Atlantic corals under climate change: modelling distribution shifts to predict richness, phylogenetic structure and trait-diversity changes

Abstract

Climate change is altering species distributions worldwide. Particularly, global warming is driving range contractions and expansions of tropical species, such as corals. The use of climatic projections, via species distribution models to predict species distributional shifts, can identify threaten species and help to set priority areas of conservation. In this study, we assessed if distributional shifts of 45 Atlantic reef-forming corals (scleractinian), and the main environmental variables driving their distributions, correlated with their phylogeny and/or their functional traits; i.e. whether expected contractions and expansions affected specific clades, or specific coral traits. We also estimated the potential loss and/or gain of species richness, phylogenetic diversity (PD) and phylogenetic species variability (PSV), as well as the phylogenetic structure of Atlantic reef communities (‘clustering’, ‘overdispersion’ or ‘randomness’), under a future climate scenario (A2-IPCC-2100). The potential loss of Atlantic corals in the future will be randomly distributed across their phylogeny, i.e. potential extinctions will not only affect one section of the phylogeny, therefore alleviating an inordinate loss of evolutionary history. Nearly all current and future communities presented a ‘random’ phylogenetic structure. No correlation was found between distributional shifts and coral traits. Environmental variables did not show a significant correlation with the phylogeny neither with coral traits. Predicted changes in species richness, PD and PSV vary across the Atlantic; certain areas display large evolutionary diversity losses. Species belonging to isolated clades (high evolutionary distinctiveness) contribute to quantitative increases, or decreases, of PD and PSV, becoming crucial species for conservation. These findings highlight the importance of combining SDMs with phylogenetic/functional metrics to develop conservation strategies to assess the future of corals.