Genetic structure of regional water vole populations and footprints of reintroductions: a case study from Southeast England

An important consideration when implementing species management is preserving genetic variation, which is fundamental to the long-term persistence of populations and adaptive potential of the species. The European water vole Arvicola amphibius is of high conservation importance in the United Kingdom due to its documented decline in both distribution and abundance. Conservation strategies for this species include protecting source populations, increasing habitat availability and connectivity, non-native predator control and reintroduction. We used mtDNA control region sequences and eight microsatellite markers from samples collected from 12 localities in southeast England, to determine how genetic variation is structured amongst regional water vole populations and to what extent population structure has been influenced by reintroductions. We found high haplotype diversity (h) across native populations in the southeast region and evidence that divergent lineages had been introduced to the region. We detected significant structure between watersheds with mtDNA from native populations and evidence of finer scale structure between populations within watersheds with both mtDNA and microsatellites. We suggest that management strategies should aim to conserve genetic diversity at a population level and that watersheds are a practicable unit for prioritising management within regions. We propose that introductions to restore or augment water voles within watersheds should consider the genetic composition of regional populations and highlight that genetic data has an important role in guiding future conservation options that secure adaptive potential in the face of future environmental change.