From metapopulation theory to conservation recommendations: Lessons from spatial occurrence and abundance patterns of Maculinea butterflies

Abstract

Classic metapopulation theory assumes relatively frequent population extinctions and colonisations on local habitat patches and consequently its interest is focused on spatial presence–absence patterns rather than on local population densities and their dynamics. However, the latter may also be important for metapopulation functioning, especially in the case of low turnover of local populations. We investigated spatial occurrence and abundance patterns of three species of endangered Maculinea butterflies in the Kraków region, southern Poland, in relation to various habitat parameters. For all three species investigated we found almost complete occupancy of their foodplant patches. The few patches lacking Maculinea populations were significantly smaller and more isolated. Foodplant availability proved to be the main factor limiting population densities for M. alcon, but not for M. teleius and M. nausithous, for which patch size and shape mattered the most. Small and highly internally fragmented patches supported higher densities of these two species. We hypothesise that the negative density–area relationship as well as positive impact of patch fragmentation on butterfly densities derive from differences in relative abundance of Myrmica ant hosts, which are a vital resource for myrmecophilous Maculinea butterflies. Since ants are under strong parasite pressure from Maculinea within their foodplant patches, and spread mainly through nest budding from surrounding refuge areas, their densities can be expected to be higher on small and fragmented patches. This underlines the importance of not only foodplant patches, but also their surroundings for the conservation of Maculinea butterflies.