Phylogenetic analysis of ITS sequences suggests a Pliocene origin for the bipolar distribution of Scleranthus (Caryophyllaceae)

Abstract

Scleranthus is a genus of about 12 species of herbaceous plants or subshrubs native to Eurasia and Australasia. Here Scleranthus is shown to consist of European and Australasian clades, which diverged within the last 10 million years. Biogeographic implications of this dating and alternative hypotheses explaining the disjunct north-south distribution of the genus, are discussed. The trans-Tasman distributions of S. biflorus and S. brockiei are of recent origin and therefore consistent with long-distance dispersal rather than vicariance explanations. Morphological and ITS sequence data sets are significantly incongruent and trees derived from them differ over relationships among Australasian species. Hybridisation and introgression or lineage sorting are invoked to explain this discordance. Within the family Caryophyllaceae, Scleranthus ITS2 sequences have greater similarity to sequences from representatives of the subfamilies Alsinoideae and Caryophylloideae than to sequences from representatives of the subfamily Paronychioideae.