Spatial genetic analysis of the grass snake, Natrix natrix (Squamata: Colubridae), in an intensively used agricultural landscape

Abstract

Both the conversion of natural habitats to farmland and efforts at increasing the yield of existing crops contribute to a decline in biodiversity. As a consequence of land conversion, specialised species are restricted to remnants of original habitat patches, which are frequently isolated. This may lead to a genetic differentiation of the subpopulations. We used seven microsatellite markers to examine the genetic population structure of the grass snake, Natrix natrix (Linnaeus, 1758), sampled in remnants of pristine habitat embedded in an intensively used agricultural landscape in north-western Switzerland. The study area, a former wetland, has been drained and gradually converted into an agricultural plain in the last century, reducing the pristine habitat to approximately 1% of the entire area. The grass snake feeds almost entirely on amphibians, and is therefore associated with wetlands. In Central Europe, the species shows severe decline, most probably as a result of wetland drainage and decrease of amphibian populations. We found no genetically distinct grass snake populations in the study area covering 90 km 2 . This implies that there is an exchange of individuals between small remnants of original habitat. Thus, gene flow may prevent any genetic differentiation of subpopulations distributed over a relatively large area. Our results show that a specialized snake species can persist in an intensively used agricultural landscape, provided that suitable habitat patches are interconnected.

Patterns of gene flow across multiple anthropogenic infrastructures: Insights from a multi-species approach

“…This snake species is considered to exhibit good dispersal abilities, with individuals travelling over more than 1 km in less than a month (Pettersson, 2014). A previous study did not detect any genetic structure in this species in a intensively used agricultural landscape, indeed suggesting good dispersal ability in fragmented environments (Meister et al, 2010). Maniola jurtina is an univoltine butterfly which is very common in Europe with locally very high densities.…”

Conservation genetics of the eastern yellow-bellied racer (Coluber constrictor flaviventris) and bullsnake (Pituophis catenifer sayi): River valleys are critical features for snakes at northern range limits

“…Some snake species can maintain gene flow even across large geographic distances (e.g. Natrix natrix ; [ 21 ]), but in these situations, corridors of suitable habitat are present to facilitate the movement of individuals between isolated patches. The isolation of racer and bullsnake populations in separate river valleys on the northern Great Plains suggests that there is little possibility of natural rescue dispersal from existing populations within Canada in the event of local extirpations.…”

“…Elaphe obsoleta obsoleta ; [ 18 ], Gloydius halys ; [ 19 ]). In addition, landscapes containing both suitable hibernacula and summer habitat for northern snakes (e.g., [ 20 ]) may be patchily distributed at range margins, a situation that is exacerbated by human activities that cause habitat loss and fragmentation [ 21 ]. Thus, gene flow may only occur among northern snake populations when individuals travel long distances away from dens to breed; however, successful dispersal may be uncommon, resulting in highly subdivided populations.…”

Thirty-five years of spatial autocorrelation analysis in population genetics: an essay in honour of Robert Sokal (1926-2012)

“…Finally, the relatively new field of landscape genetics (Manel et al ., ), based on an integration between landscape ecology and population genetics (Holderegger & Wagner, , ), is growing rapidly, with several recent applications (Meister et al ., ; Perez et al ., ). Based on this integrated framework, most of the analyses have been carried out on a landscape/regional geographic scale.…”