Updated Taxonomy of Iris scariosa (Iridaceae) Inferred from Morphological and Chloroplast DNA Sequence Data with Remarks on Classification of Iris subg. Iris

<i>Iris scariosa</i> is a rhizomatous perennial whose taxonomy and distribution range still remain unclear. The results of our examination of literature, specimens, and wild plants have shown that <i>I. glaucescens</i>, described from Kazakhstan, and <i>I. timofejewii</i>, considered to be endemic to the Republic of Dagestan, Russia, are very closely related to <i>I. scariosa</i>. We have carried out molecular phylogenetic analyses for the first time to clarify the taxonomy of <i>I. scariosa</i>. For this, we sequenced six chloroplast DNA regions of an extended sampling that comprised the accepted species <i>I. glaucescens</i> and <i>I. timofejewii</i>, which has revealed their strong affinity to the accession of <i>I. scariosa</i> from the vicinity of Astrakhan, Russia. A thorough revision of the morphological characters has confirmed the lack of evident differences between <i>I. scariosa</i> and <i>I. timofejewii</i>. Thus, the analyses support a broad species circumscription of <i>I. scariosa</i>. We here reduce <i>I. timofejewii</i>, as well as <i>I. curvifolia</i>, considered to be endemic to Xinjiang, western China, to synonymy of <i>I. scariosa</i>. Color illustrations, updated nomenclature, and data on distribution of <i>I. scariosa</i> are provided. A lectotype for <i>I. astrachanica</i> and a neotype for <i>I. timofejewii</i> are designated here. Also, the phylogenetic relationships within <i>I</i>. subg. <i>Iris</i> are outlined, and an updated classification of the subgenus is proposed. We have recovered six major lineages within four major clades which we recognize as sections. Here, we propose two new nomenclatural combinations, a revised taxonomic treatment, and a new identification key to <i>I</i>. subg. <i>Iris</i>.