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Background: Dactylicapnos is a climbing herbaceous vine, distributed from the Himalayas to southwestern China, and some of the species have important medicinal values. However, the chloroplast genomes of Dactylicapnos have never been investigated. In this study, chloroplast genomes of seven Dactylicapnos species covering all three sections and one informal group of Dactylicapnos were sequenced and assembled, and the detailed comparative analyses of the chloroplast genome structure were provided for the first time. Results: The results showed that the chloroplast genomes of Dactylicapnos have a typical quadripartite structure with lengths from 172,344 bp to 176,370 bp, encoding a total of 133–140 genes, containing 88–94 protein-coding genes, 8 rRNAs and 37–39 tRNAs. 31 codons were identified as relative synonymous codon usage values greater than one in the chloroplast genome of Dactylicapnos genus based on 80 protein-coding genes. The results of the phylogenetic analysis showed that seven Dactylicapnos species can be divided into three main categories. Phylogenetic analysis revealed that seven species form three major clades which should be treated as three sections. Conclusions: This study provides the initial report of the chloroplast genomes of Dactylicapnos, their structural variation, comparative genomic and phylogenetic analysis for the first time. The results provide important genetic information for development of medical resources, species identification, infrageneric classification and diversification of Dactylicapnos. [ABSTRACT FROM AUTHOR]

Background: The Sino-Himalayan flora harbors highly diverse high-elevation biotas, but our understanding of its evolutionary history in temporal and spatial dimensions is limited. In this study, we integrated a dated phylogenetic tree with comprehensive species distribution data to investigate changes over time and space in floristic elements, including the tropical, Tethys, northern temperate, and East Asian floristic elements, across the entire Sino-Himalaya and its three floristic regions: the Yunnan Plateau, Hengduan Mountains, and East Himalaya regions. Results: Our results revealed that the Sino-Himalayan flora developed from lowland biomes and was predominantly characterized by tropical floristic elements before the collision between the Indian subcontinent and Eurasia during the Early Cenozoic. Subsequently, from the Late Eocene onwards, the uplifts of the Himalaya and Hengduan Mountains transformed the Sino-Himalayan region into a wet and cold plateau, on which harsh and diverse ecological conditions forced the rapid evolution of local angiosperms, giving birth to characteristic taxa adapted to the high altitudes and cold habitat. The percentage of temperate floristic elements increased and exceeded that of tropical floristic elements by the Late Miocene. Conclusions: The Sino-Himalayan flora underwent four significant formation periods and experienced a considerable increase in endemic genera and species in the Miocene, which remain crucial to the present-day patterns of plant diversity. Our findings support the view that the Sino-Himalayan flora is relatively young but has ancient origins. The three major shifts in the divergence of genera and species during the four formation periods were primarily influenced by the uplifts of the Himalaya and Hengduan Mountains and the onset and intensification of the Asian monsoon system. Additionally, the temporal patterns of floristic elements differed among the three floristic regions of the Sino-Himalaya, indicating that the uplift of the Himalaya and surrounding areas was asynchronous. Compared to the Yunnan Plateau region, the East Himalaya and Hengduan Mountains experienced more recent and drastic uplifts, resulting in highly intricate topography with diverse habitats that promoted the rapid radiation of endemic genera and species in these regions. [ABSTRACT FROM AUTHOR]

Aims: The tropical niche conservatism (TNC) hypothesis and the out of the tropics (OTT) hypothesis propose mechanisms generating patterns of species diversity across warm‐to‐cold thermal gradients at large spatial scales. These two hypotheses both integrate ecological and biogeography‐related evolutionary factors, but they predict opposite patterns for phylogenetic structure. Mount Namjagbarwa possesses one of the longest elevational gradients for flowering plant diversity in the world. We aim to analyse the elevational patterns of the phylogenetic structure of flowering plants in this mountain, and investigate underlying causes for the emergence of the patterns. Location: Mt. Namjagbarwa located at the eastern edge of the Himalaya. Methods: Species distribution data of Mt. Namjagbarwa were extracted from specimen records in online sources, literature, herbarium and our fieldwork. Bioclimatic data were extracted from the CHELSA database. Mt. Namjagbarwa was divided into 100‐m elevational belts, which were grouped into three elevation segments (100–2000 m, 2000–4000 m and 4000–5200 m) for data analysis. We calculated phylogenetic metrics for each belt. The relationships of phylogenetic metrics with elevation and climatic factors were analysed using generalized additive models and structural equation models. Results: A typical hump‐shaped pattern of species richness was observed along the elevational gradient of Mt. Namjagbarwa. However, the phylogenetic structure showed a zig‐zag pattern with the three elevation segments, each of which has different formation mechanisms. Temperature tolerance played important roles throughout the entire elevational gradient in species richness and phylogenetic structure. Main conclusions: Neither TNC nor OTT alone can fully explain the patterns of floristic assembly of the entire elevational gradient of Mt. Namjagbarwa. OTT and TNC are better explanation for the patterns of low and middle elevations respectively. Potential mechanisms for species assembly of different elevation segments in Mt. Namjagbarwa region alternate between niche convergence and niche conservatism. The patterns observed in this study are likely to be common across the entire Himalaya. This is important for preserving the evolutionary potential of mountain biodiversity. However, more studies are needed to determine the underlying mechanisms generating the zig‐zag pattern of the phylogenetic structure in the Himalaya. [ABSTRACT FROM AUTHOR]

The Himalayas and the Hengduan Mountains of southwest China are hotspots of both climatic and species diversity. Yet, the distribution patterns of semi‐arid plant communities that have arisen throughout the region's complex uplift history remain insufficiently understood. In particular, the striking disjunctions of plants associated with dry river valleys that solely occur on the eastern and western ends of the Himalayan arc, but are absent in between, lack a sound explanation. Here we aim to disentangle the more recent environmental drivers behind the disjunction of the semi‐woody shrub Rumex hastatus found in dry river valleys of the western Himalayas and the Hengduan Mountains. We used ecological niche modeling and enhanced random forest parameterizations (down‐sampling) to infer suitable and unsuitable habitats within the study area during the last glacial maximum, under present climate conditions, and under four future climate scenarios. Annual and seasonal precipitation contributed the strongest to the discrimination between occurrences and the distribution gap, with the latter showing much higher rainfall amounts. The gap was also characterized by low overall habitat suitability, whereas occurrence probabilities in dry river valleys inhabited by R. hastatus were very high. However, some suitable but isolated habitats within the gap were detected in Bhutan and the southeastern Tibetan Plateau. The identified distribution gap was consistent in all simulated scenarios from the last glacial maximum to the near future. Our results suggest that the South Asian summer monsoon system acts as a persistent ecological barrier maintaining the disjunct distribution of dry river valley‐dwelling plants in the western Himalayas and the Hengduan Mountains. [ABSTRACT FROM AUTHOR]

Unlike the well‐understood cold limit of trees, the causes of the dry trailing edge of trees await explanation. Here we aimed at explaining the drought limit of an evergreen oak species (Quercus pannosa s.l.) in a typical dry valley of the upper Yangtze region, SE Himalaya, where rains (ca. 250 mm/a) are largely confined to the typical monsoon season (July–August) with drought during the remaining 9–10 months. We capitalized on an unintentional year‐round irrigation treatment with trees growing along the overflow of a water reservoir serving as moist controls. We measured shoot water potential (Ψ), leaf conductance (g), flushing phenology, leaf mass per area (LMA), foliar and stem δ13C, leaf nutrients, and non‐structural carbohydrates across the transition from non‐monsoon to monsoon season, from April to August 2018. At the dry site, Ψ and g were high during the monsoon but declined to <−3 MPa as drought proceeded in the non‐monsoon season. Irrigated oaks retained high values year‐round. Oaks experiencing the natural drought flushed at the full strength onset of the monsoon only, that is, 80 days later than irrigated oaks. The annual shoot increment in oaks under natural drought was ca. 10% of that in irrigated oaks. However, mature foliage showed no difference in LMA and δ13C between dry and moist sites. We conclude that these oaks drastically reduce their activity in response to drought, with growth strictly confined to the monsoon season, the minimum duration of which, presumably is setting the range limit. [ABSTRACT FROM AUTHOR]

Geoclimatic factors related to the uplift of the Himalaya and the Quaternary climatic oscillations influence the population genetic connectivity in the Himalaya–Hengduan Mountains (HHM) biodiversity hotspot. Therefore, to explore the relative roles played by these two factors, we examined the population dynamics and dispersal corridors of Incarvillea arguta (Royle) Royle incorporating ensemble species distribution modelling (SDM). Thirty‐seven populations were genotyped using plastid chloroplast DNA and low copy nuclear gene (ncpGS) sequences. Phylogeographic analysis was carried out to reveal the genetic structure and lineage differentiation. Ensemble SDMs were carried out for distributional change in the last glacial maximum, present, and future. Finally, the least cost path method was used to trace out possible dispersal corridors. The haplotypes were divided into four clades with strong geographical structure. The late Miocene origin of I. arguta in the western Himalaya ca. 7.92 Ma indicates lineage diversification related to the uplift of the HHM. The variability in habitat connectivity revealed by SDM is due to change in suitability since the Pleistocene. A putative dispersal corridor was detected along the drainage systems and river valleys, with strong support in the eastern Hengduan Mountains group. Our results support the signature of geoclimatic influence on population genetic connectivity of I. arguta in the HHM. We proposed that the major drainage systems might have assisted the rapid dispersal of isolated riverine plant species I. arguta in the HHM. The population genetic connectivity, using the fine‐tuned ensemble SDMs, enables scientists and policymakers to develop conservation strategies for the species gene pool in the HHM biodiversity hotspots. [ABSTRACT FROM AUTHOR]

Unlike the well-understood alpine treeline, the upper range limits of tree taxa that do not reach the alpine treeline are largely unexplained. In this study, we explored the causes of the exceptionally high elevation (4270 m) occurrence of broad-leaved evergreen oaks (Quercus pannosa) in the south-eastern Himalayas. We assessed the course of freezing resistance of buds and leaves from winter to summer at the upper elevational limit of this oak species. Linked to leaf phenology, we analyzed freezing resistance and assessed minimum crown temperature for the past 65 years. We also examined potential carbon limitation at the range limit of this species. Last season buds and leaves operated at a safety margin of 5.5 and 11 K in mid-winter. Once fully dehardened early in July, last season foliage is damaged at −5.9 and new foliage at −4.6 °C. Bud break is timed for late June to early July when low temperature extremes historically were never below −3.0 °C. The monsoon regime ensures a long remaining season (149 days), thus compensating for the late onset of shoot growth. Compared with a site at 3450 m, specific leaf area is reduced, foliar non-structural carbohydrate concentrations are similar and the δ13C signal is higher, jointly suggesting that carbon limitation is unlikely at the range limit of this species. We also show that these oaks enter the growing season with fully intact (not embolized) xylem. We conclude that the interaction between phenology and freezing tolerance results in safe flushing, while still facilitating shoot maturation before winter. These factors jointly determine the upper range limit of this oak species. Our study illuminates an exceptional case of broad-leaved evergreen tree performance near the treeline, and by exploring a suite of traits, we can underpin the central role of flushing phenology in such a stressful environment. [ABSTRACT FROM AUTHOR]

Specialized bracts of Himalayan 'glasshouse' plants are well known for adapting to diverse stresses in alpine environments, thus ensuring normal sexual reproduction. However, little information is available on how such specialized plants cope with the elevational increase in stress. In this study, we determine the elevational pattern of ultraviolet (UV) protection provided by the translucent bracts of Rheum nobile , a giant 'glasshouse' plant species, endemic to the high Himalayas, and examine its effect on pollen germination and pollen tube growth. Both UV-A and UV-B radiation in the open air increased with elevation, but their intensity beneath bracts remained constant with elevation, suggesting that the bracts of R. nobile growing at higher elevations have an increased ability to screen UV radiation. Enhanced UV-B radiation, equivalent to that experienced at higher elevations (4800 m a.s.l.) compared to that at lower elevations (4200 m a.s.l.), significantly reduced pollen germination and pollen tube growth. Pollen grains from plants at higher elevations were not more tolerant to UV-B radiation. UV absorbance and the content of flavonoids in bracts increased with elevation, but a similar trend was not found in either UV reflectance or adaxial trichome density, suggesting that bract UV absorbance may play a more active role than bract UV reflectance in helping plants cope with the increasing UV radiation. Our results indicate that the bracts of R. nobile have the ability to cope with enhanced UV radiation with increasing elevation through increased UV absorbance, thus protecting pollen grains from injury caused by higher levels of UV radiation, and consequently ensuring normal sexual reproduction in stressful high-alpine conditions. [ABSTRACT FROM AUTHOR]

Background Perennity of giant rosette species in combination with a single 'big bang' reproduction followed by death of the genetic individual is relatively rare among plants. Such long-lived monocarpic plants are usually slow growing and can be found in deserts, bogs or in alpine regions of the tropics or sub-tropics. Due to their longevity, monocarpic perennials risk losing everything before reproduction, which make them particularly susceptible to disturbances. Because of the inherent difficulties in assessing whether long-lived populations are growing or declining, usually neither their demography nor the consequences of increasing grazing pressure are known. Methods We used integral projection modelling (IPM) to measure the growth rate and passage time to flowering of Rheum nobile , a monocarpic perennial, and one of the most striking alpine plants from the high Himalayas. Rosettes which were no longer found due to disturbances or grazing by yaks were either treated as missing or as dead in two series of analysis, thereby simulating demography with and without the impact of grazing cattle. Data were collected from plants at 4500 m a.s.l. in Shangri-la County, Yunnan Province, south-west China. In four consecutive years (2011–2014) and in two populations, 372 and 369 individuals were measured, respectively, and size-dependent growth, survival and fecundity parameters were estimated. In addition, germination percentage, seedling survival and establishment probability were assessed. Key results The probability of survival, flowering and fecundity were strongly size dependent. Time to reach flowering size was 33.5 years [95 % confidence interval (CI) 21.9–43.3, stochastic estimate from pooled transitions and populations]. The stochastic population growth rate (λ s) of Rheum nobile was 1.013 (95 % CI 1.010–1.017). When disturbance by grazing cattle (yaks) was accounted for in the model, λ s dropped to values <1 (0.940, 95 % CI 0.938–0.943). Conclusion We conclude that natural populations of this unique species are viable, but that conservation efforts should be made to minimize disturbances by grazing and to protect this slow-growing flagship plant from the high Himalayas. [ABSTRACT FROM AUTHOR]

Clarifying the relationship between distribution patterns of organisms and geological events is critical to understanding the impact of environmental changes on organismal evolution. Quercus sect. Heterobalanus is now distributed across the Himalaya-Hengduan Mountains ( HHM) and warm lowland in East China, yet how the distribution patterns of this group changed in response to the HHM uplift remains largely unknown. This study examines the effect of tectonic events in the HHM region on the oaks, providing a biological perspective on the geological history of this region. Fifty-six populations of Quercus sect. Heterobalanus were genotyped using four chloroplast DNA regions and nine nuclear simple sequence repeat loci to assess population structure and diversity, supplemented by molecular dating and ancestral area reconstructions. The underlying demographic dynamics were compared using ecological niche models of the species distributions during the last glacial maximum and the present. These analyses illustrate that Quercus sect. Heterobalanus diversified as the HHM uplifted and climatic cooling during the mid-Miocene, colonizing the cold habitats from warm broadleaf mixed forests. Lineages in cold highlands and warm lowlands have diverged as a consequence of local adaptation to diverging climates since the late Miocene. Our results suggest that continuous uplift of the HHM in the late Miocene to early Pliocene accompanied by simultaneous cooling triggered the differentiation of oaks. The biogeography of Quercus sect. Heterobalanus illuminates the geological events responsible for the modern-day HHM. [ABSTRACT FROM AUTHOR]

Studying the drivers of host specificity can contribute to our understanding of the origin and evolution of obligate pollination mutualisms. The preference-performance hypothesis predicts that host plant choice of female insects is related mainly to the performance of their offspring. Soil moisture is thought to be particularly important for the survival of larvae and pupae that inhabit soil. In the high Himalayas, Rheum nobile and R. alexandrae differ in their distribution in terms of soil moisture; that is, R. nobile typically occurs in scree with well-drained soils, R. alexandrae in wetlands. The two plant species are pollinated by their respective mutualistic seed-consuming flies, Bradysia sp1. and Bradysia sp2. We investigated whether soil moisture is important for regulating host specificity by comparing pupation and adult emergence of the two fly species using field and laboratory experiments. Laboratory experiments revealed soil moisture did have significant effects on larval and pupal performances in both fly species, but the two fly species had similar optimal soil moisture requirements for pupation and adult emergence. Moreover, a field reciprocal transfer experiment showed that there was no significant difference in adult emergence for both fly species between their native and non-native habitats. Nevertheless, Bradysia sp1., associated with R. nobile, was more tolerant to drought stress, while Bradysia sp2., associated with R. alexandrae, was more tolerant to flooding stress. These results indicate that soil moisture is unlikely to play a determining role in regulating host specificity of the two fly species. However, their pupation and adult emergence in response to extremely wet or dry soils are habitat-specific. [ABSTRACT FROM AUTHOR]

Background:Cushions are the typical nurse species of high-elevation environments. However, few studies have explored the differences in facilitative power and environmental amelioration between nurse plants of different species that share a common cushion morphology. Aims:To compare the nurse effects of different alpine cushion plants and their mechanism. Methods:We compared the effects of two co-occurring cushion species,Potentilla articulataandArenaria polytrichoideson species richness, Shannon–Wiener diversity and the evenness of vascular plant assemblages in the Himalayas. In addition, we compared the temperature and the soil nutrients within and outside the two cushion species. Results:The presence of either cushion species significantly increased the species richness and diversity in comparison with the areas outside the cushions;P. articulatacushions were associated with greater species richness thanA. polytrichoides. Substrate temperatures were similar under the two species and in open areas, but nitrogen and potassium levels were higher under either of the two cushion species than they were outside. Soil phosphorus and potassium concentrations were significantly higher beneathP. articulatathan beneath theA. polytrichoidescushions. Conclusions:Our results indicate that facilitation of local species richness by cushion plants contributes to the structure of the alpine plant community in the eastern Himalayas. The intensity of the nurse effect varies with the soil nutrient level beneath different benefactor species. [ABSTRACT FROM AUTHOR]

Anaphalis is the largest Asian genus in the tribe Gnaphalieae (Asteraceae) and has its greatest species diversity in the eastern Himalayas. The nuclear internal and external transcribed spacers were sequenced for Anaphalis species, with an emphasis on the eastern Himalayan taxa to examine the monophyly and construct the phylogenetic relationships of and within the genus. The results suggest that all species of Anaphalis are nested with Helichrysum, showing a close relationship with a Mediterranean-Asian group of Helichrysum. Although the monophyly of Anaphalis is only weakly supported, two clades within the genus are well recognized, each consisting of two subgroups. The inferred phylogenetic relationships within Anaphalis correspond to the shape of leaf base, rather than the morphology of the capitula and phyllaries that are usually used for species delimitation and classification in the genus. All four subgroups of Anaphalis are common and diversified in the eastern Himalayas with multiple dispersals out of this region. The sole North American species of Anaphalis is best hypothesized to be the result of long-distance dispersal or overland migration via Bering land bridge from Asia. Our analyses suggest that the extant distribution of Anaphalis has most likely resulted one radiation into the eastern Himalayas followed by repeated independent dispersals and/or radiations mostly into eastern Asia but also into the western Himalayas, North America, and southeast Asia. [ABSTRACT FROM AUTHOR]

The karyotypes of six species of Solms-laubachia and one each of Parrya and Desideria (Brassicaceae) from the Himalayan-Hengduan Mountains (Tibet, Sichuan and Yunnan provinces) were investigated. Chromosome counts of S. xerophyta, S. lanata, S. platycarpa and D. baiogoinensis are reported for the first time and found to be diploid with 2n = 14. Diploid counts were also made of S. retropilosa, a species previously known to be a tetraploid. The karyotype formulae of D. baiogoinensis, S. eurycarpa, S. pulcherrima, S. retropilosa, S. xerophyta and S. platycarpa are 2n = 14 = 6 m + 6sm + 2st, whereas those of S. lanata and P. nudicaulis are 2n = 14 = 6 m + 2sm + 6st and 2n = 14 = 8 m + 4sm + 2st, respectively. Karyotypes and counts of S. eurycarpa and S. pulcherrima are in agreement with prior studies. The relationships within Solms-laubachia and among the three genera are discussed. Speciation within Solms-laubachia may have been the result of primarily intrachromosomal variation at the diploid level, and the genus probably evolved within the Himalayan-Hengduan Mountains instead of migrating from other regions. [ABSTRACT FROM AUTHOR]

Abstract: Maianthemum (Ruscaceae) comprises 28–38 species and includes the two traditionally recognized genera: Maianthemum sensu stricto and Smilacina. Thirty-seven samples representing 22 species of Maianthemum and six closely related outgroup taxa were sequenced for eight chloroplast and nuclear markers (trnL-F, rps16, rpl16, psbA-trnH, rbcL, ndhF, trnK, and ITS) with a total length of nearly 10,000 base pairs. Phylogenetic analyses supported the monophyly of Maianthemum with Maianthemum sensu stricto nested within Smilacina. Almost all species from the eastern Himalayan region in SW China except for Maianthemum tatsienense and M. stenolobum form a well supported clade. This clade is characterized morphologically by short filaments and large anthers, relatively large flowers, and pubescent stems and leaves. Maianthemum tatsienense and M. stenolobum from SW to central China form another clade. The other species from eastern Asia (central to NE China and Japan) and the New World fall into several clades. The intercontinental disjunction between eastern Asia and North America in Maianthemum sensu stricto is estimated to be at 1.68 million years ago (mya) with the Bayesian relaxed clock relying on uncorrelated rates. A recent radiation at about 2.04mya is suggested in the high mountains of SW China, corresponding to the geographical heterogeneity in that region after the uplift of the Himalayas. Long distance dispersal by birds may have facilitated the evolution of their intercontinental disjunction and their biogeographic diversifications in SW China. [Copyright &y& Elsevier]