University of Missouri - Saint Louis

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Announcement

An oral examination in defense of the dissertation for the degree

Doctor of Philosophy

David Kenfack
Doctorat 3eme Cycle in Plant Systematics, April 1995, University of Yaoundé I, Cameroon.
Maitrise ès Science in Plant Biology, May 1987, University of Yaounde I, Cameroon.

Systematics and evolution of Carapa (Meliaceae-Swietenioideae)

Abstract

Species form the bases of analyses in biogeography, ecology and conservation. Despite of the progress in molecular systematics in recent years, botanists, particularly monographers, still usually use morphological characters for diagnosing and delimiting species. Such characters are difficult to use in 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 and often, are 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. 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, most of which are currently placed in synonymy. The need for systematic studies of Carapa with a reassessment of species boundaries became apparent as species of the genus are increasingly becoming socio-economically important in many countries 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 gennus 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, morphologically distinct species occurred in the same geographic area and were also phylogenetically related. A classic revision with the description of the 27 species in the genus is provided.  

Defense of Dissertation Committee