Phylogenetic species delimitation unravels a new species in the genus Sclerorhachis (Rech.f.) Rech.f. (Compositae, Anthemideae)

Sclerorhachis is a small genus and belongs to subtribe Handeliinae of tribe Anthemideae (Compositae). While according to the Flora Iranica only two species of the genus are indicated for Iran (i.e. S. platyrachis and S. leptoclada), the genus constitutes a taxonomically very interesting group here due to the presence of several isolated populations deviating from others morphologically. In the present study, we have used phylogenetic analyses as well as sequence-based species delimitation methods for clarifying species boundaries in Sclerorhachis. We used sequence information from the nrDNA regions ITS (ITS1–5.8S–ITS2) and ETS along with the plastid intergenic spacer region rpl32–trnL(UAG) in an array of sequence-based species delimitation methods: (1) the Bayesian implementation of generalised mixed Yule-coalescent (bGMYC) model and (2) a Bayesian implementation of the Poisson tree processes (bPTP) method. We compared the results of these methods with species delimitations derived from the statistical parsimony networks constructed with TCS and the application of a monophyletic species concept. When the results of phylogeny-based methods, species delimitation approaches, and morphological evidences are jointly considered, our study supports the classification of S. leptoclada as an independent species and reveals a new species of Sclerorhachis in the Binalud Mountains (described as S. binaludensis). It also indicates a new record of the species S. caulescens (formerly only known from Afghanistan) for Iran. Additionally, a morphologically deviating and phylogenetically independent population group of S. platyrachis was found along the NE boundary of Iran, which is considered being conspecific with the Turkmenistan species S. kjurendaghi. As a consequence, the present study indicates that Sclerorhachis is represented in the territory of Iran by five independent, evolutionary significant units (i.e. species).