Integrating individual behaviour and landscape genetics: the population structure of timber rattlesnake hibernacula

Abstract

Individuals of many species show high levels of fidelity to natal populations, often due to reliance on patchily distributed habitat features. In many of these species, the negative impacts of inbreeding are mitigated through specialized behaviours such as seasonal mating dispersal. Quantifying population structure for species with these characteristics can potentially elucidate social and environmental factors that interact to affect mating behaviour and population connectivity. In the northern part of their range, timber rattlesnakes are communal hibernators with high natal philopatry. Individuals generally recruit to the same hibernaculum as their mother and remain faithful to that hibernaculum throughout their lives. We examined the genetic structure of Crotalus horridus hibernacula in the northeastern USA using microsatellite loci. Sampled hibernacula exhibited only modest levels of differentiation, indicating a significant level of gene flow among them. We found no significant correlation between genetic differentiation and geographical distance, but did find significant positive correlation between genetic differentiation and a cost-based distance metric adjusted to include the amount of potential basking habitat between hibernacula. Therefore, thermoregulation sites may increase gene flow by increasing the potential for contact among individuals from different populations. Parentage analyses confirmed high levels of philopatry of both sexes to their maternal hibernaculum; however, approximately one-third of paternity assignments involved individuals between hibernacula, confirming that gene flow among hibernacula occurs largely through seasonal male mating dispersal. Our results underscore the importance of integrating individual-level behaviours and landscape features with studies of fine-scale population genetics in species with high fidelity to patchily distributed habitats.

Fine-scale population genetic structure and sex-biased dispersal in the smooth snake (Coronella austriaca) in southern England

“…To date only four published studies have used genetic data to investigate sex-biased dispersal in snakes, all of which have found a male-bias (Rivera et al, 2006;Keogh et al, 2007;Clark et al, 2008;Dubey et al, 2008). Malebiased dispersal in mammalian species has been attributed to a female-defence polygyny mating system (Greenwood, 1980), and while polygyny has been regarded as typical for snakes (Duvall et al, 1993), more Smooth snake molecular ecology AP Pernetta et al recent research suggests that this may not always be the case (Rivas and Burghardt, 2005).…”

Landscape features influence gene flow as measured by cost-distance and genetic analyses: a case study for giant pandas in the Daxiangling and Xiaoxiangling Mountains

“…For example, the mobility of forest species is favored by wooded landscapes, and correlation coefficients between dispersal data and the LCD measures were slightly stronger than with Euclidean distance measures (see, for example, roe deer, [16]; martens, [17]; mountain vizcacha, [7]). A previous study [19] found a significant positive correlation between genetic differentiation and a cost-based distance metric adjusted to include the quantity of potential basking habitat between hibernacula.…”

“…However, most animals live in heterogeneous habitats, and individual movement is greatly influenced by landscape elements [14,15] that introduce bias into results based on a EUD measure. The least-cost path distance (LCD), which defines a measure of landscape connectivity, was, therefore, introduced as a more suitable means for assessing the inferred effects of landscape structure on gene flow [16-19]. The least-cost path avoids landscape regions that are more resistant to movement and prefers paths through permeable features.…”

“…Models of functional connectivity, created using cost distance analysis, can be tested by analyzing highly variable genetic markers to determine potential movement and dispersal throughout a landscape [16,19,23,24]. Estimates of cost distances are based on major features that influence individual movement or dispersal (such as the distribution of wooded habitat for roe deer [16], basking habitat for timber rattlesnake hibernacula [19]) or a landscape resistance model [25]. Factors such as topographic (altitude, gradient, and slope) or anthropogenic factors (road construction, human residence) may also influence the movement or dispersal of individuals.…”

“…Factors such as topographic (altitude, gradient, and slope) or anthropogenic factors (road construction, human residence) may also influence the movement or dispersal of individuals. Animal movement is modeled as a trade-off that mitigates many factors [19,26] and reflects the process of habitat selection.…”