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Abstract
Pikas (Ochotona, Ochotonidae) are small, short-eared lagomorphs that inhabit steppes and mountains in northern and central Asia and alpine regions in western North America. I examined the dispersal patterns, genetic structure and mating system of a collared pika ( O. collaris) population from the southwest Yukon. Additionally, I reconstructed the phylogeny of the genus Ochotona using several mitochondrial genes.
Limited mark-recapture data suggests that juvenile collared pikas seldom disperse over 300 m from their natal dens, and that adults rarely travel off of an established territory. This behaviour could result in frequent inbreeding if individuals tend to mate with their nearest neighbours. However, because collared pikas are difficult to capture before they have dispersed, I decided to examine their dispersal behavior using indirect genetic methods. Pikas were captured within a four-square-kilometer study site from 1999 to 2008, and each pika caught (n=364) was genotyped at fifteen variable microsatellite loci. The data revealed very fine-scale genetic structuring in the population in all but two years, which is consistent with a pattern of limited dispersal. Parentage analyses also demonstrated that collared pikas disperse a mean of approximately 600 m from their natal dens and that they display no sex-biased dispersal. The population was able to maintain its genetic diversity despite undergoing a population bottleneck, likely due to receiving a small number of immigrants from other populations. The mating system of collared pikas was largely polygynandrous, as there was evidence that both males and females produced offspring with multiple partners. Collared pikas also appear to make breeding forays to mate with individuals up to one kilometer away, and this ensures that their genes disperse and settle farther than they do.
Phylogenetic analyses were conducted using two data sets: one that contained cytB and ND4 sequences from 49 Ochotona specimens and another that contained six mitochondrial genes from nine Ochotona species. Maximum-likelihood and maximum-parsimony analyses both recovered three main clades within Ochotona: one of steppe-dwelling pikas primarily from the Qinghai-Tibet Plateau, one of pikas from mountainous regions surrounding the Qinghai-Tibet Plateau, and one of alpine-dwelling pikas from northern Asia and North America.
