Landscape influences on dispersal of white-tailed deer and attendant risk of chronic wasting disease spread as assessed by a landscape genetics approach

摘要

Understanding factors that influence the spread of wildlife diseases is crucial for designing effective surveillance programs and appropriate management strategies. The potential introduction of chronic wasting disease (CWD) to Iowa is of significant management concern because it is found in free-ranging white-tailed deer (Odocoileus virginianus) populations in several bordering states, including Wisconsin. To address this concern, I used a landscape genetics approach to characterize deer population genetic structure and its correlation with landscape features relevant to deer dispersal. I used female deer, the traditionally philopatric sex, because they are expected to show a stronger signal of local genetic structure than males. In the first part of the study, I used both biparentally-inherited microsatellite markers and maternally-inherited mitochondrial DNA (mtDNA) sequence to characterize genetic connectivity between white-tailed deer populations in Iowa and Wisconsin separated by the Mississippi River. Clustering analyses indicated that deer across the study area represented a single population. There was no significant genetic isolation by distance at the level of a county, but there was a significant pattern at the individual level out to 29 km, indicating that genetic structure exists primarily at a fine spatial scale. I found indirect evidence of significantly higher male than female dispersal across the Mississippi River. In the second part of the study, I used mtDNA to characterize population genetic structure of female white-tailed deer in the agriculturally-dominated landscape of northeastern Iowa where only 15% of the habitat is forested. Although female deer in the region were found to be a single population, there was evidence of isolation by distance at both the county level and out to 19 km at the individual level. However, spatial genetic structure did not significantly correlate with the absolute percentage of forest cover separating individuals. The permeability of the Mississippi River to deer dispersal and the minimal spatial genetic structure that indicates dispersal rates and distances are fairly large suggest that there is considerable potential for CWD spread to Iowa and then within the state.