Phylogenetic relationships and a new sectional classification of Croton (Euphorbiaceae) in Australia

Abstract

A molecular phylogeny, morphological descriptions, species lists and a key to the sections of Croton L. (Euphorbiaceae) recognised for Australia are presented. The molecular phylogenetic results supported the recognition of six sections, to account for the 29 native Australian species. The monophyly of each of these sections was highly supported in the Bayesian and maximum-likelihood analyses of nuclear ITS and plastid trnL–F DNA sequences, whereas their relationships to each other and to other groups were less well resolved. Croton may represent one, two or three separate arrivals to Australia, with support for hypotheses of subsequent dispersals from Australia to Pacific islands and to Asia. Croton sections Argyrati, Arnhemici, Caudati, Dockrilliorum and Insulares are newly described. Croton section Gymnocroton Baill., previously placed in synonymy, is again recognised. Croton armstrongii S.Moore is excluded from the Australian flora.