Landscape barriers influence genetic connectivity among white-tailed deer in an area affected by chronic wasting disease

Chronic wasting disease (CWD) is a fatal transmissible spongiform encephalopathy, which can affect white-tailed deer (Odocoileus virginianus). Transmission of CWD is facilitated by proximal contact between infected and... [ view full abstract ]

Chronic wasting disease (CWD) is a fatal transmissible spongiform encephalopathy, which can affect white-tailed deer (Odocoileus virginianus). Transmission of CWD is facilitated by proximal contact between infected and susceptible individuals; therefore, movement of infected individuals, both within and among populations, may be important in driving the geographic spread of CWD. Previous studies suggest that linear landscape elements, such as roads, rivers, and ridges, influence demographic dispersal in eastern white-tailed deer populations. Identifying landscape characteristics that direct or impede deer movement may help predict CWD transmission dynamics. In this study, we assess the effects of potential dispersal barriers on patterns of white-tailed deer genetic population connectivity using nine microsatellite markers. Tissue samples (N=957) were collected from three physiographic provinces in central Pennsylvania and Maryland where CWD has been observed within both captive and free-ranging populations. Patterns of genetic connectivity were assessed at three hierarchical spatial scales: (1) among physiographic provinces, (2) among sampling units within physiographic provinces, and (3) among individuals within sampling units. A hierarchical clustering analysis suggests that at broad scales, geographic boundaries reduce gene flow among deer populations. Network analyses revealed areas of higher inter-individual and inter-population genetic differentiation around major roads, urban centers, large lakes, and ridges, which suggests that these features reduce gene flow. These barriers, however, seem relatively permeable, as evidenced by low pairwise FST values among all sampling localities (FST < 0.05). Our results suggest that linear landscape elements do influence patterns of white-tailed deer gene flow, and subsequently effective dispersal events, at multiple spatial scales. In future studies, modeling gene flow as a function of both barriers and landscape matrix resistance may improve the ability of genetic connectivity surfaces to predict disease transmission dynamics, especially for highly mobile species such as white-tailed deer.