Abstract
The disjunct distribution of forests in the Qinghai‐Tibetan Plateau (QTP) and adjacent Helan Shan and Daqing Shan highlands provides an excellent model to examine vegetation shifts, glacial refugia and gene flow of key species in this complex landscape region in response to past climatic oscillations and human disturbance. In this study, we examined maternally inherited mitochondrial DNA ( nad 1 intron b/c and nad 5 intron 1) and paternally inherited chloroplast DNA ( trn C‐ trn D) sequence variation within a dominant forest species, Picea crassifolia Kom. We recovered nine mitotypes and two chlorotypes in a survey of 442 individuals from 32 populations sampled throughout the species’ range. Significant mitochondrial DNA population subdivision was detected ( G ST = 0.512; N ST = 0.679), suggesting low levels of recurrent gene flow through seeds among populations and significant phylogeographical structure ( N ST > GST , P G ST = N ST = 0.093). This provides evidence for highly efficient pollen‐mediated gene flow among isolated forest patches, both within and between the QTP and adjacent highland populations. A lack of isolation to pollen‐mediated gene flow between forests on the QTP and adjacent highlands is surprising given that the Tengger Desert has been a geographical barrier between these two regions for approximately the last 1.8 million years.