Late Cretaceous-Early Eocene origin of yams (Dioscorea, Dioscoreaceae) in the Laurasian Palaearctic and their subsequent Oligocene-Miocene diversification

Aim: Dioscorea (Dioscoreaceae) is a predominantly pantropical genus (< 600 species) that includes the third most important tropical tuber crop and species of pharmacological value. Fossil records from both the Northern and Southern Hemispheres were used to test hypotheses about the origin of the genus Dioscorea, and to examine potential macroevolutionary processes that led to its current distribution. Location: Pantropical distribution. Methods: Divergence times were estimated using the most comprehensive phylogeny of the group published to date based on plastid sequences and fossil calibrations, applying a relaxed-clock model approach. Ancestral areas and range shifts were reconstructed using time-stratified likelihood-based models, reflecting past continental connectivity and biogeographical models incorporating the spatial range of fossils. Results: Fossil-informed biogeographical analysis supported colonization of the Nearctic by ancient yam lineages from the western Palaearctic and subsequent migration to the South. Most of the pantropical South American, African and Southeast Asian lineages experienced a relatively recent diversification in the Oligocene-Miocene. Long-distance dispersals were inferred for the colonizations of the New World, Africa and Madagascar. Main conclusions: Dioscorea likely originated between the Late Cretaceous and the Early Eocene in the Laurasian Palaearctic, followed by possible dispersal to South America via the Eocene North Atlantic Land Bridge.This study was supported by Fundación BBVA (FBBVA) BIOCON 05-093/ 06 project (PC, JGSM) and by Instituto de Estudios Altoaragoneses project (J.V.). J.V. benefited from a PhD fellowship funded by FBBVA and two research stays at Kew Gardens funded by European SYNTHESYS GB-TAF and DGA-CAI grants. J.G.S-M. was supported by Araid and Ramón y Cajal postdoctoral contracts. P.C. was partially funded by Bioflora Research Team grant cofunded by the Aragón Government and the European Social Fund. I.S. was supported by grant CGL2012-40129-C02-01 from the Spanish Ministry of Science.Peer Reviewe