Phylogeny and divergence times of the African and Malagasy Podocarpus (Podocarpaceae) and their taxonomic and biogeographic implications

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Abstract Podocarpus is the most speciose genus of the podocarp family (Podocarpaceae) widely distributed in the mountain forests of subtropical and tropical Asia, the Neotropics and Australasia, where its members have been shown to have had multiple origins. In contrast, tropical Africa is comparatively depauperate of Podocarpus , with four to seven species and three varieties on Madagascar and three species in continental Africa. Whether the Malagasy and African Podocarpus had a single (monophyletic) or multiple origins has not rigorously been tested with a detailed sampling of the Madagascar species. All Malagasy species and the Southeast African P. henkelii are currently classified in P. sect. Scytopodium of subg. Podocarpus , which is characterized by female cones with small, green‐yellowish, non‐fleshy, leathery receptacles. The other African species, P. elongatus and P. latifolius (including P. milanjianus ), are presently placed in P. sect. Podocarpus , which differs by having female cones with large, fleshy, mostly bright red receptacles. The monophyly of these sections as delimited by de Laubenfels (therefore the phylogenetic and taxonomic values of the fleshiness of female cones) has yet to be rigorously assessed with molecular data. Assessing the phylogenetic relationships among the Malagasy and African species is relevant to understanding the broad origins of Madagascar's biota, the majority of which seems to be the result of the Cenozoic transoceanic dispersals mostly from Africa. Whether the Malagasy Podocarpus also fit within this pattern requires a time‐calibrated molecular phylogenetic framework. We conducted the Bayesian phylogenetic and dating analyses of Podocarpus based on combined nuclear (nrITS) and plastid ( matK , trnL intron, trnL‐F intergenic spacer) sequence data to address these systematic and biogeographic issues. Here, we show that the Malagasy Podocarpus strongly form a monophyletic group that is sister to an African clade (also including P. henkelii ). Podocarpus sect. Scytopodium is resolved paraphyletic with respect to P. sect. Podocarpus . The fleshiness of the receptacles of female cones does not seem to be a reliable taxonomic character for delimiting these sections. Geographic proximity, instead, appears to be a better predictor of evolutionary history than morphology. We adopt a broadened circumscription of P. sect. Podocarpus that now encompasses the African and Malagasy sister clades. This broadly delimited type section is diagnosed by the presence of marginal resin canals in the leaves. Our analyses fail to confirm the monophyly of the morphologically diverse P. madagascariensis sensu de Laubenfels or resolve the phylogenetic relationships within the sister African and Malagasy lineages, which appear to have been the result of a single Late‐Cenozoic transoceanic dispersal possibly from the Neotropics followed by late‐Miocene–mid‐Pleistocene diversification. The relatively recent colonization of Podocarpus in Africa and on Madagascar has been attributed in part to the Neogene climate fluctuations, which resulted in habitat fragmentation and repeated contraction and expansion of restricted forest refugia. The African Cenozoic Afrocarpus and Podocarpus lineages and the Malagasy Cenozoic Podocarpus lineage, respectively, seem to have entirely replaced the Mesozoic podocarps in Africa and on Madagascar.

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