Landscape drivers of butterfly and burnet moth diversity in lowland rural areas
Déterminants paysagers de la diversité des papillons de jour et des zygènes dans les zones rurales de plaine
Résumé
Context Butterflies have been continuously declining for several decades in Europe due to many factors, such as farming intensification. Rural landscapes have undergone dramatic changes leading to homogenized landscapes. Objectives In this study, we investigated how landscape composition, structure and connectivity impact butterfly communities according to their ecological and biological traits. Methods We made use of 5669 Lepidoptera surveys performed at 4525 distinct locations in lowland Central France. We considered 19 ecological groups based on habitat specialization, mobility, diet, voltinism or overwintering strategy. Generalized linear mixed-effect models were used to relate the species richness of these groups to landscape variables defined in circular zones with radius from 250 m to 5 km. Results Richness of most species groups co-varied with landscape variables, with the exception of mobile, imago-overwintering, monophagous and polyphagous species. Habitat proportion explained more variation in butterfly diversity than habitat connectivity or habitat diversity. Moreover, the best proportion models were generally found for the 250-m circular zones. Thirteen species groups were disfavored by cropland amount. Except for forest specialists and high mobility group, no other group was more diverse in landscapes dominated by a single land cover type. Rather, for total diversity and 14 groups, species richness peaked for forest proportions varying between 40 and 80%, and for total diversity and nine groups for grassland proportions ranging from 30 to 60%. Conclusions These results indicate that landscape homogenization is contributing to the ongoing decline in butterflies, and support preserving and (re)creating mosaics of grasslands and forests.