Climatic niche evolution and species diversification in the C ape flora, S outh A frica

Abstract

Aim To evaluate the evolutionary dynamics of the ecological niche by quantifying the modes and rates of ecological niche evolution (with a particular focus on climatic parameters) and species diversification. Location Greater C ape Floristic Region, southern A frica. Methods Using the genus B abiana ( I ridaceae) from the C ape flora, S outh A frica, we study the evolutionary dynamics of the ecological niche, which includes a characterization of the ecological niche, an assessment of phylogenetic signal, comparisons of different macroevolutionary models, and the estimation of rates of niche evolution (and their variation within and between clades) and lineage diversification, while accounting for phylogenetic uncertainty. Results A principal components analysis ( PCA ) identified mean annual precipitation and mean annual temperature as the most important climatic determinants differentiating species within B abiana . All parameters show significant phylogenetic signal, and the best‐fit model of evolution is the O rnstein– U hlenbeck process with two distinct precipitation optima for two neighbouring biomes: the F ynbos and the S ucculent K aroo. Evolutionary rates of climatic niches vary by more than an order of magnitude over the phylogeny, and rates of niche evolution and lineage diversification are both higher in the F ynbos biome than in the S ucculent K aroo. Main conclusions Our results show a possible link between rates of climatic niche evolution and rates of species diversification, indicating that rates of niche evolution might be driving diversification rates.

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