Climate change threatens species richness and phylogenetic diversity of endemic woody plants in Caatinga dry forest

In seasonal tropical dry forests, warmer and drier climate conditions projected for the coming decades may reduce the distribution ranges of many woody plants, threatening biodiversity maintenance. Using ecological niche modelling for 70 endemic woody plant species of the Brazilian Caatinga, we assessed how climate change may affect structural and phylogenetic dimensions of assemblages that evolved exclusively within this ecosystem. Models were run for the current period, 2041–2060, and 2081–2100 under two greenhouse gas emission scenarios. By 2100, at least 70 % of species are projected to lose suitable habitat, and up to 11 % may become globally extinct under the pessimistic scenario. The effects of climate change are consistent across both narrow- and wide-range species. Species richness, phylogenetic diversity, and phylogenetic structure are projected to decline across the Caatinga. The number of phylogenetically clustered assemblages is expected to increase by 85–237 %, depending on the phylogenetic metric and climate scenario, whereas the number of overdispersed assemblages is expected to decline. Overall, the impacts of climate change on Caatinga biodiversity may be more severe than previously reported, with the ecosystem projected to host impoverished assemblages of endemic woody plants and lose substantial evolutionary history by the end of this century.