Resource use in two contrasting habitat types raises different challenges for the conservation of the dryad butterfly Minois dryas

Abstract

The suitability of any location for a given species is determined by the available resources. However, there are many species that occur in more than one habitat type and their successful conservation may be particularly difficult. The dryad Minois dryas, a locally endangered butterfly, occurs in two contrasting habitats—xerothemic and wet grasslands. We investigated the influence of various habitat characteristics, such as vegetation height, grass cover, proximity of shrubs, plant species composition, Ellenberg indices of trophic and microclimatic conditions, on the microhabitat selection by the species. The nectaring of randomly selected butterflies was observed and habitat characteristics were compared at random points within the meadow and at the butterfly’s nectaring and resting places. The butterflies generally preferred to stay close to shrubs and avoided invasive goldenrods. Thermal conditions and the availability of nectar plants were the factors limiting the dryad’s use of wet grassland. In xerothermic habitats grass cover affected the distribution of butterflies. Concerning the availability of larval host plants, wet meadows proved potentially more favourable, whereas nectar resources for adults were more abundant in xerothermic grasslands. Based on our findings, conservation strategies for this butterfly must differ in the two habitats. Rotational mowing in xerothermic grasslands and the removal of invasive goldenrods in wet grasslands are the recommended actions. At a larger spatial scale, a habitat mosaic composed of xerothermic and wet grasslands in close proximity would seem to be the most suitable areas for the conservation of the dryad.