Comparative taxonomic investigation and its systematics application in Astragalus L. sect. Aegacantha Bunge (Fabaceae-Galegeae) from Pakistan; A phylogenetic approach

Abstract

The species of Astragalus L. sect. Aegacantha Bunge, occurring in a specific geographical range comprises eighteen species present in Pakistan. The present study was circumscribed seventeen delimiting species within the section with morphological, anatomical and seed macro- and micromorphological characterizations. In morphological study, shape and size of stipule, calyx, vexillum, wing, keel, stamen, pistil and pod were assessed and illustrated. In spine anatomy most reliable characters i.e. (outline shape, cortical cell and collenchymatous layers, numbers of vascular bundles, types of sclerenchymatous and pith parenchymatous cells, diameter of dorsal-median and ventral lateral vascular bundles, diameter of pith) were studied. In addition, in seed macro- and micromorphology were assessed using stereomicroscopy and scanning electron microscopy in order to describe and evaluate the diagnostic features in the species. The seed shape, size, colour, surface ornamentation and epidermal cells features were most significant characters in the systematic implication of studied species. Therefore, UPGMA and cluster biplot (K-means cluster analysis) analyses were performed for the phylogenetic relationship among studied species within section. Further, based on studied characters taxonomic keys were constructed for easy and adequate identification of species. The results of this study contribute novelties traits that will be helpful in phylogenetic and evolutionary study of section Aegacantha.