Taxonomic Relationships in the Aloe Morijensis (Xanthorrhoeaceae) Complex
Loading...
Date
2015
Authors
Uleh, Amodu Mark
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Cutler and his colleagues (1980) investigated evolutionary relationships in the tetraploid
shrubby species of Aloe in Kenya. They concluded that the tetraploid shrubby species,
Aloe kedongensis and Aloe nyeriensis had evolved from a form very close to the diploid
Aloe morijensis S. Carter & Brandham in which chromosome doubling had occurred,
followed by spreading northwards from Morijo in Narok County. However, in contrast to
the tetraploid shrubby species that have aloitic cells which produces exudates, A.
morijensis has fibres in the leaves in place of the aloitic cells that produce distinctive
exudates in most aloes. A return to aloitic cells from fibres would be a reverse of an
evolutionary trend, which is unlikely in science. Hence, this conjectured origin of the
shrubby species and their relationship with A. morijensis was investigated, vis-a-vis the
tetraploid shrubby A. nyeriensis Christian and A. kedongensis Reynolds, using anatomical
characters not employed by Cutler et al. The presence of lignified cells was seen in the
base, middle and apex of the lamina of A. morijensis while in the case of the tetraploid
shrubby species only aloitic cells were found. These results suggest that it is very
unlikely that A. morijensis is the ancestor of the tetraploid shrubby aloes. Also, Aloe
morijensis has been found at several localities in Kenya in addition to the type locality
near Morijo, and also in Tanzania, but there appear to be some differences between the
populations. Population variation was investigated by considering morphological,
anatomical and phytochemical characters. The Kruskal- Wallis Test was used to analyze
data generated for phytochemistry while the morphological characters were coded into
numerical values and a dendrogram drawn using Minitab software to show relationships
among the fibrous species. Results suggest that the Eastern variant of A. morijensis
should be recognized as a distinct variety. The chromosome number of A. tegetiformis
L.E. Newton was not determined by the nomenclatural author. In view of its location
further north than the tetraploid shrubby species, its relationship with A. morijensis was
also investigated. Results confirm that A. tegetiformis is a species distinct from A.
morijensis.
Description
Department of Plant and Microbial Sciences, 78p. 2015, QK 495 .L72M3