Taxonomic and phylogenetic β-diversity of regional assemblages of angiosperm species in relation to geographic and climatic determinants in Africa

Abstract

Aim

Beta-diversity quantifies the change in taxonomic and phylogenetic composition between areas, and is a scalar between local (α) and regional (γ) diversity. Geographic distance, which reflects dispersal limitation, and climatic distance, which reflects environmental filtering, are major drivers of β-diversity. Here, we analyse a comprehensive data set of angiosperms in regional floras across Africa to assess the relationships of β-diversity, and its components, to three major types of environmental variables (current climate, Quaternary climate change and topographic heterogeneity) thought to drive β-diversity.

Location

Africa.

Taxon

Angiosperms.

Methods

Africa was divided into 27 regions. Species lists of angiosperms for each region were collated. The relationships of both taxonomic and phylogenetic β-diversity, and their respective turnover and nestedness components, with geographic and environmental distances were assessed.

Results

This study showed that (1) regions of the lowest β-diversity are located in moist tropical climates, (2) the turnover and nestedness components of β-diversity are negatively correlated with each other, (3) taxonomic β-diversity is higher than phylogenetic β-diversity across Africa, (4) variation in β-diversity of angiosperms is more strongly associated with current climate than with Quaternary climate change and topographic heterogeneity and (5) the variation in taxonomic β-diversity and its turnover component that is independently explained by geographic distance is much larger than that is independently explained by climatic distance for angiosperms in Africa.

Main Conclusions

The finding that geographic distance explained more variation than climatic distance suggests that dispersal limitation plays a greater role than environmental filtering in shaping angiosperm β-diversity in Africa. Of climatic factors, current climate plays a more important role than Quaternary climate change in shaping angiosperm β-diversity in Africa.