Spatial and climatic drivers of β‐diversity in assemblages of angiosperm genera across the world

Abstract β‐diversity quantifies the change in taxonomic and phylogenetic composition between areas. It can be partitioned into two additive components (turnover and nestedness). Geographic distance, which reflects dispersal limitation, and climatic distance, which reflects environmental filtering, are major drivers of β‐diversity, but few studies have assessed their relative importance to β‐diversity at a global scale. Here, we investigate the relationship of β‐diversity of angiosperm genera in regional floras worldwide to climatic conditions within regions and to geographic and climatic distances between regions. We found that (1) current climate has a stronger effect on phylogenetic turnover than does Quaternary climate change; (2) of the current climate variables examined, mean annual temperature is the strongest driver of phylogenetic turnover, followed by precipitation seasonality; (3) regions with high precipitation seasonality have high phylogenetic β‐diversity and phylogenetic turnover; and (4) at a global scale, the variation in phylogenetic turnover explained jointly by geographic and climatic distances is, on average, much larger than that explained uniquely by either distance, but that geographic distance explains more variation in phylogenetic turnover than climatic distance. Synthesis . These results reveal the synergistic role of geographic isolation and climatic filtering in determining the composition of floras worldwide, with less influence of Quaternary climate changes.