James, O. E.1, Ajuru*1,M.G. and Ozimede, C.O2.
Abstract
Numerical taxonomy is a veritable and useful tool in plant classification and identification studies. However the potentials and opportunities offered by this field have not been maximally harnessed in plant systematics. This study demonstrated the significance of numerical taxonomy in plant classification studies by using species of Euphorbiaceae as a case study. Numerical taxonomy differs from conventional taxonomy in the sense that the later equate taxonomic relationships with evolutionary relationships whereas the former views and treats them in three ways which includes: Phenetic- based on overall similarities; Cladistic- based on a common line of descents and Chronistic- based on temporal relation among various evolutionary branches. Usually, the species to be classified are called Operational Taxonomic Units (OTUs). In this report, characters were spotted out and then codified numerically. These numerically coded characters were recorded in the form of appropriate numbers in a manner that indicate that the differences among them are proportional to their dissimilarities. Seven species of Euphorbiaceae were subjected to cluster analysis using 60 diagnostic characters as it is already an established concept among taxonomists that the more characters used in numerical taxonomic studies, the more efficient the result would be. The Numerical taxonomic methods adopted to analyze these characters drawn from morphological, epidermal and anatomical lines of evidence proved effective as results validated previous systematics. This is because all operational taxonomic units (OTUs) belonging to same genus were clustered as a group indicating that they are more related to each other. Recommendation was made for numerical taxonomy to be applied to other groups of plant for classification studies.
Keywords: Diagnostic characters; Euphorbiaceae; Numerical Taxonomy; Operational
Taxonomic Unit; Phenetic; Cladistic; Chronistic