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Habitat fragmentation and land use intensification are major threats to biodiversity worldwide, affecting both species (SD) and genetic (GD) diversity. It remains unclear whether SD and GD respond to the same components of landscape changes and to what extent they correlate in fragmented systems. We explore the role of current and historical patch and landscape features on SD and GD, in and between forest fragments, along a gradient of landscape matrix permeability. We seek the circumstances under which SD and GD correlate. Within three contrasted agricultural landscapes of northern France, we assessed vascular plant SD and the GD of two plant species with contrasted life history traits in all forest fragments. Species richness and expected heterozygosity were taken as proxies for SD and GD respectively. Using regression and correlation analyses, we explored relationships between SD/GD and local, landscape and historical factors; and between SD and GD. When landscape permeability is above a certain threshold, SD and GD appear to be patterned by the same processes, which results in a positive SD-GD correlation. This permeability threshold is species-specific, depending upon species’ dispersal traits and niche width. The SD-GD correlation depends upon current and past landscape permeability, so that the lack of correlation emerges as the rule in weakly permeable landscape matrices, especially when fragments are small. Landscape matrix permeability and patch features drive SD and GD of vascular plants within and between forest fragments. A generalist, fast-colonizing species better reflects diversity patterns in fragmented forests.

International audience; Purpose Most of the agricultural landscape in Europe, and elsewhere, consists of mosaics with scattered fragments of semi-natural habitat like small forest fragments. Mutual interactions between forest fragments and agricultural areas influence ecosystem processes such as nutrient cycling, a process strongly mediated by the macrodetritivore community, which is however, poorly studied. We investigated macrodetritivore distribution patterns at local and landscape level and used a key functional trait (desiccation resistance) to gain mechanistic insights of the putative drivers. Methods Macrodetritivores were sampled in forest edges-centres of 224 European forest fragments across 14 landscapes opposing in land use intensity. We used a multilevel analysis of variance to assess the relative contribution of different spatial scales in explaining activity-density and Shannon-diversity of woodlice and millipedes, together with a model-based analysis of the multivariate activity-density data testing the effect on species composition. Secondly, we tested if desiccation resistance of macrodetritivores varied across communities at different spatial scales using linear mixed effect models. Results Forest edge-centre and landscape use intensity determined activity-density and community composition of macrodetritivores in forest fragments, while fragment characteristics like size and continuity were relatively unimportant. Forest edges and higher intensity landscapes supported higher activity-density of macrodetritivores and determined species composition. Forest edges sustained woodlouse communities dominated by more drought tolerant species. Conclusions Landscape use intensity and forest edges are main drivers in macrodetritivore distribution in forest fragments with desiccation resistance a good predictor of macrodetritivore distribution. Key functional traits can help us to predict changes in community structure in changing landscapes.