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As the highest and largest plateau in the world, the Qinghai-Tibet Plateau, with its numerous endemic species, is one of the important alpine biodiversity hotspots. Only recently have the evolutionary histories and underlying adaptations of these alpine plants become clear, through research mostly based on testable experiments and analyses. In this issue, we collected a total of 13 papers related to such aims. In addition, we selected a few published papers to highlight the major findings in the recent past. We also outlined the outlook and direction of future research. [ABSTRACT FROM AUTHOR]

The aim of the present study was to examine the phylogeographic and evolutionary history of Picea likiangensis, a dominant species of the conifer forests in the eastern declivity of the Qinghai-Tibetan Plateau. We collected 422 individuals from 42 natural populations of three major varieties classified under this species. In conifers, mitochondrial (mt) DNA and chloroplast (cp) DNA dispersed by seeds or pollen experience very different levels of gene flow. To this end, we examined the sequence variation of two mtDNA fragments ( nad5 intron 1 and nad1 intron b/c) and three cpDNA fragments ( trnL-trnF, trnS-trnG and nadhK/C). We found that cpDNA probably introgressed from P. purpurea into remote populations of P. likiangensis through long-distance dispersal. Multiple refugia seem to have been maintained for P. likiangensis during the Last Glacial Maximum because the cpDNA and mtDNA haplotypes recovered were fixed in the different regions. Postglacial expansions were only detected at the distributional edges of this species where a single cpDNA or mtDNA haplotype was fixed in adjacent populations. However, genetic imprints of postglacial expansions from these two sets of markers were different in the western and southeastern regions, which may result from the long-distance dispersal of the cpDNA, as well as its fast lineage sorting during intraspecific divergences. Analysis of molecular variance further suggested that genetic differentiation between the three varieties is higher at cpDNA markers than at mtDNA markers, which supports the previous viewpoint that cpDNA markers with a high rate of gene flow may be more effective in delimitating closely related taxa. Together, the results of the present study highlight the evolutionary complexity of a widely distributed species owing to interactions among local and edge expansion, long-distance dispersal, and intraspecific divergences at two sets of DNA genomes with different rates of gene flow. [ABSTRACT FROM AUTHOR]

Numerous temperate plants now distributed across Eurasia are hypothesized to have originated and migrated from the Qinghai-Tibet Plateau (QTP) and adjacent regions. However, this hypothesis has never been tested through a phylogeographic analysis of a widely distributed species. Here, we use Hippophaë rhamnoides as a model to test this hypothesis., We collected 635 individuals from 63 populations of the nine subspecies of H. rhamnoides. We sequenced two maternally inherited chloroplast (cp) DNA fragments and also the bi-paternally inherited nuclear ribosomal ITS., We recovered five major clades in phylogenetic trees constructed from cpDNA and internal transcribed spacer (ITS) sequence variation. Most sampled individuals of six subspecies that are distributed in northern China, central Asia and Asia Minor/Europe, respectively, comprised monophyletic clades (or subclades) nested within those found in the QTP. Two subspecies in the QTP were paraphyletic, while the placement of another subspecies from the Mongolian Plateau differed between the ITS and cpDNA phylogenetic trees., Our phylogeographic analyses supported an 'out-of-QTP' hypothesis for H. rhamnoides followed by allopatric divergence, hybridization and introgression. These findings highlight the complexity of intraspecific evolutions and the importance of the QTP as a center of origin for many temperate plants. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

Delayed selfing could provide ovules with an opportunity to be fertilized as a means of “pollination assurance” before the flowers wilt. It could, thus, be regarded as an adaptation to unpredictable pollinator environments. Within the alpine biennial Gentianopsis paludosa, the showy flowers and herkogamy at the early stage of a flower's life cycle may favor outcrossing. As the flower ages, anthers contact the central stigma due to the elongation of all filaments, resulting in autonomous selfing. Flower visitors are extremely rare in a high altitude population; and examination of the mating system indicates that G. paludosa is self-pollinated under natural conditions in this population. While at the lower altitude, the bumblebee visitation rate is relatively high but possibly unreliable. Stigma receptivity is the highest on the third day of anthesis, and decreases thereafter. Pollen viability is the highest when flowers open, and gradually decreases later. Self-pollination of G. paludosa occurs at the late stage of a flower's lifecycle when stigma receptivity and pollen viability have both decreased, suggesting delayed selfing and assurance of seed production. This delayed selfing could assure seed production under the constraints of pollinator scarcity, but ensure outcrossing when pollinators were available. Such a flexible pollination mechanism is highly adaptive in the alpine environment of the Qinghai-Tibetan Plateau. [ABSTRACT FROM AUTHOR]

To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau (QTP) responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the genetic distribution pattern of 101 individuals of Potentilla glabra, comprising both the interior QTP and the plateau edge. Phylogenetic and network analyses of 31 recovered haplotypes identified three tentative clades (A, B and C). Analysis of molecular variance (amova) revealed that most of the genetic variability was found within populations (0.693), while differentiations between populations were obviously distinct ( Fst= 0.307). Two independent range expansions within clades A and B occurring at approximately 316 and 201 thousand years ago (kya) were recovered from the hierarchical mismatch analysis, and these two expansions were also confirmed by Fu's FS values and ‘ g’ tests. However, distant distributions of clade C and private haplotypes from clades A and B suggest that they had survived the Last Glacial Maximum (LGM) and previous glaciers in situ since their origins. Our findings based on available limited samples support that multiple refugia of a few cold-enduring species had been maintained in the QTP platform during LGM and/or previous glacial stages. [ABSTRACT FROM AUTHOR]