Comparison of historic and contemporary population genetics can provide insights into the nature of population expansions or contractions, and temporal changes in abundance, genetic diversity, or population connectivity. This study is evaluating the change in the distribution and abundance of fisher (Martes pennanti) in California through time using both historic and contemporary genetic material. Fisher populations in California are thought to have declined precipitously over the last 150 years and currently only two populations remain in the state that are both geographically and genetically isolated (one in Northwestern California and one in the Southern Sierra Nevada). Our question is whether the isolation of these two populations is a result of a recent anthropogenically induced population decline or a more ancient demographic event. We analyzed DNA from 40 museum specimens dated from 1882-1920 and hair samples from 90 individuals collected from 2006-2008. We amplified mitochondrial DNA (mtDNA) at the control region and cytochrome b and analyzed nuclear DNA using 10 microsatellite loci.
Results/Conclusions
Mitochondrial DNA haplotypes were obtained for 35 of the 40 museum specimens and all 90 of the contemporary samples. We found three haplotypes in the Northwestern California fisher population, but only one different haplotype in the Southern Sierra Nevada. Microsatellite genotypes were obtained for 21 of the historical samples and 90 contemporary samples. We found significant temporal shifts in allele frequencies between historical and contemporary samples in both regions indicating large amounts of genetic drift likely due to small population size or population bottlenecks. We also found high levels of genetic structure, both spatially (between Northwestern California and the Southern Sierra Nevada) and temporally (between historic and contemporary samples). These high levels of population structure along with the haplotype differences between Northwestern California and the Southern Sierra Nevada suggest long standing genetic isolation between the two regions.