Systematics of Lapeirousia (Iridaceae-Ixioideae) in Tropical Africa

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Abstract
The genus Lapeirousia, a member of the predomonantly African subfamily Ixiodeae of iridaceae, is one of five genera of tribe Watsonieae and is the only one that is widespread in southern and tropical Africa. In this revision of the tropical members of the genus, 16 species are recognized, 14 assigned to the largely tropical sect. Paniculata (subg. Paniculata) and two to the largely temperate southern African sect. Sophronia (subg. Lapeirousia). One new species, L. angolensis, is described and L. teretrifolia is raised from subspecies to species rank. The center for tropical African Lapeirousia is northern Namibia, but species occur across south tropical Africa to Mozambique and north to Ethiopia, Sudan, and Nigeria. Lapeirousia is one of few genera well represented in both tropical Africa and the winter-rainfall region of temperate southern Africa, and it is unique in its wide distribution in drier parts of Africa rather than the well-watered eastern highland areas of the continent. Variation among the species is largely floral, and flowers range from completely actinomorphic to medianly zygomorphic and from short-tubed to extremely long-tubed. An unusual degree of chromosomal variation occurs in sect. Paniculata with numbers ranging from n = 8, 7, 6, 5, 4, to 3 and karyotypes from strongly bimodal to relatively uniform. Chromosome cytology correlates to some degree with patterns of morphological variation and provides independent support for the phylogeny of the tropical species.

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