Systematics and evolution of Carapa Aubl. (Meliaceae-Swietenioideae)

Species are the bases of analyses in evolution, biogeography, ecology and conservation. Despite recent progress in molecular systematics, botanists, particularly monographers, still usually use morphological characters that are not analyzed explicitely for diagnosing and delimiting species. Such characters are difficult to use for recognising so-called cryptic species, morphologically similar populations that are, at least to some extent, reproductively isolated. Most of these cryptic species are part of apparently widespread species but can be uncovered with the aid of molecular techniques.;Carapa, commonly known as crabwood or andiroba, is a member of the Mahogany family Meliaceae and comprises trees disjunctly distributed in tropical forests in Africa and America. The taxonomy of Carapa has long been controversial. Even the monophyly of the genus has been disputed because of the morphological similarity to the mangrove Xylocarpus Koen. Of the three species currently recognized in the genus, two, widespread, are known to present substantial morphological variation that has been used in the past to distinguish several taxa. The need for systematic studies of Carapa with a reassessment of species boundaries became apparent as species of the genus are becoming increasingly socio-economically important throughout its distribution range.;Phylogenetic inferences from sequence data of the nuclear ITS ribosomal DNA strongly supported the monophyly of Carapa and its sister relationship with the African genus Khaya A. Juss. The four clades recovered within Carapa, concordant with geography, suggest an African origin of the genus with a single introduction to America. Univariate analysis of leaf, floral and seed characters, and Principal Coordinate Analysis of floral characters in the context of this molecular phylogeny suggested that there are 27 species in the genus, including 15 previously described and 12 novelties. In general, species in the same geographic area were phylogenetically related, yet were morphologically distinct, even in sympatry. A classic revision with a key, illustrations, the description of the 27 species in the genus, and citation of specimens seen is provided.