TAXONOMIC STUDY OF THE Cyperus dives DELILE COMPLEX IN EAST AFRICA

Abstract

Cyperus dives complex comprises four taxa: Cyperus alopecuroides Rottb, Cyperus dives Delile, Cyperus imbricatus Retz and Cyperus exaltatus Retz; whose taxonomic recognition varies among different authors. This study investigated the morphological variation within and between taxa in the complex in the East African region. Herbarium Specimens deposited at the East African Herbarium (EA) and Makerere University Herbarium (MUH) were examined. Morphometric data on gross morphology was collected and analysed using Cluster, Principal Component, Discriminant and Univariate analyses, using the GenStat statistical package version 2014 by VSN International Ltd. Data on distribution patterns were gathered from herbarium specimen labels and Gazetteers consulted where coordinates details were missing. Arc Map10.42 software was used to generate map to identify where various taxa within the complex are located. Examination of achenes using the scanning electron microscope (SEM) was also done. In Principal Component Analysis (PCA), the first axis accounted for 38.4% of the total character variation. Here C. imbricatus formed a distinct group; with the other three taxa exhibiting considerable overlap. Cluster analysis followed the same pattern for the 39 OTUs studied; where C. imbricatus formed a very distinct cluster, with the other three taxa showing high levels of intermixing to form one large cluster. Discriminant analysis also reveals a clear separation between C. imbricatus and the other three along root 2 while in univariate analysis it showed significant levels of statistical difference with the other three species in most of the characters used in the analysis. Based on these analyses C. imbricatus is clearly distinct from the rest of the taxa in the complex. Variations seen across the taxa were mostly in respect of length of the nutlet, stigma, filament and anther. Also, the leaf sheath width and inflorescence length. Based on these results, it can be concluded that, Cyperus dives complex consists of one distinct species (C. imbricatus) and three variables (C. alopecuroides, C. exaltatus and C. dives) that should be considered for ranking at the infraspecific level. The distribution patterns of the taxa within the complex are apparently based on their ecological preferences with some overlaps in the distribution, whereas the presumed distinct species showed a wide distribution and altitude range among all the taxa.