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Aims: A comprehensive understanding of the genetic variation of walnuts (Juglans regia and J. sigillata) in the Himalaya and its potential drivers are essential for the conservation and sustainable utilization of these plant genetic resources. In this study, we aimed to uncover the genetic landscape of walnuts and potential drivers in the Himalaya for better utilization, awareness, sustainable management and conservation of the extant genetic resources of walnuts in the vast Himalayan landscape. Location: The Himalaya biodiversity hotspot. Methods: A total of 1410 wild or feral walnut trees from 65 populations of J. regia and J. sigillata across four countries in the Himalaya were collected. The genetic diversity, population structure, hybridization and gene flow were thoroughly investigated based on the chloroplast genome and 31 nuclear microsatellite markers. The patterns and drivers of the walnut genetic landscape were further explored. Results: We detected three genetic groups of J. regia (JR1, JR2, JR3), one of J. sigillata (JS) and two hybrid types (JR1 × JS and JR3 × JS) of walnut in the Himalaya, with the western Himalaya identified as the genetic diversity hotspot of J. regia. The spatial genetic pattern of the J. regia was significantly influenced by geographic and climatic factors. Human‐mediated dispersal probably promoted the hybridization and gene introgression between J. regia and J. sigillata, which reshaped the genetic landscape of walnut populations in the Himalaya. Main Conclusions: The extant genetic landscape of walnuts in the Himalaya was driven by natural and anthropogenic forces. Regarding conservation, the western and eastern Himalaya are the genetic reservoir of J. regia and J. sigillata, and hence, pure individuals should be urgently protected from frequent hybridization and introgression. In addition, we propose the utilization of natural hybrid resources coupled with new breeding techniques that combine genomic and phenotypic data. [ABSTRACT FROM AUTHOR]

Mountain ecosystems support a significant one‐third of all terrestrial biodiversity, but our understanding of the spatiotemporal maintenance of this high biodiversity remains poor, or at best controversial. The Himalaya hosts a complex mountain ecosystem with high topographic and climatic heterogeneity and harbors one of the world's richest floras. The high species endemism, together with increasing anthropogenic threats, has qualified the Himalaya as one of the most significant global biodiversity hotspots. The topographic and climatic complexity of the Himalaya makes it an ideal natural laboratory for studying the mechanisms of floral exchange, diversification, and spatiotemporal distributions. Here, we review literature pertaining to the Himalaya in order to generate a concise synthesis of the origin, distribution, and climate change responses of the Himalayan flora. We found that the Himalaya supports a rich biodiversity and that the Hengduan Mountains supplied the majority of the Himalayan floral elements, which subsequently diversified from the late Miocene onward, to create today's relatively high endemicity in the Himalaya. Further, we uncover links between this Miocene diversification and the joint effect of geological and climatic upheavals in the Himalaya. There is marked variance regarding species dispersal, elevational gradients, and impact of climate change among plant species in the Himalaya, and our review highlights some of the general trends and recent advances on these aspects. Finally, we provide some recommendations for conservation planning and future research. Our work could be useful in guiding future research in this important ecosystem and will also provide new insights into the maintenance mechanisms underpinning other mountain systems. [ABSTRACT FROM AUTHOR]

The grassland in the Hindu Kush Himalayan (HKH) region is one of the largest and most biodiverse mountain grassland types in the world, and its ecosystem service functions have profound impacts on the sustainable development of the HKH region. Monitoring the spatiotemporal distribution of grassland aboveground biomass (AGB) accurately and quantifying its response to climate change are indispensable sources of information for sustainably managing grassland ecosystems in the HKH region. In this study, a pure vegetation index model (PVIM) was applied to estimate the long-term dynamics of grassland AGB in the HKH region during 2000–2018. We further quantified the response of grassland AGB to climate change (temperature and precipitation) by partial correlation and variance partitioning analyses and then compared their differences with elevation. Our results demonstrated that the grassland AGB predicted by the PVIM had a good linear relationship with the ground sampling data. The grassland AGB distribution pattern showed a decreasing trend from east to west across the HKH region except in the southern Himalayas. From 2000 to 2018, the mean AGB of the HKH region increased at a rate of 1.57 g/(m2·yr) and ranged from 252.9 (2000) to 307.8 g/m2 (2018). AGB had a positive correlation with precipitation in more than 80% of the grassland, and temperature was positively correlated with AGB in approximately half of the region. The change in grassland AGB was more responsive to the cumulative effect of annual precipitation, while it was more sensitive to the change in temperature in the growing season; in addition, the influence of climate varied at different elevations. Moreover, compared with that of temperature, the contribution of precipitation to grassland AGB change was greater in approximately 60% of the grassland, but the differences in the contribution for each climate factor were small between the two temporal scales at elevations over 2000 m. An accurate assessment of the temporal and spatial distributions of grassland AGB and the quantification of its response to climate change are of great significance for grassland management and sustainable development in the HKH region. [ABSTRACT FROM AUTHOR]

Geographical names and the entities they represent act as a fundamental cornerstone across numerous disciplines. However, inconsistent geographical names and arbitrarily defined regional geographical scales are common, hindering cross-disciplinary communication and synthesis. The Pan-Tibetan Highlands, comprising the Tibetan Plateau, Himalaya, Hengduan Mountains and Mountains of Central Asia, is a case in point. To rectify these inconsistencies of terminology, we employed a multi-disciplinary approach to standardize the nomenclature of the Tibetan Plateau and the three adjacent mountain regions, defining their spatial extent using historical and contemporary perspectives. A literature meta-analysis indicated that 'Tibetan Plateau', 'Himalaya' and 'Hengduan Mountains' are the most suitable names for these regions in terms of both priority (earliest use) and popularity, whereas 'Mountains of Central Asia' emerges as appropriate for the mountain chains to the west of the Tibetan Plateau. The new term 'Pan-Tibetan Highlands' is proposed to replace the less precise and arguably misleading 'High Mountain Asia' for these regions collectively. Additionally, new geographical boundaries, applicable back through time, are proposed for each region, based on geological and geomorphological features. Using these new boundaries, the Pan-Tibetan Highlands area is 3.95 × 106 km2 with a mean elevation of 3824 m, while the Tibetan Plateau is smaller (1.82 × 106 km2) and higher (4465 m) than commonly assumed. Across the Pan-Tibetan Highlands, the proportion of protected areas is far below the proposed 30% anticipated in the post-2020 Global Biodiversity Framework target with only a few exceptions. Additionally, the Hengduan Mountains showed the highest vascular plant species richness and endemism, followed by Himalaya, Mountains of Central Asia and the Tibetan Plateau. The obvious conservation gap in the Pan-Tibetan Highlands calls for urgent research-based optimization of conservation networks. Our approach benefits quantitative spatial analysis by providing well-defined geographical scales for various fields, aiding cross-disciplinary comparisons and synthesis. • Inconsistent geographical names and scales hinder cross-disciplinary comparisons and synthesis. • A multi-disciplinary approach is employed to resolve these inconsistencies of Tibetan Plateau and adjacent mountain regions. • Names and geographical limits of the Pan-Tibetan Highlands and its sub-regions are proposed in spatiotemporal contexts. • The observed conservation gap in the Pan-Tibetan Highlands calls for urgent action of conservation. • The integrative approach can be used to clarify toponyms and spatial extents in other regions. [ABSTRACT FROM AUTHOR]