Molecular phylogenetics of the Dissochaeta alliance (Melastomataceae): Redefining tribe Dissochaeteae

The Dissochaeta alliance (= subtribe Dissochaetinae) is a group of woody climbing taxa within tribe Dissochaeteae (Melastomataceae) and comprises 90 species mainly distributed in Southeast Asia. The circumscription of the alliance and its genera has been problematic when based on only morphological characters. With a broad sampling of relevant taxa, this study aims at a natural circumscription of and revised generic delimitation within this alliance. A molecular phylogeny based on two nuclear (nrETS, nrITS) and four chloroplast (ndhF,psbK‐psbL,rbcL,rpl16) markers confirmed the non‐monophyly of Dissochaeteae s.l. Taxa traditionally placed in Dissochaeteae are found in three lineages in distant positions within Melastomataceae. The Medinilla alliance is resolved within Sonerileae + Oxysporeae, while the monophyleticDinophora/Ochthocharislineage forms a polytomy with Marcetieae, Melastomateae, Microlicieae, and Rhexieae; and the well‐supported Dissochaeta alliance is sister to Cambessedesieae. Based on the molecular results, Dissochaeteae is redefined to exclude the Medinilla alliance andDinophora/Ochthocharis. It consists of six successively branching major clades, which we treat as six genera,Pseudodissochaeta,Creochiton,Dalenia(Dissochaetasect.Dalenia),Diplectria(Dissochaetasect.Diplectria),MacrolenesandDissochaetas.str. To avoid a paraphyleticDissochaeta,DaleniaandDiplectriaare resurrected,Macrolenesis expanded to include theDissochaeta rostratacomplex, and a narrowly circumscribedDissochaetas.str. is adopted. A re‐investigation of morphological characters based on herbarium material provides support of newly defined taxa. Two sections forMacrolenesare newly proposed, and two sections ofDissochaetas.str. are maintained. Important morphological traits such as habit and floral characters are discussed to show the morphological support for each delimited genus and the establishment of a new classification of the tribe.