title: Revisiting the evolutionary events in Allium subgenus Cyathophora (Amaryllidaceae): Insights into the effect of the Hengduan Mountains Region (HMR) uplift and Quaternary climatic fluctuations to the environmental changes in the Qinghai-Tibet Plateau.
abstract: The respective roles that the Hengduan Mountains Region (HMR) uplift around 4-3 Ma and Quaternary climatic oscillations played in causing the environmental changes in the Qinghai-Tibet Plateau (QTP) remain unknown. Here, we reconstruct the evolutionary history of two varieties of Allium cyathophorum and A. spicatum of subgenus Cyathophora, restricted to the HMR and the western QTP, respectively. Forty-five populations were surveyed for chloroplast and nuclear sequence variation to evaluate phylogenetic relationships, dates of divergence and ancestral area/inflorescence reconstructions. In addition, analyses were conducted on discernable micromorphologies, cytotypes and seed size variation. Our results indicated that two varieties of A. cyathophorum are separate species, i.e. A. farreri and A. cyathophorum, and the initial split of Cyathophora was triggered by the HMR uplift around 4-3 Ma. Subsequently, A. spicatum originated through the strengthened aridification in the western QTP induced vicariance of the ancestral populations in the HMR during the early Pleistocene. A self-sustaining allotetraploid species from A. farreri and A. cyathophorum was established during an interglacial period of penultimate glaciation of the QTP. Seed size variation also supports these by the colonization-competition tradeoff among small and large seeds. Our findings appear to suggest that the HMR uplift could have strengthened the development of the Asian monsoon regimes in this region and aridification in the western QTP, while the Quaternary climatic oscillations spurred the allopatric species' range shifts and created new open microhabitat for the alloploid species.
authors.affiliation: Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, PR China.
authors.forename: Min-Jie
authors.initials: MJ
authors.lastname: Li
authors.affiliation: Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, PR China.
authors.forename: Jin-Bo
authors.initials: JB
authors.lastname: Tan
authors.affiliation: Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, PR China.
authors.forename: Deng-Feng
authors.initials: DF
authors.lastname: Xie
authors.affiliation: Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, PR China.
authors.forename: De-Qing
authors.initials: DQ
authors.lastname: Huang
authors.affiliation: Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, PR China.
authors.forename: Yun-Dong
authors.initials: YD
authors.lastname: Gao
authors.affiliation: Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, PR China. Electronic address: xjhe@scu.edu.cn.
authors.forename: Xing-Jin
authors.initials: XJ
authors.lastname: He
mesh_terms: D000490:Allium / Q000145:classification* / Q000235:genetics; D005075:Biological Evolution; D018742:DNA, Chloroplast; D004777:Environment; D014644:Genetic Variation; D010802:Phylogeny; D058974:Phylogeography; D018609:Tibet
chemical_list: D018742:DNA, Chloroplast
keywords: Allium subg. Cyathophora; Environmental changes; Hengduan Mountains Region; Qinghai-Tibet Plateau; Quaternary climatic oscillations; Speciation