The Phylogeny of Mallotus s.str. (Euphorbiaceae) Inferred from DNA Sequence and Morphological Data

Mallotus s.str. is a monophyletic, large, palaeotropical genus in the family Euphorbiaceae. We investigated the phylogeny of the genus in order to (1) determine the evolutionary relationships within the Mallotus s.str. clade; (2) assess whether the six sections as circumscribed in the traditional classification reflect clades and evaluate the characters used in the classification; and (3) determine what are additional new clades and their supporting morphological characters. For this purpose we assembled different datasets: plastid (matK) and nuclear (gpd) DNA sequences, macromorphological features and leaf anatomical data. We found that Mallotus sect. Mallotus, sect. Polyadenii and sect. Stylanthus are monophyletic, M. sect. Axenfeldia and sect. Rottleropsis are polyphyletic, and M. sect. Philippinenses is paraphyletic. Six additional clades with morphological synapomorphies were also identified. An analysis of quantitative morphological data, in combination with qualitative morphological and molecular datasets resulted in almost completely resolved phylogenies and increased support values. However, the higher-level relationships between the clades are not supported in our analyses and the position of many taxa is still ambiguous.