Winter-green host-plants, litter quantity and vegetation structure are key determinants of habitat quality for Coenonympha oedippus in Europe

The knowledge on species’ habitat preferences at local scales across its range is an essential condition for defining the most appropriate habitat management for the conservation of any species. In this study, we combined field observations from three European countries with breeding experiments under field conditions to identify oviposition and larval preferences of Coenonympha oedippus at the micro-scale level across contrasting habitat types (wet vs. dry). Despite the wide geographical range and the different habitats we found some common features: (1) vegetation structure of the herb layer is an essential factor for oviposition site electivity and successful development of premature stages; (2) high cover of litter and/or dwarf shrubs in the microhabitat (larval 45–70 %, oviposition 40–50 %) creates a herb layer rich in gaps; at their edges eggs are deposited and the caterpillars are adequately sun-exposed; (3) egg-laying females are not selective regarding oviposition substratum; (4) oviposition height is adjusted to positions with direct sunlight or warm substratum; (5) the host-plants coverage in oviposition sites was high: between 45 and 50 % in wet habitats, and between 18 and 41 % in dry habitats (depending on whether only plants observed as hosts in this study are counted, or whether all potential host species are included); (6) the most important host-plant is Carex panicea (wet) and Carex humilis (dry), but Molinia caerulea (wet) and Festuca rupicola (dry) are also used regularly; (7) the availability of winter-green host-plants in the vicinity of hibernated larvae plays a substantial role in their survival. As regular mowing or grazing would remove the litter and destroy the gaps, the management should be restricted to selective reed cutting or manual shrub removal. Only selective mowing during winter (December–February) can be recommended for keeping the habitat open where the reduction of bushes is not sufficient.