مطالعه تاكسونومي و فيلوژني جنس .Psephellus Cass در ايران

The study of taxonomy an‎d phylogeny of the genus Psephellus Cass. in Iran

زيست شناسي گياهي و جانوري

The genus Psephellus Cass. (Asteraceae) comprises nearly 114 species an‎d is taxonomically one of the most complex an‎d morphologically variable genera of the tribe. This taxonomic complexity, together with its limited current circumscription, necessitates a comprehensive eva‎luation based on morphological, molecular, an‎d historical-biogeographical evidence across its distribution range in Iran, Turkey, an‎d the Caucasus. To this end, we investigated the relationships, divergence times, an‎d evolutionary patterns within Psephellus using nuclear ribosomal ITS sequences an‎d the chloroplast region trnL–trnF, an‎d reconstructed phylogenetic trees. The separate phylogenetic analyses of ITS an‎d trnL–trnF provided several noteworthy results; however, the combined dataset yielded a more resolved phylogeny. The monophyly of Psephellus was strongly supported in the combined analysis, whereas individual datasets provided relatively weaker support (BS = 68). Overall, the molecular phylogeny confirmed many of the traditionally recognized taxonomic sections, although certain discrepancies persisted. The analyses also indicated a clear separation between sections Psephelloidei an‎d Odontolophoidei, as well as the distinct placement of Hyalinella. The divergence time estimation suggested that Psephellus originated approximately 6/97 million years ago, during the late Miocene. Several key diagnostic traits showed repeated evolutionary changes within the major clades, highlighting morphological convergence in the genus. In this study, the collection an‎d taxonomic investigation of 14 species of the genus Psephellus in Iran were carried out. The sections an‎d species were described, an‎d two new species from Iran, P. sennikovianus Negaresh an‎d P. avajiqensis Negaresh, were introduced. In addition, identification keys for the sections an‎d species occurring in Iran were prepared. Chromosome counts revealed that P. incanescens has 2n = 2x = 60 an‎d P. avajiqensis has 2n = 2x = 30, both of which are reported here for the first time worldwide. The results of this study highlight the necessity of revising the current classification of the genus Psephellus based on molecular an‎d morphological data an‎d provide valuable insights into the evolutionary history an‎d diversification patterns of this genus.

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