Re-assessment of subspecific taxa in Astragalus section Anthylloidei (Fabaceae) based on molecular evidence

Abstract

The taxonomic and phylogenetic status of several taxa previously recognized as subspecies in Astragalus sect. Anthylloidei is re-assessed based on DNA sequences and morphological features. We focused on Astragalus ebenoides (subsp. ebenoides and subsp. naghadehensis), Astragalus murinus (subsp. murins and subsp. bornmuelleri), Astragalus remotiflorus (subsp. remotiflorus and subsp. melanogramma), Astragalus nigrohirsutus (=Astragalus remotiflorus subsp. nigrohirsutus), Astragalus submitis (=Astragalus submitis subsp. submitis) and Astragalus yushensis (=Astragalus submitis subsp. maassoumii). A total of 15 accessions representing 14 ingroups and one outgroup were analysed for nrDNA ITS and plastid DNA, rpl32 gene and rpl32-trnL(UAG) intergenic spacer. Phylogenetic trees were constructed using neighbour joining, Bayesian and maximum parsimony methods. The phylogenetic analyses of both datasets revealed that the subspecies described formerly under each of the studied species are distinct and should be elevated to specific rank. The nucleotide sequence variations observed among different subspecies, along with morphological characters, provided appropriate criteria in setting the species boundaries. The new combinations and a diagnostic key to the studied species are provided.