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The contemporary genetic structure of animal populations is sculpted by past events, including demographic bottlenecks and expansions and movement of animals by humans. In an analysis of microsatellite DNA of black bears (Ursus americanus; n = 540) across California, we discovered distinct population structure and genetic evidence of 2 historic colonization events. First, genotypes of bears sampled in southern California are most related to those from the Yosemite National Park region and not with spatially intervening populations. Historical records recount the translocation of 28 black bears from the Yosemite National Park area of the central Sierra Nevada to the San Bernardino Mountains in southern California in the 1930s. Second, before colonization of California by Europeans, the Central Coast region was inhabited by the now extinct California grizzly bear (Ursus arctos californiensis), but not black bears. Following an apparent competitive release and range expansion during the past century, black bears now inhabit the Central Coast region of California. Black bears in California's Central Coast display lower genetic diversity (founder effect) and a genetic signature most closely allied with black bears from the southern Sierra Nevada. In both these cases, molecular genetic techniques allowed historical reconstruction of anthropogenic events leading to changes in animal distributions. [ABSTRACT FROM AUTHOR]

Little is known about the relationship between animal movements and the emergent structure of populations, especially for species occupying large continuous distributions. Some such mammals disperse disproportionately into habitat similar to their natal habitat, a behavioural bias that might be expected to lead to habitat-conforming genetic structure. We hypothesized that coyotes (Canis latrans) would exhibit such natal-biased dispersal, and used 13 microsatellite loci to test, correspondingly, whether genetic structure conformed to major habitat breaks. First, we used a model-based approach to assign coyote genotypes to distinct genetic clusters irrespective of geographical location. Visualization on a geographical information system revealed a strong concordance between the locations of cluster assignments and habitat bioregions, not explainable in terms of physical dispersal barriers or intervening low-quality habitat. Next, we used a multiple Mantel test, which controlled for effects of geographical distance (itself, marginally significant; P = 0.06), to statistically determine that genetic distance was indeed higher between than within bioregions (P < 0.001). Whereas previously published examples of landscape effects on gene flow have typically been explainable in terms of species-wide habitat affinities or dispersal barriers, our finding that genetic subdivisions were associated with unobstructed boundaries between contiguous habitats suggests a role for intraspecific variability in habitat affinities as a factor underlying genetic structure. In addition, our data combined with previously published data suggest a pattern of genetic isolation-by-distance throughout western North America, consistent with independent evidence that the western half of the coyote range predates European settlement.