The basal position of the small American genusMicroteawithin the core Caryophyllales was suggested only recently in accordance with molecular phylogeny. However, the specific relationships within the genus were not traced. The results of our phylogenetic analysis based on thematK chloroplast gene suggest the monophyly ofMicrotea, andAncistrocarpusand other related genera should be included in it.Microteais divided into two major sister clades: clade A consisting ofM.glochidiata,M.maypurensisandM.tenuifolia, and clade B comprisingM.debilis,M.sulcicaulis, M.scabrida,M.celosioides, andM.papillosa. The nrDNA dataset (ITS), although containing only a limited number of accessions, shows the same species number in clade A, and the remaining species studied (M.debilis,M.scabridaandM.celosioides) form clade B. Subgeneric status is assigned to clades A and B corresponding with the names Microteasubgen.Ancistrocarpus subgen. nov. and Microteasubgen.Microtea, respectively. The diagnostic characters at the subgeneric level are as follows: length of pedicels, number of flowers at each node, number of stamens and styles. A multivariate analysis of 13 distinguishing morphological characters supports the results of phylogenetic analysis. All species have similar pericarp and seed ultrasculpture and anatomy, and they share the reticulate pericarp surface (independent of presence or absence of finger-shaped outgrowths on its surface) and rugose or slightly alveolate seed ultrasculpture. On the basis of morphological characters, we accept 10Microteaspecies. A checklist includes a new diagnostic key, morphological descriptions and distribution patterns of each species.Galeniacelosioidesis the oldest legitimate name available for the plants previously known asMicroteapaniculata, for which the combinationMicroteacelosioidesis validated here. The neotypes ofGaleniacelosioidesandMicroteasprengeliiwere designated from the collections of Prinz Wied at BR. The nameM.foliosais discussed and finally synonymized withM.scabrida. The lectotypes ofAncistrocarpusmaypurensis(≡Microteamaypurensis), Microteadebilisvar.ovata (=M.debilis),M.glochidiata, M.maypurensisvar.angustifolia (=M.tenuifolia), M.glochidiataf.lanceolata (=M.maypurensis),M.longebracteata(=M.celosioides), M.paniculatavar.latifolia (=M.scabrida),M.portoricensis,M.scabrida,M.sulcicaulis, andPotamophilaparviflora(=M.maypurensis) are designated.Microteasulcicaulisis reported for the first time as native to Bolivia, andM.maypurensisis reported from Indonesia (Java), where it is found as an alien plant with an unclear invasion status.
