Demographic history and incomplete lineage sorting obscure population genetic structure of the Texas mouse (Peromyscus attwateri)

The Texas mouse, Peromyscus attwateri, is a relatively habitat-specific species that exhibits a discontinuous distribution across the south-central United States To examine the evolutionary history and contemporary population genetic structure of P attwateri we sequenced an 1,100-base pair fragment of the mitochondrial cytochrome b gene for 210 individuals from 22 localities, resulting in 89 unique haplotypes. Low nucleotide diversity (pi = 0 0043) and a median-joining haplotype network indicated low levels of divergence among haplotypes with little geographic structure. Demographic analyses indicated the presence of 2 significant range expansions: the 1st coinciding with the end of the last glacial maximum of the Pleistocene approximately 14 thousand years ago (kya) and the 2nd more recent expansion during the hypsithermal (9-5 kya) of the Holocene Coalescent simulations under a model of no gene flow Indicated that the lack of divergence among populations most likely is attributable to incomplete lineage sorting, and the observed gene flow statistic = 1 16) suggests that populations became isolated approximately 7.5 kya This finding substantiates the hypothesis that the thermal maximum of the hypsithermal may have had a significant impact on small mammals as well as other organisms in the south-central United States DOI 10 1644/09-MAMM-A-242.1