Major speciation accompanied the dispersal of Vireya Rhododendrons (Ericaceae, Rhododendron sect. Schistanthe) through the Malayan archipelago: Evidence from nuclear gene sequences

The species within Rhododendron sect. Schistanthe (= sect. Vireya), a taxon unique for its tropical habitat, distinctive leaf scales, and tailed seeds, have diversified greatly in morphological features. The section contains over 300 species, occurring mainly on the Malay Peninsula, New Guinea, and the islands between. An analysis based on the combined sequences of three nuclear genes supports a phylogeny in which sect. Schistanthe (less R. santapaui) is monophyletic, with well-defined clades corresponding to subsections Euvireya, Malayovireya, Pseudovireya, and Discovireya. Within subsect. Euvireya, molecular-phylogenetic groupings follow geography more closely than traditional taxonomic groupings based upon morphology. One of the two most derived clades contains exclusively species from New Guinea, Australia, and the Solomon Islands. The results are consistent with a stepwise phylogeographic history of sect. Schistanthe, beginning in Asia, proceeding eastward and reaching New Guinea within the last 15 Ma, when movement of the Australian tectonic plate brought New Guinea into the Malesian domain.