Many landscapes do not suffer wholesale habitat destruction but exhibit degradation through management. In this study, we used landscape genetics to investigate the population structure and landscape connectivity for yellowbelly racers (Coluber constrictor) in the tallgrass prairie. The goal was to identify how land management (grazing/burning) alters the habitat and influences the genetic structure of a snake population. Our first aim was to elucidate the genetic structure using 14 microsatellite markers on 84 individual snakes. Our second aim was to define species-specific landscape connectivity in the tallgrass prairie.
Results/Conclusions
We hypothesized that the racer population in a landscape of contiguous grassland was not one large randomly breeding population (panmictic), but instead exhibits genetic structure correlated with the presence of woody cover and other landscape features. Using radio-tracking data of 12 snakes we were able to show that the use of habitats differed significantly from random for C. constrictor with shrubby areas more preferred than grassland devoid of shrubs (t = -2.67, P = 0.004). Through radio-tracking data we found an average daily movement of 68 m and the average summer homerange of 6.4 ha for females and 21.6 ha for males. The furthest distance traveled by both sexes was 1.5 km which was to their winter hibernaculum. We overlaid the genetic landscape on a remotely sensed image in a geographic information system to visualize congruence between population clusters and landscape features such as woody cover. We correlated population structure to landscape heterogeneity using isolation by distance to define functional connectivity and to identify important corridors and barriers. We used Mantel tests to compare the correlation between the pair-wise genetic matrix (ar) and the geographical matrices to test for the impact of landscape on gene flow. As evidenced from radio-tracking data, racers move through areas of greater habitat structure (shrubs and gallery forest), and thus we hypothesized that genetic structure of snakes would be related to these features.
