Genetic sampling of palmer's chipmunks in the Spring Mountains, Nevada

摘要

Palmer's chipmunk (Neotamias palmeri) is a medium-sized chipmunk whose range is limited to the higherelevation areas of the Spring Mountain Range, Nevada. A second chipmunk species, the Panamint chipmunk (Neotamias panamintinus), is more broadly distributed and lives in lower-elevation, primarily pinyon-juniper (Pinus monophylla-Juniperus osteosperma) habitat types. Panamint chipmunks are not closely related to Palmer's, but field identification of the 2 species is unreliable. Palmer's chipmunk is a species of concern in the state of Nevada and is listed by the International Union for Conservation of Nature (IUCN) as endangered. As such, conservation of Palmer's chipmunks is a priority in the Spring Mountains National Recreation Area. We sampled putative Palmer's chipmunks from 13 sites distributed across the Spring Mountains during 2010-2011. We removed Panamint chipmunks by using DNA-based identifications and then analyzed the genetic population structure of Palmer's chipmunks by using a panel of 9 microsatellites. Of the 228 samples that were genotyped, 186 were Palmer's; there was no evidence of hybridization between species. Four sites had exclusively Panamint chipmunks, 5 had exclusively Palmer's chipmunks, and 3 had a mixture of the 2 species. In this study, Palmer's chipmunks were exclusively captured at sites above 2400 m elevation, and Panamint chipmunks were exclusively captured at sites below 2200 m. Panamint chipmunks were trapped in areas typed as pinyon-juniper, but they were also trapped at sites typed as ponderosa pine (Pinus ponderosa) and mixed conifer. Both species were trapped at 3 sites; at all 3 sites, the lowerelevation traps contained Panamint chipmunks and the higher ones Palmer's chipmunks. Population structure within Palmer's chipmunks was minimal: heterozygosity was relatively high, and the populations displayed no signs of recent bottlenecks. Indications are that the distribution of Palmer's chipmunk is limited to higher-elevation areas in the Spring Mountains, but within this area, Palmer's chipmunk occurs as a single, large, well-connected, and stable population.