Host plant and habitat preference of the endangered Euphydryas maturna (Lepidoptera: Nymphalidae): evidence from northern Europe

1. The aim of the present study was to evaluate host plant and habitat preferences in the Estonian populations of Euphydryas maturna, a regionally polyphagous but often locally specialised butterfly endangered in most parts of its European range. 2. Laboratory trials suggested that Fraxinus excelsior, Viburnum opulus and Melampyrum pratense are plants recognised by ovipositing females as potential hosts. These plants also supported development of the larvae, with the poorest growth performance on M. pratense. 3. Both a transect count‐based habitat occupancy analysis and a country‐wide landscape occupancy analysis revealed the abundance of F. excelsior as the primary determinant of the occurrence of E. maturna. In contrast, the occurrence of E. maturna was not associated with habitats colonised by M. pratense. 4. The results suggest that European ash, F. excelsior, is the main, if not the only, host plant of E. maturna in Estonia. The use of V. opulus cannot be excluded, although, due the relative scarcity of this plant, an important role for it as a determinant of the distribution of E. maturna is unlikely. Melampyrum pratense is not likely an alternative host of E. maturna in Estonia, which contrasts with the situation in neighbouring Finland. 5. This study adds to the evidence of geographical differences in host specialisation in melitaeine butterflies. The results imply that conservation actions should focus on securing the favourable status of the locally used host plant; the populations of F. excelsior are currently threatened by a fungal disease, ash dieback.