Sampling affects the detection of genetic subdivision and conservation implications for fisher in the Sierra Nevada

The small population of fisher (Pekania pennanti) in the southern Sierra Nevada is completely geographically and genetically isolated putting it at increased risk of extinction. Previous research using a clustered sampling scheme found a high amount of genetic subdivision within the southern Sierra Nevada population hypothesized to be caused by the Kings River Canyon. In this study, we use a larger and more geographically continuous set of genetic samples (n = 127) than was previously available to test this hypothesis and evaluate the genetic structure of the population. Both spatial and non-spatial population assignment models found three primary genetic clusters with moderate divergence between the clusters (F-ST = 0.05-0.13) at 10 microsatellite loci. These clusters appear to be associated with areas around the Kings River and Mountain Home State Demonstration Forest. One model also detected additional fine scale subdivision north of the Kings River that may be evidence of founder effects from a recent population expansion. The amount of population subdivision detected in this study is lower than previously found and indicates that while certain landscape features may reduce gene flow, these landscape features may be less of a barrier than initially thought. In the previous work, samples were collected in clusters which can inflate estimates of population structure by increasing the likelihood of oversampling related individuals. This study demonstrates how clustered sampling from a continuously distributed population can affect the assessment of population subdivision and influence conservation implications.