| Roads can cause loss of genetic diversity in wildlife populations, but the genetic effects of roads are not well understood in continuously distributed populations in landscapes that limit movement. I used simulations and empirical studies to evaluate the impacts of roads on genetic diversity at the level of both populations and neighborhoods in wildlife populations that are continuously distributed across landscapes.;Using individual-based spatially explicit simulations, I assessed the effect of roads on genetic diversity. I varied landscape types, road avoidance rates, and roadkill rates independently. I found that resistant landscapes and roads reduce genetic diversity, but that roadkill has no greater effect than road avoidance on genetic diversity, and roadkill may be less influential than road avoidance. Moreover, I found that roads and landscapes limited genetic diversity at the neighborhood level more than at the population level.;I studied the impacts of roads on microsatellite genetic variation in two populations of desert kangaroo rat and one population of Merriam's kangaroo rat from Arizona. I found that roads cause no detectible decrease in genetic diversity in habitat near roads, and I also found minimal evidence for genetic differentiation due to roads. This suggests that roads have not had detectible effects on genetic diversity in these populations.;I also analyzed datasets of larger, more widespread populations of alpine newts and roe deer that were divided by major roads and rail lines. I found that neighborhood genetic diversity in alpine newts decreases in proximity to a road, but not relative to a rail line. However, in roe deer I found no pattern of decreasing neighborhood genetic diversity. I also found that alpine newts and roe deer both have minute but similar levels of genetic differentiation relative to road and rail lines.;In sum, I found that roads can decrease neighborhood genetic diversity in alpine newts and potentially other species, but that factors such as dispersal ability, time since establishment of the road, and road characteristics may prevent the development of these patterns. |
