Integrative systematics supports the establishment of Winitia, a new genus of Annonaceae (Malmeoideae, Miliuseae) allied to Stelechocarpus and Sageraea

Abstract

The generic circumscriptions of Stelechocarpus and Sageraea (Annonaceae) are assessed using molecular phylogenetic, macromorphological, and pollen morphological evidence. For molecular phylogenetic analysis the combined seven plastid markers: rbcL exon, trnL intron, trnL-F spacer, matK exon, ndhF exon, psbA-trnH spacer, and ycf1 exon constituting c. 7 kb are used. The results corroborate the recognition of a maximally supported clade as a new genus, Winitia. It is weakly to moderately supported as sister to Stelechocarpus burahol, the type and only species of Stelechocarpus. A clade consisting of Winitia and Stelechocarpus is strongly supported as sister to Sageraea, which is monophyletic with strong support. Winitia consists of two species, one of which (W. expansa) is proposed as a new species endemic to Thailand, whereas one new combination (W. cauliflora) is made. The new genus is primarily characterized by (1) multicolumellar stigmas (≥ 5 columns per stigma) and (2) pollen grains with a very thin tectum, a more or less columellate/coarsely granular infratectum, and a very distinct basal layer. The macromorphology and pollen morphology of the three genera (Stelechocarpus, Winitia, and Sageraea) are highlighted.