Contribution to pollen morphology of Astragalus L. section Aegacantha Bunge (Galegeae, Fabaceae) and its systematic significance

ABSTRACTAstragalus L. sect. Aegacantha Bunge has 57 described species mostly confined in Southwest Asia and Central Asia. Here, we studied the pollen morphology of 17 species from this section present in Pakistan. Pollen morphology of sect. Aegacantha species is poorly investigated despite its systematic importance. The main aim of this study is to determine and document the pollen characters that can help in the taxonomic identification of species in this difficult section. Pollen slides were prepared following acetolysis and examined by both light and scanning electron microscopy. Pollen size varies, with the polar axis ranging from 32.91-43.10 μm and the equatorial axis from 22.91-28.47 μm. The shape of pollen is sub-prolate (1.15-1.33) to prolate (1.34-2.00), small to medium in size, radially symmetrical, isopolar, trizonocolporate to tricolporate and monads. Sculpturing variations (i.e. reticulate, microreticulate, perforate, microperforate, regulate, microregulate and granulate) were observed around the apertural, meridional and polar regions. Ordination (PCA) analysis revealed that the quantitative characters of pollen morphology are the most reliable characters for delimitation of section Aegacantha species. Cluster (UPGMA) analysis shows a partial relationship between the Aegacantha taxa clustered based on pollen characters and supports the general morphology. Further, this study shows that the pollen traits provide a baseline for phylogenetic optimization in the investigated Aegacantha section.KEYWORDS: TaxonomypalynologyphylogenySEM-analysisPCAUPGMAPakistanDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also.