Data from: Evidence for ephemeral ring species formation during the diversification history of Western Fence Lizards (Sceloporus occidentalis)

Divergence is often ephemeral, and populations that diverge in response to
regional topographic and climatic factors may not remain reproductively
isolated when they come into secondary contact. We investigated the
geographic structure and evolutionary history of population divergence
within Sceloporus occidentalis (Western Fence Lizards), a habitat
generalist with a broad distribution that spans the major biogeographic
regions of Western North America. We used double digest RAD sequencing to
infer population structure, phylogeny, and demography. Population genetic
structure is hierarchical and geographically structured with evidence for
gene flow between biogeographic regions. Consistent with the
isolation-expansion model of divergence during Quaternary
glacial-interglacial cycles, gene flow and secondary contact are supported
as important processes explaining the demographic histories of
populations. Although populations may have diverged as they spread
northward in a ring-like manner around the Sierra Nevada and southern
Cascade Ranges, there is strong evidence for gene flow among populations
at the northern terminus of the ring. We propose the concept of an
“ephemeral ring species” and contrast S. occidentalis with the classic
North American ring species, Ensatina eschscholtzii. Contrary to
expectations of lower genetic diversity at northern latitudes following
post-Quaternary-glaciation expansion, the ephemeral nature of divergence
in S. occidentalis has produced centers of high genetic diversity for
different reasons in the south (long-term stability) versus the north
(secondary contact).