Genetic structure in the Anaxyrus boreas species group (anura, Bufonidae): an evaluation of the Southern Rocky Mountain population

The Anaxyrus boreas species group is comprised of four species endemic to the western United States: A. boreas, A. canorus, A. exsul, and A. nelsoni. Disjunct populations of the widespread western toad Anaxyrus boreas from Colorado and southern Wyoming, the southern rocky mountain population (SRMP), were previously candidates for listing under the United States Endangered Species Act (ESA) as a distinct population segment (DPS), but were removed due to a lack of significant genetic differentiation in preliminary studies. The purpose of this study was to conduct phylogeographic and population genetic analyses of A. boreas and three related species using mitochondrial DNA sequence data and nuclear microsatellite genotype data. The study is specifically focused on testing the evolutionary significance of the SRMP.