Molecular phylogenetics of the palm subtribe Ptychospermatinae (Arecaceae)

We examined the phylogeny and intergeneric relationships among the 12 genera of the palm subtribe Ptychospermatinae. While many of these taxa are familiar, cultivated ornamental palms in warm areas of the world, the monophyly of the subtribe and its component genera required testing. We also examined the biogeographic relationships of this lineage, which has a significant radiation east of Wallace's Line.

Phylogenetic analyses were based on maximum parsimony and Bayesian analyses of nucleotide sequences of two low-copy nuclear genes: intron 4 of phosphoribulokinase and intron 23 of RNA polymerase II. Biogeographical reconstructions were explored using S-DIVA.

The two-gene, combined analysis yielded a monophyletic subtribe with six major clades. The biogeographical analysis suggests that the subtribe originated in New Guinea.

The phylogenetic hypotheses support the monophyly of the subtribe. The genera Drymophloeus, Ponapea, and Veitchia, as presently circumscribed, are not monophyletic. The resurrection and expanded circumscription of the genus Ponapea are supported. A newly discovered species of Adonidia is confirmed as sister species to Adonidia merrillii. Our phylogenetic hypothesis suggests that the Ptychospermatinae diverged into six major clades with repeated radiations into Australia and the western Pacific. The presence of Adonidia to the west of Wallace's Line is likely to be the result of long-distance dispersal. The following new combinations are made to restore monophyly to Veitchia and Ponapea: Veitchia pachyclada, V. subisticha, V. lepidota, and Ponapea hentyi.