A carnivores’ oasis? An isolated fisher (Pekania pennanti) population provides insight on persistence of a metapopulation

Abstract

Landscape level species assessments are rarely available to inform conservation planning. Recent advances in multi-taxa survey techniques, however, have made them more obtainable by improving efficiency of collecting species occurrence data and genetic samples. Here, we used a multi-taxa survey technique to provide a landscape level portrait of fisher (Pekania pennanti) population status in a portion of the northern Rockies where the species’ history has been heavily influenced by humans. From 2010 to 2014 we deployed 497 winter forest carnivore bait stations across a 23,000\xa0km2 study area centered on northern Idaho, United States. The stations collected remote camera images and hair samples for DNA analysis. We used 12 microsatellite loci to identify 58 individual fisher in the study area. We identified two fisher populations for which we estimated effective population size (Ne) and genetic neighborhood size (NS). We calculated local genetic diversity measures [observed (Ho) and expected (He) heterozygosity, allelic richness (Ar), fixation index (FST), and number of migrants per generation (Nm)] and mapped continuous gradients of genetic diversity [Ar and inbreeding coefficient (FIS)] across the study area. We identified a fisher population in the West Cabinet Mountains [Ne of 26 (15.3–55.5), NS of 50–60] which is effectively isolated from the small population we detected in the Saint Joe/Coeur d’Alene Mountains [Ne of 6.5 (2.7–15), NS of 10–25]. We determined fisher have been effectively extirpated from the Selkirk and Purcell mountains and the lack of genetic connectivity between the two small remaining populations casts doubt on long term viability. Our study suggests northern Rockies fisher populations are vulnerable to landscape barriers and successful recovery will depend on future management and augmentation. We recommend these factors be considered when determining how, and if, species recovery should proceed.