Numerical taxonomy of Cassia sensu lato

Abstract

Cassia s. I. is one of the large genus of flowering lants, occurs naturally in the tropics around the world. It was found that some species are difficult to determine due to their morphological complexes. Accordingly, this genus was separated by some workers into three genera, namely Cassia L. s. s., Senna Miller and Chamaecrista Moench. However, some authors still placed all species in a single genus, i.e. Cassia s. I. In order to confirm their taxonomic status, 508 specimens of 18 taxa were investigated in this thesis by numerical taxonomic techniques. Three multivariate morphometric analyses, namely factor analysis, cluster analysis and canonical discriminant analysis were used. The total 32 vegetative and reproductive morphological characters were focused on these analyses. The results of factor analysis revealed that most vegetative and most reproductive characters were separated on the two factor components. In cluster analysis, the Cassia s.I. can be separated into four groups viz. Chamaecrista, Senna alata, Senna and Cassia s.s. at average taxonomic distance 1.30. Nevertheless, the fourth group also included Senna spectabilis. The four-cluster grouping was discussed. From overall canonical discriminant analyses, it can be concluded that there are three groups within the genus Cassia s.I., as was proposed by Irwin and Barneby earlier. The most important characters for canonical discriminant analysis are filament length, fruit length, ovary stalk length. เท addition, Senna obtusifolia L., a new recorded species for Thailand, was found during specimen collections.