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Plant species shift ranges in response to climate fluctuation over time. However, differentiation related to heterogeneity in space has been illustrated only rarely. Here we selected Hippophaë neurocarpa S. W. Liu & T. N. Ho (Elaeagnaceae), a shrub endemic to the Qinghai-Tibet Plateau, to exemplify this process. We characterized the genotypic, phenotypic, and climatic variations among 27 populations of this species sampled across its entire distribution. Genotype analyses revealed six highly differentiated groups that may have resulted from expansions in spatial range. Despite recent fluctuation in size, it is likely that most groups survived the last glacial maximum in situ. Instead of two previously described subspecies, we identified four morphotypes (stellate, peltate, and two additional types) that can be characterized based on leaf trichomes. This phenotypic subdivision is consistent with a climate gradient defined by temperature and precipitation, although similar phenotypes may derive from distinct genotypes. Collectively, we propose that the demographic history of H. neurocarpa is characteristic of an early spatial range expansion combined with a recent bottleneck, subsequently subdivided into multiple morphotypes following local adaption to heterogeneous climates. [ABSTRACT FROM AUTHOR]

Plateau uprisings and climatic oscillations are considered to have caused extensive allopatric divergences that account for the rich species diversity of the Qinghai- Tibetan Plateau ( QTP). However, secondary contact during range shifts in the Quaternary glacial cycles or inter-uplift stages may have restored the gene flow between species and so counteracted these divergences, particularly in rapidly-adapting dominant elements. We tested this hypothesis by determining the phylogeographical history of Dasiphora ( Rosaceae), a genus of two species that are widely distributed on the QTP and co-exist in numerous localities. We sequenced two chloroplast DNA fragments ( rbcL, trnT- L) for 559 individuals from 87 populations. Bayesian methods were used to identify phylogenetic relationships and to estimate divergence times. Demographic histories were inferred using neutrality tests, mismatch distribution analysis, and coalescent simulation. A total of 112 haplotypes that clustered into three major groups were identified. The formation of these groups and their subgroups was dated to between the Pliocene and the late Pleistocene. In addition, we found that some groups underwent multiple extensive expansions. Species-specific haplotypes were identified for each species, although these haplotypes phylogenetically intermixed. These results suggest that recent plateau uplifts and climatic oscillations might have caused the deep divergences observed within this genus. However, later range expansions probably blurred these divergences and possible species boundaries. Our results shed new light on the complex evolutionary history of the QTP alpine plants. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 777-788. [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]