ur lab studies the ecology and evolution of symbiosis. Through the use of molecular, phylogenetic, and experimental tools, we use culture-independent means to study species interactions between bacteria and their animal hosts, with a current emphasis on the microbes of ants, butterflies, aphids, and guppies. We seek to not only identify macroevolutionary trends in host-symbiont interactions, but to also reveal the functional significance of bacteria in animal ecology.

Symbiosis

ost eukaryotic species engage in intimate and prolonged associations with other organisms, termed symbioses.

Such interactions play important roles in the nutrition, defense, reproduction, and genome evolution of insects, one of the most diverse groups of animals on the planet. Our research focuses on the significance of bacteria that shape nutrition and reproduction of insects and other eukaryotes.

Through collaborative initiatives, we are currently studying the nutritional significance of gut bacteria in ants [with collaborators Corrie Moreau (from the Field Museum of Natural History) and Naomi Pierce (from the Department of Organismic and Evolutionary Biology at Harvard University)], and the importance of gut microbes in energy extraction in guppies (with collaborator Sue Kilham from the Department of Biology at Drexel University).

In addition, we are also investigating the roles of bacterial symbionts in defense against natural enemies (with collaborator Kerry Oliver, from the Department of Entomology at the University of Georgia).

Trophic evolution

he position of organisms on the food chain varies widely, from primary producers to predators. Evolutionary shifts in trophic position have been governed, in part, by changes in behavior, digestive physiology, and gut morphology.

But recent findings from animals reveal that these dietary shifts are also correlated with changes in their symbiotic microbes. Given the nutritional roles that have been documented for many of these bacteria, it appears that microbes have played important roles in the dietary evolution within some animal groups.

Our lab aims to characterize the interplay between animal diets and their microbial gut symbionts through a combination of experimental and molecular analyses. We are currently investigating whether bacteria have influenced the trophic evolution of the ants and whether shifts in habitat, diet, and predation pressure are associated with changes in gut microbes of Trinidadian guppies.

Coevolution

he histories of many interacting organisms have been tightly intertwined over evolutionary timescales, and the engaged partners have served as sources of selective pressure and evolutionary novelty through both antagonistic and cooperative strategies. Molecular phylogenetics has enabled us to characterize the evolutionary histories of these interactions, enabling a description of the fidelity displayed by these relationships.

Current research in the lab focuses on evolutionary histories of symbioses between insects and heritable symbionts such as Wolbachia, and also between ants and their symbiotic gut bacteria. We also aim to understand how defensive symbionts of aphids and their parasitic wasps have coevolved through antagonistic interactions.