigated the inter- and intraspecific variability in Hg and Se concentrations, Se:Hg molar ratios, and HBVSes in 30 species of offshore fishes, including blue marlin, swordfish, red snapper, cobia, golden tilefish, great barracuda, and greater amberjack. Mercury concentrations in muscle tissue were determined using a Direct Mercury Analyzer and Se concentrations using microwave acid digestion and ICP-MS analysis. There was inter- and intraspecies variability in Hg and Se concentrations. Blue marlin had the greatest Hg and Se concentrations. 73.3% of species had individuals that exceeded the adverse biological effects threshold level in fishes (0.5 μg/g wet weight), 60% of species had individuals that exceeded the Texas Department of State Health Services (TDSHS) human health-based standard (0.7 μg/g wet weight), and 46.7% of species had individuals that exceeded the Food and Drug Administration action limit (1.0 μg/g wet weight). All species had a mean Se:Hg molar > 1:1 suggesting that Se may have a protective effect against Hg toxicity, and 81.5% of species had a negative relationship between Se:Hg molar ratio and body length. All species had a positive mean HBVSe suggesting there may be health benefits from their consumption. The TDSHS needs to update their Hg advisory list to include cobia, great barracuda, greater amberjack, golden tilefish, and sailfish. Due to the intraspecies variability in Se:Hg molar ratios and HBVSes, more research is needed to determine if they can be used as additional seafood safety criterion in risk assessment.

Bio: Joe is from Plano, TX and received his B.S. in Biology from Texas A&M University – Corpus Christi in 2022 where he researched larval fish diversity in Aransas Pass and Packery Channel. His passion for marine science and wildlife started with watching Animal Planet and the Crocodile Hunter as a young boy. Joe started his M.S. in Aquatic Resources in Fall 2022, where he is advised by Dr. Jessica Dutton. His interests include Magic the Gathering, model building, and video games. After graduation, Joe hopes to find a career where he can continue to work with marine fishes.

Spatial Variability in Selenium: Mercury Molar Ratios and Selenium Health Benefit Values in Fishes and Shellfishes from the Matagorda Bay System and San Antonio Bay

Major Advisor: Dr. Jessica Dutton

Committee Members:

1. Dr. Timothy Bonner
2. Dr. Clay Green

Join Zoom Meeting
https://txstate.zoom.us/j/83696597686?pwd=n6FdpD4G1a0Xb9EAibBI3xDwu8CFmm.1

Meeting ID: 836 9659 7686         Passcode: mercury

Mercury (Hg) is a nonessential trace element that is toxic to marine life and humans at low concentrations. Selenium (Se), an essential trace element, has an antagonistic relationship with Hg and can form a toxicologically inert mercury selenide (HgSe) complex. It has been proposed that if the Se:Hg molar ratio is greater than 1:1 (i.e., Se is in molar excess of Hg), then Se may have a protective effect against Hg toxicity. Selenium and Hg concentrations can also be used to calculate the selenium health benefit value (HBVSe), which conveys the relative health benefits (positive HBVSe), or health risks (negative HBVSe) associated with consumption of a fish or shellfish species. Due to the discharge of Hg by the Aluminum Company of America (Alcoa) into Lavaca Bay, TX, one square-mile of the bay in Point Comfort was closed to the retention of fishes and blue crab in 1988 and later listed as a Hg Superfund site by the U.S. Environmental Protection Agency (EPA). Since 2001, Alcoa has measured Hg concentrations annually in red drum (Sciaenops ocellatus) and juvenile blue crab (Callinectes sapidus); however, Hg and Se concentrations in other commercially and recreationally important fish and shellfish species in the Superfund site and other areas of the Matagorda Bay system and San Antonio Bay have been largely overlooked. Furthermore, no studies have examined the Se:Hg molar ratios or HBVSes for any species or bays. This study investigated Hg and Se concentrations, Se:Hg molar ratios, and HBVSes in red drum, black drum (Pogonias cromis), spotted seatrout (Cynoscion nebulosus), southern flounder (Paralichthys lethostigma), Atlantic croaker (Micropogonias undulatus), striped mullet (Mugil cephalus), hardhead catfish (Ariopsis felis), blue crab, white shrimp (Litopenaeus setiferus) and eastern oyster (Crassostrea virginica) caught in the Superfund site and compared the values to the same species caught in western Lavaca Bay, Tres Palacios Bay, southern Matagorda Bay, and San Antonio Bay. For every species except hardhead catfish, the Superfund site had the highest Hg concentrations and Hg concentration declined with distance from the Superfund site in red drum, black drum, southern flounder, Atlantic croaker, striped mullet, and blue crab. Except for hardhead catfish, all Se:Hg molar ratios in all bays were greater than 1:1, suggesting that Se may have a protective effect against Hg toxicity.  For all species and bays combined, 53.4% had a negative relationship between Se:Hg molar ratio and body length, 1.7% had a positive relationship and 44.9% showed no relationship. The HBVSes were positive for all species and locations except for hardhead catfish; however, hardhead catfish are rarely consumed. While this study has examined Se:Hg molar ratios and HBVSes as seafood safety criteria for possible use in risk assessment, more research is needed, especially to determine at what ratio (i.e., 1:1, 5:1, or greater) Se is protective against Hg toxicity.

Bio: Jordan is from Austin, TX. She received her B.S. in Biology with a focus on Marine Science from the University of Texas at Austin in 2021. She has always had a passion for science and nature and began her M.S. in Aquatic Resources from Texas State University in the Fall of 2022, where she was advised by Dr. Jessica Dutton. Jordan’s interests include doing anything outdoors and hanging out with her dogs. After graduation, she plans to continue to pursue a career in marine toxicology. 

 

Assessing the distribution and survival of mussel communities in the Upper Colorado River Basin, Texas after exceptional drought conditions

Major Advisor: Dr. Astrid Schwalb

Committee Members: 

1. Dr. Aubrey Harris
2. Dr. Clay Green

Zoom link: https://txstate.zoom.us/j/84116595886

Meeting ID: 841 1659 5886

Freshwater mussels (Order Unionida) provide important ecosystem services, yet they are among the most imperiled organisms in the world. Drought is a major threat to mussels, especially in drier regions, as mussels are relatively sedentary and cannot easily escape adverse conditions. Droughts often lead to severe community-wide declines. After a major drought in 2011/2012 led to declines in mussels in rivers of Texas, the state experienced yet another exceptional drought during the summers of 2022 and 2023. The objectives of this study were (1) to examine whether mussels continued to decline due to recent droughts or persisted by comparing the distribution between surveys in 2021 and 2023 in the upper Colorado River basin and (2) to examine survival and recapture probability in different parts of the San Saba River with a mark recapture study. Thirty survey sites were chosen that had been previously sampled in 2021 in the mainstem Colorado, Concho, San Saba, and Llano Rivers. Semiquantitative tactile timed searches were performed at each site, and mussels were identified to species and returned to the river. The mark-recapture study was started in spring 2021, when 309 mussels were tagged with passive integrative transponders at four sites in the San Saba River. A hydraulic (HEC-RAS) model was used to assess hydraulic conditions at the mark-recapture sites. Overall, there were no significant differences in abundance (T₂₉= 0.40, p=0.34) and species richness (T₂₉ = -1.6, p=0.11) between the same sites in 2023 vs. 2021, and community composition was similar between the years. While survival estimates were ≥ 0.9 at all sites, recapture rates were considerably lower in the lower segment of the San Saba River (27 and 50%) than in the upper segment sites (54 and 96%). The lower recapture rates in the lower segment, may have been a result of transportation during higher flows. Although mussel communities seemed to persist after the recent droughts, it should be noted that mussel communities had been already impoverished by previous droughts. In addition, mortality was detected at a few sites that completely dried, suggesting that declines may continue as drought frequency and intensity increases. In order to protect mussels and the ecosystem services they provide, mitigation strategies and better water management are urgently needed.

Bio: Eleanor Krellenstein is from South Salem, NY and graduated from Texas State with her B.S. in biology in December 2021. After graduation, she hopes to pursue a career in aquatic conservation.

An exploration of population genetic and reproductive patterns in a freshwater mussel and hybridization in a wetland flowering plant system

Major Advisor(s):  

1. Tim Bonner
2. Noland Martin

Members: 

1. Sam Borstein
2.  Charles Randklev
3. Michael Arnold

Understanding the distribution of biodiversity across landscapes has been a goal of biological studies since the beginnings of the field. Biologists have long questioned how new species are formed and maintained, and what ecological factors play a role in the process of diversification. It is now possible to address many evolutionary and ecological questions using modern population genetic tools in virtually any system of interest. This provides the opportunity to scale questions across many diverse taxa and to address questions regarding population structure, gene flow, and reproductive isolation in a repeatable fashion. With these modern genomic tools, in addition to a few well-tested reproductive methods, this dissertation aims to address a wide scope of questions ranging from understanding the current state of population genetic structure and basic reproductive biology in a rare freshwater mussel, to attempting to unravel the dynamics of introgression and reproductive isolation in a recently discovered hybrid zone between two closely related Louisiana Iris species. Together, the chapters in the proposed dissertation will demonstrate a diverse and adaptable set of skills used in a wide range of biological settings, all aimed at understanding the basic biology of diversity, reproduction, and speciation. In the first chapter of this dissertation, I will explore the standing genomic variation and the environmental factors that explain it in a rare freshwater mussel of regional interest, Pleurobema riddellii, also known as the Louisiana Pigtoe. In the second chapter I will address the basic reproductive life history in the same under-studied freshwater mussel species in an attempt to quantify and characterize the reproductive cycle. Finally, I address hybridization and patterns of introgression in a classic speciation system, the Louisiana Irises (Iridaceae), to explore whether divergent natural selection in allopatry plays a role in maintaining species boundaries in a hybrid zone. The three chapters of my dissertation will provide valuable insights into several basic biological questions and several larger scale evolutionary questions across two widely different taxonomical groups. In addition, this dissertation will provide insights into the speciation process and how it manifests in the genome. The results of this dissertation will serve a wide range of fields of study and will serve to inform future work in both of the systems being studied.

Bio:  Born and raised in Dallas, Texas where I grew up playing soccer and playing music. My research interests include using powerful genomic sequencing techniques to investigate how evolutionary forces shape the distribution of genomic variation across space, time, and organisms. I am fascinated by modern DNA sequencing techniques, and I plan to be involved in research that utilizes next generation sequencing tools to answer questions relating to hybridization and speciation.

Determination and comparison of dietary sources of the endangered Houston toad (Bufo houstonensis), with the sympatric Gulf Coast toad (Bufo nebulifer) in Lost Pines ecoregion

Major Advisor: Dr. Mike Forstner

Committee Members: 

1. Dr. Paula Williamson
2. Dr. Weston Nowlin

Zoom: https://txstate.zoom.us/j/85461026873pwd=ajieVLldTaIgnVMvgNeUGuAECXEalW.1

Houston toads (Bufo houstonensis) are critically endangered and have been facing declines for decades due to habitat loss and fragmentation, although populations have persisted in Bastrop County, Texas. Many studies highlight Houston toad preference for habitat conditions, like those in the Lost Pines Ecoregion, yet few consider their dietary preferences, which may coincide with location. Furthermore, the sympatric congener, Gulf Coast toad (Bufo nebulifer), are widely studied, although few publications discuss dietary habits. My study evaluates prey availability and the trophic position of Houston toads and Gulf Coast toads at various post-wildfire habitats on Griffith League Ranch (GLR) in Bastrop County, Texas. I evaluated the frequency and availability of arthropods available at various occupied Houston toad habitats, as well as the trophic position and degree of dietary overlap between sympatric Houston toad and Gulf Coast toad populations. Arthropods (n=2,265) were collected across six terrestrial habitat types at GLR using pitfall traps, identified to lowest taxonomic level practical and the most abundant prey groups were processed for isotope analysis. Toads were captured by hand near breeding ponds. Toe clips were obtained from the longest toe on the left hind limb, preserved in 95% ethanol and later processed by isolating bone collagen for stable isotope analysis. I used the package “nicheROVER” in R to estimate niche size and overlap between the two toad species and among arthropod groups. My results indicate that the most abundantly available ground-dwelling prey items in the Lost Pines Ecoregion are Coleoptera (n=605), Diplopoda (n=587), Araneae (n=234) and Formicidae (n=166). The severity of burn events did not affect isotopic composition of prey groups across any of the wildfire affected forested habitat types. Furthermore, the trophic niche size of Houston toads (20.7378±2.85) was not substantially different from that of Gulf Coast toads (18.4907±3.08) sampled from the same habitat type. The isotopic composition of B. nebulifer was routinely enriched in relation to B. houstonensis indicating B. nebulifer are foraging at a slightly higher trophic level. The “nicheROVER” estimates reported an 85.25% probability of an individual B. nebulifer occupying the trophic niche space of B. houstonensis, which is substantial and indicates interspecific competition is occurring on the GLR in Bastrop County, Texas. Overall, these results depict the available prey items for endangered Houston toad and abundant Gulf Coast toad populations and emphasizes that dietary competition is likely to be occurring when in sympatry. My research provides insight to the dietary habits of an endangered species and can help identify suitable habitats for future populations.

Bio: Rachel Brown is from Willis, Texas and graduated from Schreiner University in Spring 2020 with her B.S. in Biology. Since joining Dr. Forstner’s lab in pursuit of her M.Sc. in Wildlife Ecology, Rachel has begun work as a high school biology teacher. After graduation, she hopes to continue inspiring a love for all things science in her students and raise awareness for wildlife conservation and sustainability efforts among younger generations.
 

Bridging the Gap Between Science and the Community Through Service-Learning and Third Spaces

Major Advisor: Dr. Kristy Daniel

Committee Members:

1. Dr. Carrie Jo Bucklin, Texas State University
2. Dr. Colleen Myles, Texas State University
3. Dr. Leila Siciliano-Martina, Texas State University
4. Dr. Rebecca Swanson, University of Nebraska-Lincoln

Zoom Link: https://txstate.zoom.us/j/83058047309

In an effort to combat rising misinformation and negative stereotypes about science, science educators have pushed to find ways to build connections between scientists and community members within public venues. By reaching out to communities where they spend their personal time and are relaxed, they are typically more receptive to having conversations and learning about science. My study will provide multiple opportunities for budding scientists and the public to engage with one another regarding pertinent science issues that impact the community. My first study will explore how students enrolled in a field biology Education Abroad servicelearning course in Western Europe change their perceptions of engaging in science within their community. My second study will further explore the role of service-learning in changing student perceptions of science within communities by recruiting university students enrolled in a biology interpretation service-learning course held in Central Texas. My third study will be a comparative investigation between these two groups of students to capture evidence in similarities or differences in their perceptions of science and scientists within their community as well as their intent to continue to volunteer as a scientist within their community. My fourth study will shift focus to explore perceptions of science and scientists from the viewpoint of community members. I will leverage the use of third spaces, such as beer gardens and breweries, to engage with adults in science learning opportunities. Specifically, I seek to understand how these participants report their perceptions of science and scientists within their community and their support for integrating science within their community. My data sources for these studies will include questionnaires, reflective responses about experiences, and interactive tasks (e.g., token voting boxes, sticker response charts, and graffiti wall prompts). I will use a combination of qualitative and quantitative methods to address all of my research questions. By better understanding how budding scientists and the public view the role of and support for science and scientists within their community, we can better approach how to connect scientists with local officials to improve discussions about public policy and community improvement efforts. Overall, reaching people where they choose to spend their recreational time and understanding perceptions of science and scientists can help build a more scientifically literate public and improve relationships between scientists and their home communities they hope to serve.

Bio: Jill earned her B.S. in Interdisciplinary Studies at Texas State University. During her studies, she worked as an intern through the university's Aquatic Science Adventure Camp and through GirlStart, an Austin-based STEM non-profit. After graduating, she served as a 5th grade science teacher in Dripping Springs, Texas. In July of 2022, Jill graduated with her M.A. in Middle School Science Education from Western Governors 
University, and in 2023 she left the classroom to return to Texas State as a PhD student. Jill is a board member of the Informal Science Education Association of Texas, a Certified Interpretive Guide & Trainer through the National Association for Interpretation, and a Texas Master Naturalist in the Hays County Chapter. In her free time, she enjoys hiking, camping, reading, and spending time with her husband and dogs.

Between A Rock and A Hard Place: An Investigation Of Rock Squirrel (Otospermophilus variegatus) Behavioral Response To Anthropogenic Change

Major Advisor: Dr. Joseph Veech

Committee Members: 

1. Dr. Andrea Aspbury
2. Dr. Susan Schwinning

As human populations grow, urbanization is transforming landscapes, leading to habitat loss and fragmentation. Urban adaptors, like rock squirrels (Otospermophilus variegatus), often exhibit behavioral flexibility in response to changing environments. While rock squirrels play vital roles in natural ecosystems, their capacity to adjust to urban environments may involve altered habitat use, potential synanthropy, and changes in social dynamics. Urbanization may influence behaviors such as foraging and vigilance that are crucial for survival. My study investigated the effects of urbanization on rock squirrel behavior at five different locations in central Texas along the eastern edge of the species geographic range. I examined vigilance and foraging behavior of rock squirrels at sites that differed in the amount of surrounding urbanization. Behavioral data, documented as the fraction of time spent in different activities, were extracted from videos obtained from wildlife cameras placed outside of occupied burrows at the study sites. For statistical analysis, the main unit of replication was a camera placed at a burrow on a given day (N = 234). I used nested ANOVA to test for differences in squirrel behavior among urbanization categories and study sites. In addition, burrows were mapped at each site to determine their spatial dispersion as either random, clumped, or over-dispersed. My results indicate that rock squirrels perceive and adjust their behavior to urbanized environments differently based on the level of urbanization. Specifically, total vigilance, the proportion of the total recorded video time (in seconds) per day during which the squirrel exhibited vigilance, was significantly greater in low (P = 0.0003) and medium (P < 0.0001) urbanization than in high urbanization sites, suggesting heightened alertness in less urbanized settings. Despite these heightened vigilance levels, no significant differences were observed in the hypervigilant picket-pin posture across urbanization levels. Additionally, squirrels in medium urbanization sites exhibited reduced foraging behavior compared to their counterparts in both low (P = 0.004) and high (P = 0.002) urbanization sites, possibly due to a trade-off between vigilance and foraging. Although burrows were never randomly dispersed, there was no clear association between spatial pattern (over-dispersed vs. clumped) and level of urbanization. Overall, these results emphasize the behavioral complexity of rock squirrels adjusting to varying levels of urbanization. My research contributes valuable insights into the success of synanthropes in urban environments and enhances our understanding of wildlife behavior in rapidly changing anthropogenic landscapes. 

Bio: Elisa Williams' journey into the world of wildlife and conservation began on a ranch in north Texas, where she spent her childhood surrounded by nature. This early exposure to the natural world sparked a deep curiosity and passion for understanding and preserving wildlife habitats. Over the years, Elisa’s love for the outdoors evolved into a dedicated pursuit of conservation biology. In 2020, she earned her B.S. in Biological Sciences and a minor in Wildlife Management at North Carolina State University. In the fall of 2022, she joined Dr. Joe Veech’s lab to pursue an M.S. degree in Population and Conservation Biology. Her work is fueled by personal commitment to protecting the ecosystems that have inspired her since childhood, driving her to advocate for sustainable practices and conservation efforts across diverse landscapes.

Nest Predation, Roost Site Selection and Habitat Assessment of the Critically Endangered White-Bellied Heron Ardea insignis in Bhutan

Major Advisor: Dr. M. Clay Green 

Committee Members:

1. Dr. Andrea Aspbury, Texas State University
2. Dr. Chris Nice, Texas State University
3. Dr. Dhan Bdr Gurung, College of Natural Resources, Royal University of Bhutan
4. Dr. Sherub Sherub, Ugyen Wangchuck Institute for Conservation and Environment Research, Bhutan

Meeting ID: 873 0377 2007    

Passcode: 824754

Zoom Link: 

https://txstate.zoom.us/j/87303772007?pwd=LDSHOa3MaN6T5FZ4xJBaKIfiMWpoDS.1

The White-bellied Heron (Ardea insignis) is the world’s rarest Ardeid on the brink of extinction with only 60 individuals recorded across their range countries. However, there is a paucity of critical information regarding their basic biology and ecology, which impedes effective management and conservation efforts. Also, threats to the species are not sufficiently mitigated. Habitat loss and degradation, along with ~50% of nest failure due to predation and other unknown reasons, are leading causes of their declining population and low recruitment rates. Therefore, this study aims to explore the dynamics of nest predation and investigate the factors influencing roost site selection and assess both existing and potential habitats to support future captive release efforts, crucial for addressing the urgent knowledge gap. I will utilize artificial nests and camera trapping methods to gain a comprehensive understanding of potential nest predators and the factors affecting nest survival rates in their breeding habitats. Additionally, I will assess the effectiveness of predation enclosures in mitigating the impact of mammalian predators such as rodents, civets, and primates. I will use multi-dimensional, organism-centered approaches to understand the role of ecological and anthropogenic factors in the White-bellied Heron’s roost site selection and employ eDNA techniques to evaluate current and potential habitats. This study will help glean vital information on potential nest predators and their behavior for prioritizing nest protection and improving breeding success of the White-bellied Heron. Understanding roost characteristics at spatial and temporal scales is critical for the protection of the White-bellied Heron and its riverine habitat. Furthermore, the study will contribute to the creation of a dedicated genetic repository, including the development of reliable and simple sampling techniques, and a gene database for the long-term monitoring of the White-bellied Heron. Overall, this study will guide evidence-based conservation and management interventions, while also addressing the risks associated with habitat loss and population decline.

Bio: Pema is from Bhutan, where he is conducting his PhD research. He received his B.S. in Life Sciences from Sherubtse College (Royal University of Bhutan), a Post Graduate Diploma in Biology Education from Samtse College of Education (RUB), and M.S. in Biology (Wildlife) from Prince of Songkla University, Thailand. He is currently a member of IUCN’s Heron Specialist Group and the White-bellied Heron Working Group. Pema worked as a high school teacher in Bhutan, teaching biology and environmental science for five years before joining Dr. Green’s Avian Ecology Lab in Spring 2022. He enjoys being outdoors, hiking, exploring nature, and wildlife photography.

Benthic Macroinvertebrate Community Responses to Climate and Disturbance Gradients: Testing Predictions of the Stream Biome Gradient Concept

Major Advisor: Dr. Weston Nowlin, Department of Biology, Texas State University

Committee Members: 

1. Dr. Benjamin Schwartz, Department of Biology, Texas State University
2. Dr. Mariana Perez Rocha, Department of Biology, Texas State University
3. Dr. Amy Yarnall, U.S. Army Engineer Research and Development Center 

Zoom: https://txstate.zoom.us/j/84226349639pwd=9wXZ08U0mq2Pkx0L4O8Gm0pt8dKfxa.1 

Rivers are complex, spatially structured networks, and often span environmental gradients that affect the composition and diversity of biological communities. The Stream Biome Gradient Concept (SBGC) posits that the composition of the surrounding terrestrial landscape, which is largely determined by climate conditions, has a large impact on community composition and ecosystem functioning. Ecologists have long known that benthic macroinvertebrates respond to these environmental and perturbation gradients across riverscapes, but there is a need to examine how large-scale environmental gradients influence macroinvertebrate communities and whether these responses are consistent with the SBGC. The purpose of this study was to empirically assess predictions of the SBGC as it applies to benthic macroinvertebrate communities in four differing river basins using taxonomic and functional trait approaches. Benthic invertebrates, water chemistry and quality, hydrology, and land use data were collected for 57 sites across four drainage basins in Texas, (USA) that represent a range in dominant terrestrial biomes (i.e., desert, grassland, savannah, and forest). I assessed patterns in site-level diversity and composition as well as β -diversity (and its components – nestedness and replacement) across and within the study drainages. I found that benthic invertebrate functional trait and taxonomic richness differed among lotic biome types (i.e., richness was greatest in forest and savannah biomes), but macroinvertebrate taxonomic composition was primarily influenced by local-scale environmental conditions. Nestedness was generally the more dominant component contributing to taxonomic and functional trait β -diversity both within and across basins. Local- and watershed-scale conditions generally had the greatest pure effects on taxonomic and functional trait β -diversity and nestedness. However, variability in annual discharge influenced the strength of replacement in spatial patterns in β -diversity. Overall, this study found that several predictions of the SBGC were supported but local-scale environmental conditions play an important role in benthic invertebrate communities. I hypothesize that deterministic processes (i.e., environmental filtering) and stochastic processes (i.e., dispersal) are likely the most critical drivers of β-diversity patterns across complex drainages.

Bio:  Kierra Determan grew up on a small farm in South Dakota, and her love of nature prompted her to pursue Biology and Sustainability degrees at the University of South Dakota with minors in Conservation & Biodiversity and Natural Science. After graduating with those degrees in 2020, she went on to become a Fisheries Technician at the University of Illinois for two years before attending Texas State University in 2022. Outside of school, she has a passion for baking, hiking, traveling, coloring, reading, swimming, and playing with her cat Butters. She also loves to explore new areas and try contemporary Asian restaurants. She was excited for the opportunity to join the Nowlin lab in 2022 to combine her interests in rivers and macroinvertebrates. After graduation, she will be starting an Environmental Specialist position at the University of Iowa, where she will continue working with benthic macroinvertebrates and water quality in streams across Iowa. 

The Comparative Anatomy of Extrafloral Nectaries in the Cactus Family (Cactaceae)

Major Advisor: Dr. David E. Lemke

Committee Members:

1. Dr. Paula Williamson
2. Dr. Root Gorelick, Carleton University

Zoom: https://txstate.zoom.us/j/84512634250 

Extrafloral nectaries (EFNs) are specialized glands that unlike floral nectaries, which function primarily in pollination, are typically associated with plant defense, attracting invertebrates whose presence and activity can reduce herbivory. EFNs were first observed in cacti in 1837 and have been noted in at least 25 different genera. Morphologically, cactus EFNs have been categorized as belonging to one of four distinct groups: short, obviously modified spines (type 1 EFNs); nectaries that resemble ordinary spines with no readily apparent modifications (type 2 EFNs); nectaries associated with small foliage leaves occurring adjacent to an areole (type 3 EFNs); and nectar-secreting regions of epidermis situated below an areole (type 4 EFNs). Although the distribution of these morphological types has been examined, little is known of their anatomical structure. My study refines this previous classification scheme characterizing type 1 EFNs as short, blunt projections consisting of a basal vascularized stalk filled with subnectary parenchyma and a broad secretory head containing layers of nectary parenchyma. Secretion appears to occur through ruptures in the cuticular covering of the gland. Type 1 EFNs are the most diverse group, with forms that range from spine-like, with an elongated secretory head containing fiber-like cells, to more specialized examples with flattened secretory heads that only contain isodiametric secretory cells. These EFNs can be phylogenetically informative on a species level within genera. In type 2 EFNs, nectar is produced in an area of small, isodiametric cells with dense cytoplasm at the base of a spine, then transported upwards to the sites of secretion. Type 3a and 3b EFNs secrete nectar from stomata in foliage leaves or modified leaf tissue. These stomata are located over subjacent vascular tissue with type 3a EFNs being associated with vegetative tissue and type 3b EFNs located on the exterior of pericarpel. Type 4 EFNs are also associated with leaf tissue but secrete nectar though open pits in patches of dark-red epidermis that are connected to subjacent vascular tissue.

Bio:  Jackson Burkholder grew up attending Colorado Cactus and Succulent Society events, and what started as one or two small plants every year has turned into an obsession with desert flora. This inspired him to attend college at Colorado State University where he earned his B.S. in Horticulture with minors in Nursery & Landscape Management and Japanese. Outside of his studies, Jackson takes care of his large collection of primarily South American cacti and has been involved in multiple organizations focused on his favorite plants including the Cactus and Succulent Society of America and the International Cactaceae Academic Network.  In addition to botany, Jackson is also interested in photography and in repairing and restoring antique scientific equipment.  He was excited to join the Lemke Lab in 2019 and combine all his interests by studying plant anatomy.  After graduation he hopes to continue conducting botanical research either by pursuing a PhD or by working at a botanical garden.

Patterns of Macroinvertebrate Diversity and Composition in a Spatially Complex River Basin: Taxonomic and Functional Approaches

Major Advisor:  Dr. Weston Nowlin, Department of Biology, Texas State University

Committee Members: 

1. Dr. Benjamin Schwartz, Department of Biology, Texas State University
2. Dr. Mariana Perez, Department of Biology, Texas State University
3. Dr. Richard Johansen, U.S. Army Engineer Research and Development Center

Join Zoom Meeting: 

https://txstate.zoom.us/j/87913507951?pwd=5elb6MnknLFYclclh59XxhrbxzGrI9.1

Riverine benthic macroinvertebrate community composition and diversity respond to environmental gradients (i.e., climate, land use, water quality) and flow disturbances (i.e., frequency of drought or flooding).  There is a paucity of data exploring how larger-scale watershed and environmental gradients influence the taxonomic and functional trait composition and diversity of macroinvertebrate communities within a single large river drainage. In this thesis, I examined the relative strength of environmental drivers on benthic macroinvertebrate communities at multiple spatial scales using a spatially nested study design of 102 sites distributed throughout the Colorado River basin, Texas, USA; this basin includes the Colorado, Concho, San Saba, Llano, and Pedernales rivers. I assessed variation in local diversity (α-diversity) and between sites (β-diversity) at taxonomic and functional trait-based levels using distance-based redundancy analyses and variation partitioning. Spatial processes driving each of these were modeled using Moran eigenvector maps (MEMs). Taxonomic α-diversity differed among rivers, while functional trait α-diversity exhibited less variation. Across all sites and rivers, local-scale environmental conditions (i.e., canopy cover, water quality, and flow velocity) and broad-scale spatial structuring (determined via MEM vectors) explained the greatest amount of variation in macroinvertebrate community composition at taxonomic and functional trait levels. However, functional trait-based models explained considerably more variation than taxonomic-based models. Flow disturbance regimes had a relatively minor role in determining macroinvertebrate community composition. When b-diversity patterns across all sites and rivers were assessed, replacement was the main facet driving b-diversity both in terms of taxonomy and functional traits. These results indicate that local scale environmental conditions are important in determining macroinvertebrate composition, but larger-scale spatial structuring of communities (i.e., upstream to downstream) also plays an important role. Replacement was the more important component of b-diversity at both the taxonomic and functional trait levels, which might be due to the Colorado basin being a single hydrologically connected system, despite its relatively large size. Hydrological disturbance regime was found to have a relatively minor role in influencing the taxonomic and trait composition of macroinvertebrate communities and this lack of influence may be due to the way in which hydrological regimes were classified in this study and the relatively fast lifespans of many invertebrates. Overall, this thesis demonstrates that community composition at taxonomic and functional trait levels is influenced by environmental drivers at multiple spatial scales and that future studies should incorporate temporal dynamics of communities in order to forecast how communities respond to future environmental changes, such as climate change and land use practices.

Bio: Miranda Sams graduated from Cedarville University with a B.S. in Environmental Science. After working around the world with NGOs and environmental consulting agencies, Miranda decided to pursue a M.S. in Aquatic Biology. She started her M.S. in Dr. Weston Nowlin’s lab in the Spring of 2023. Beginning in August, Miranda will continue her work as a Ph.D. student in Dr. Nowlin’s lab. She enjoys all outdoor activities, traveling, and dancing.

An Evaluation of Enriched Aerobic Bacterial Communities Capable of Biodegrading TCE Under Different pH and Temperature

Major Advisor: Dr. Bob McLean

Co-Advisor: Dr. Sangchul Hwang

Committee Member: Dr. Manish Kumar

Zoom Link:
https://txstate.zoom.us/j/82081718008?pwd=YVU3aXlFS3kyS0VhZ21GdGtjSDB5Zz09

Trichloroethylene (TCE) is a widely used halogenated organic compound in industrial cleaning and degreasing. It frequently contaminates groundwater, soil, and the biosphere, and direct human exposure to TCE significantly affects multiple organs, including the heart, kidneys, liver, and central nervous system. As a priority pollutant listed by the US-EPA, various strategies have been implemented for TCE remediation. However, bioremediation stands out as a low-cost, sustainable, and eco-friendly technique for the complete mineralization of TCE. Global temperature increases have direct and indirect effects on the environment at macroscale, microscale, surface, and subsurface levels. Therefore, this study aims to investigate the effect of temperature and pH on TCE degradation using an enriched bacterial community. A sediment sample from the Concho River in San Angelo, TX, was collected based on urban runoff of oil, gasoline, kerosene, and other contaminants. This sample was used to enrich aerobic bacterial communities in an M9 minimal mineral salt buffer with TCE, followed by transferring the culture to fresh M9 salt buffer with TCE to obtain a stable, enriched aerobic bacterial community. This enrichment process indicated that the bacteria were potentially metabolizing TCE as a sole carbon substrate or surviving in its presence. Optical density was measured at 600 nm for turbid samples, and plate screening on M9 agar plates with inoculated bacteria and TCE was used to visually observe mixed cultures of different colony-forming units (CFUs). Experimental 5-day incubation periods were conducted with samples containing 1 g/L glucose, 0.5 g/L yeast extract, specific bacterial inoculum concentrations, and TCE concentrations diluted within the range of 0-25 ppb, spiked with 2 ppb 1-chlorobutane. Samples were analyzed for chlorinated volatile organic compounds using gas chromatography and mass spectrometry. Various parameters, such as temperature and pH shifts, were adjusted during each 5-day experiment to optimize environmental conditions for TCE biodegradation. The results indicated that the optimal environmental parameters for in situ bioremediation of TCE were 4% inoculum, 15℃, pH 6, with 40 mg/L TCE. Optical density proved unreliable for quantifying bacterial cell growth, so the IDEXX most probable number (MPN) analysis was used for bacterial cell count. Additionally, 16S rRNA amplicon sequencing was performed on Concho bacterial stock samples incubated at 25℃ for 24 hours, and on samples with 4% inoculum at 15℃, pH 6 in 40 mg/L TCE after 5 days to identify bacterial communities in stock growth and optimized environmental conditions. In the future, other remediation techniques such as biosorption (adsorption and absorption), physical removal of contaminated sites (ex situ), oxidation and reduction (venting and mineralization), in conjunction with bioremediation using bioreactors, could be employed to achieve the most effective results.

Bio: Joe Ball graduated at Texas State University with a B.S. in Microbiology. After working for Micro-Bac International that utilizes bacteria to degrade waste, Joe decided to pursue this type of research as a research assistant in Dr. Hwang’s Lab (HEDGE) in the Spring of 2023. The DOE project in HEDGE Lab aims to clean up the environment with multiple remediation techniques. Joe’s research goal is to find unique bacteria capable of biodegrading contaminants in the environment. Joe plans to get hired through the DOE to help them clean up their contaminated sites all around the nation.  

Analyzing Colony Structural Characteristics to Assess Establishment of Reintroduced Black-tailed Prairie Dogs (Cynomys ludovicianus) 

Major Advisor: Dr. Joseph Veech

Committee Members: 

1. Dr. David Lemke
2. Dr. Ivan Castro-Arellano

The reintroduction of a species to portions of its former range where it has become locally extinct presents many challenges. As such, there is a need to develop methods to monitor whether the species has established self-sustaining populations at the reintroduction sites. The black-tailed prairie dog (Cynomys ludovicianus; BTPD) has been extirpated from large portions of its historical range, particularly in Texas. Reintroduction of BTPD is an on-going task in their overall conservation. My study explored the structural spatial dynamics of BTPD burrows as a potential indicator of colony establishment. I used colony age classes as a surrogate for establishment phase in order to derive hypotheses in the context of selfish-herd theory. A selfish herd forms and is maintained when prey individuals at the center of a group are safer from predators that are more likely to detect and capture individuals on the margin. Each individual seeks to decrease its “domain of danger” by moving toward the center of the herd. In the case of BTPD, this should result in burrow densities and spacing patterns that reflect greater survival probability at the center of a colony, as would be most likely observed in an established colony. Further, BTPD activity should be most prominent at the center and other centerto-edge differences should exist. I mapped burrows and measured physical characteristics at 14 colonies throughout north and west Texas. I then used ANOVA to test for differences among colony age classes and zones (central vs. peripheral). Although not all hypotheses were supported, field mapping of both newly-reintroduced and well- established colonies revealed that well-established colonies exhibited a consistently high proportion (> 0.9) of active mounded burrows across both central and peripheral zones. Conversely, newly-reintroduced colonies showed a relatively greater proportion of these burrows in the central zone but significantly fewer in the peripheral zone, suggesting an increase in active mounded burrows as colonies mature, specifically towards the colony edge. Therefore, the proportion of active mounded burrows could serve as a practical indicator of colony establishment and inform management decisions, potentially reducing the need for ongoing intervention once parity between zones is observed. Additionally, I investigated the potential of satellite imagery for remote monitoring. Although the satellite imagery analysis was not definitive, it indicated that with further refinement, this technology holds promise for identifying BTPD colonies and assessing areas of activity. Overall, my study provides detailed knowledge of BTPD colony structural characteristics and suggests that monitoring of active burrows is a useful tool in assessing success of BTPD reintroduction.

Bio: Erin Berkenkamp is a dedicated researcher and Certified Associate Wildlife Biologist®. She earned her B.S. in Wildlife Biology from Texas State University in 2017. Since then, she has worked as a consultant, applying ecological principles to the conservation and management of wildlife species and their habitats. This experience inspired her research into the development and implementation of science-based conservation practices aimed at protecting vulnerable species and sensitive habitats, with a specific focus on species reintroduction as a habitat restoration strategy. Her research, focusing on black-tailed prairie dog (Cynomys ludovicianus) reintroduction monitoring techniques, underscores the importance of ensuring that conservation interventions are effective and adaptive. Erin believes these efforts are crucial for preserving biodiversity and ensuring a sustainable future for coming generations.

The Use of Mixed Diatom Cultures and the Influence of their Microbial Communities on the Treatment of Reverse Osmosis Concentrate 

Major Advisor: Dr. Keisuke Ikehata

Co-Advisor: Dr. Benjamin Schwartz

Committee Member: Dr. Jason Martina

Zoom Link: 
https://txstate.zoom.us/j/6627949450?pwd=c0Z4b3hPc1gxOFRzSW1KVHF2UUlLZz09  

More frequent drought conditions and a rapidly growing population have intensified the need for alternative water resources and integrated resource management. Desalination of brackish groundwater and wastewater reuse offer alternative sources of freshwater, in which the use of reverse osmosis (RO) is commonplace. However, the freshwater recovery in RO systems is limited by the presence of constituents like silica (SiO₂) and calcium, and the waste stream, RO concentrate (ROC), requires careful management. The use of a class of silica-based microalgae, diatoms, has been proposed to remove silica, calcium, and nutrients from ROC which would allow for further treatment of the ROC and increased freshwater recovery in RO systems. While this method has shown to be effective with multiple isolated diatom species, the use of mixed diatom cultures was previously untested. Mixed cultures of brackish diatoms were collected from coastal wetlands in southern Texas and tested for their ability to remove constituents from ROC compared to a unialgal culture that has been studied extensively. It was hypothesized that the abundant microbial community and increased diversity in the mixed cultures could lead to greater ecosystem function and robustness. The effect of major functional microbial groups in the diatom cultures on ROC treatment was examined through the use of antimicrobials and the resistance to invasion by competing green algae was studied. Further, the microbial communities present in the diatom cultures used for this process were analyzed for the first time through metagenomics and the relationship between biodiversity and ROC treatability was explored. This research demonstrated a greater efficiency in ROC treatment by various mixed diatom cultures compared to a unialgal culture, a greater robustness in one mixed culture, and the complex relationship between diatoms and other microbial groups.

Bio: Emma Clow grew up in the pacific northwest before moving to Arizona where she graduated from Arizona State University with a B.A. in Earth and Environmental Science and a minor in Biological Sciences. She moved to San Marcos, TX in 2020 before deciding to pursue her master’s degree in Aquatic Resources. Emma hopes to contribute to the responsible management and conservation of our most precious natural resource: water.

Exploring Outcomes from Participating in Outdoor Science Activities

Major Advisor:  Dr. Kristy Daniel

Committee Members:

1. Dr. Paula Williamson
2. Dr. Michelle Forsythe

Today’s youth often lack opportunities to participate in science practices outdoors. The purpose of this study was to capture fifth-grade student responses to an outdoor science activity booklet to discover what outcomes the students received from the activity. Further, I wished to understand to what extent are elements from an outdoor science activity about pollination transferable to differing topics of outdoor science activities. The booklets contained four post-activity questions to find what each student found most enjoyable, important, helpful, and what aspects made the participants feel most like a scientist. Student responses were deductively organized into categories and emergent themes to reveal that students most enjoyed taking part in outdoor science practices. Participants reported that science practices were the most influential elements of the outdoor science activities. Science practices were also most responsible for students to feel like scientists and led many students to enjoy the activities. Science content was most important and helpful and the hands-on data collection and analysis aspects of the activities were significant. Finally, being outside fostered enjoyment of the science activities. Short outdoor activities, such as Pollination Partners, promote children's scientific interest and identity development. Using what we learned through deductively coding student responses, we can implement tools children found beneficial into future science activities to ensure participants experience enjoyment, learning, and feeling like a scientist.

Bio: Carolyn is a researcher who is passionate about wildlife conservation, Texas endangered species, and biology education. She completed her BS in Environmental Science with a track in sustainability at Sam Houston State University before joining the Daniel Biology Education Research Group in the Fall of 2022 to pursue her MS in Biology. Her research seeks to understand what elements of outdoor science activities lead 8-12 year olds to feel like scientists. After her graduation, Carolyn will remain under Dr. Daniel’s supervision to work toward her PhD in Integrative Biology and Aquatic Resources. She looks forward to her PhD projects in which she seeks to further understand how community members interact with the 7 Principles of Leave No Trace.

The Role of IBR5 in Auxin-Mediated Protein Degradation in Arabidopsis

Major Advisor: Dr. Nihal Dharmasiri, Department of Biology, Texas State University 

Co-chair: Dr. Sunethra Dharmasiri, Department of Biology, Texas State University

Committee Member: Dr. Hong-Gu Kang, Department of Biology, Texas State University

The plant hormone auxin controls plant growth and development by primarily regulating cell division, cell elongation, and cell differentiation. These processes are regulated by the expression of auxin-related genes, which is achieved through the degradation of AUX/IAA repressors through the ubiquitin proteasome pathway involving the SCFTIR1/AFBs complex. This complex comprises the F-box protein TIR1/AFBs, along with ASK1, CUL1, and RBX1. Prior research found the involvement of IBR5 in the auxin response pathway since the primary root growth of ibr5 mutant lines showed resistance to auxin. The IBR5 gene encodes a dual-specificity phosphatase, which has an essential yet unknown function in the auxin signaling pathway. It was previously found that the localization of the auxin co-receptor TIR1 is affected in ibr5-1 null mutant, and two different reporters, GFP (Venus) and GUS that represent AUX/IAA repressors, showed contradictory results in their degradation pattern. Additionally, previous work indicated  that the overexpression of IBR5 stabilizes AUX/IAA proteins through an unknown mechanism. Here we show additional data to confirm that the difference in subcellular localization of these two AUX/IAA reporters lead to different pattern of repressor degradation. Furthermore, this work shows that wild type IBR5 protein interacts with several AUX/IAA proteins in-vitro, and this interaction is not dependent on auxin. Collectively these results suggest that IBR5 may sequester AUX/IAA proteins from degradation leading to the accumulation of repressor proteins in IBR5 overexpression background. In-depth future investigation is worthwhile to determine whether the phosphatase activity of IBR5 is necessary for the regulation of AUX/IAAs stability.

Bio: Emran is from Sylhet, Bangladesh, and completed his BSc in Biotechnology and Genetic Engineering from Sylhet Agricultural University, Bangladesh. He joined the lab of Dr. Nihal Dharmasiri at Texas State University to obtain his MS in Biology. His research focuses on revealing the molecular mechanisms mediated by IBR5, which is a dual-specificity phosphatase, to regulate the plant auxin signaling pathway. After his graduation, he will join the Molecular and Developmental Biology PhD program at Cincinnati Children's Hospital Medical Center. He is enthusiastic to become a molecular biologist who can contribute to disclosing molecular mechanisms involved in human diseases.

Enhancement of the Lateral Line System of Subterranean Salamanders (Eurycea)

Major Advisor: Dr. Dana M. García 

Committee Members:

1. Dr. Chris C. Nice
2. Dr. Pamela B. Hart, The University of Alabama

Join by Zoom:

https://txstate.zoom.us/j/88637178695?pwd=cituWXNEdGFjTDBkd0k5RGN0YlpIZz09&from=addon

The genus Eurycea inhabits a range of groundwater habitats including surface and subterranean. In contrast with their surface-dwelling relatives, subterranean Eurycea exhibit characteristics associated with life in perpetual darkness, including reduced pigmentation and eyes, raising the possibility that other sensory systems may be enhanced to enable subterranean salamanders to navigate their dark world. To test the hypothesis that subterranean Eurycea have a more extensive lateral line system, the mechanosensory neuromasts of the anterior lateral line (ALL) of three subterranean and four surface populations were quantified. Two subterranean populations have significantly more ALL neuromasts than all four surface populations. One subterranean population has significantly more ALL neuromasts than three of the surface populations but does not differ significantly from one surface population. Distribution of neuromasts among five craniofacial regions was analyzed. A PCA of these regions shows that mandibular and post-orbital neuromasts are especially strong contributors to the variation between surface and subterranean populations. Serendipitously, PAX6 was observed in the neuromasts of Eurycea, a novel localization of the transcription factor protein which is known to be involved in eye and central nervous system development. To determine if this protein plays a role in the expansion of the lateral line system in subterranean salamanders, PAX6 labeling in neuromasts was compared between one surface and one subterranean salamander at three stages of development. Fluorescence intensity of PAX6 labeling in neuromasts is significantly higher in the subterranean species at adulthood but not at one- or three-months post oviposition. These results suggest a correlation between the hypertrophy of the ALL system of Eurycea, a subterranean lifestyle, and the sustained presence of PAX6 in neuromasts into adulthood.

Bio: Brittany is from Montgomery, Texas. She became involved in research on the ocular development of subterranean salamanders as an undergraduate in Dr. Dana García’s NSF Summer Fellowship at Texas State University. Eager to expand on this research, she began her master’s degree in the Fall of 2022. Brittany enjoys benchwork as well as field work and hopes to put her passion and experience to work in a position in the US Fish and Wildlife Service.

A Study of Undergraduate Students’ Interpretations of Tree-Thinking by Using Eye Movements

Major Advisor:  Dr. Kristy Daniel

Committee Members:

1. Dr. Noland Martin
2. Dr. Cynthia Luxford 

Tree-thinking is the ability to correctly understand, use, and generate phylogenetic trees. Unfortunately, students often face difficulties interpreting trees correctly for a multitude of reasons. The purpose of this study is to analyze the eye movement patterns of students to determine how introductory biology students visually access trees during interpretation tasks and identify areas in which they are struggling to interpret. I used an eye-tracking system to capture participants' eye movements (both fixation duration and counts) while solving tree thinking problems. I used the results to generate heat maps illustrating the major areas of the diagrams visually accessed when solving tree-thinking questions. By analyzing these eye movements, I have identified differences in eye movement patterns and time spent on tasks between participants who answered tasks correctly compared to participants who answered incorrectly. This study revealed that participants who misinterpreted the tree tasks were more likely to spend more time considering the task, were less focused within the tree diagram and attended to more distracting areas of the tree rather than informative features, spent more time trying to interpret the question of the task rather than the diagram, and were over-confident in their tree-thinking skills. While tree-thinking instruction has been expanded in introductory biology courses, more interventions are needed to enhance students' comprehension of phylogenetic trees. By identifying elements of these diagrams that are causing confusion and distractions for learners, we can begin focusing on how to adapt instruction in ways that enhance informative regions and promote more proficient tree-thinking.

Bio: Mallika is a research enthusiast who wants to explore new things. She completed her BSc and MSc in Zoology from Jagannath University, Bangladesh. Mallika joined the Daniel Education Biology Research group at Texas State University for her second Master’s in Biology in Fall 2022 under Dr. Daniel’s supervision. Her research project is visual assessments of college biology students' phylogenetic tree-thinking. After graduating, she will be pursuing her Doctoral program in the same research lab. 

1. Dr. Chris Nice
2. Dr. David Rodriguez
3. Dr. Chris Kellogg (USGS)
4. Dr. Sarah Gignoux-Wolfsohn (UMass-Lowell)

Neuromodulation of Olfactory Immune Responses in Rainbow Trout (Oncorhynchus Mykiss)

Major Advisor: Dr. Mar Huertas  

Committee Members:

1. Dr. Dana Garcia, Texas State University
2. Dr. Lauren Fuess, Texas State University
3. Dr. Yuan Lu, Xiphophorus Genetic Stock Center, Texas State University
4. Dr. Erika Calvo-Ochoa, Hope College  

Zoom Link: https://txstate.zoom.us/j/84687267464pwd=eFlKSE5jNEpUTlk3b0hDQ1JCQkxjdz09

Meeting ID: 846 8726 7464    Passcode: 338248

Trout can smell viruses and the resulting olfactory signals can activate the fish brain immune system. Preliminary results in our laboratory showed that trout can also smell bacterial odorants with high sensitivity and its detection elicits an avoidance behavioral response, thus the trout olfactory immune function is likely tunned for a variety of pathogenic odors. However, the brain integration process for these olfactory immune responses is unknown. The integration of environmental signals within the vertebrate brain is mediated by different neuromodulators which subsequently trigger behavioral responses and immune system activation. I hypothesize that the integration of olfactory bacterial signals is mediated by brain neurosteroid neuromodulation, which leads to the activation of the neuroimmune system and results in the avoidance behavior in rainbow trout. To test our hypothesis, we will first measure neurosterodoigenic brain responses in trout after nasal exposure to inactivated Yersinia ruckeri by measuring mRNA expression of different neurosteroidogenic enzymes and neurosteroid production by ELISA. Second, we will do a detailed mapping of the olfactory-immune pathway by pinpointing the specific locations of neurosteroidogenic enzymes and activated immune factors in the rainbow trout brain using multiple “in situ” hybridization and spatial transcriptomics techniques. Preliminary results showed a time (15 mins, 4 hours, 24 hours, and 7 days after bacteria odor exposure) and location-dependent (nose, olfactory bulb, telencephalon, diencephalon, optic tectum, and cerebellum) expression of several neurosteroidogenic enzymes, which were parallel to localized production of neurosteroids. Our findings indicate the involvement of neurosteroids in the rapid bacterial odor identification via the olfactory system in rainbow trout. Investigating the olfactory-immune brain pathway for bacterial odor detection in rainbow trout will help to understand the role of neurosteroids in olfactory processing. Moreover, it can help to identify specific targets of action that can contribute to designing a more effective nasal vaccine to treat enteric red mouth diseases caused by Y. ruckeri in rainbow trout.

Bio: Maruf is from Bangladesh and graduated with his bachelor’s from Bangabandhu Sheikh Mujibur Rahman Agricultural University in Bangladesh from the faculty of Fisheries before getting his Master’s degree in Marine Biology from the University of Texas Rio Grande Valley, Brownsville, TX. His love for biology and a desire to work on fish physiology led him to focus on fish physiology and olfaction in his Ph.D. degree. He is supported by his lab, friends, and family on his academic journey.

Nuclear tRNA-derived RNA fragments (tRFs) trigger immunity in Arabidopsis and potentially function as a mobile signal in systemic acquired resistance

Major Advisor:  Dr. Hong-Gu Kang

Committee Members:

1. Dr. Nihal Dharmasiri (Texas State University)
2. Dr. Sunethra Dharmasiri (Texas State University)
3. Dr. Sibum Sung (The University of Texas at Austin)
4. Dr. Joe Louis (University of Nebraska-Lincoln)

Zoom Link: https://txstate.zoom.us/j/89437707227

Plants respond to stress through rapid and extensive changes in gene expression, orchestrated by intricate modifications in chromatin structure. They also possess a unique long-distance immunity known as Systemic Acquired Resistance (SAR), which offers protection against future attacks, indicating the presence of delicate signaling molecules in these immune responses. However, the identity and mechanisms of these signaling molecules remain poorly understood.

Our research on effector-triggered immunity (ETI) to Pseudomonas syringae pv tomato (Pst) in Arabidopsis revealed the significant role of DCL1 (Dicer-Like 1) in modulating ETI, emphasizing small RNAs' (sRNAs) importance. Deep-sequencing of nuclear sRNAs preceding defense gene induction uncovered the rapid accumulation of a 31-nt tRNA fragment (tRF^31Asp2) in a DCL1-dependent manner. Remarkably, infiltration of Arabidopsis with tRF^31Asp2 alone induced over 500 defense genes and immunized the plants against Pst and aphids. Additionally, we discovered that tRF31^Asp2 exhibited sequence-specific binding to genomes, including those within defense genes, indicating that the interaction between the tRF and the genome likely triggers transcriptional activation. Furthermore, our investigation revealed that tRF^31Asp2 was mobile, with its mobility enhanced by avirulent Pst, and translocated to the nucleus of distal tissue. To further explore this intriguing observation, nuclear sRNAs were deep-sequenced in leaves neighboring those infected. As a control, DIR1, a lipid transport protein known to be involved in SAR and itself capable of movement within plants, was used. Surprisingly, 16-nt-long tRFs, particularly those generated from Asp-tRNA (tRF^16Asp), were induced by avirulent Pst in a DIR1-dependent manner, suggesting that these tRFs might be a SAR mobile signal.

My study identifies a potent candidate molecule that modulates transcriptional reprogramming in response to infection and signals from neighboring leaves. This groundbreaking discovery unveils a mechanism in which sRNAs carry precise targeting information, guiding essential transcriptome changes. This paves the way for a promising new technological approach, enabling the precise engineering of stress responses.

Bio: Dinesh was born in the far-western part of Nepal. He earned his B.S. Biotechnology degree from Purbanchal University, Nepal in 2011 and M.S. Biotechnology from the Bangalore University, India in 2016. He then moved to San Marcos for pursuing his Ph. D in plant molecular immunology lab of Dr. Hong-Gu Kang in Fall, 2017. After graduation, Dinesh plans to continue his passion for research. Apart from academics, he is passionate about sports. 

Major advisor: Dr. Dana M. García

Committee members:

1. Dr. Gar Yee Koh
2. Dr. Robert J. C. McLean

Join Zoom Meeting: 

https://txstate.zoom.us/j/88507100096pwd=NHNIWU5DVzhZR3dCWGpoNUk3Z2pwUT09

Meeting ID: 885 0710 0096 
Passcode: Passcode115682

Vitamin D is an essential vitamin, and worldwide many people experience vitamin D deficiency, leading many individuals around the globe to suffer from different illnesses such as cardiovascular disease, tuberculosis, diabetes, and cystic fibrosis. Vitamin D is well known for its main function in maintaining bone health; however, in recent years vitamin D has been recognized for its function in autoimmune health, integrity of the gut barrier, and gut microbiome composition. In this study, I hypothesized that vitamin D supplementation through diet would have an impact on gut microbiome composition and gut integrity, in the latter case by influencing expression of mRNA encoding tight junction proteins ZO-1, occludin, and claudin. Using C57BL/6J mice as a model, I assigned mice to 4 diet groups as follows: 1) standard diet (AIG-93G purified diet; CTR), 2) CTR + antibiotics (AB), 3) CTR + 5000 international units (IU) of vitamin D3 (VD), and 4) VD + antibiotics (VD + AB). Antibiotics consisting of 0.5 g/L vancomycin, 1 g/L neomycin sulfate, 1 g/L metronidazole, and 1 g/L ampicillin were given in water throughout the experimental period. The microbiome was assessed using DNA extraction, 16s PCR sequencing, and analysis using microbiome analyst. The results indicated that the supplementation of VD via diet had a positive impact on gut microbiome composition, leading to an increase in representation of Firmicutes phyla in the VD group in comparison to the CTR, while also showing an increase in the Dubosiella newyorkensis species in VD. Furthermore, qRT-PCR suggested that vitamin D supplementation improved gut integrity, since ZO-1 and occludin genes having higher rates of mRNA expression in mice consuming a VD diet in comparison mice on the control diet. This study indicates that vitamin D supplementation can potentially be used as a treatment for certain illnesses by treating underlying causes such as gut dysbiosis and permeability of the gastrointestinal tract.

Bio: Ethan Constantine is from the Dallas TX area and graduated from Texas A&M University Corpus Christi in 2020 with a B.S. in Biomedical Sciences. In his free time, he enjoys working out, running, and trains in kick boxing and muay tai. After graduating from Texas State University, he plans to take a gap year before continuing his education.

Drawing as a Generative Learning Activity: An Exploratory, Qualitative Investigation on a Nature Journaling Seminar Course

Major Advisor: Dr. Kristy L. Daniel

Committee Members:

1. Dr. Carrie Jo. Bucklin
2. Dr. Paula S. Williams

Drawing encourages critical thinking skills by pushing learners to use discernment and prior knowledge of a subject matter to create an external representation of their mental understanding. While visual representations play a key role in science education, it is less common to prompt students to draw their own visual representations to communicate their uniquely constructed ideas. This exploratory, qualitative study investigated drawing as a generative learning activity in a nature journaling seminar course by examining students’ use of drawing techniques taught in class, as well as dissecting their reported reflections on how drawing impacted their journaling experience. The students (n=11) were required to complete a nature journal using prompts developed to encourage reflection, drawing technique practice, and scientific thinking. We coded and analyzed student responses for trends in drawing technique usage, such as hatching and use of color. Student drawings reflected a steady increase of technique usage as more techniques were introduced in class, with a decline once drawing instruction ceased. Students reported that the practice of drawing nature observations increased their mindfulness and attention to detail in their written entries. Our findings provide insight to the benefit of drawing practices in nature journaling, as well as the effects of drawing instruction on student perceptions. Teaching drawing techniques with instructional guidance can provide students with the opportunity to take an active role in their education and deepen their understanding of, and connection with, the natural world. 

Bio: Hannah Baratang graduated with two A.S. degrees in Chemistry and Organismal Biology from Central Texas College at the age of 17. She graduated with a B.S. in Biology from Texas A&M - Central Texas at the age of 19. She joined the Daniel Biology Education Research Group at Texas State University in the Spring of 2023 to pursue a M.S. in Biology under Dr. Daniel's supervision. Since joining the research group, she has been an active member of Research Rangers, developed and illustrated the Good Gall-y! outdoor science activity, and independently organized a series of live music events in the San Marcos DIY scene.

Optimizing Chitosan-Functionalized Hollow Silica Microspheres for Isolation and Concentration of Nucleic Acids

Major Advisor:  Dr. Shannon Weigum

Committee Members:

1. Dr. Adeyemi A. Olanrewaju
2. Dr. Manish Kumar 

This research investigates Wastewater-Based Epidemiology (WBE), a tool utilized for detection and concentration analysis of wastewater samples. WBE is useful for monitoring and management of public health threats like viral outbreaks such as COVID-19. In current research, the development of this assay uses the unique properties of hollow silica microspheres coupled with chitosan as a binding agent, a method effective in the detection of various RNA and antigens in wastewater samples. The utilization of hollow silica microspheres, selected for the high surface area and buoyant properties, aided by chitosan, creates an efficient and selective binding process. This combination can be manipulated for the sensitivity of detection but also supports the capture of a wide range of viral particles and RNA molecules. Capture of oligonucleotides is achieved by chitosan binding to the surface of the hollow silica microspheres. This thesis research served to find the optimal conditions for nucleic acid binding, isolation, and long-term microsphere stability when functionalized with chitosan. The preparation of functionalized microspheres has been reduced. The incubation time of functionalized microspheres with L-Cysteine has been reduced to 10 minutes under end over end rotation.  The optimal binding conditions of oligonucleotides has been found utilizing a surrogate. It was found that the functionalized microspheres can bind nucleic acids at saturation within 1 hour. The incorporation of reduced incubation times has reduced the overall protocol by over 24hrs. A protocol has been developed to stabilize microspheres after lyophilization and storage. The addition of Trehalose, a cryoprotectant, increases stability after lyophilization and storage. SEM or Scanning electron microscopy was used to image the chitosan shell on the hollow silica microspheres. The functionalized microspheres containing various treatments applied was examined for disruptions in the chitosan surface and binding kinetics. The implications of this research are vast and transformative. By increasing efficiency and stability and reducing sample preparation costs, this research increases access to WBE for public healthcare and diagnostic testing. The adoption of methods can aid in early outbreak detection and the assessment of community health, therefore contributing to more informed and effective public health strategies and interventions.

Bio:  Omari began undergraduate studies at Southern Methodist University. He then finished his B.S. in Biology at the University of Houston. In the fall of 2022, he joined Dr. Weigum’s Optical Biosensors and Nanomaterials lab. After Graduation he plans to further his studies and pursue a joint MD/JD program.

Optimization of Molecular Buoys for use in the Isolation and Amplification of SARS-CoV-2 RNA from Wastewater

Major Advisor:  Dr. Shannon Weigum

Committee Members:

1. Dr. Rodney Rohde
2. Dr. Kelly Woytek

Wastewater based epidemiology (WBE) is an emerging tool used in the surveillance of viruses and viral diseases, such as SARS-CoV-2 and COVID-19. WBE comprises wastewater sampling and processing, isolation of target viruses and purification of target viral nucleic acids, and quantification through molecular means such as RT-qPCR. Isolation and purification are crucial steps in estimating viral loads and positivity rates in a given watershed. Current CDC-recommended methods in viral isolation can be costly, time consuming, or are otherwise inaccessible for widespread use. Our aim is to develop a rapid and accessible bio-separation method using inexpensive materials. In the present work, hollow silica microspheres, or “molecular buoys”, were functionalized with chitosan, a cationic polysaccharide, to capture nucleic acids in diluted stool. Scanning electron microscopy (SEM) was used to examine chitosan surface loading and fluorescently-tagged DNA aptamer (a surrogate oligonucleotide) diluted in stool was used to examine nucleic acid binding capacity. In addition, optimization of nucleic acid capture, reduction of assay time, and limit of detection (LOD) were explored. Under SEM, we observed shell formation on the surface of chitosan-functionalized microspheres that was absent in non-functionalized microspheres. Additionally, optimization of the assay wash protocol reduced assay time, bringing total assay time to around 35 - 40 minutes. Finally, a preliminary LOD was found to be 40 copies/uL in diluted stool. These findings suggest that functionalized hollow silica microspheres may be an effective, low-cost, and rapid method in the isolation of viral nucleic acids for use in WBE.

Bio:  Alexandra received a Bachelor of Science in Biology from the University of Missouri-Columbia in 2021. She then moved to Austin and worked in a contract lab for a year. She joined the Optical Biosensors and Nanomaterials lab, lead my Dr. Shannon Weigum, in August 2022. After graduation, Alexandra plans to continue her education and pursue a career in virology. 

A Prototypical Thermal-Preference Assessment Device for Studying Factors Affecting the Thermal Biology of Small Aquatic Animals

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

Committee Members: 

1. Dr. Shannon E. Weigum, Department of Biology, Texas State University
2. Dr. Alan W. Groeger, Department of Biology, Texas State University
3. Randy Gibson, Supervisory Biologist, San Marcos Aquatic Resources Center

Zoom link: https://txstate.zoom.us/j/85811727971pwd=M3ozWmFrL3A4ckhxbzBJRWlGVnZvUT09

Passcode 205373

Come see the Thermal Preference Assessment Device (TPAD) I have created for studying the thermal biology of small aquatic organisms such as Melanoides tuberculata. The TPAD was created in response to my review of prior thermal biology studies which revealed a wide range of thermal-gradient device designs and operational theories, many of which were plagued by design flaws that would prevent the formation of a stable, linear gradient. This, coupled with a ubiquitous lack of published performance data and assembly documentation would render replicating these devices difficult at best. The goal of this study was to design and build a proof-of-concept device capable of generating customizable, stable, thermal gradients for use in thermal biology studies, which conformed to the following specifications; 1) quick generation of stable, linear thermal gradients with extremes of 10 °C to 30 °C for at least 24 hours; 2) precise temperature controls, allowing the thermal gradient to be moved back and forth in the trough; and 3) free, unobstructed movement for organisms of varying size classes and modalities within the Testing Arena. The TPAD is driven by a novel counter-current exchange system, powered by computer-controlled thermoelectric Peltier heater/coolers. The Peltier units heat and cool water running counterflow through two pairs of vertically stacked exchange conduits. The exchange conduits are designed so that every segment serves as an individual heater/cooler for the water at that point, with the output temperature increasing incrementally from one end of the Testing Arena to the other. The TPAD was shown to be capable of producing a linear thermal gradient suitable for testing many small organisms of conservation concern from local waters and then maintaining the gradient for 24 hours. The Testing Arena was found to comfortably house organisms including M. tuberculata and Cambarus spp., though there were shaded areas which were favored by cover-seeking organisms. I think, despite not reaching all our original goals, that the TPAD demonstrates the potential of the counter-current exchange model as a refined method of conducting thermal preference tests. Work on the TPAD Design Phase II, a larger, more flexible, and more efficient model based on the success of Phase I, is already underway.

Bio: Matthew Tanner Donelon is from Georgetown, Texas. He graduated with a B.S. in Wildlife Biology from Texas State University in 2019, where he realized his love for innovation in wildlife management strategies. After graduation, Matthew will pursue work as an environmental consultant or engineer.