Chromosomal studies on the alpine genus Dolomiaea

Chromosomal characteristics are important for our understanding of the evolutionary history of species diversification. However, these characteristics are as yet unknown for some plant genera, especially those in alpine regions. In this study, our aim was to investigate the chromosome numbers and karyotypes of Dolomiaea, an alpine genus occurring in the Qinghai-Tibet Plateau and adjacent regions, for the first time. We report the chromosome numbers and karyotypes of 10 species originally assigned to Dolomiaea, one species which has been suggested should be transferred to this genus and one species from the closely related genus Himalaiella. Two chromosome numbers, i.e. 2n = 36 and 2n = 34, were found in these 12 species. One B chromosome was observed in two species. Karyotypes of all the species examined are relatively asymmetrical, and are classified as Stebbins' types 3B and 2B. These findings suggest that polyploidization events played a minor role in species diversification in this alpine genus. Aneuploidy and karyotypic differentiation at the diploid level, instead, contributed greatly to species diversification in this genus. However, many lines of evidence indicate that the ancestor of the genus originated from an ancient polyploidization event. In addition, our results provide cytological evidences of the transference of Frolovia frolovii and Saussurea costus to Dolomiaea, a recent proposal based on molecular phylogenetic context

Spatiotemporal Evolution of Calophaca (Fabaceae) Reveals Multiple Dispersals in Central Asian Mountains

BackgroundThe Central Asian flora plays a significant role in Eurasia and the Northern Hemisphere. Calophaca, a member of this flora, includes eight currently recognized species, and is centered in Central Asia, with some taxa extending into adjacent areas. A phylogenetic analysis of the genus utilizing nuclear ribosomal ITS and plastid trnS-trnG and rbcL sequences was carried out in order to confirm its taxonomic status and reconstruct its evolutionary history.Methodology/principal findingWe employed BEAST Bayesian inference for dating, and S-DIVA and BBM for ancestral area reconstruction, to study its spatiotemporal evolution. Our results show that Calophacais monophyletic and nested within Caragana. The divergence time of Calophaca is estimated at ca. 8.0 Ma, most likely driven by global cooling and aridification, influenced by rapid uplift of the Qinghai Tibet Plateau margins.Conclusions/significanceAccording to ancestral area reconstructions, the genus most likely originated in the Pamir Mountains, a global biodiversity hotspot and hypothesized Tertiary refugium of many Central Asian plant lineages. Dispersals from this location are inferred to the western Tianshan Mountains, then northward to the Tarbagatai Range, eastward to East Asia, and westward to the Caucasus, Russia, and Europe. The spatiotemporal evolution of Calophaca provides a case contributing to an understanding of the flora and biodiversity of the Central Asian mountains and adjacent regions