Molecular phylogeography of common garter snakes (Thamnophis sirtalis) in western North America: implications for regional historical forces

Complete ND2 and partial ND4 and cytochrome b mitochondrial DNA (mtDNA) sequences were analysed to evaluate the phylogeographic patterns of common garter snakes (Thamnophis sirtalis) in western North America. This species is widely distributed throughout North America, and exhibits extensive phenoty...

Full description

Saved in:
Bibliographic Details
Published in:Molecular ecology 2002-09, Vol.11 (9), p.1739-1751
Main Authors: Janzen, Fredric J., Krenz, James G., Haselkorn, Tamara S., Brodie JR, Edmund D.
Format: Article
Language:English
Subjects:
Animals
Biological Evolution
Colubridae - anatomy & histology
Colubridae - classification
Colubridae - genetics
DNA, Mitochondrial - analysis
DNA, Mitochondrial - genetics
Ecosystem
Environment
Genetics, Population
Geography
Likelihood Functions
molecular phylogeography
North America
Phylogeny
snakes
subspecies
Thamnophis sirtalis
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Complete ND2 and partial ND4 and cytochrome b mitochondrial DNA (mtDNA) sequences were analysed to evaluate the phylogeographic patterns of common garter snakes (Thamnophis sirtalis) in western North America. This species is widely distributed throughout North America, and exhibits extensive phenotypic variation in the westernmost part of its range. The overall phylogeographic pattern based on mtDNA sequences is concordant with results from studies of other species in this region, implicating historical vicariant processes during the Pleistocene and indicating bottleneck effects of recent dispersal into postglacial habitat. Indeed, the topology is statistically consistent with the hypothesis of both southern (Great Basin and California) and northern (Haida Gwaii) refugia. Specifically, we identified genetic breaks among three major clades: Northwest Coastal populations, Intermountain populations, and all California populations. The California clade contained the only other well‐supported branching patterns detected; relationships among populations within the two northern clades were indistinguishable. These molecular splits contrast sharply with all prior geographical analyses of phenotypic variation in T. sirtalis in this region. Our results suggest that the extensive phenotypic variation in western T. sirtalis has been shaped more by local evolutionary forces than by shared common ancestry. Consequently, we consider all morphologically based subspecies designations of T. sirtalis in this region invalid because they do not reflect reciprocal monophyly of the mtDNA sequences.
ISSN:0962-1083
1365-294X
DOI:10.1046/j.1365-294X.2002.01571.x