The relevance of transition habitats for butterfly conservation

Abstract

Biodiversity is declining across the globe. Main drivers causing the vanishing of species are habitat destruction and the transformation of former heterogeneous landscapes into homogeneous and intensively used landscapes. Modern land management focuses on the creation of landscape configuration with sharp boundaries between ecosystems. In consequence, transition zones between two ecosystems such as between forest and open grassland are rare, as it counteracts the efficient and commercial use of space. However, there are many species relying on such transition zones between habitats, as the Clouded Apollo butterfly Parnassius mnemosyne. This highly endangered butterfly species occurs in light deciduous forests, interspersed with extensively used grasslands. In our study, we analysed habitat requirements of this butterfly species. We recorded larvae and feeding marks at its primary larval food plant, Corydalis cava, and assessed microhabitat characteristics, including microclimatic conditions. We captured high-resolution multispectral aerial imagery with an unmanned aerial vehicle. We subsequently combined ground-truthing data with information from high resolution aerial pictures to calculate habitat suitability models. We found that P. mnemosyne larvae mainly occur in the transition zone between deciduous light forest and extensively used grasslands with C. cava. Caterpillars of P. mnemosyne are particularly found around trees, basking on foliage and grass to rapidly reach high operation temperatures. Results from Species Distribution Models underline the relevance of transition zones between habitats for P. mnemosyne, and for biodiversity in general. The Clouded Apollo may serve as excellent indicator species for light deciduous forests, and as flagship to promote the conservation and restoration of transition zones between habitats in nature conservation.