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

QUIROGA, M. P.; MATHIASEN, P.; IGLESIAS, A.; ROBERT MILL; PREMOLI, A.C.

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 43 p. 372 - 383

0305-0270

Aim The genus Podocarpus(Podocarpaceae) provides an opportunity to contrast biogeographical hypotheseswithin and among continents, and to analyse divergence between disjuncttropical and temperate forests of South America. We developed a calibratedphylogeny of Podocarpus in order to reconstruct ancestral areas andpotential expansion routes withinPodocarpaceae.Location Podocarpusconsists of two extant subgenera: Foliolatus from Asia and Oceania, and Podocarpuslocated in Gondwanan continents and north to the Caribbean. The paper focusesmainly on the area occupied by the latter subgenus.Methods We combinedpreviously published and novel DNA sequences with fossil records. New speciessequenced are members of Podocarpus subgenusPodocarpus from South and CentralAmerica. We assembled DNA sequences of the chloroplast (matK and rbcL) andnuclear (ITS1 and ITS2) to analyse phylogenetic relationships within Podocarpus subgenus Podocarpus by Bayesian methods, which were calibrated usingmacrofossils that could be confidently identified as modern genera. Ancestralareas were inferred using the dispersal?extinction?cladogenesis (DEC) model. Results The phylogeneticreconstruction inferred a minimum age for the origin of Podocarpus s.l. in the late Cretaceous?early Palaeogene (63 Ma) andstrongly supported monophyly of the genus Podocarpusand of subgenera Podocarpus and Foliolatus. Subgenus Podocarpus consists of two monophyletic,latitudinally structured clades. One clade consists of temperate Americanspecies while the other includes species from tropical-subtropical Africa andSouth America.Mainconclusions The history of thesubgenera 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 America mostprobably diverged from widespread ancestors as a result of a persistent aridbarrier that was established prior to the late Palaeogene. The calibrated agefor the Tropical?Subtropical clade suggests an Atlantic?subtropicalbiogeographical corridor between South America and Africa long after thebreakup of Gondwana and the stabilization of the circum-Antarctic current.