Ecological divergence and the history of gene flow in the Nearctic milksnakes (Lampropeltis triangulum complex)

Many phylogeographic studies on species with large ranges have found genetic-geographic structure associated with changes in habitat and physical barriers preventing or reducing gene flow. These interactions with the geographic space, contemporary and historical climate, and biogeographic barriers may have complex effects on population genetic structure and speciation. While allopatric speciation at biogeographic barriers is considered the primary mechanism for generating species, more recently it has been shown that parapatric modes of divergence may be equally or even more common. With genomic data and better modeling capabilities we can more clearly define causes of speciation in relation to biogeography and migration between lineages, the location of hybrid zones with respect to the ecology of parental lineages, and differential introgression of genes between taxa. Here we examine the origins of three Nearctic milksnakes (Lampropeltis elapsoides, L. triangulum, and L. gentilis) usin...