Congratulations to the following ecology and evolutionary biology graduate students on their competitive and prestigious awards from the University of Michigan Rackham Graduate School: Camden Gowler, Iris Holmes and Joanna Larson were awarded Rackham Predoctoral Fellowships. Holmes also received a Susan Lipschutz Award.

Camden Gowler collecting live Daphnia and other zooplankton from Whitmore Lake. Image: Meagan Simons

Gowler studies the ecology and evolution of host-parasite interactions. Parasites are everywhere in nature. In fact, most parasite species can infect multiple host species, and most host species are susceptible to infection by multiple parasite species, he explained. Additionally, both host and parasite species can evolve rapidly, so host-parasite interactions change over time. All of this makes studying host-parasite interactions quite complicated. However, Daphnia (tiny freshwater crustaceans) and the many fungal, bacterial, and other microbial parasites that infect Daphnia are a great system for disentangling the ecology and evolution of host and parasite communities.

“In my dissertation, I use field surveys, network analyses, mathematical models, and lab experiments to understand how different host species influence parasite infections in another host species, how parasites differ in their ability to infect multiple host species, and how parasites evolve over the course of an epidemic,” said Gowler. “I found that particular host and parasite species disproportionately contribute to cross-species transmission, and parasite virulence (how harmful they are to the host) can evolve rapidly over the course of a natural epidemic. Since most infectious diseases of humans originate from other host species, understanding cross-species transmission and the evolution of harmful parasitic traits has implications for human health as well.” Gowler's advisor is Professor Meghan Duffy.  

Iris Holmes in “maximum field mode” in Nicaragua. Image: Ivan Monagan

Regarding her research, Holmes explained, “Within their bodies, all animals carry a multitude of bacteria called the 'microbiome,' which together help their host digest food and ward off diseases. Understanding why each animal has its specific community of bacteria is key to developing a full picture of how animals interact with their environment.”

Holmes studies the bacteria in snakes and lizards to better understand the factors that determine which bacteria occur in which hosts at both small and large scales of space and time. “Understanding host-microbiome relationships can help with conservation of threatened species as they are faced with stress from their changing environments, including new diseases and parasites.” Holmes advisors are Professors Alison Davis Rabosky and Dan Rabosky.  

Joanna Larson holding a cane toad at Los Amigos Field Station in southern Peru. Image: Alison Davis Rabosky

Larson’s research addresses an enduring question in biology – why species are unevenly distributed between geographic regions and between groups of organisms. Particularly intriguing is that there are more species in the tropics than in temperate areas, a pattern known as the latitudinal diversity gradient, she explained. Using the large datasets on diets and morphology that she created, Larson explores how frogs use ecological resources along this gradient in the Americas. She also investigates how morphological diversity (variety in body shapes and proportions) is distributed across frogs globally. A key question she asks is whether groups of frogs that have more species relative to other groups will also have more morphological richness or whether the processes that generate species are decoupled from those that lead to body shape evolution.

The detailed information on frog diets that her study will generate can also be applied to other areas of research, such as conservation biology. Frogs are a heavily threatened group and understanding their environmental requirements can aid in designing effective conservation strategies. Ecological specialists are more sensitive to anthropogenic disturbances, so identification of unappreciated dietary specialization in frogs by this project can have importance implications for extinction risk assessments.

The Rackham Predoctoral Fellowships support outstanding doctoral students who have achieved candidacy and are actively working on dissertation research and writing in support of students working on dissertations that are unusually creative, ambitious and impactful. The fellowship provides three terms of support including a stipend of just over $32,000, candidacy tuition and required fees for 12 months and GradCare health and dental insurance during the fellowship period.

The Susan Lipschutz Award recognizes Rackham students who have demonstrated exceptional scholarly achievement, a sense of social responsibility and service, and a lively interest in promoting the success of women in the academic community. Larson's advisor is Professor Dan Rabosky.