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

Abstract

AbstractAimThe genusPodocarpus(Podocarpaceae) provides an opportunity to contrast biogeographical hypotheses within and among continents, and to analyse divergence between disjunct tropical and temperate forests of South America. We developed a calibrated phylogeny ofPodocarpusto reconstruct the ancestral areas and potential expansion routes within Podocarpaceae.LocationPodocarpusconsists of two extant subgenera:Foliolatusfrom Asia and Oceania, andPodocarpuslocated in Gondwanan continents and north to the Caribbean. The paper focuses mainly on the area occupied by the latter subgenus.MethodsWe combined previously published and novelDNAsequences with fossil records. New species sequenced are members ofPodocarpussubgenusPodocarpusfrom South and Central America. We assembledDNAsequences of the chloroplast (matK andrbcL) and nuclear (ITS1 andITS2) to analyse phylogenetic relationships withinPodocarpussubgenusPodocarpusby Bayesian methods, which were calibrated using macrofossils that could be confidently identified as modern genera. Ancestral areas were inferred using the dispersal–extinction–cladogenesis model.ResultsThe phylogenetic reconstruction inferred a minimum age for the origin ofPodocarpuss.l. in the late Cretaceous–early Palaeogene (63 Ma) and strongly supported monophyly of the genusPodocarpusand of subgeneraPodocarpusandFoliolatus. SubgenusPodocarpusconsists of two monophyletic, latitudinally structured clades. One clade consists of temperate American species while the other includes species from tropical‐subtropical Africa and South America.Main conclusionsThe history of the subgenera withinPodocarpusis older than previously reported: they can be traced back to late Cretaceous–early Palaeocene biogeographical connections between Australasia and South America through Antarctica. Latitudinally disjunct lineages within South America most probably diverged from widespread ancestors as a result of a persistent arid barrier that was established prior to the late Palaeogene. The calibrated age for the Tropical–Subtropical clade suggests an Atlantic–subtropical biogeographical corridor between South America and Africa long after the breakup of Gondwana and the stabilization of the circum‐Antarctic current.