Land-use intensification reduces multi-taxa diversity patterns of Small Woodlots Outside Forests in a Mediterranean area

Land-use intensification exacerbates landscape fragmentation, increasing the negative effects on biodiversity. In this context, the biodiversity value of Trees Outside Forests (TOF; scattered trees, tree lines and small woodlots) is often overlooked by landscape planning and conservation programs, which typically focus on protecting larger and more intact areas. More empirical studies on taxa inhabiting TOF are needed to support and promote their conservation in human-altered lands. However, we are not aware of any study focusing on multiple taxa living in small woodlots outside forests (SWOFs) in the Mediterranean basin. We investigated how diversity patterns of multiple taxa in SWOFs respond to a land-use intensification gradient, from natural areas to more disturbed ones (agricultural and urban areas), in a Mediterranean biodiversity hotspot. We explored the influence of land-use types on species richness and composition of vascular plants and six ground-dwelling invertebrate groups (pseudoscorpions, spiders, darkling beetles, rove beetles, ground beetles, and ants). Species composition was more sensitive than species richness to land-use change, highlighting the need to consider a suitable measure for interpreting ecological processes. We observed a strong influence of land use embedding SWOFs on the mean composition and beta diversity of taxa: land-use intensification led to a general homogenization of diversity patterns, especially among agricultural and urban areas. In our study area, vascular plants responded more sensitively to land-use change than invertebrates. For most invertebrates: the higher the land-use intensity, the lower the species composition dissimilarity due to the dominance of good dispersers or disturbance-tolerant species. More vagile species and disturbance-tolerant species can move across open habitats and colonize new areas, reducing compositional differences and potentially boosting species pools. We demonstrated that SWOFs play a key role in supporting viable populations of invertebrates, also in human-altered lands, underlining the need to promote their conservation in this Mediterranean fragmented landscape to avoid homogenization from driving a generalized biodiversity loss.