The origin and accumulation of hybrid incompatibilities in Tigriopus californicus

University Of Southern California, Los Angeles CA

Investigators

Abstract

Understanding the mechanisms by which new species arise is a fundamental goal of biology. Diverging populations accumulate genetic differences that may cause conflicts (reduced fitness) when populations come back together and hybridize. This leads to further isolation of the populations, and, eventually, to speciation. Speciation work in model systems has concentrated on conflicts involving the gender-determining chromosomes, but a great number of organisms across the tree of life lack these chromosomes. This project uses a copepod, a small marine invertebrate, to understand how genetic conflicts underlying speciation evolve in organisms without gender-determing chromosomes. By hybridizing pairs of populations from a known evolutionary tree, the study will assess how different types of conflicts (nuclear-nuclear vs. nuclear-mitochondrial) accumulate over time and whether the same chromosomal regions evolve conflicts in evolutionarily independent lineages. It will assess the repeatability of evolutionary trajectories by tracking genetic changes in large, lab-based hybrid populations and will identify potential candidate genes involved in conflicts. This project relates to issues of biodiversity and conservation by exploring how the lack of sex chromosomes impacts species diversification and consequences of hybridization. Its focus on the evolution of nuclear-mitochondrial conflicts, an important cause of disease, gives this study potential biomedical applications. The project will train a postdoctoral researcher, Ph.D. students, and numerous undergraduate researchers. It will also include outreach to diverse communities in and around Los Angeles, including a collaboration with the Aquarium of the Pacific aimed at promoting awareness of the evolutionary processes currently at work in the ocean and their importance.