Phylogeny and proposed circumscription of Breynia, Sauropus and Synostemon (Phyllanthaceae), based on chloroplast and nuclear DNA sequences

Abstract

Previous estimates of phylogeny in the Phyllanthaceae, Phyllantheae, have been hampered by undersampling of species from morphologically distinctive groups and using too few gene regions. To increase the phylogenetic resolution, sequences of two nuclear (ITS1–5.8S–ITS2) and Phytochrome C (PHYC)) and two non-coding chloroplast (accD–psaI, trnS–trnG) DNA markers were analysed using maximum parsimony and Bayesian inference with expanded sampling in Breynia, Glochidion, Sauropus and Synostemon. Our results supported reinstatement of Synostemon, previously included in Sauropus s.str., to generic rank, and provided evidence towards its future infrageneric classification. The results also indicated expansion of Breynia to include Sauropus s.str.; this combined monophyletic group consists of two strongly supported clades. Finally, we showed monophyly for Glochidion, which is sister to Phyllanthus subg. Phyllanthodendron, both still remaining undersampled. Morphological features characteristic of Breynia, Sauropus and Synostemon are discussed, as well as the desirability of dividing Phyllanthus into smaller genera.

Phylogenetic reconstruction prompts taxonomic changes in <I>Sauropus</I>, <I>Synostemon</I> and <I>Breynia</I> (<I>Phyllanthaceae</I> tribe <I>Phyllantheae</I>)

“…Unfortunately, it is obvious that some species are difficult to place, or cannot be placed in any existing section (see Van Welzen 2003). The molecular phylogenetic reconstruction of Sauropus (Pruesapan et al 2008(Pruesapan et al , 2012 only very partly agrees with the infrageneric classification by Airy Shaw (1969). Only two clades with combinations of the sections could be recognised (summary in Fig.…”

“…Twenty three species, based on Pruesapan et al (2012), were selected to represent the sections of Sauropus as proposed by Pax & Hoffmann (1922) and Airy Shaw (1969) The type of Sauropus (Sa. androgynus (L.) Merr.…”

“…In practice, only Chakrabarty & Balakrishnan (2009) and Wagner & Lorence (2011) have published new combinations under Phyllanthus. Later, Chakrabarty & Balakrishnan (2012) reverted to the recognition of Breynia at generic rank probably because of Pruesapan et al (2012).…”

“…Sauropus in the strict sense (excluding Synostemon; Pruesapan et al 2008Pruesapan et al , 2012 and Breynia are two closely related tropical Asian-Australian genera with up to 52 and 35 species, respectively (Webster 1994, Govaerts et al 2000a, b, Radcliffe-Smith 2001. Sauropus comprises mainly herbs and shrubs, whereas species of Breynia are always shrubs.…”

“…1, respectively). To date, the purely Sauropus group is mainly unresolved (Pruesapan et al 2008(Pruesapan et al , 2012. The inclusion of morphological data in phylogenetic analyses may provide better resolved relationships within the group.…”