Phylogenetic structure of understorey annual and perennial plant species reveals opposing responses to aridity in a Mediterranean biodiversity hotspot

Aridity is a critical driver of the diversity and composition plant communities. However, how aridity influences phylogenetic structure functional groups (i.e. annual perennial species) far less understood than its effects on species richness. As perennials have to endure stressful conditions during summer drought, as opposed annuals that avoid it, they may be subjected stronger environmental filtering. In contrast, more susceptible interannual climatic variability. Here we studied components understorey communities, along regional gradient in Mediterranean drylands. Specifically, asked: (1) How do richness (S) (PS) communities respond aridity? (2) What contribution other topo-edaphic variables predicting S PS for both components? (3) does taxonomic turnover vary with spatial distances? We assessed annuals' perennials' richness, at deep shallow levels, distances. found no relationship between aridity, whereas showed unimodal pattern. The contrasting responses negatively correlated variables. clustering intermediate-to-higher levels annuals, lower perennials. Both distance rather suggesting adaptation local factors. Overall, our results show decoupling response Our findings significant implications land management strategies under climate change.