Partitioning of arthropod species diversity in temperate meadows,wildflower areas and pastures

To counteract the rapidly ongoing species decline in modern agroecosystems, most European countries have developed and adopted agri-environment schemes. The efficiency of these schemes, however, ranges from successful to nearly ineffective. To estimate the efficiency of the Swiss agri-environment scheme in particular, we investigated the contribution of extensively managed pastures and meadows and wildflower areas to beetle, heteropteran bug and spider diversity. Extensively managed meadows were shown to contribute most to landscape-scale richness (highest species richness for beetles and bugs), followed by wildflower areas (bugs). Meadows harboured approximately twice as many beetle species unique to this habitat type than wildflower areas and pastures. Bug species unique to a specific habitat type were similar between meadows and wildflower areas, but much lower (approximately 30%) in pastures. To increase beetle species richness, extensively managed meadows should be represented more often in the landscape because meadows harboured the highest number of species and most uniquely found species. To increase species richness of true bugs, both meadows and wildflower areas should be represented more often in the landscape because they harboured more species and more uniquely found species compared to pastures. Across arthropod taxa and habitat types, β diversity was more important for γ diversity than α diversity, indicating that distinctiveness, rather than within-site diversity, was key in determining the contribution of sites to γ (landscape) diversity. This substantiates the argument that increasing the number of sites is efficient to increase landscape species richness. The turnover component of β diversity was far more important than the nestedness component for all arthropod taxa and habitat types and accounted for 79.0% to 95.4% of total β diversity. In conclusion, extensively managed meadows and wildflower areas should be particularly promoted by the Swiss agri-environment scheme, as they contributed more to landscape species richness and species uniqueness than pastures.