Alpine Botany最新文献

The monumental work of Olov Hedberg provided deep insights into the spectacular and fragmented tropical alpine flora of the African sky islands. Here we review recent molecular and niche modelling studies and re-examine Hedberg’s hypotheses and conclusions. Colonisation started when mountain uplift established the harsh diurnal climate with nightly frosts, accelerated throughout the last 5 Myr (Plio-Pleistocene), and resulted in a flora rich in local endemics. Recruitment was dominated by long-distance dispersals (LDDs) from seasonally cold, remote areas, mainly in Eurasia. Colonisation was only rarely followed by substantial diversification. Instead, most of the larger genera and even species colonised the afroalpine habitat multiple times independently. Conspicuous parallel evolution occurred among mountains, e.g., of gigantism in Lobelia and Dendrosenecio and dwarf shrubs in Alchemilla. Although the alpine habitat was ~ 8 times larger and the treeline was ~ 1000 m lower than today during the Last Glacial Maximum, genetic data suggest that the flora was shaped by strong intermountain isolation interrupted by rare LDDs rather than ecological connectivity. The new evidence points to a much younger and more dynamic island scenario than envisioned by Hedberg: the afroalpine flora is unsaturated and fragile, it was repeatedly disrupted by the Pleistocene climate oscillations, and it harbours taxonomic and genetic diversity that is unique but severely depauperated by frequent bottlenecks and cycles of colonisation, extinction, and recolonisation. The level of intrapopulation genetic variation is alarmingly low, and many afroalpine species may be vulnerable to extinction because of climate warming and increasing human impact.

With the aim to explore how plants acclimate to elevation changes in the understudied (sub)alpine tropics we tested two hypotheses along a 1000-m elevation gradient in Mexico: (H1) due to a severe increase in abiotic constraints at higher elevations, the functional traits of the plant species will converge toward more resource conservation, and (H2) the specific growth forms and biogeographic origins present in the (sub)alpine tropics may influence the interspecific trait variation along the gradient. We measured five aboveground functional traits: specific leaf area (SLA), leaf dry-matter content (LDMC), leaf thickness, leaf area and plant height, of 11 species representing four growth forms: rosette, tussock grass, shrub and tree the soil microclimate. Microclimatic data revealed a steep decrease in soil water content at higher elevations. Across all species and all individuals, SLA, plant height and leaf area decreased with elevation, whereas LDMC and leaf thickness increased, all of which revealing adjustments towards resource conservation in line with H1. Consistently with H2, the functional traits of the growth forms that were characteristic of tropical alpine regions (tussock grasses and erect shrubs) were less sensitive to changes in elevation compared to more generalist growth forms such as forbs. In addition, within the growth form “rosette” the functional traits of species of tropical biogeographic origin changed with elevation, whereas those of Holarctic origin did not. Our data indicate a convergence of plant traits toward improved resource conservation at higher elevations, which may be influenced partially by the growth form and the biogeographical origin of plant species.

The Himalaya–Hengduan Mountain (HHM) region consists of two global biodiversity hotspots characterized by a high degree of plant endemism. However, little is known about how these endemic species are formed and maintained in relation to the regional geomorphology of the past or current time. Thus, this study investigated the genetic structure of the herbaceous genus Acanthocalyx (Caprifoliaceae) endemic to the HHM to demonstrate if major geographic or ecological barriers in the HHM region have influenced its phylogeographic patterns. Our analyses revealed distinct genetic structures within A. alba and A. nepalensis and indicated that A. delavayi may have recently evolved from isolated peripheral populations of A. nepalensis. In particular, we not only confirmed a well-known genetic structure of alpine plants between the Himalayas and the Hengduan Mountains but also discovered a notable floristic boundary (bounded by 30° to 31°N latitude) within the Hengduan Mountains from A. alba. This study provides new insights into the dispersal and intraspecific genetic variation of Acanthocalyx and highlights the importance of geomorphological features for the diversification of HHM alpine flora.

Although mountainous habitats contribute substantially to global biodiversity, comparatively little is known about biogeographic patterns of distributions of alpine species across multiple mountain ranges. Here, we present a detailed analysis of the distributions and phylogenetic affinities of alpine seed plant lineages across North, Central, and South American mountain systems. Using a large dataset that characterizes the elevational niches of American seed plants in a continuously valued way, we related the proportion of alpine habitat occupied by plant lineages to their biogeographic distributions at a regional scale and place these results in a phylogenetic context. We found alpine species diversity to be greatest in the central Andes and western North America, and that assemblages with lower phylogenetic diversity contained species with a greater degree of alpine specialization. In particular, near-Arctic/boreal alpine communities were characterized by low phylogenetic diversity and higher degrees of alpine specialization, whereas the opposite was observed for southern Patagonian communities. These results suggest that abiotic filtering alone in these climatically similar regions is unlikely to explain alpine community assembly. Nevertheless, the overall relative rarity of alpine specialists, and the tendency for such specialists to be most closely related to montane lineages, suggested that filtering was still an important factor in shaping alpine community structure. This work corroborates the importance of a nuanced and scale-dependent perspective on the ‘history-filtering’ debate axis, as both factors have likely contributed to modern biodiversity patterns observed in alpine plant communities across the Americas.

Species diversity may be underestimated even in well-explored mountain regions due to the lack of in-depth research in taxonomically intricate groups. Filling such knowledge gap is necessary to optimize conservation management, specially for species occurring in vulnerable ecosystems such as Southern European mountains. Campanula sect. Heterophylla is a complex group with a high proportion of endemic taxa in European mountain ranges, and whose species delineation is often controversial due to extensive morphological variation. We investigated the phylogenetic relationships and evolutionary entity of its taxa occurring in the Pyrenees, with a special focus on the Pyrenean endemic C. jaubertiana (which is sometimes included as a subspecies of or merged with C. cochleariifolia); and C. andorrana, a taxon allegedly endemic to Andorra (Eastern Pyrenees) and of uncertain taxonomic value. We obtained chloroplast genome and nuclear ribosomal DNA sequences, including several individuals of the three focus taxa, and conducted morphometric analyses. Phylogenetic analyses show that C. jaubertiana sensu lato (s. l.; i.e. including C. andorrana) constitutes a clearly distinct lineage that is not even closely related to C. cochleariifolia; consistent differences in floral morphology were detected between them. Our results support two main evolutionary lineages within C. jaubertiana s. l., one corresponding to populations in Central Pyrenees, and another one in Eastern Pyrenees plus Catalan Pre-Pyrenees. Given the degree of genetic and morphological differentiation, we propose the species rank for each lineage (C. jaubertiana and C. andorrana, respectively) and provide a taxonomic treatment. These two Pyrenean endemics likely diverged through transverse allopatric speciation.

Understanding in what way cold-adapted mountain species have responded to historical climatic fluctuations in southern European refugia and investigating the genetic variation of endemic species is fundamental to predict their survival under contemporary global climate change. Veronica aragonensis (Plantaginaceae) is a tetraploid species endemic to the Iberian Peninsula that survived the climatic oscillations of the Quaternary. This species is adapted to cold environments and is included in several regional Red Lists due to its small and disjunct distribution range in high-mountain habitats (Pyrenees, Pre-Pyrenees and Baetic System). With the aim of deciphering the phylogeographical processes that underlie the presently disjunct distribution pattern of V. aragonensis and to evaluate its conservation status, we used 9 microsatellite loci to genotype 324 individuals from 12 populations representing the three disjunct areas where the species is distributed. Our results suggest that range fragmentation of an ancient continuous distribution of V. aragonensis—particularly in the low elevation mountain ranges located between the Pyrenees and the Baetic System—during the Last Glacial Maximum is the most plausible explanation for the disjunct distribution pattern of the species. Lastly, the intraspecific genetic patterns are discussed to predict how this endemic species can be affected by global climate warming. Based on the genetic data obtained here, an appropriate evaluation of the conservation status of V. aragonensis and some management strategies are provided.

Co-flowering plant species often share pollinators, which could result in interspecific pollination. Despite some evidence suggesting plant species with overlapping pollinators influence each other’s pollination, the relationship between pollinator sharing and heterospecific pollen transfer (HPT) is not well explained at the community level. Here, we sampled a plant-pollinator visitation network to calculate the degree of pollinator sharing, and we identified pollen deposition on stigmas of co-flowering species to construct a HPT network in a sub-alpine meadow in southwest China. We also analyzed floral colour using reflectance spectra to measure the flower reflectance dissimilarity between each pair species. We found that there was no pollen transfer between most species pairs with shared pollinators. A higher proportion of HPT links between plant species pairs with shared pollinators was observed than between pairs with distinct pollinators. More pollen grains were transferred from donor to recipient species with greater pollinator sharing. Flowers with more dissimilar flower colours exchanged less heterospecific pollen. Our study evaluated the effect of pollinator sharing in shaping pollen transfer patterns among co-flowering species, which may shed light on the ecological implications of plant–pollinator interactions, mediated by pollinator sharing.

Polyploids with odd-ploidy levels may play an important evolutionary role as they enable backcrosses with their parental cytotypes. We chose the ploidy-variable Senecio carniolicus species group to address the overarching question if pentaploid individuals, which occur at high frequencies in immediate contact zones of parental tetraploids and hexaploids, mediate effective interploidy gene flow. We employed a set of approaches including relative genome size (RGS) determination and viability tests of pollen, RGS of the embryo, viability tests and germination experiments of seeds, and RGS and survival experiments of seedlings to tackle the following specific questions. Is pollen of pentaploid individuals viable suggesting regular meiosis in spite of the odd-ploidy level? Are the five sets of chromosomes split into 2.5 compliments, or rather into two and three compliments? Do crossings between pentaploid individuals produce viable seeds and seedlings, suggesting that pentaploids are an independent evolutionary unit? We found that pollen stainability is not strongly reduced in pentaploids and that the five chromosome complements are most often split into 2.5 complements. Seeds originating from homoploid crossings of pentaploids show a very low viability whereas backcrosses with tetraploids or hexaploids were more successful. No significant difference in seedling survival was observed among the different crossings but seedlings emerging from 5x5x crosses were significantly smaller than both, seedlings from backcrosses and from homoploid parental crosses. Altogether, our results indicate that pentaploids may play an important evolutionary role as mediators of gene flow but that they rather do not form an independent evolutionary unit.

Alpine plants complete their seasonal phenological cycle during two to three snow-free months. Under climate change, snowmelt advances and the risk of summer droughts increases. Yet, photoperiodism may prevent alpine plants from benefiting from an earlier start of the growing season. To identify the drivers of flowering phenology in the seven main species of an alpine grassland, we experimentally shifted the snowmelt date through snow manipulations, and excluded precipitation during summer. With “time-to-event” models, we analysed the beginning of main flowering with respect to temperature sums, time after snowmelt, and calendar day (photoperiod). We identified two phenology types: four species tracking snowmelt dates directly or with a certain lag set by temperature sums, including the dominant sedge Carex curvula, Anthoxanthum alpinum Helictotrichon versicolor, and Trifolium alpinum, and three species tracking photoperiod: Geum montanum, Leontodon helveticus and Potentilla aurea. Photoperiodism did not act as daylength threshold but rather modulated the thermal sums at flowering. Hence, photoperiod delayed flowering after earlier snowmelt. The grass A. alpinum was the only one of seven species that clearly responded to drought by earlier and longer flowering. The remarkably high importance of snowmelt dates for both phenology types suggests an earlier onset of flowering in a warmer climate, particularly for non-photoperiod-sensitive species, with an increasing risk for freezing damages and potential disruptions of biotic interactions in the most frequent type of alpine grassland across the Alps. Consequentially, the distinct microclimate and species-specific responses to photoperiod challenge temperature-only based projections of climate warming effects on alpine plant species.