Evolutionary relationships, biogeography and morphological characters of (Molluginaceae), with special emphasis on the genus composition in Sub-Saharan Africa.

is a small genus of Molluginaceae with 8-10 species mostly distributed in the tropics of the World. Its composition and evolutionary relationships were poorly studied. A new molecular phylogeny constructed here using nuclear (ITS) and chloroplast (, ) markers confirmed the monophyly of the genus. Based on ITS analysis, the following well-supported lineages are present within : the lineage is recovered as sister to the remainder of the genus followed by Three other clades are: with ; and ; the latter is represented by a sample from North America, and as sister to + + . On the plastid gene tree, + form a sister clade to all other species. The next clade is formed by and followed by plus an American sample of . The next branch comprises as sister to + + . seems to have originated from Africa around the Late Eocene or Early Miocene, with further radiations to Australia and the Americas during the Late Miocene or Late Pliocene. Compared with the previous limited character set used for the diagnostics, we have found ten new morphological and carpological traits distinguishing members. In both trees based on nuclear and plastid datasets, the major phylogenetic clades cannot be characterized by the peculiar morphological characters. Many shared character states leading to their contrasting pattern in the multivariate analysis model are interpreted as a high homoplasy in the phylogenetically distant species. We paid special attention to the composition of the genus in Sub-Saharan Africa, a region with the greatest species diversity. Our results provide new insight into the taxonomy of in this region. Glinus lotoides var. virens accepted in many previous works is a synonym of that is closely related to based on molecular analysis and morphological characters. The status of the American populations of needs further investigation due to different characters of the specimens from the Old and the New World. Many specimens previously identified as G. lotoides var. virens and as the intermediates × belong to and (≡ ); the latter species is resurrected from synonymy after 200 years of unacceptance. In some African treatments, was known under the invalidly published name . is distributed in the southern and eastern parts of tropical Africa, and previously assumed to be endemic to West Africa is indeed a species with a wide distribution across the tropical part of the continent. previously accepted as endemic to West Tropical Africa together with other new synonyms (G. oppositifolius var. lanatus, , ) is considered here as G. oppositifolius var. keenanii (≡ Mollugo hirta var. keenanii), a variety found across the entire distribution of (Australia, Asia, and Africa). The presence of the American in Africa is not confirmed, and all records of this species belong to . The lectotypes of some names (, , , , , ) as well as a neotype of are designated. A new key to the identification of all species in Sub-Saharan Africa is provided. A checklist is given of all accepted species in this region (, , , s.l., , and ) with their nomenclature, morphological description and geographical distribution.