The Evolutionary Trend of Morphological Characters of Astragalus sect. Alopecuroidei based on Phylogeny of nrDNA ITS and cpDNA trnH-psbA Sequences

Astragalus L. (Fabaceae) with over 2500 species is the largest genus of flowering plants on Earth. Astragalus sect. Alopecuroidei DC. with over 50 species is one of the largest sections of the Old World Astragalus represented by 27 taxa in Iran. In the present study, 26 taxa of sect. Alopecuroidei and Astragalus caraganae of sect. Astragalus, as well as two species of sect. Chronopus as outgroups were selected. Seventeen morphological characters for these 29 taxa based on phylogeny of nrDNA ITS and cpDNA trnH-psbA were analyzed. The Maximum Parsimony method was used to construct a phylogenetic tree. The matrix of morphological characters was mapped on the molecular tree using Mesquite version 2.74. The results of the study indicate that, among the previously proposed subsections of Alopecuroidei, subsect. Bibracteolati is monophyletic, but the subsect. Microtropi and Megalotropi are not monophyletic. The evolutionary trend of morphological characters based on molecular phylogeny shows that three characters including the existence of bracteole, length of peduncle, and length of keel limb are synapomorphies for some clades of the Alopecuroidei sect. The other characters show homoplasy (parallelism and reversal) within this section.