Beetle communities in agricultural landscapes: relative influences of climate, landscape, plant communities and agricultural practices

Agricultural field margins are semi-natural habitats that play a key role in conservation and restoration, supporting threatened biodiversity of agroecosystems. However, most research on field margin biodiversity has focused on plant communities, while insect populations remain largely understudied. To address this gap, we leveraged a national monitoring network across France to provide a comprehensive taxonomic and functional characterisation of beetles, a highly diverse insect group of significant agricultural interest. We examined how climate, landscape, vegetation and agricultural practices influence the structure of field margin beetle communities. Using a combination of molecular and morphological approaches and multivariate analyses, we investigated beetle communities within the herbaceous field margins of 374 agricultural sites across continental France sampled between 2020 and 2023. Our surveys revealed a high diversity of beetles, with 797 species recorded, including hundreds of flower visitors and auxiliary species. Estimates based on accumulation curves suggest a richness of up to 1200 species, corresponding to approximately 10 % of the French beetle fauna. We also identified five community types, each having specific taxonomic and functional characteristics and associated with specific climatic, soil, landscape and agricultural environments. While large-scale climatic gradients were the main drivers shaping these community types, local vegetation played a key role in determining species richness. By contrast, agricultural practices appear to be an important structuring factor for both community types and richness. Finally, this study provides the first in-depth characterisation of beetle communities in French field margins, offering a solid baseline for future research and improving our understanding of the complex interactions among climatic, landscape, vegetation, and agricultural drivers.