Land use patterns skew sex ratios, decrease genetic diversity and trump the effects of recent climate change in an endangered turtle

AimChanges in both land use and climate can cause population declines and species extinctions, but the relative effects of these two stressors are often dependent on species-specific life histories. Turtles are highly threatened as a taxonomic group and are particularly sensitive to environmental change due to their life history, habitat preferences and physiology. We used both sex data and genetic diversity across a landscape-scale gradient in land use intensity and recent climate change to characterize the relative effects of these factors on three turtle species (including the endangered Blanding's turtle, Emydoidea blandingii) with different life histories and thus different vulnerabilities to environmental change. LocationWisconsin, USA. MethodsTurtles were captured and sampled for genetic analyses at 18 sites. Sampled individuals were genotyped for species-specific sets of microsatellite markers, and population-level genetic diversity was assessed using rarefied allelic richness and heterozygosity. The relative effects of road density, public land area and recent climate change on genetic diversity and sex ratio were evaluated using regression methods and model-selection criteria. ResultsIncreased land use intensity was associated with male-skewed sex ratios and decreased genetic diversity in E.blandingii but not co-occurring species. Recent climate change did not explain variability in either sex ratio or genetic diversity for any of the three species examined. Main conclusionsChanging land use has multiple impacts on turtle populations that are modulated by species-specific life history traits. Extensive terrestrial movements associated with nesting in E. blandingii increase female vulnerability to road mortality, which in turn has led to declines in genetic diversity. The predicted effects of recent climate change may have been dampened by behavioural plasticity. We suggest that the disproportionate effect of land use on E. blandingii warrants greater legal protection for this species.