Assessing reintroduction schemes by comparing genetic diversity of reintroduced and source populations: A case study of the globally threatened large blue butterfly (Maculinea arion)

An important factor in reintroductions is the amount of genetic diversity captured in the introduced individuals. Introduced populations are initially small, and thus vulnerable to genetic drift and stochastic events. The level of genetic diversity maintained is important for the long-term persistence of populations and their evolutionary potential to react to, for example, climate changes. The national extinction of many butterfly species has been pronounced in many European countries. The globally Vulnerable large blue butterfly (Maculinea arion) went extinct in the UK in 1979 and was later reintroduced from Oland in Sweden. We investigated the genetic diversity of reintroduced large blues nineteen generations after translocation on five sites in the UK, and seven sites on Oland, including the source population. We found similar levels of genetic diversity in the reintroduced and source populations, but the UK and Swedish populations were genetically differentiated; we also found significant genetic differentiation among reintroduced UK populations only a few kilometres apart. The reintroduced populations had several private alleles not found in the source population in 2011, and thus may already represent a unique subset of genetic diversity of the north-western populations of M. arion. Our results show that the IUCN and other protocols followed in the 1990s for translocating and maintaining the maximum available genetic diversity during reintroductions were largely adequate for this species, and hence will be valuable for informing the growing use of reintroductions as a strategy for the conservation of endangered species of insect.