A broadly sampled 6-loci plastid phylogeny of Atraphaxis (Polygoneae, Polygonoideae, Polygonaceae) reveals new taxa: IV. Cryptic species related to A. bracteata in Mongolia

The taxonomic diversity of the genus Atraphaxis in Mongolia and adjacent territories was studied. Maximum Likelihood and Bayesian analyses applied for six concatenated plastid regions (cpDNA trnL(UAA) intron, trnL– trnF IGS, and rpl32–trnL(UAG) IGS regions, rps16 intron, trnH-psbA, matK), and to the ITS1–5.8S–ITS2 regions of nrDNA of 46 species of the genus Atraphaxis, as well as reconstruction of plastid haplotype and ITS ribotype networks, revealed the following three new species sympatrically distributed in southern Mongolia: A. alashanica, A. gubanovii, and A. mongolensis. Molecular data and morphological characteristics indicate the hybrid nature of these species from (1) A. bracteata and A. ledebourii, (2) A. ledebourii and A. alashanica, and (3) A. pungens and A. alahanica. Atraphaxis bracteata was involved in the origin of A. selengensis, whereas A. manshurica arose as a hybrid of A. ledebourii and A. bracteata. The morphological characters of the species are illustrated by original photo tables. Distributional maps of the Mongolian species, descriptions of the new species, and an identification key to 22 Atraphaxis species from Mongolia and adjacent regions are also provided.