New Caledonian radiations
The origins and evolution of the rich and distinctive flora of New Caledonia have long attracted the attention of botanists. Kew scientists have recently collaborated on three studies dedicated to this biodiversity hotspot: two on the radiation and biogeography of lineages of Rubiaceae and Ebenaceae and one on an endemic genus of Sapindaceae.
The first study (Barrabé et al., 2014) focussed on Psychotria s.l. (Rubiaceae), the second richest New Caledonian genus with some 85 species, and allied genera. Dated phylogenetic trees revealed four colonisation events occurring within a relatively short time during the Neogene, long after the islands re-emerged from the sea during the mid-Eocene. These lineages show different evolutionary histories: Geophila did not diversify, Margaritopsis diversified only moderately, one of the two Psychotria lineages appears to be relictual whereas the other has undergone the most rapid recorded diversification of any endemic lineage in the archipelago.
The second study focussed on Diospyros, the largest genus of Ebenaceae and, with more than 500 species, one of the largest angiosperm genera. Analysis of four plastid markers (Turner et al., 2013a) revealed that New Caledonian Diospyros species fall into three clades that again show disparate degrees of diversification with one, five and 21 species. The largest clade derived from an ancestor that colonised New Caledonia about 9 million years ago, and analysis of amplified fragment length polymorphisms (Turner et al., 2013b) suggested the progenitor was widespread and split into two groups that fragmented into many diverging populations. The analysis also revealed evidence of cryptic species, for which more study of morphology and ecology are required.
In the third study (Munzinger et al, 2013), a taxonomic revision of the endemic New Caledonian genus Podonephelium (Sapindaceae) recognised nine species within the genus, four of which are newly described and one infraspecific taxon is elevated to the rank of species. The study also made preliminary IUCN Red List assessments of the species.
Barrabé, L., Maggia, L., Pillon, Y., Rigault, F., Mouly, A., Davis, A.P. & Buerki, S. (2014). The assemblage of New Caledonian Psychotria (Rubiaceae) lineages reveals different evolutionary histories, and the largest recorded plant radiation for the island. Molecular Phylogenetics and Evolution 71 15-35 Available online
Munzinger, J., Lowry II, P.P., Callmander, M.W. & Buerki, S. (2013). A taxonomic revision of the endemic New Caledonian genus Podonephelium Baillon (Sapindaceae). Systematic Botany 38: 1105–1124. Available online
Turner, B., Munzinger, J., Duangjai, S., Temsch, E.M., Stockenhuber, R., M. H. J. Barfuss, M.H.J., Chase, M.W. & Samuel, R. (2013a). Molecular phylogenetics of New Caledonian Diospyros (Ebenaceae) using plastid and nuclear markers. Molecular Phylogenetics and Evolution 69: 740-763. Available online
Turner, B., Paun, O., Munzinger, J., Duangjai, S., Chase, M.W. & Samuel, R. (2013b). Analyses of amplified fragment length polymorphisms (AFLP) indicate rapid radiation of Diospyros species (Ebenaceae) endemic to New Caledonia. BMC Evolutionary Biology 13: 269. Available online