Taxonomy and phylogenetics of Allium section Decipientia (Amaryllidaceae): morphological characters do not reflect the evolutionary history revealed by molecular markers

Abstract

Phylogenetic and phylogeographic patterns in Allium section Decipientia (subgenus Melanocrommyum) were analysed, including most species of this section and representative species of most other sections of the monophyletic Allium subgenus Melanocrommyum. We constructed a molecular phylogenetic tree based on predominantly noncoding sequences from nuclear ribosomal RNA and four plastid regions. In Allium section Decipientia, 2n = 16 and 2n = 20 chromosomes were confirmed and, in part, newly reported. All plants with 2n = 20 form a clade that is sister to the European A. decipiens and A. quercetorum with 2n = 16 in the ITS analysis and are genetically distant from the Eurasian steppe species with 16 chromosomes, A. tulipifolium and A. robustum. The plastid analysis does not reveal a clear relationship between these three monophyletic groups. The karyotype of A. tulipifolium is similar to those of other members of subgenus Melanocrommyum, but only preliminary chromosomal dimensions could be presented for the species with 2n = 20 chromosomes. The latter group comprises A. grande, A. subscabrum, A. viridulum and the newly described taxa A. koksuense and A. lepsicum. Allium tulipifolium and A. robustum have been placed in a new section Tulipifolia, and all species with 2n = 20 have been placed in a new subsection, Viceniprason, of section Decipientia. A nomenclatorial conspectus and a key for determination of the members of Allium sections Decipientia and Tulipifolia are also provided. According to the time divergence estimation, subgenus Melanocrommyum diversified c. 25 Mya in the late Oligocene. The split between most species of the section Decipientia and other taxa in this subgenus was estimated as early Miocene, which furthermore diversified into two sister clades in mid Miocene. Allium decipiens split off from the ancestors of the 2n = 20 species also in the mid Miocene. Further branching in this species group is of rather young age, and occurred within the last 6 Myr (late Miocene to late Pliocene and Pleistocene).