For sexually reproducing organisms, a large part of their fitness depends on how well they compete for and obtain mating opportunities. This “sexual selection” was recognized as a strong driver of evolution by Darwin, and has since been invoked to describe broad scale patterns of biodiversity. As an evolutionary geneticists, we answer fundamental questions about how natural and sexual selection shape mating interactions and behaviors, species interactions, and ultimately speciation. Our experimental work is highly integrative combining population and molecular genetics with behavioral experiments to understand the genetic basis of sexual behaviors and reproductive isolation. Studying the mechanistic and genetic links between sexual selection and reproductive isolation will enable biologists to determine the influence of this force on generating biodiversity. A common theme in our research is to connect processes operating within populations to lineage diversification and speciation by integrating behavioral phenotypes with the genes and molecular mechanisms underlying these traits. Specific examples of our main research foci include: 1) The genetic basis of female choice and incipient speciation and 2) The consequences of a shared genetic basis of traits important to both sexual selection and reproductive isolation. We also have interests in 3) the role that selfish elements play in the evolution of hybrid incompatibilities.
We use races of D. melanogaster that show partial reproductive isolation as a model to understand how female preference evolves. Reproductive isolation between these “incipient species” is asymmetric with African (abbreviated Z) females strongly rejecting Cosmopolian/Non-African (abbreviated M) males. We are characterizing the phenotypic and genetic contributions of a strong candidate gene, desat2, to this reproductive isolation. Additionally, we use population genetics to identify new candidate genes, and are validating their role in the specific African (Z) female mate preference. Our overall goal is to determine which male traits are targets of reproductive isolation and which female genes are responsible for making mating decisions. In previous work we have used experimental evolution of Caenorhabditid nematodes to ask questions about rapid evolution of mating preferences and hope to continue this in the near future.
One common assumption in evolutionary biology is that sexual selection unilaterally drives the evolution of reproductive isolation. This shared genetic basis is foundational to many models of speciation but remained untested until recently. We use the sister species D. pseudoobscura and D. persimilis to test hypotheses centered on how selection for increased reproductive isolation in sympatry (reinforcement) can affect sexual selection and sexual interactions within natural populations. In addition to demonstrating that reinforcement acts on gametic interactions in this system, we have identified genomic regions that are differentiated between allopatric and sympatric populations and include loci with known roles in sperm competition.
We have an ongoing interest in the role that selfish elements play in the evolution of hybrid incompatibilities and reproductive isolation. We are currently collaborating with Dan Barbash to determine which factors may be interacting with Zhr, which is a large satellite on the D. melanogaster X chromosome, to cause hybrid incompatibilities. We have also used the D. virilis clade to ask how dysgenesis and polymorphic transposable elements might contribute to hybrid inviability.