Morphological, anatomical, cytological and biochemical aspects of evolution in East African shrubby species of Aloë L. (Liliaceae)

Abstract

Twelve previously described shrubby species of Aloé L. from Kenya, Congo, Tanzania and Uganda were investigated using a multidisciplinary. approach. Half of the species were found to be tetraploids (24, 28), and because of the rarity ot tetrapolody in the genus it is suggested that these are very closely related and of common origin. Studies of their gross morphology and leaf surface sculpturing reveal clinical variation patterns. These patterns indicate the diploid species likely to be similar to the ancestor of the tetraploids, and the geographic region where the chromosome doubling probably occurred. Variations in the composition of the leaf exudates largely confirm the conclusions drawn from the cytological and anatomical observations. A taxonomic revision based on the experimental findings changes the status of Rift Valley forms of A. kedongensis to a subspecies of A. nyeriensis and also enlarges the latter to include A. ngobitensis.