Population ecology and conservation genetics of the smooth snake (Coronella austriaca) in a fragmented heath landscape

Abstract

Coronella austriaca is the United Kingdom’s rarest snake, being confined to the lowland heathlands of Dorset, Hampshire and Surrey. As a result, it remains the least understood; despite being listed as a key biodiversity action plan species. Substantial loss and fragmentation of its primary UK habitat - lowland heathland - has occurred in recent times, and yet research examining the population ecology and conservation genetics of this species remains limited. As a result, this PhD research was developed to fill this need. Based on three years of data collection, a combination of field studies, laboratory experiments, mathematical modelling and genetic analyses, were employed in an attempt to answer questions of relevance to the future conservation management of this species.
Modelling smooth snake occupancy of remnant heathland patches using an information-theoretic approach showed patch size and the percentage of grassland in surrounding matrix habitats to be the primary determinants of smooth snake presence. Field-based studies based on 27 arrays of artificial refugia showed the size of trees and prey abundance to be important in determining mean smooth snake capture rates at occupied sites.
Eight previously described microsatellite markers were used to complete the first assessments of the genetic population structure of C. austriaca at two spatial scales. Initial fine-scale analysis of structuring based on 11 sampling localities within a heathland/coniferous forest mosaic found significant population structuring as a result of isolation-by-distance effects, in addition to evidence of male-biased dispersal. At the wider scale, analysis of seven distinct populations across Dorset also found small but significant differences in genetic diversity. The observed patterns were not consistent with isolation-by-distance effects, nor was there any evidence of them being a result of habitat patch size or isolation. Phylogenetic analysis of the coarse-scale microsatellite data showed some evidence of population clustering based on their geographic locality in relation to the historical extent of Dorset’s heathland, suggesting they represent distinct management units.
The reproductive ecology of C. austriaca was also examined using a combination of field data and microsatellite analysis. In contrast to continental populations, there was no relationship between female body size and litter size. However, there was a negative relationship between relative clutch mass and female body size, suggesting that there may be a trade-off between female survival and reproductive output. Microsatellite based genotyping of neonates from 16 litters born in the laboratory provides the first evidence of multiple paternity occurring in C. austriaca.

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