Genetic variation and fine-scale population structure in American pikas across a human-modified landscape

Abstract

Natural resource extraction can represent a major human modification to the landscape. Habitat reclamation is becoming an increasingly important strategy for abating the loss of biodiversity associated with these developments; however, the demographic and genetic consequences of colonizing artificial habitat remain unknown in many species. Here, we investigated the genetic consequences of landscape modifications for the American pika (Ochotona princeps) relative to two major developments in British Columbia, Canada: a large open-pit copper mine (Highland Valley Copper) under partial reclamation and a bisecting major highway (97C). We assessed microsatellite genotypic data for 109 individuals across 15 sites located either within the mine on artificial habitat or on adjacent natural habitat both north and south of the highway. There were no significant differences in levels of heterozygosity, allelic richness or inbreeding between natural (n = 7) and artificial sites (n = 8). However, pikas residing on artificial habitat exhibited significantly higher relatedness estimates. Bayesian clustering analyses revealed two distinct genetic units corresponding to north and south of the highway, with further substructure detected in the south. Likewise, high genetic friction was detected in the central region of the area, largely corresponding to the highway and modified landscape associated with the mine. At a finer scale, pairwise estimates of differentiation and migration rates suggest little gene flow may be occurring among sites across the sampling area, with some evidence for directional migration from artificial to natural sites. Overall, artificial habitat has been successful in promoting occupancy for American pikas, however, barriers to gene flow likely associated with resource extraction and road construction limit connectivity across the landscape.