Barriers to Intraspecific Gene Flow Among Highly Divergent Salamander Lineages

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This research examines in detail the patterns and processes of limited gene exchange between two highly divergent genetic lineages in the widespread spotted salamander (Ambystoma maculatum). During the climatic cycles of the Pleistocene, spotted salamander populations were isolated in two independent refugia, resulting in highly divergent genetic races. These populations have subsequently expanded their ranges, resulting in contact zones of different ages and geographical overlap. The main goal of this proposal is to assess the genetic consequences of genetic isolation and subsequent re-contact using nuclear DNA markers and collections along three of these contact zones. Mating experiments will be used to quantify patterns of mate choice and the degree of genetic exchange (or lack thereof) that occur between the lineages.Studies of reproductive isolation are critical to our understanding of differentiation and speciation. Divergence among lineages within species can be examples of incipient speciation and therefore help us understand the process that ultimately leads to novel species and the generation of biodiversity. This research also has implications for conservation because it documents the distribution of genetic diversity in a widespread species; information crucial to interpreting the genetic consequences of habitat fragmentation and new contact zones in this and other taxa.