|Over 3000 species of Drosophila and related genera provide us with an enormous source of morphological, ecological, and behavioral diversity to explore. At the same time, the genetic and molecular tools available in Drosophila are unrivaled in their power to examine and manipulate the molecular pathways that generate this diversity. We focus on groups of closely related species that have distinct phenotypes yet retain the ability to hybridize. Such models offer unique opportunities for the synthesis of developmental and evolutionary genetics. We study a variety of traits and questions, but all our research is united by a cross-disciplinary approach that brings molecular tools to bear on evolutionary questions.
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The origin of evolutionary innovations
One of our favorite models are the sex combs: male-specific structures used by flies during courtship and mating. Sex combs are an example of evolutionary innovation: they evolved recently in one Drosophila lineage and underwent rapid and dramatic diversification. By integrating developmental genetics and genomics with phylogenetic and quantitative-genetic techniques, we seek to understand how sex combs originated and evolved at the molecular level. Our approach is based on analyzing the structure of developmental pathways. Comparative analysis of gene interactions in different species can reveal how the genetic circuit responsible for sex comb development was assembled in the course of evolution, and how changes in this circuit produced the diversity of adult morphologies.
Genetic basis of parallel evolution
Another favorite model in the lab is pigmentation. Color patterns evolve rapidly in Drosophila and other animals and provide numerous examples of divergent and convergent evolution. By analyzing the genetic basis of similar phenotypes in different lineages, we ask whether phenotypic convergence reflects repeated changes in the same genes; alternatively, can changes in different genes produce the same phenotypes? Our goal is to understand the structure and evolution of the entire molecular pathway that controls pigmentation, so that each evolutionary change can be placed in a mechanistic context. This systematic approach allows us to test whether the structure of developmental pathways biases the fixation of natural variation, and thus the genetic basis of evolution.
Genetic control and evolution of sexual dimorphism
Males and females of many animal species differ in their morphology, physiology, and behavior. Much of our research is aimed at understanding the genetic and developmental mechanisms responsible for generating these differences between sexes. We look at how sex-specific transcription and splicing are regulated, how the sex determination pathway is integrated with spatial patterning and cell differentiation to produce sexually dimorphic traits, and how the evolution of these interactions contributes to phenotypic diversification.
Molecular genetics and ecology of host-symbiont interactions
Different Drosophila species are adapted to a wide variety of food sources, including fruit, mushrooms, flowers, cacti, tree sap and cambium, and even such exotic substrates as bat droppings or the nephric glands of land crabs. Like all animals, flies harbor complex microbial communities in their guts. We are interested in the function of these communities in facilitating ecological adaptation. We are combining environmental genomics with experimental approaches to understand the roles of host genotype and diet in shaping the composition of gut microbial communities, as well as the contribution of these communities to host metabolism, physiology, and fitness.