Molecular and morphological revision of the Allium saxatile group (Amaryllidaceae): geographical isolation as the driving force of underestimated speciation

Abstract

The taxonomic circumscription of Allium saxatile s.l. (Amaryllidaceae), widely distributed from Italy to China, has been controversial with the number of accepted species ranging from three to seven. The aims of this study include a morphological and molecular revision of the group, a thorough nomenclatural study of available names and the reconstruction of possible phylogenetic relationships in the A.saxatile group. We studied c. 2000 herbarium specimens and successfully sampled 86 accessions of the A.saxatile group and a few related species to reconstruct a molecular phylogenetic tree based on internal transcribed spacer (ITS) and two plastid DNA regions (rpl32-trnL and trnL-trnF). The monophyletic A.saxatile group consists of 15 geographical entities united in two geographically justified clades. Two yellow-flowered species, A.obliquum and A.petraeum, were clearly nested in the A.saxatile clade in the ITS and plastid DNA analyses. The oldest names in the group, i.e. A.saxatile and A.globosum from the Caucasus, represent genetically identical populations and should be synonymized. The taxonomic conspectus in this article includes 15 species and a nothospecies. We describe five new species (A.austrodanubiense sp. nov., A.schistosum sp. nov., A.cretaceum sp. nov., A.montanostepposum sp. nov., A.kirilovii sp. nov.), a nothospecies (A.xagarmyschicum nothosp. nov.) and raise a variety to species level (A.rubriflorum comb. nov.).(c) 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 67-101.