Genetic structure of the endangered, relict shrub Amygdalus mongolica (Rosaceae) in arid northwest China

In the present study we selected the endangered species Amygdalus mongolica to investigate the influence of climatic fluctuations on the spatial genetic patterns and evolutionary history of organisms in arid northwest China. The intraspecific genetic variation and demographic history of A. mongolica were investigated using two cpDNA sequences (psbK-psbI and trnL-trnF) from 174 individuals in 15 populations across most of its covered range. Significant genetic differentiation among populations was identified, which resulted from fragmented populations coupled with the enhanced aridification and desertification of the Pleistocene. Twelve haplotypes clustered into two clades, corresponding to the Western region (northernmost Gansu, Hexi Corridor and Alxa Left Banner) and the Eastern region (Urad Houqi, Yinshan Mountains, Urad Zhongqi and Daqing Mountains) respectively. Five independent Pleistocene refugia in different mountainous areas were identified. Amygdalus mongolica has likely experienced westward shifts from refugia along the margins of the Ulanbuhe and Tengger deserts, and also postglacial re-colonisation northward along the Hexi Corridor.