Molecular phylogenetics of Tribe Phyllantheae (Phyllanthaceae) - COMPLETED 2008

Phyllanthus purpusii male flower. Credit: A. McRobb

As part of the phylogenetic study of Euphorbiaceae sensu lato, phylogenetic relationships within tribe Phyllantheae were critically examined. This is the largest tribe of family Phyllanthaceae, containing c. 1,200 species, the vast majority of which belong to the genus Phyllanthus. Nuclear ribosomal ITS and plastid matK DNA sequence data for c. 100 species of tribe Phyllantheae were analysed including representatives of all published subgenera of Phyllanthus (except Cyclanthera) and several undescribed and hitherto unplaced infrageneric groups. Results for ITS and matK are largely concordant. We recognise six major lineages in tribe Phyllantheae: Flueggea sensu lato, Lingelsheimia, Margaritaria, Phyllanthus sensu lato, Plagiocladus and Savia section Heterosavia. Richeriella should be united with Flueggea and the generic status of Plagiocladus (= Phyllanthus diandrus) is confirmed. Infrageneric clades within Phyllanthus are resolved, but relationships among the core groups remain unclear. Results confirm paraphyly of Phyllanthus with embedded Breynia, Glochidion, Reverchonia and Sauropus. Subgenera Isocladus, Kirganelia and Phyllanthus are polyphyletic, whereas other subgenera appear to be monophyletic. Phyllanthus maderaspatensis is sister to all other species of Phyllanthus sensu lato, and the genus appears to be of Old World origin. The unique branching architecture & phyllanthoid branching of most Phyllanthus taxa has been lost (and/or has been derived) repeatedly. Reverchonia is sister to P. amarus, arborescent section Emblica to herbaceous Urinaria, the free-floating aquatic P. fluitans to the variable weed P. caroliniensis, and the phyllocladous section Choretropsis to the delicate leafy P. claussenii. Taxonomic divisions based on similar pollen morphology are largely confirmed, and related taxa share similar distributions.

This project formed part of a PhD study by Hashendra Kathriarachchi, based at the University of Vienna, and supervised by Petra Hoffmann. The results were published, and the PhD awarded, in 2006. In many clades though, the sampling was insufficient to fully understand the relationships within Phyllanthus.  A phylogenetic classification of Phyllanthaceae was published in 2006 and  revisions of Wielandia and Heterosavia were published in 2007 and 2008 repectively