Refugial isolation and divergence in the Narrowheaded Gartersnake species complex (Thamnophis rufipunctatus) as revealed by multilocus DNA sequence data

Molecular Ecology
By: , and 

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Abstract

Glacial–interglacial cycles of the Pleistocene are hypothesized as one of the foremost contributors to biological diversification. This is especially true for cold-adapted montane species, where range shifts have had a pronounced effect on population-level divergence. Gartersnakes of the Thamnophis rufipunctatus species complex are restricted to cold headwater streams in the highlands of the Sierra Madre Occidental and southwestern USA. We used coalescent and multilocus phylogenetic approaches to test whether genetic diversification of this montane-restricted species complex is consistent with two prevailing models of range fluctuation for species affected by Pleistocene climate changes. Our concatenated nuDNA and multilocus species analyses recovered evidence for the persistence of multiple lineages that are restricted geographically, despite a mtDNA signature consistent with either more recent connectivity (and introgression) or recent expansion (and incomplete lineage sorting). Divergence times estimated using a relaxed molecular clock and fossil calibrations fall within the Late Pleistocene, and zero gene flow scenarios among current geographically isolated lineages could not be rejected. These results suggest that increased climate shifts in the Late Pleistocene have driven diversification and current range retraction patterns and that the differences between markers reflect the stochasticity of gene lineages (i.e. ancestral polymorphism) rather than gene flow and introgression. These results have important implications for the conservation of T. rufipunctatus (sensu novo), which is restricted to two drainage systems in the southwestern US and has undergone a recent and dramatic decline.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Refugial isolation and divergence in the Narrowheaded Gartersnake species complex (Thamnophis rufipunctatus) as revealed by multilocus DNA sequence data
Series title Molecular Ecology
Volume 20
Issue 18
Year Published 2011
Language English
Publisher Blackwell Publishing
Publisher location Malden, MA
Contributing office(s) Western Ecological Research Center
Description 23 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Molecular Ecology
First page 3856
Last page 3878
Country United States