Gene flow and the restoration of genetic diversity in a fluctuating collared pika (Ochotona collaris) population

Abstract

Changes in the density of small mammal populations can alter their genetic diversity and structure over time. Repeated density declines may gradually erode a population’s genetic variability, and ultimately undermine its long-term viability. We investigated changes in the genetic diversity and structure of a fluctuating collared pika (Lagomorpha: Ochotona collaris) population over 12 years. There are concerns that the long-term persistence of the collared pika is at risk due to climate change, as pika populations are sensitive to environmental variability and inhabit a region undergoing particularly rapid warming. The study population declined abruptly during 2000 and 2003; however, it subsequently recovered and failed to show any genetic signature of having undergone a bottleneck. There was also no evidence for widespread inbreeding before or after the population declines. Using a spatial autocorrelation analysis, we also documented positive fine-scale genetic structure (<250 m) in the population during 7 out of the 12 years examined. Although the genetic structure is consistent with low average dispersal distances, a GeneClass2 analysis indicated that the collared pika population received immigrants from other populations, some of which survived and bred. Thus, like many other fluctuating small mammal populations, the collared pika population studied here appears to be resilient to density fluctuations. Dispersal distances were adequate for allowing gene flow into the study population and preventing declines in genetic variability.