The Genus Syngonanthus (Eriocaulaceae) in Eastern and Southern Africa

Abstract

Summary. A key, descriptions and notes on circumscription and identification are given for the 9 species of Syngonanthus Ruhland which occur within the area covered by the Flora of Tropical East Africa and Flora Zambesiaca. S. exilis S. M. Phillips, S. mwinilungensis S. M. Phillips and S. wahlbergii (K6rn.) Ruhland var. sinkabolensis S. M. Phillips are described as new. Seed morphology as seen under the scanning electron microscope is discussed and photomicrographs provided. The basic structure of the surface sculpturing of the seed is found to be uniform throughout. Kimpouni studied the genus in central Africa for the "Flore d'Afrique Centrale". The present paper is a precursor for the accounts in the Flora of Tropical East Africa and the Flora Zambesiaca. The area of high endemism in the genus identified by Kimpouni in southern Zaire certainly extends to northern Zambia. Two new species are described in this paper from the Mwinilunga area of northwest Zambia, and other problematical specimens from Zambia may represent further new species. Most of the African species form part of a variable complex and the delimitation of the individual species presents great difficulty, as pointed out by Hess (1955, p.185). In stark contrast to the situation in Eriocaulon, the morphology of the flowers and seed-coat in African Syngonanthus is remarkably uniform, offering few taxonomically reliable characters. Specific delimitation hence rests largely on a combination of characters, often vegetative which are themselves highly variable and subject to environmental influence. The situation is exacerbated by a paucity of collections, so that the significance of individual variants is difficult to assess. There is evidence from some mixed collections of hybridisation between species, for example S. schlechteri x wahlbergii (Haarer 2046 from Uganda). It seems likely that there are few barriers to gene flow across specific boundaries throughout most of the African complex.