The influence of gene flow and landscape location on genetic variation in two threatened carnivores: The Canada lynx and San Joaquin kit fox

Genetic variation has been correlated with individual fitness and population growth rates. Population genetic theory predicts that the amount of genetic variation in a neutral region of a genome is primarily a function of effective population size. In theory, populations on the periphery of a species geographic range have small effective population sizes and fewer connections to other populations, leading to a reduction in genetic variation. However, the influence of location on the landscape on genetic variation has largely been ignored. I combine principles of landscape ecology and population genetics to determine the effect of location on the landscape on genetic variation in two threatened, mid-sized carnivores; the Canada lynx (Lynx canadensis) and the San Joaquin kit fox (Vulpes macrotis mutica). Both species are thought to be highly mobile although data describing interpopulation movements are largely unavailable.; Using microsatellite DNA, I estimated population subdivision and rates of gene flow between populations, for each species. Subsequently, I used a geographic information system (GIS) to build a coarse range map of each species' geographic range, and defined populations as core or peripheral based on an operational definition derived from the first principles of conservation biology. I then asked if location on the landscape is related to genetic variation in terms of mean number of alleles per locus, observed and expected heterozygosity.; Lynx showed low genetic substructure across their entire geographic range (F_st = 0.03) indicative of high levels of gene flow. A matrix of geographic distances between populations was not significantly correlated with a matrix of pairwise F_st estimates (isolation by distance model), despite populations being separated by over 3,100 km. However, I found a reduction in the mean number of alleles per population on the periphery of the range, suggesting that gene flow cannot fully mitigate the impact of being located on the periphery. Kit fox also displayed low genetic substructure (F_st = 0.04); yet pairwise F_st estimates compared to geographic distances suggested that they followed an isolation by distance model (z = 219.48 P = 0.02). Kit fox did not show reductions in genetic variation in peripheral populations as compared to core populations. In models with distance to the periphery, abundance, and effective population size, only effective population size could predict mean number of alleles per locus. Shape of the geographic range and the amount of human influence across each species' geographic range may explain why genetic variation is influenced by landscape location for Canada lynx, but not for kit fox.