Although climate change has been implicated as a major catalyst of diversification, its effects are thought to be inconsistent and much less pervasive than localized climate or the accumulation of species with time. Focused analyses of highly speciose clades are needed in order to disentangle the consequences of climate change, geography, and time. Here, we show that global cooling shapes the biodiversity of terrestrial orchids. Using a phylogeny of 1,475 species of Orchidoideae, the largest terrestrial orchid subfamily, we find that speciation rate is dependent on historic global cooling, not time, tropical distributions, elevation, variation in chromosome number, or other types of historic climate change. Relative to the gradual accumulation of species with time, models specifying speciation driven by historic global cooling are over 700 times more likely. Evidence ratios estimated for 212 other plant and animal groups reveal that terrestrial orchids represent one of the best-supported cases of temperature-spurred speciation yet reported. Employing >2.5 million georeferenced records, we find that global cooling drove contemporaneous diversification in each of the seven major orchid bioregions of the Earth. With current emphasis on understanding and predicting the immediate impacts of global warming, our study provides a clear case study of the long-term impacts of global climate change on biodiversity.
Original languageEnglish
Article numbere2102408120
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number29
Early online date10 Jul 2023
Publication statusPublished - 18 Jul 2023

Data Availability Statement

Nucleotide accessions, phylogenetic trees, input and output files for analyses have been deposited in Data Dryad (121). All study data are included in Dryad and/or SI Appendix.


We thank the Younger Laboratory (The Milner Centre for Evolution) for comments on earlier drafts. We thank Hélène Morlon and Fabien Condamine for advice regarding implementing RPANDA. We thank the Darwin Correspondence Project,Riley-Anne Prydderch,Georgia Keeling,and Kaïn van den Elsen. We also thank Simon Pugh Jones, MBE, DSc of the Writhlington Orchid Project, for advice and images.


  • Biodiversity
  • Macroevolution
  • Climate Change
  • Biogeography
  • Diversification
  • biodiversity
  • biogeography
  • macroevolution
  • diversification
  • climate change

ASJC Scopus subject areas

  • General Agricultural and Biological Sciences
  • General


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