Aim The Tibetan Plateau harbours the highest alpine and endemic plant diversity in the world, attributed to rapid diversification during the plateau uplift and Quaternary climate fluctuations. However, there is little understanding of which hypotheses associated with these geological and climatic processes garner strong support as explanations for the observed diversity patterns. Here, we test support for hypotheses related to uplift and climate changes that could account for the high endemicity and phylogenetic diversity of the world’s highest plateau. Location Tibetan Plateau (TP). Time period Neogene, Quaternary and current period. Major taxa studied Tibetan endemic seed plants. Methods We collated data on endemic seed‐plant distribution based on county‐level mapping from published monographs and online databases. We calculated species richness (SR) and phylogenetic diversity for endemic herbs, shrubs, trees, and all plants for 0.5‐degree × 0.5‐degree grid cells covering the TP. We derived environmental and evolutionary predictors to evaluate eight biogeographical hypotheses associated with plateau uplift and climate fluctuations, and used partial regression analysis and mixed conditional autoregressive (CAR) models to assess the relative contribution of each predictor to the extant diversity of the TP. Results We found plateau uplift independently explained more variance in diversity than climate fluctuations, but there were also strong interaction effects. The full CAR models including all predictors explained 37%–75% of the total variation across diversity measures and life forms. The predictor representing the montane museum hypothesis explained the most variation (c. 25%), but each predictor explained at least 6%. Main conclusions These results demonstrate that both the plateau uplift and Quaternary climate fluctuations had large impacts on current patterns of species diversity, but the influence of plateau uplift was more pronounced than that of climate changes. Our study suggests that plateau uplift and climate changes are the original drivers of complex biogeographical processes accounting for the biodiversity of the TP.

The Qinghai-Tibet Plateau sensu lato (QTP s.l.) harbors an exceptionally high biodiversity, especially at its southeastern margin: this area encompasses the Hengduan Mountains and the eastern Himalayas, which have been listed as biodiversity hotspots. To the contrary, the plateau interior (namely the Qinghai-Tibet Plateau sensu stricto, QTP s.s.) is relatively species-poor because of its particularly harsh climate. With contrasting geological histories and environmental conditions of the Hengduan Mountains, the Himalayas, and the QTP s.s., it would be expected that floristic compositions and diversity patterns of these three regions would differ between each other. To compare the floristic diversity of these three regions, we assembled data on seed plant's distribution in the three regions based on county-level mapping from published monographs and online databases, and we then analyzed their floristic features and species diversity patterns (horizontal and elevational). We found that the Hengduan Mountains hosted the most seed plant species (8,439), as expected. The highest percentage of shrub (22.88%) and tree species (9.80%) were in the Himalayas, whereas herbaceous species (81.50%) were relatively more prominent in the QTP s.s.. The Hengduan Mountains also had the most species-rich genera (10) with more than 50% of their total species diversity in China. Also, temperate genera dominated across these three regions, with a highest percentage (77.61%) within the QTP s.s.. Across the QTP s.l., species diversity gradually decreased from the southeastern part to the northwest, and most of seed plants were distributed in the southern and eastern margin of the Hengduan Mountains and East Himalayas. Along elevational gradients, species richness all demonstrated a hump-shape curve, but the most species-rich elevation zone differed for each type of life-form across the three regions. Our study sets a base for exploring the origin and evolution of mountain taxa, as well as provides a snapshot of the current plant distribution, which will certainly be modified by climate change.

Himalayan hemlock (Tsuga dumosa) experienced a recolonization event during the Quaternary period; however, the specific dispersal routes are remain unknown. Recently, the least cost path (LCP) calculation coupled with population genetic data and species distribution models has been applied to reveal the landscape connectivity. In this study, we utilized the categorical LCP method, combining species distribution of three periods (the last interglacial, the last glacial maximum, and the current period) and locality with shared chloroplast, mitochondrial, and nuclear haplotypes, to identify the possible dispersal routes of T. dumosa in the late Quaternary. Then, both a coalescent estimate of migration rates among regional groups and establishment of genetic divergence pattern were conducted. After those analyses, we found that the species generally migrated along the southern slope of Himalaya across time periods and genomic makers, and higher degree of dispersal was in the present and mtDNA haplotype. Furthermore, the direction of range shifts and strong level of gene flow also imply the existence of Himalayan dispersal path, and low area of genetic divergence pattern suggests that there are not any obvious barriers against the dispersal pathway. Above all, we inferred that a dispersal route along the Himalaya Mountains could exist, which is an important supplement for the evolutionary history of T. dumosa. Finally, we believed that this integrative genetic and geospatial method would bring new implications for the evolutionary process and conservation priority of species in the Tibetan Plateau.

Aim: Species diversity in the region of the Qinghai-Tibet Plateau has been extensively explored, whereas the distribution of genetic diversity remains poorly understood in this species-rich area, parts of which are listed as biodiversity hotspots. In this study, we aimed to map the patterns of genetic diversity and divergence of plant species in this region, and to identify potential evolutionary hotspots for conservation planning.Location: Region of the Qinghai-Tibet Plateau (QTP). Methods:We compiled published molecular data for 60 plant species, and calculated intra-population genetic diversity and inter-population genetic divergence using haplotype sequences (chloroplast or mitochondrial DNA). We analysed the relationships between genetic diversity and longitude, latitude and elevation. We mapped the landscapes of genetic diversity and divergence for each species in GIS, and combined the resulting landscapes in order to identify hotspots of high genetic diversity and divergence.Results: There were no significant relationships between genetic diversity and longitude, latitude and elevation. For most species, areas characterized by high genetic diversity and divergence were located across the Hengduan Mountains. Nine evolutionary hotspots across the region of the QTP were identified. Main conclusions:The Hengduan Mountains are a remarkable hotspot of all three dimensions of biodiversity (genes, species and ecosystems), yet patterns of genetic diversity were partially incongruent with the distribution of species diversity. For example, several hotspots of genetic diversity were located on the QTP proper, which is relatively species poor. This partial geographic mismatch between species and genetic diversity highlights the need to consider both aspects in conservation programs. Our study suggests that more protected areas in the region of the QTP need to be established in order to protect genetic diversity and thus adaptive potential. K E Y W O R D Sbiodiversity conservation, comparative phylogeography, evolutionary hotspots, genetic divergence, genetic diversity, Qinghai-Tibet Plateau, Quaternary refugia | 311 YU et al. Pedicularis kansuensisA,