Molecular and fossil evidence disentangle the biogeographical history of Podocarpus, a key genus in plant geography

QUIROGA, M.P., P. MATHIASEN, A. IGLESIAS & A.C. PREMOLI

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 p. 372 - 383

0305-0270

Aim The genus Podocarpus (Podocarpaceae) provides an opportunity to contrastbiogeographical hypotheses within and among continents, and to analysedivergence between disjunct tropical and temperate forests of South America.We developed a calibrated phylogeny of Podocarpus to reconstruct the ancestralareas and potential expansion routes within Podocarpaceae.Location Podocarpus consists of two extant subgenera: Foliolatus from Asiaand Oceania, and Podocarpus located in Gondwanan continents and north tothe Caribbean. The paper focuses mainly on the area occupied by the lattersubgenus.Methods We combined previously published and novel DNA sequences withfossil records. New species sequenced are members of Podocarpus subgenusPodocarpus from South and Central America. We assembled DNA sequences ofthe chloroplast (matK and rbcL) and nuclear (ITS1 and ITS2) to analyse phylogeneticrelationships within Podocarpus subgenus Podocarpus by Bayesian methods,which were calibrated using macrofossils that could be confidentlyidentified as modern genera. Ancestral areas were inferred using the dispersal?extinction?cladogenesis model.Results The phylogenetic reconstruction inferred a minimum age for the originof Podocarpus s.l. in the late Cretaceous?early Palaeogene (63 Ma) andstrongly supported monophyly of the genus Podocarpus and of subgeneraPodocarpus and Foliolatus. Subgenus Podocarpus consists of two monophyletic,latitudinally structured clades. One clade consists of temperate American specieswhile the other includes species from tropical-subtropical Africa and SouthAmerica.Main conclusions The history of the subgenera within Podocarpus is olderthan previously reported: they can be traced back to late Cretaceous?earlyPalaeocene biogeographical connections between Australasia and South Americathrough Antarctica. Latitudinally disjunct lineages within South Americamost probably diverged from widespread ancestors as a result of a persistentarid barrier that was established prior to the late Palaeogene. The calibratedage for the Tropical?Subtropical clade suggests an Atlantic?subtropical biogeographicalcorridor between South America and Africa long after the breakup ofGondwana and the stabilization of the circum-Antarctic current.