Format: ORAL

Oscar A. Pe´rez-Escobar1, Diego Bogarin2*, Natalia Przelomska1,3, William J. Baker1, Alexandre Antonelli1,4,5,6

1Royal Botanic Gardens, Kew, London, UK. 2Lankester Botanic Garden, Universidad de Costa Rica, San Jose, Costa Rica. 3University of Portsmouth, Portsmouth, UK. 4Gothenburg Global Biodiversity Centre, Gothenburg, Sweden. 5University of Oxford, Oxford, UK. 6Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China.

Orchids represent one of the most striking examples of flowering plant diversification, thriving in nearly all terrestrial environments and often standing out as one of the most species-rich plant groups in tropical floras. However, their origin, spread across the globe, and hotspots of speciation remain uncertain due to the lack of an updated, densely sampled, robust phylogenomic framework. We present the most densely sampled phylogeny of the Orchidaceae utilizing combined high-throughput and Sanger sequencing datasets. Our analysis covers all five subfamilies, and included representative sampling for 17 out of 22 tribes, 40 out of 49 subtribes, 285 out of 736 genera, and ~7% (1,921) of the 29,524 accepted species. By integrating curated geographical distribution records, we infer geographic range evolution, diversity, and speciation patterns. We found that the orchids most recent common ancestor probably lived in the Late Cretaceous Laurasia. Despite their ancient origin, modern orchid species diversity mainly originated over the last 5 million years, with highest speciation rates in montane forests of Panama and Costa Rica. These results alter our understanding of the geographic origin of orchids, previously proposed as Australian, and pinpoint Central America as a region of recent and explosive speciation.