Taxonomic studies on the cissus quadrangularis L. Complex in Kenya

Abstract

The genus Cissus L. (vitaceae) is largely tropical in occurrence. Cissus quadrangularis L. and the closely related C. cactiformis Gilg and C. quinquangularis Chiov. are succulent plants that present systematic problems? Controversy has existed as to whether they should be considered as one species under the name C.quadrangularis. Following a taxonomic investigation of the complex in Kenya, by the use of field observations, and morphological, anatomical, palynological and chromosome studies, the material gathered is delimited into ten taxa.

Field observations and herbarium studies reveal that some taxa are very widespread and occupy a wide range of habitats and altitudes, while others are localized and have patchy distribution patterns. The localized taxa are commonly found in southeastern Kenya especially in coast Province. Some of the habitats where the plants grow are disturbed mainly because of vegetation clearing and overgrazing. The flora and dependent fauna of the affected habitats are threatened.

Various taxa are used locally as sources of medicine and fibre by the local communities. They are also used as hedge plants and for ornamental purposes especially in urban areas. Some of the plants are used by the traditional communities for obscure magical and superstitious purposes.

It is concluded that C.cactiformis and quinquangularis are two separate taxa distinct from C.quadrangularis at specific rank. Other characteristics that distinguish the disputed taxa have also been realized in the study. In addition, undescribed taxa that have hitherto either been included in C.quadrangularis or unknown are recognized. It is proposed that these comprise five new species, one new variety and one taxon whose status remain uncertain. The main diagnostic characters of the taxa comprising the complex are vegetable and include stem, leaf and root characters. Fruit shape and surface sculpture are important taxonomic characters for some taxa.

Some of the taxa are potential economic plants for some aridareas. They could be utilised as choice plants in horticulture and as sources of pharmaceutical products and fibres.