Phylogenetic systematics, cytogenetics and taxonomic revision of the genus Koellensteinia Rchb. f. (Orchidaceae)

Abstract

The Neotropical biodiversity is product of many evolutionary processes, but several of them we are just beginning to realize and understand. To accomplish this task, well-sampled and dated phylogenies are necessary for the understanding of Neotropical diversification. The family Orchidaceae is one of the largest families of plants, with about 25000 species and 850 genera. Orchidaceae is one of the best studied families of angiosperms with regard to intra-familiar phylogenetic relationships. However, several studies have shown that traditional classifications were incorrect and required revision. Moreover, until recently, there were no reliable fossils in the family, which is crucial for correctly estimate the age of orchid groups. In this sense, this project proposes the study of Koellensteinia Rchb. f., a South American genus of Orchidaceae. Koellensteinia has about 17 species distributed in South America, with center of distribution in Brazil. The group has several taxonomic uncertainties related to the delimitation of its species and even of the genus itself. Recent phylogenetic studies indicate that Koellensteinia is a paraphyletic group, and its relationship with close genera like Aganisia, Otostylis and Paradisanthus remains unclear.The main objective of this project is to develop a phylogenetic hypothesis for Koellensteinia and nearby genera, in order to understand the evolutionary history of this Neotropical orchid group. In this context, a biogeographical analysis of Koellensteinia will be conducted, including a detailed population approach of the complex K. eburnea-K. tricolor. Plant samples are being collected in Brazil and other South American countries. DNA of the specimens will be extracted from fresh or silica gel dried leaves. We will formerly use DNA regions previously analyzed for other Zygopetalinae genera (ITS, matK, rbcL e trnL-F) for the positioning of Koellensteinia within the subtribe. Tests will be performed with nuclear and plastidial regions with higher mutation rates to clarify the infrageneric relationships. The sequences will be deposited in GenBank. The phylogenetic and biogeographic analyzes will be performed by Bayesian, parsimony and maximum likelihood methods. The molecular dating will be inferred by Bayesian method with inclusion of fossils for molecular calibration. (AU)