Dissertation Research: A Hybrid Zone Lens on Rapid Speciation During Refugial Isolation in the Field Vole (Microtus agrestis)

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Hybrid zones are natural laboratories that allow researchers to identify the changes that have caused populations to diverge into different, reproductively isolated species. This project will investigate a hybrid zone where two historically isolated populations of field voles now interbreed. Researchers will sample multiple individuals across the hybrid zone and identify the genomic regions involved in the formation of new species. One graduate student and a number of undergraduate students from diverse educational, cultural, and economic backgrounds will be trained in cutting-edge genetic techniques. This research will also be used as an active learning tool during a course specifically designed for first-year undergraduate students from historically underrepresented groups in the biological sciences. The vole genus, Microtus, is a model system to investigate the process of speciation because it has a diversification rate 60-100 times higher than other vertebrates. The distribution of genetic variation within the field vole (Microtus agrestis) has been heavily shaped by glacial cycles. The species includes distinct evolutionary lineages that survived in separate glacial refugia during recent glacial maxima and are highly differentiated. This research will focus on a hybrid zone between two of these lineages and use transcriptome sequencing to identify fixed genetic differences between them. These genomic regions will serve as targets for subsequent analyses of individuals from across the hybrid zone. Using genomic cline analyses that consider the genetic composition of individuals across this transect, researchers will characterize variation across the hybrid zone revealing loci that show restricted introgression. These loci will be considered candidate genes related to reproductive isolation responding to factors, such as selective differences associated with the differing environments of the hybridizing forms, and genetic incompatibilities between them. The results from these analyses will provide a conceptual and empirical groundwork for the genetic architecture underlying speciation driven by isolation in glacial refugia and provide a set of candidate loci to investigate speciation in other mammalian groups.