Category: Awards and Degree Completions

Our very own Kaylee Arnold won best talk for her presentation, “The gut microbial diversity of a Chagas disease vector varies across coinfection status throughout central Panama” in the Medical, Urban, & Veterinary Entomology section of the Entomological Society of America at their annual meeting. Read below for her abstract. Congratulations, Kaylee!

Chagas disease is caused by the parasite Trypanosoma cruzi that is carried in the guts of hematophagous triatomine vectors. Triatomines are often coinfected with the parasite T. rangeli, which is non-pathogenic to mammals but can reduce fitness of their triatomine hosts. This study examined the gut microbial diversity of T. cruzi infected, coinfected, and uninfected triatomines (n = 288) throughout central Panama. We hypothesized that single and coinfected triatomines would have greater gut microbial diversity than uninfected individuals due to pathogen-microbe interactions within the gut, which can facilitate the proliferation of less dominant bacterial taxa.

Coinfections were found in 13% of individuals (40/288) and there was significantly greater alpha diversity in coinfected individuals when compared to both single and uninfected samples (Dunn’s test of multiple comparisons, p < 0.001). Furthermore, single T. cruzi infections were found in 34% of sampled individuals (91/288) and also displayed significantly greater alpha diversity when compared to uninfected individuals (Kruskal-Wallis H test, p < 0.001). Across all samples, Sphingomonas was the most dominant taxa, and decreased in relative abundance compared to uninfected individuals. Finally, the beta diversity across infected samples was significantly different compared to uninfected samples (PERMANOVA p = 0.001 using Bray-Curtis dissimilarity). These results highlight patterns of microbial diversity which may be impacted by vector infection status and will be important to consider when developing vector control strategies.

Congratulations, Lexi! Here is the abstract of her thesis, entitled Invertebrate herbivory of understory trees in the Georgia Piedmont in response to soil warming:

As the global mean surface temperature increases, changes in biogeochemical cycling have the potential to have cascading effects on plant and invertebrate interactions. Previous warming studies have primarily been conducted in recently glaciated, more fertile soils, and the response of plant and invertebrate interactions to warming is unclear in lower latitude, less fertile soils of the Georgia Piedmont. In this study, I examined leaf and soil chemistry (%N, C:N) and herbivore damage (% leaf area consumed) from understory tree seedlings of the Georgia Piedmont. Carbon and nitrogen foliar content and invertebrate herbivory did not respond to warming in any year, but there were interactive effects of temperature and species. Overall, warming did not have an indirect effect on plant-herbivore interactions, which is likely due to Piedmont soils containing less available nitrogen. However, species-level variation in response to warming has implications for forest composition changes.

Written by Mikey Fager, OSE undergraduate and Rosemond lab member

Humans and aquatic biota both rely heavily on the many services that river and stream systems provide. Water managers and conservation scientists need to determine the possible effects that increases in the frequency and duration of droughts due to climate change may have on ecosystem processes within these systems. Looking at the ways that different taxa in the systems respond to low-flow conditions can be immensely helpful in improving water infrastructure and management for both humans and aquatic organisms

Laura’s masters thesis research does just this, as she analyzed a variety of literature to assess how algae, invertebrates, and fishes respond to extended periods of low flow in streams and rivers, using the Upper Flint River Basin as her focal system. In the first two chapters, Laura hypothesized that algal biomasses would increase, while richness and density of aquatic invertebrates (particularly filter-feeders) and fish abundance would decrease during periods of low flows. She also outlined the different studies she would be reviewing for each taxonomic group, while noting the importance of considering study context such as stream size and average flow variation when drawing conclusions and discussing implications. Laura found that when low-flow events occur, abundance of algae generally increases, while the numbers of aquatic invertebrates and fishes tend to decline. She goes on to explain that droughts can lead to other events like loss of key plant species and warmer overall channel temperatures, which will likely compound the effects of low flows. Laura’s research expertly identifies the areas of concern that water managers, conservationists, and other stakeholders need to consider. Her work highlights essential research to be done towards understanding the explicit responses perennial systems have to low-flow events, in order for managers and ecologists alike to alleviate the stress that droughts may cause. 

Rack, L., 2020. Evaluating Low Streamflow Effects on Biota to Support Management in Perennial Systems. Master’s Thesis, University of Georgia.

By Kate Sabey, Ezenwa Lab

Wild animals commonly experience trade-offs in their investment among different physiological processes, including reproduction, nutrition, and immune function. In particular, given its importance for pathogen defense, many studies have sought to measure when and why animals modulate their investment in immunity. However, since animals encounter a range of conditions in natural environments, the observation of these physiological trade-offs are likely shaped by a variety of intrinsic and extrinsic factors.

Through her masters thesis research, Ashley explored such context-dependence in immune dynamics. In her first chapter, she examined variation in relationships between testosterone and immunity in free-ranging American alligators, finding that the effects of testosterone on microbial killing depended on levels of co-circulating hormones, the microbe of interest, and temperature. In her second chapter, Ashley further explored relationships between immune performance and temperature across vertebrate species, finding that the effects of temperature on immune performance depended on host thermoregulation strategy. For example, ectotherms experienced trade-offs between immune performance at the host’s optimal temperature and the consistency of immune performance across temperatures, but these trade-offs were absent in endotherms. Together, Ashley’s work emphasizes the importance of considering both intrinsic and extrinsic variation when assessing the immune performance of wild vertebrates. Importantly, accounting for this context-dependence will be crucial in understanding the relevance of physiological trade-offs across animal systems.

Congratulations, Ashley!

Kate Sabey, a PhD Candidate in the Ezenwa Lab and an IDEAS Trainee, was selected as a P.E.O. Scholar. Kate’s research focuses on the relationship between the gut microbiome and infection status of wild African ungulates, using disease ecology and genomic approaches. After completing her dissertation work through the Department of Infectious Diseases, Kate will proceed with veterinary medicine training as part of her dual DVM-PhD degree. Well done, Kate!

See the post from the UGA Graduate School here.

Emily Bertucci is the inaugural recipient of the new Dr. Rebecca Reyburn Sharitz and Carl Byrne Hatfield Fellowship. Emily, advised by Dr. Ben Parrott, is researching the proximate mechanisms that produce variation in biological aging – specifically, epigenetic changes that occur with age and how normal age-related changes are impacted by exposures to stressful environments.  This year, she is investigating how exposures to stress during sensitive life stages alters the epigenome and produces variation in aging and life history traits at the individual and population levels.

CONGRATULATIONS Emily!