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- Title
Molecular phylogenetic and morphological study of Kohautia (Spermacoceae, Rubiaceae), with the recognition of the new genus Cordylostigma.
- Authors
Groeninckx, Inge; Ochoterena, Helga; Smets, Erik; Dessein, Steven
- Abstract
Kohautia Chain. & Scham. belongs to the predominantly herbaceous Rubiaceae tribe Spermacoceac. Species of Kohautia can easily be distinguished from other Spermacoceae by their monomorphic short-styled flowers in which anthers and stigma are included in the corolla tube, with the stigma always positioned below the anthers. Mainly because of this unique floral morphology, Kohautia was considered to be a distinct genus. Molecular data (atpB-rbcL, pelD, rps16, trnL- imP, ETS, ITS) confirm that the genus is biphyletic. Two distantly related clades correspond to the subgenera Kohaulia and Pach)stigma Bremek. A similar type of floral organisation thus seems to have evolved twice independently, resulting in similarj but distantly related lineages. In order to translate the biphyletic nature of Kohautia into a formal classification, the two subgenera are recognized at generic level. A substitute name, Cordylosligma Groeninckx & Dessein is proposed for K. subg. Pkchystigma because of the existence of Pachystigma Hochst. in the Rubiaceae tribe Vanguerieae. Floral, pollen and seed characters were studied to morphologically characterize Kohautia s.str. and Cordylosligma. By optimizing pollination syndrome and pollen characters onto the molecular phylogeny, we investigated pollination shifts and pollen evolution within the two genera. Detailed floral morphological studies show that the nectar guides in the psychophilous species of Kohautia s.str. and Cordylostigma evolved in different ways but result in the same visual effect.
- Subjects
RUBIACEAE; MOLECULAR phylogeny; PLANT morphology; ANTHER; FLORAL morphology; POLLINATION; POLLEN
- Publication
Taxon, 2010, Vol 59, Issue 5, p1457
- ISSN
0040-0262
- Publication type
Article