Exploring the generic delimitation of Phyllagathis and Bredia (Melastomataceae): A combined nuclear and chloroplast DNA analysis

Phyllagathis Blume and Bredia Blume (Sonerileae s.l., Melastomataceae) are two closely related Asian genera with similar morphology and overlapping geographical range. Their generic circumscription and phylogenetic relationships are far from fully understood. We present here a molecular phylogenetic investigation for the two genera using nuclear ribosomal internal transcribed spacer and chloroplast (trnV-trnM) sequence data. Seventeen genera of Sonerileae s.l. were included in the analyses, with Phyllagathis and Bredia densely sampled to cover their geographical range and morphological diversity. We identified 14 well supported species clusters within Sonerileae s.l.-Medinilla. Phylogenetic analyses together with reconstruction of morphological characters clearly indicated the taxonomic mess in generic delimitation of Sonerileae s.l. Many of the characters traditionally used in generic delimitation were highly homoplasious. Bredia and Phyllagathis, as well as Allomorphia, Anerincleistus, Fordiophyton, and Oxyspora, were revealed to be non-monophyletic. Bredia, as currently defined, contains two groups of species with different phylogenetic affiliations. Bredia should be recircumscribed to exclude the Bredia-Phyllagathis clade I and accommodate the Bredia-Phyllagathis clade II as the type of the genus is included in the latter clade. Most species sampled in Phyllagathis spread across eight well supported clades throughout the phylogenetic tree. The type of Phyllagathis showed no close affiliation with other members of Phyllagathis nor its putative relatives. Phyllagathis, as presently circumscribed, is heterogeneous, encompassing multiple evolutionary lineages. As sequence data of nuclear ribosomal internal transcribed spacer and chloroplast trnV-trnM failed to resolve the phylogenetic relationships among these lineages, the formal taxonomic adjustment of Phyllagathis is postponed until further evidence can be gathered.