Molecular phylogeny of Ochrosia sensu lato (Apocynaceae) based on rps16 intron and ITS sequence data: Supporting the inclusion of Neisosperma

Molecular phylogeny of Ochrosia sensu lato (Ochrosia sensu stricto and Neisosperma) was investigated by maximum parsimony analysis of sequence data from chloroplast DNA (rps16 intron) and rps16 intron + Internal Transcribed Spacer (ITS). Nineteen species including two varieties (23 accessions) were defined as the ingroup, comprising ten species of Ochrosia s.str. and nine species of Neisosperma. For analysis using rps16 intron region, Rauvolfia sumatrana, R. verticillata and R. serpentina, Vinca major, and V. minor of the tribe Vinceae were used as the outgroup. The aims of this study are to evaluate the usefulness of rps16 intron to infer phylogenetic relationships within Ochrosia sensu lato and to confirm conclusions from previous analysis. In this study, rps16 region was proved to be sufficiently informative to infer phylogenetic relationships at infrageneric level. The strict consensus of most parsimonious trees produced from rps16 sequences data showed that Ochrosia species formed a monophyletic clade highly supported with 97% bootstrap value, whilst Neisosperma was paraphyletic. The Ochrosia clade was found to be nested within Neisosperma, with N.acuminata as a sister taxon to it. All Ochrosia and Neisosperma species were grouped into one clade. However, this clade was not well supported (only has 61% bootstrap value). Consequently, although the results does not contradict recognizing only one genus (Ochrosia sensu lato), but it is not convincing enough. The strict consensus tree produced from sequence data analysis using rps16 intron + ITS showed a more robust monophyletic clade of Ochrosia sensu lato, supported with 100% bootstrap value. Neisosperma - again - was found to be paraphyletic, with monophyletic clade of Ochrosia (strongly supported with 93% bootstrap value) nested within, suggesting the inclusion of Neisosperma into Ochrosia and recognition of only one genus. These findings supported our previous result, using ITS region.