Global variation in diversification rate and species richness are unlinked in plants.

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Smith, Stephen A., Baker, William J., Antonelli, Alexandre, Eiserhardt, Wolf L., Tietje, Melanie, Govaerts, Rafaël
• Other Authors: {"funder_name":"Villum Fonden, Denmark","funder_doi":"http://dx.doi.org/10.13039/100008398","funder_position":"0","funder_ror":"https://ror.org/007ww2d15","funder_award": "Grant no. 00025354" },{"funder_name":"Vetenskapsrådet, Sweden","funder_doi":"http://dx.doi.org/10.13039/501100004359","funder_position":"1","funder_isni":"0000 0001 1506 5964","funder_ror":"https://ror.org/03zttf063","funder_award": "Grant no. 2019-05191" },{"funder_name":"Stiftelsen för Strategisk Forskning, Sweden","funder_doi":"http://dx.doi.org/10.13039/501100001729","funder_position":"2","funder_ror":"https://ror.org/044wr7g58","funder_award": "Grant no. FFL15-0196" },{"funder_name":"Royal Botanic Gardens, Kew, United Kingdom","funder_doi":"http://dx.doi.org/10.13039/501100001296","funder_position":"3","funder_isni":"0000 0001 2097 4353","funder_ror":"https://ror.org/00ynnr806"},{"funder_name":"Aarhus Universitets Forskningsfond, Denmark","funder_doi":"http://dx.doi.org/10.13039/501100002739","funder_position":"4","funder_isni":"0000 0001 1956 2722","funder_ror":"https://ror.org/01aj84f44","funder_award": "Research Grant" }
• Format: Article in Journal/Newspaper
• Language: English
• Published: National Academy of Sciences 2022
• Subjects: Diversification; Biogeography; Biodiversity; Macroecology; Plant diversity drivers; Antarc*; Antarctica
• Online Access: https://doi.org/10.1073/pnas.2120662119

Species richness varies immensely around the world. Variation in the rate of diversification (speciation minus extinction) is often hypothesized to explain this pattern, while alternative explanations invoke time or ecological carrying capacities as drivers. Focusing on seed plants, the world’s most important engineers of terrestrial ecosystems, we investigated the role of diversification rate as a link between the environment and global species richness patterns. Applying structural equation modeling to a comprehensive distribution dataset and phylogenetic tree covering all circa 332,000 seed plant species and 99.9% of the world’s terrestrial surface (excluding Antarctica), we test five broad hypotheses postulating that diversification serves as a mechanistic link between species richness and climate, climatic stability, seasonality, environmental heterogeneity, or the distribution of biomes. Our results show that the global patterns of species richness and diversification rate are entirely independent. Diversification rates were not highest in warm and wet climates, running counter to the Metabolic Theory of Ecology, one of the dominant explanations for global gradients in species richness. Instead, diversification rates were highest in edaphically diverse, dry areas that have experienced climate change during the Neogene. Meanwhile, we confirmed climate and environmental heterogeneity as the main drivers of species richness, but these effects did not involve diversification rates as a mechanistic link, calling for alternative explanations. We conclude that high species richness is likely driven by the antiquity of wet tropical areas (supporting the “tropical conservatism hypothesis”) or the high ecological carrying capacity of warm, wet, and/or environmentally heterogeneous environments.