Phylogeographical patterns of two closely related desert shrubs, Nitraria roborowskii and N.sphaerocarpa (Nitrariaceae), from arid north-western China

摘要

To investigate the influence of climate aridification and oscillations on the genetic diversity and evolutionary processes of organisms in the Quaternary in north-western China, we selected Nitraria roborowskii and N.sphaerocarpa and examined the geographical apportionment of genetic variation in their vast range. In the study, 21 plastid haplotypes were identified in N.roborowskii based on two plastid DNA regions. We found significant genetic differentiation between populations in both N.roborowskii and N.sphaerocarpa. We also found similar phylogeographical patterns of allopatric divergence and regional range expansion in both species, but the degree of allopatric divergence in N.roborowskii was lower. Finally, areas to the south of the Alxa Desert, the Hexi Corridor and Ningxia Province were identified as possible refugia for N.roborowskii.