Biodiversity in agricultural landscapes: Grassy field margins and semi-natural fragments both foster spider diversity and body size

Abstract

Agricultural intensification is one of the most important drivers of biodiversity loss. To preserve taxonomic diversity in agricultural landscapes, there is an increasing need for refuge areas within agroecosystems, but best practices for providing such sites are debated. Here, we compared the taxonomic diversity and trait composition of spiders, being important terrestrial predators, among cereal fields, grassy field margins, set aside fields sown with wildflowers, and semi-natural sites within an agricultural landscape in western Germany. Spider taxonomic diversity was similarly high in all non-crop habitats, indicating a surprisingly high value of field margins and set-aside fields. Cereal fields, in contrast, were dominated by a few, mainly euryecious species. Moreover, community mean body size was smallest on cereal fields but highest on semi-natural sites, suggesting that spider body size may serve as a valuable indicator of the level of anthropogenic disturbance. Spider communities differed partly among non-crop habitats, stressing the need for combining different conservation measures to maximize taxonomic biodiversity and trait composition. These should also include remnants of natural vegetation, which were especially important for large and red list species and therefore for reaching the aims of nature conservation.