Disentangling the influence of local and landscape factors on alpha and beta diversities: opposite response of plants and ground‐dwelling arthropods in wet meadows

Abstract A large number of studies have tried to understand the determinants of local species richness, i.e. α‐diversity. Studies dealing with β‐diversity are considerably less numerous but their number has increased in the recent years. In this study, we assessed the relative importance of local and landscape (i.e. composition and connectivity) variables in explaining α‐ and β‐diversities (species turnover and nestedness) of three highly diverse groups, differing in mobility and dispersal: plants, spiders, and carabids. Sampling took place in 2013, using suction samplers for arthropods and phytosociological relevés for vegetation, in 77 hay meadows distributed along 200 km of the Loire Valley (France). We found plant α‐diversity to be driven by local factors, whereas spider and carabid α‐diversities were mostly determined by landscape factors (by composition and connectivity, respectively). Nestedness was negligible for the three groups. Plant β‐diversity was also mainly influenced by local factors, whereas spider β‐diversity was driven by landscape factors (composition and connectivity, equally). Surprisingly, carabid β‐diversity was mainly influenced by local factors and landscape connectivity. Despite these differences, plant, spider, and carabid β‐diversities were not different, suggesting comparable dispersal abilities and/or a low connectivity at large scale, which is in accordance with the high species turnover observed here. Managing biodiversity in meadows consequently necessitates acting at local and landscape scales, the first targeting plants and the second arthropods.