Phylogeny and Taxonomy of Allium Section Longibidentata (R.M.Fritsch) R.M.Fritsch (A. Subgenus Melanocrommyum): Resurrection of Allium simile Regel

During fieldwork in the western Tian Shan Mountain range, somewhat different forms of Allium fetisowii s.l. were observed in its eastern and western parts. A detailed morphological study using principal component analysis (PCA) revealed the presence of two well-separated taxa within A. fetisowii s.l. A molecular study based on nrITS and four plastid markers (trnL–trnF, rpl32–trnL, trnQ–rps16 spacers, and the rps16 intron) confirmed their status at the species level. Allium fetisowii Regel s. str. occurs in the eastern part, whereas the name A. simile Regel applies to the plants growing in the western part. Together with A. chychkanense, these species constitute section Longibidentata, which is supported by molecular data. The nomenclatural history of these three species is explained. A taxonomic conspectus is provided, the distribution is mapped, and an identification key is presented.