Sophia Anreder

Author: Sophia Anreder | Major: Biology | Semester: Spring 2025

My name is Sophia Anreder, and I am a student at the Fulbright College of Arts and Sciences, majoring in biology with a minor in Spanish. My mentor is Dr. J.D. Willson of the Biological Sciences department, and my research is of spring 2025. My future plans include studying abroad in Puebla, Mexico and then working as a Medical Assistant at ENT Center of the Ozarks during my gap year before applying to medical school.

Blog post content:

Throughout the spring of 2025, I have worked alongside my honors mentor, Dr. Willson, to study what factors drive spatial distribution of the Oklahoma salamander (Eurycea tynerensis) within headwater streams of the Ozark highlands of Arkansas. Headwaters are sensitive and essential microhabitats within the Ozark Mountains, yet they are often overlooked in conservation efforts. These critical waterways support a diverse assemblage of species, including salamanders. However, water conditions and amphibians are in rapid decline worldwide due to climate change, driving a greater demand for conservation efforts in Arkansas. To monitor the environmental stress present in headwater systems, stream amphibian occupancy can be used as an indicative metric due to their complicated life histories. Therefore, exploring spatial distribution of amphibious species in these headwater streams is key for predicting species responses to environmental changes and designing appropriate ecological reserves that protect biodiversity. My research identifies where among headwater streams salamander abundance drops off in relation to stream size and what physical characteristics drive spatial distribution of E. tynerensis throughout the Ozarks. This was accomplished by conducting visual encounter surveys (VES) at multiple sites alongside streams in the Ozark region and using negative binomial regression to relate salamander detection to several covariates, including stream width, stream width variation, and substrate composition.

I became interested in this topic after taking both General Ecology and Herpetology with Dr. Willson and learning about the rich biodiversity of amphibians and reptiles found within Arkansas. Studying the Oklahoma salamanders specifically interested me since they are endemic to the Ozark highlands and due to their unique life histories. These salamanders can either metamorphosize into terrestrial adults or remain aquatic through paedomorphosis. Additionally, I hoped to further contribute to the limited existing literature that studies their spatial distribution.

This semester, I finalized my data set and completed my honors thesis by conducting a VES at 51 different sites across 11 streams. I completed these five-minute visual surveys for salamander detection by flipping rocks within 1 meter along the stream’s edge and recording several other covariates, such as temperature, stream width and depth, and stream substrate composition. Using a negative binomial regression, I modeled captures as a function of habitat characteristics. I then performed model selection using an information-theoretic approach. The final model that best fit statistical and ecological relevance included mean stream width and stream width variation as significant predictors of salamander abundance, while other factors measured did not, such as average sand/silt substrate percentage, air temperature, or canopy cover.

I found that salamander abundance significantly decreased with increasing mean stream width, especially in streams smaller than 5.0-7.5 meters wide. Additionally, stream width variation was positively associated with higher salamander abundance, which suggests that stream salamander abundance may be enhanced in diversely structured streams. These findings suggest that smaller, more variable watersheds may provide more suitable habitat for E. tynerensis which have important implications for headwater stream management and conservation. To accomplish effective management of these fragile lotic systems within Arkansas, understanding the influence of stream structure on salamander occupancy is required to mitigate the effects of stream fragmentation and habitat degradation. These effects can threaten headwater systems by disrupting natural flow and channel morphology, which includes the construction of dams or road crossings. Additional degradation of stream integrity, such as pollution, sedimentation, fish stocking, and invasive species, can further compromise the ability of species to persist in these headwater streams. The results of this study indicate that conservation efforts should prioritize areas of smaller stream width and higher stream width variation, specifically those smaller than 7.5 meters of average stream width. This identified threshold of predicted salamander abundance could be used to assess and quantify the amount of quality salamander habitat within a given watershed and used to assess population viability at larger spatial scales, emphasizing the importance of habitat quality and continuity.

Field work is highly engaging and interactive, but it has also taught me a lot. The lack of rainfall this past fall and spring allowed me to practice how to remain adaptable, especially during data collection, and to work with given conditions instead of against them. Thanks to my mentor, Dr. Willson, we were able to find interesting relationships regarding salamander distribution even with subpar weather conditions. I am deeply grateful for the Honors College Research Grant, which allowed me the opportunity to independently conduct a research project in collaboration with my mentor, Dr. Willson. This support allowed me to discover my passion for research and the pursuit of knowledge, and I have grown as a student in and out of the classroom. Through the Honors College Research Grant, I was allowed to fully engage with a topic that is not only intriguing but also valuable in broader contexts for the conservation and protection of our state’s natural beauty.