Evolutionary History of a Desert Shrub <i>Ephedra przewalskii</i> (Ephedraceae): Allopatric Divergence and Range Shifts in Northwestern China

<div><p>Based on two chloroplast DNA sequences, <i>psb</i>A<i>-trn</i>H and <i>trn</i>T<i>-trn</i>F, phylogeographical patterns of a desert shrub, <i>Ephedra przewalskii</i>, were examined across most of its geographic range in northwestern China. A total of sixteen haplotypes were detected. There was a common haplotype in each basin, that was haplotype A in Tarim Basin, haplotype G in Junggar Basin, and haplotype M in Qaidam Basin. Genetic variance mainly occurred among populations, geographic regions, and eleven geographic groups subdivided by SAMOVA analysis. <i>E</i>. <i>przewalskii</i> likely had a smaller and more fragmented geographic range during the Last Glacial Maximum, which was determined based on ecological niche modelling. Three groups of <i>E</i>. <i>przewalskii</i> populations were detected to have experience range expansion, and this was based on significant values of Fu’s F_S, Tajima’s D, and unimodel mismatch distributions. The cold and dry climate during the glacial period of the Quaternary is postulated to have been a driver for significant genetic isolation and divergence among populations or groups in <i>E</i>. <i>przewalskii</i>, whereas the warmer and wetter climate during the interglacial period is speculated to have provided favourable conditions for range expansion of the species.</p>