Scale-dependent resource use in the Euphydryas aurinia complex

Butterflies of the European Euphydryas aurinia complex include a series of taxa, showing morphological and eco-ethological differences. All of them are threatened by changes in land use affecting both the structural and functional connectivity of habitat patches, as well as habitat quality. In this framework, we analysed the use of resources by two of the three taxa occurring in Italy, E. (a.) glaciegenita (Alpine) and E. (a.) provincialis (Mediterranean), at ‘landscape’, ‘patch’ and ‘microhabitat’ scale. We collected data on spatial distribution of adults by Mark-Release-Recapture to understand which parameters affect adult distributions at landscape scale and to test the degree of adult aggregation at patch scale. We sampled first instar larvae within fixed plots and compared the microhabitat characteristics of occupied vs. unoccupied host plants. We found that both populations were affected by management at landscape scale, with contrasting patterns depending on both sites and sex. The food plants were not a limiting factor for adult distribution, probably because they were abundant in the study areas. Within patches, males of E. (a.) glaciegenita showed aggregate distributions in comparison to those of E. (a.) provincialis, suggesting the existence of a “lek strategy”. At microhabitat scale, we observed that females carefully chose their egg-laying sites according to host plant density and microclimatic cues, even though selection was driven by distinct factors in the two populations. Understanding the ecological requirements of all life stages is essential to develop appropriate conservation strategies to preserve butterflies of the E. aurinia complex in Italy.