Phylogenetic structure of conifers in regional floras in relation to climate and environmental heterogeneity worldwide

Despite having only about 670 species worldwide, conifers are one of the ecologically and economically most important plant groups. They have a rich fossil record and previous studies have shown that their current diversity is the result of past radiations, extinction, and dispersal events, restricting many genera to either the Northern or Southern Hemisphere, and concentrating species richness in specific regions. However, it remains poorly explored how this translates into patterns of phylogenetic diversity. In this study, we used a species‐level megaphylogeny and species lists for 391 geographic units worldwide to calculate six metrics of phylogenetic diversity and disparity, and to relate these to climatic factors. We found that the different metrics provided different patterns, reflecting deep and shallow evolutionary history, but that overall southeastern China had the highest values. We also found that patterns of phylogenetic diversity and disparity were better explained by current than historical climate, by temperature‐ than precipitation‐related variables, and by climatic seasonality than by climatic extremes. These patterns differ in many important regards from those known from ferns and angiosperms. Most notably, species‐poor conifer assemblages tend to have high phylogenetic dispersion, being composed of few species belonging to distinct lineages, rather than few lineages with many species each, as is typical for ferns and angiosperms. We conclude that the ecological and evolutionary processes determining community assembly in conifers differ fundamentally from those seen in ferns and angiosperms, reflecting their low global species richness.