Grassland type and presence of management shape butterfly functional diversity in agricultural and forested landscapes

Abstract

Alteration of agricultural land use has led to a widespread loss of biodiversity in human-dominated landscapes. Degradation and gradual disappearance of natural and semi-natural habitats has become a global conservation problem. Together, intensive agriculture and the abandonment of extensively farmed areas endanger the wildlife of European landscapes. Our study aims to explore the complex processes that affect butterfly functional diversity and functional community composition in low-productive and threatened grasslands. We examined the functional characteristics of butterfly communities in response to three factors: habitat type (calcareous grassland vs. orchard meadow), management (managed vs. abandoned), and landscape context (forested vs. agricultural landscape). We surveyed butterflies of 20 calcareous grasslands and 20 orchard meadows in Central Germany. Both habitats are characterised by high structural diversity and extensive cultivation. To test the effects of our investigated variables, we selected six functional traits (overwintering, voltinism, wing length, diet, flight period, territoriality) for each butterfly species, and assigned values to them based on the literature. For our statistical analyses, we used single trait and multi-trait approaches. Our results showed that habitat type had the strongest filtering effect on butterfly functional traits of the three design variables. Functional diversity indices, such as functional richness and divergence values, were higher in calcareous grasslands than in orchard meadows. We found that calcareous grasslands are characterised by butterflies having more specialist traits (e.g., fewer food plants, fewer generations), which are favoured by grassland management and the vicinity of forests. Therefore, to maintain the threatened butterfly fauna of calcareous grasslands, extensive management should focus on these grasslands in forested landscapes. • Extensive management maintains higher butterfly diversity. • Both orchard meadows and calcareous grasslands harbour a valuable butterfly fauna. • Habitat type had the strongest filtering effect on butterfly functional traits. • Orchard meadows are characterised by butterflies with more generalist traits. • Calcareous grasslands are characterised by butterflies with more specialist traits.