A Rapid, Strong, and Convergent Genetic Response to Urban Habitat Fragmentation in Four Divergent and Widespread Vertebrates

Urbanization is a major cause of habitat fragmentation worldwide. Ecological and conservation theory predicts many potential impacts of habitat fragmentation on natural populations, including genetic impacts. Habitat fragmentation by urbanization causes populations of animals and plants to be isolated in patches of suitable habitat that are surrounded by non-native vegetation or severely altered vegetation, asphalt, concrete, and human structures. This can lead to genetic divergence between patches and in turn to decreased genetic diversity within patches through genetic drift and inbreeding.We examined population genetic patterns using microsatellites in four common vertebrate species, three lizards and one bird, in highly fragmented urban southern California. Despite significant phylogenetic, ecological, and mobility differences between these species, all four showed similar and significant reductions in gene flow over relatively short geographic and temporal scales. For all four species, the greatest genetic divergence was found where development was oldest and most intensive. All four animals also showed significant reduction in gene flow associated with intervening roads and freeways, the degree of patch isolation, and the time since isolation.Despite wide acceptance of the idea in principle, evidence of significant population genetic changes associated with fragmentation at small spatial and temporal scales has been rare, even in smaller terrestrial vertebrates, and especially for birds. Given the striking pattern of similar and rapid effects across four common and widespread species, including a volant bird, intense urbanization may represent the most severe form of fragmentation, with minimal effective movement through the urban matrix

Fine-scale effects of habitat loss and fragmentation despite large-scale gene flow for some regionally declining woodland bird species

Habitat loss and associated fragmentation effects are well-recognised threats to biodiversity. Loss of functional connectivity (mobility, gene flow and demographic continuity) could result in population decline in altered habitat, because smaller, isolated populations are more vulnerable to extinction. We tested whether substantial habitat reduction plus fragmentation is associated with reduced gene flow in three \u27decliner\u27 woodland-dependent bird species (eastern yellow robin, weebill and spotted pardalote) identified in earlier work to have declined disproportionately in heavily fragmented landscapes in the Box-Ironbark forest region in north-central Victoria, Australia. For these three decliners, and one \u27tolerant\u27 species (striated pardalote), we compared patterns of genetic diversity, relatedness, effective population size, sex-ratios and genic (allele frequency) differentiation among landscapes of different total tree cover, identified population subdivision at the regional scale, and explored fine-scale genotypic (individual-based genetic signature) structure. Unexpectedly high genetic connectivity across the study region was detected for \u27decliner\u27 and \u27tolerant\u27 species. Power analysis simulations suggest that moderate reductions in gene flow should have been detectable. However, there was evidence of local negative effects of reduced habitat extent and structural connectivity: slightly lower effective population sizes, lower genetic diversity, higher within-site relatedness and altered sex-ratios (for weebill and eastern yellow robin) in 10 x 10 km \u27landscapes\u27 with low vegetation cover. We conclude that reduced structural connectivity in the Box-Ironbark ecosystem may still allow sufficient gene flow to avoid the harmful effects of inbreeding in our study species. Although there may still be negative consequences of fragmentation for demographic connectivity, the high genetic connectivity of mobile bird species in this system suggests that reconnecting isolated habitat patches may be less important than increasing habitat extent and/or quality if these need to be traded off

Determining the subspecies composition of bean goose harvests in Finland using genetic methods

Management of harvested species is of great importance in order to maintain a sustainable population. Genetics is, however, largely neglected in management plans. Here, we analysed the genetics of the bean goose (Anser fabalis) in order to aid conservation actions for the commonly hunted but declining subspecies, the taiga bean goose (A. f. fabalis). We used mitochondrial DNA (mtDNA) and microsatellites to determine the subspecies composition of the Finnish bean goose harvest, as the hunting bag is thought to comprise two subspecies, the taiga bean goose and the tundra bean goose (A. f. rossicus). The latter subspecies has a more stable or even increasing population size. Other eastern subspecies (A. f. serrirostris, A. f. middendorffii) could additionally be part of the Finnish hunting bag. We estimated genetic diversity, genetic structure and sex-biased gene flow of the different subspecies. Most of the harvested bean geese belonged to the taiga bean goose, whereas most of the tundra bean goose harvest was found to be geographically restricted to southeastern Finland. The mtDNA data supported strong genetic structure, while microsatellites showed much weaker structuring. This is probably due to the extreme female philopatry of the species. The taiga bean goose had lowered genetic diversity compared to other subspecies, warranting management actions. We also detected A. f. serrirostris mtDNA haplotypes and evidence of interspecific hybridization with two other Anser species.201