A morphological and anatomical survey of Virectaria (African Rubiaceae), with a discussion of its taxonomic position

A detailed morphological and anatomical study of the tropical African genus Virectaria is presented. The observations are used to characterize the gen us, to propose a key to all eight species, and to unravel the relationships between the species using cladistics. A taxonomic survey of the genus is a lso given. Verdcourt's infraspecific taxa based on calyx morphology in V. m ajor are adopted, but it was found that morphological distinction is correl ated with ecological, habit and distributional differences. Hence, it is be tter to recognize Verdcourt's varieties spathulata and major as subspecies of V. major. The problematic systematic position of the genus is discussed in detail. New evidence is given for the exclusion of the genus from the He dyotideae and Ophiorrhizeae (subfamily Rubioideae). The recently proposed p osition in the Sabiceeae (subfamily Ixoroideae) is not convincing either, s ince none of the genera included in the Sabiceeae matches Virectaria with r espect to pollen, fruit, flower and growth habit. Exclusion from the Rubioi deae and a position near the Sabiceeae is supported by lack of raphides, se ed anatomy, placentation, stipule morphology and molecular evidence. Molecu lar data from a larger number of taxa are needed to confirm the position of the genus. (C) 2001 The Linnean Society of London.