The genetics of postmating isolation mechanisms between species of Drosophila

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Reproduction plays a pivotal role in biology and understanding how gene changes can impede interbreeding and allow for the evolution of different species is a central problem in evolution. Identifying links between genes and phenotypes, such as those that restrict gene flow between groups of individuals, is critical for understanding the process of speciation and the mechanistic origin of biodiversity. Among closely related species, differences in reproductive traits tend to be more pronounced than differences in other traits, and these differences affect the potential of species to interbreed (i.e. species compatibility). Species compatibility does not end with the mating process itself. Indeed male-male competition and female choice continue to influence compatibility long after mating. My work aims to understand the genetic basis of reproductive incompatibilities, specifically postmating postzygotic anomalies that render hybrid males sterile and postcopulatory prezygotic challenges that affect sperm competition. During the next phase of my research I aim to: 1) Test the role of previously identified genes and gene classes (e.g. proteases) in hybrid male sterility (HMS), 2) identify gene interactions and pathways contributing to HMS between species, 3) contribute towards our understanding of the mechanistic basis and phenotypic expression of incompatibilities that cause isolation between species, 4) identify common genetic basis to sperm competition and postmating prezygotic isolation between species, and 5) understand patterns of evolution of male reproductive genes in general and those linked to postmating reproductive isolation in particular, with an interest moving from coding to noncoding regulatory evolution. In my lab, we have successfully used a combination of classical genetics, genomics and molecular evolution approaches to identify candidate genes associated with variation in reproductive success. The innovation of this proposal is to combine these approaches at the genome level, with rigorous phenotypic descriptions and gene manipulation technologies to identify specific genes contributing to hybrid male sterility and sperm competitiveness. Ultimately, results will further our knowledge on species differentiation and the genetic basis underlying such process. Testing the role of changes in gene expression in HMS will be innovative and transformative towards our understanding of links between gene regulation and phenotypic manifestation. Another innovative aspect will be identifying gene interactions and pathways rather than single genes contributing to HMS and testing whether, based on common genetic mechanisms, sexual selection (sperm competition) can cause or contribute to speciation (postmating prezygotic isolation).