The significance of morphological features in the taxonomy of some members of the Araceae family

Morphological studies were carried out on 16 taxa from five genera namely Aglaonema, Dieffenbachia, Alocasia, Colocasia and Xanthosoma in the family Araceae growing in Nigeria to search out characteristics which may enhance the taxonomic status of the family. Qualitative and quantitative morphological characters were studied. Unifying and specific qualitative morphological characters were documented. The quantitative data was subjected to Single Linkage Cluster Analysis and Principal Components Analysis. All the taxa studied were herbaceous, found growing in open places, farmlands or wastelands as ornamentals or food crops. Caulescent growth habit, an advanced type of growth habit, exhibited by members of the genera Aglaonema and Dieffenbachia, clearly separated them from the members of genera Alocasia, Colocasia and Xanthosoma which exhibited acaulescent growth habit. Lanceolate, oblong and elliptic leaf shapes also separated members of the genera Aglaonema and Dieffenbachia from members of the other three genera with reniform, cordate and saggitate leaf shapes. Leaf apices observed in the taxa studied were caudate, acuminate, cirrhose, acute and mucronate while leaf bases were obtuse, acute, cordate and saggitate. These cut across the five genera and can be employed in delimiting individual species in the genera. Pinnate venation type also differentiated all the taxa belonging to Aglaonema and Dieffenbachia from the taxa belonging to Alocasia, Colocasia and Xanthosoma where palmate-pinnate venation was observed. The significance of morphological characters that revealed the phylogenetic relationship among the genera, which include the habits, leaf shape, nature of the stem/corm, and leaf type was discu