Mitochondrial and chloroplast phylogeography of Picea crassifolia Kom. (Pinaceae) in the Qinghai‐Tibetan Plateau and adjacent highlands

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 (nad1 intron b/c and nad5 intron 1) and paternally inherited chloroplast DNA (trnC-trnD) 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 < 0.05). Plateau haplotypes differed in sequence from those in the adjacent highlands, suggesting a long period of allopatric fragmentation between the species in the two regions and the presence of independent refugia in each region during Quaternary glaciations. On the QTP platform, all but one of the disjunct populations surveyed were fixed for the same mitotype, while most populations at the plateau edge contained more than one haplotype with the mitotype that was fixed in plateau platform populations always present at high frequency. This distribution pattern suggests that present-day disjunct populations on the QTP platform experienced a common recolonization history. The same phylogeographical pattern, however, was not detected for paternally inherited chloroplast DNA haplotypes. Two chlorotypes were distributed throughout the range of the species with little geographical population differentiation (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.

Dispersals of Hyoscyameae and Mandragoreae (Solanaceae) from the New World to Eurasia in the early Miocene and their biogeographic diversification within Eurasia

“…The recent range expansion from the 'hot spot' of the mountains of the southeastern TP has been observed in other plants and birds at the population level. Examples include Juniperus przewalskii (Cupressaceae) , Metagentiana striata (Gentianaceae) (Chen et al, 2008), Pedicularis longiflora (Orobanchaceae) (Yang et al, 2008), Picea crassifolia (Pinaceae) (Meng et al, 2007), and the red-necked snow finch Pyrgilauda ruficollis (Qu et al, 2005). Phylogeographic studies on these species show that populations from the wide range of the platform are dominated by one or a few haplotypes and are mostly nested within diverse haplotypes from the southeastern mountains of the TP.…”

Range shifts of Potentilla fruticosa on the Qinghai-Tibetan Plateau during glacial and interglacial periods revealed by chloroplast DNA sequence variation

“…Phylogeographic studies suggest a similar history of coniferous trees (Zhang et al, 2005;Meng et al, 2007), the dominant species in the forested zone and which occasionally grow within the alpine zone on the northeastern Plateau. These scattered conifer populations probably reflect colonization from a refugial population that existed in the past along the Plateau's edge.…”

Genetic consequences of postglacial colonization by the endemic Yarkand hare (Lepus yarkandensis) of the arid Tarim Basin

“…In contrast, studies on the Asian biota have been rather limited. The complex topography of East Asia probably provided refugia for species during times of Pleistocene glaciation [14], yet only a few plant and bird species restricted to the Qinghai-Tibetan Plateau (QTP) have been evaluated [15][16][17][18][19][20].…”