Successful translocation of the threatened Clouded Apollo butterfly (Parnassius mnemosyne) and metapopulation establishment in southern Finland

Abstract

Translocations have been advocated as a conservation tool helping species adapt to climate and land-use change, but well-documented examples of invertebrates’ translocations are rare. The paper describes a successful translocation of the threatened Clouded Apollo butterfly (Parnassius mnemosyne) in Finland, compares this to a specific failed translocation, and presents conclusions for conservation planning as to factors contributing to the success. Two apparent key characteristics of the successful translocation were greater abundance of larval resources and less open landscape. The successful site was surrounded by forest, which strongly restricted emigration, crucially supporting the survival of the small initial population. Based on 20 mated females’ translocation in 2000, the local population increased slowly, reaching 600 butterflies in 2011. A large translocation patch together with host-plant abundance enabled successful establishment of the local population. Availability of other suitable grassland patches sufficiently nearby was an additional key characteristic, facilitating the Clouded Apollo’s expansion. However, the expansion rate was low; it took seven years for the butterflies to colonise the five nearest patches, only 10–200m from the translocation patch. By 2013, they had colonised all suitable semi-natural grassland patches within 2km from the translocation site and established a seemingly viable metapopulation with 11 subpopulations. The results point to the significance of local habitat area and landscape quality, along with conditions restricting emigration, in determination of suitable translocation sites.