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While the position of alpine and arctic treelines can be predicted by climatic data, the underlying biological mechanisms are still unclear. In a recent paper in this journal (Körner C, Lenz A, Hoch G (2023) Chronic in situ tissue cooling does not reduce lignification at the Swiss treeline but enhances the risk of 'blue' frost rings. Alpine Botany https://doi.org/10.1007/s00035-023-00293-6) we presented results of an in situ stem-cooling experiment at a Swiss treeline site. The experiment provided answers to two entirely different questions, related to xylogenesis at treeline: (a) the absence of chronic effects of low temperature on lignification, and (b) a high time resolution insight into the rare occurrence of damages in young, still undifferentiated, and thus, non-lignified cells at the occasion of an exceptional early season frost event. In the last issue of Alpine Botany (August 7, 2023), our data had been re-interpreted by (Büntgen, Alpine Botany, 2023) by confusing (b) with (a). Cell death before secondary wall formation interrupts all metabolism, and thus, cannot exert a specific limitation of lignification. For the xylem to lignify, it requires a secondary cell wall in the first place. A frost damage in young tracheid cells is unsuitable for a dendrological treeline hypothesis based on a low-temperature threshold for lignification. Generally, the global pattern of treeline position is not associated with local freezing conditions. [ABSTRACT FROM AUTHOR]

In their 2013 paper, Lenz et al. illustrated how trees growing at the low-temperature limit respond to a chronic in situ warming or cooling by 3 K, by employing Peltier-thermostated branch collars that tracked ambient temperatures. The micro-coring-based analysis of seasonal tree ring formation included double-staining microtome cross sections for lignification, but these data had not been included in the publication. In this short communication, we complement these data, collected in 2009 at the Swiss treeline, and we show that a 3 K cooling that corresponds to a 500–600 m higher elevation, had no influence on lignification. However, when a frost event occurred during the early part of ring formation, the 3 K cooling produced a blue (non-lignified) layer of cells, followed by normally lignified cells for the rest of the season. Hence, the event did not affect the cambium, but interrupted cell wall maturation in cells that were in a critical developmental stage. We conclude, that chronic cooling does not affect lignification at treeline, but it increases the risk of frost damage in premature xylem tissue. [ABSTRACT FROM AUTHOR]

Polyploidization is pivotal in plant speciation, affecting adaptability, ecological tolerance and specific geographical distribution patterns. While cytotype diversity has been extensively studied in angiosperms and ferns, knowledge in homosporous lycophytes remains very limited. Our study addresses this gap, focusing on the homosporous lycophyte Huperzia selago in Central Europe. The genome size of 1330 individuals from 208 populations were assessed via flow cytometry, revealing five distinct cytotypes (2x, 3x, 4x, 5x, 6x). Challenging chromosome counting using gemmae roots yielded average counts of 140 (2x), 204 (3x), and 262 (4x) chromosomes. The hexaploid genome size (29 pg) approached the upper limits reported for lycophytes. Tetraploids were the most abundant (72.7%), while triploids (21.3%) were less common, while the remaining cytotypes comprised less than 5% of the dataset. Geographical separation of cytotypes was not observed. However, uncommon cytotypes were associated with the Alps and triploids also occured in the highest parts of Western Carpathians. Around 27.3% of populations exhibited multiple cytotypes. Except for atypical diploids, spore abortion differed between even (21.8%) and odd ploidies (65.2%). Microcharacter (stoma, spore) proportions did not linearly correspond with increasing ploidy levels. The high ploidy-level diversity and cytotype coexistence in Central European H. selago match the well documented patterns in ferns and angiosperms. These findings provide valuable insights into lycophyte polyploidy, underscoring the necessity for broader geographical sampling and application of molecular studies to elucidate phylogenetic relationships and taxonomic classifications within the genus Huperzia. [ABSTRACT FROM AUTHOR]

Pollen-mediated gene flow and spatial genetic structure have rarely been studied in alpine plants that are pollinated by dipteran insects. In particular, it is not clear how different floral traits, such as floral gender, phenology, and ancillary traits, may affect pollen dispersal distance within alpine plant populations. In this study, we conducted a paternity analysis to track pollen flow in a population of Pulsatilla alpina, an andromonoecious alpine herb producing male and bisexual flowers. We found that the pollen was dispersed over short distances (mean = 3.16 m), with a dispersal kernel following a Weibull distribution. Nonetheless, spatial genetic structure was weak in the population (Sp statistic = 0.013), pointing to effective seed dispersal and/or high inbreeding depression. The pollen dispersal distance was independent of the gender of the flower of origin but depended positively on floral stalk height and negatively on flowering date and tepal length. Although male siring success did not correlate with pollen dispersal distance, selection may favour traits that increase the pollen dispersal distance as a result of reduced bi-parental inbreeding. Our study not only provides new insights into the nature of pollen dispersal of alpine plants, but also reveals the effects of floral traits on a component of male reproductive success. [ABSTRACT FROM AUTHOR]

A little more than 10% of the vascular plant flora native to the European Alps is endemic to this area. It has long been noticed that the distribution of endemics across the Alps is very uneven. While most endemics are found along the southern edge of the Alps, with some also on its western, eastern, and northeastern edges, the northern edge of the Alps more or less between Lake Geneva in the west and Lake Traun in the east harbours almost no endemics. The distribution of endemics in the Alps has often been related to the location of glacial refugia. Accordingly, the virtual absence of endemics from the northern edge of the Alps has been explained with the unsuitability of climatic conditions for glacial survival of alpine plants there. After discussing evidence for the existence of glacial refugia for alpine species along the northern edge of the Alps and north of the Alps, I will examine how these refugia differed from refugia along the southern edge of the Alps. I conclude that the uneven distribution of endemics in the Alps is best explained by the different climate through time north and south of the Alps. These climatic differences affected the spatial structure and extent of refugia, the length of isolation of refugial populations, and selective conditions in refugia. [ABSTRACT FROM AUTHOR]

The Sino-Himalaya region is located in the southeast margin of the Qinghai-Tibetan Plateau (QTP) with several Asian rivers in this area, namely the Yarlung Zangbo River (YZR), Salween, Mekong, and Jinshajiang River and their tributaries. All these rivers currently flow independently into the Indian Ocean, the South China Sea (Pacific Ocean) and the East China Sea (Pacific Ocean). In geologic history, however, these rivers flowed southward into the Paleo-Red River (PRR), forming a huge drainage system, which then flowed into the South China Sea. From the end of the Neogene to the beginning of the Quaternary, with further uplift of the QTP, the monsoon climate was formed and strengthened bringing abundant precipitation leading to river erosion, rapid undercutting and a series of river capture events resulting in modern drainage systems and the beheading of the huge PRR. The reorganization of the PRR led to changes in the spatial pattern of river systems, subsequently affecting the geographical distribution of plants in the river valley. This paper reviews the effects of drainage evolution on the genetic structure and geographical pattern of plants in this region, and summarizes the resulting four types of discontinuous distribution patterns observed, namely: (1) the discontinuous distribution pattern between the Three River Valleys (TRV) (Salween, Mekong, Jinshajiang and their tributaries) and the Red River Basin (RRB); (2) the discontinuity between the Yarlung Zangbo River and the TRV–RRB; (3) the discontinuity among the TRV, and (4) the discontinuity between the east and west ends of the QTP. The conclusions from this review, while providing botanical evidence supporting and confirming the drainage evolution in Sino-Himalaya China, are the following: (1) the reorganization of drainage systems made the original continuous distribution pattern discontinuous, forming unique genetic and biogeographical characteristics, promoting the genetic differentiation of species and the formation of new taxa; (2) river capture events link different river systems together, bringing together the genetic diversity of different river valley species, increasing the richness of genetic diversity and the exchange of genes among populations; (3) the reorganization of river systems impacts the evolutionary history of valley plants and shapes their modern distribution patterns. [ABSTRACT FROM AUTHOR]

Studies on the origin and evolutionary history of closely related plants help to understand patterns of diversity of the mountain flora in addition to providing the basis for their identification. The genus Tephroseris includes three endemic taxa with small and disjoint distributions in the high mountains of the Iberian Peninsula and on the Maritime Alps. Tephroseris balbisiana is native to the Southwestern Alps, Tephroseris elodes to Sierra Nevada, and Tephroseris coincyi to Sierra de Gredos. These taxa have been treated under different combinations of species or subspecies due to limited morphological differentiation, but comprehensive studies have not been published so far. By combining information from phylogeny, molecular dating and genome size, we demonstrated the taxonomic distinctiveness between T. balbisiana and the two Iberian taxa. Although the lack of variability in plastid DNA hampered the precise estimation of the diversification events, some of the recovered patterns suggested a recent divergence of T. balbisiana, T. elodes and T. coincyi dating back to the Pleistocene (0.5–2.8 Mya). However, niche modeling supported a geographical overlap between the three taxa during the Last Glacial Maximum (LGM). Moreover, the fragmentation of their ancient larger distribution range, particularly in the lower elevations of the Iberian Peninsula, and migration to glacial refuges in the south-western Alps, provide the most plausible explanations for the current disjoint distribution within the Mediterranean mountains. Furthermore, based on the evidence we gathered, we inferred that the alpine T. balbisiana, as well as the Iberian taxa, should be considered as three distinct subspecies. [ABSTRACT FROM AUTHOR]

Campos de altitude are high-altitude grasslands found in the mountain ranges of southeastern and southern Brazil, which are characterized by high species richness and endemism. Because of the difficulty in delimiting this vegetation type, measuring biodiversity patterns is challenging. Here, we compared the application of two methods using spatial data to estimate angiosperm diversity in campos de altitude: (1) filtering occurrence data by elevation, canopy height, location and keywords and; (2) the same as the first, however, adding a filter of "campos de altitude" in the vegetation type of the Flora e Funga do Brasil database. Also, we discuss conservation status, plant collections, endemism, vegetation data and similarity among 14 sites harboring campos de altitude. Our two resulting lists indicated between 1087 and 2398 angiosperm species and infraspecific taxa in campos de altitude, mostly belonging to Asteraceae and Poaceae and endemic to Brazil. Extrapolations of species richness suggest a potential number of up to 4000 species. Of the taxa assessed for conservation status, 53–65% are threatened or near threatened. The flora of campos de altitude is more similar on closely located mountains rather than on mountains with similar geological characteristics and origin. We provide an editable list online destined to seek help from taxonomists to generate a more accurate species list, to support advances in knowledge on this unique tropical montane ecosystem. [ABSTRACT FROM AUTHOR]

The growing evidence for the role of introgression in evolution is challenging for species delimitation, taxonomy, and conservation. Here, we examine the isolation of Saxifraga delphinensis, a south-west alpine narrow endemic, from its sympatric congeners Saxifraga exarata and Saxifraga moschata. Our analyses, based on morphological, molecular and genome-wide data, were extended to taxa from Jura, Massif Central, north-east Iberian mountains and Pyrenees to broaden the phylogenetic scope of the study. Phylogenetic results support the close relationship between (i) S. delphinensis, Saxifraga cebennensis and one population of S. exarata from Queyras and (ii) between S. lamottei, S. giziana and S. moschata. Saxifraga exarata, which was extensively sampled, is composed of several clades and is paraphyletic to other taxa. While morphological and genetic data support the evolutionary distinctiveness of S. delphinensis, introgression with S. exarata is shown by various data and analyses. In addition, ABBA-BABA analyses and plastome phylogeny reveal a possible contribution of the north-east Iberian endemic Saxifraga vayredana into the history of S. delphinensis. Overall, the results show a complex evolutionary history with frequent hybridization and spanning several mountain ranges in Europe. [ABSTRACT FROM AUTHOR]

Climate warming in mountain areas is increasing faster than the global average, threatening alpine plants. Climate affects many traits including seeds, the longevity of which is important for conservation, facilitating genebank storage. Seeds of alpine species are considered short-lived in storage, but their longevity increases when produced under a warmer parental environment. Consequently, with climate warming, seeds of alpine species may have increased fitness and be longer-lived in genebank storage. We assessed seed longevity under artificial ageing in 10 accessions of the arctic-alpine species Viscaria alpina stored under genebank conditions for different time periods over the last 20 years. The seed collection site was in the northern Apennines, where above average warming and variable precipitation has been recorded. The time taken for viability to fall to 50% (p50) was estimated using probit analysis; correlation and general linear regression were used to investigate the effects of length of time in storage, seed mass and climate under which seeds were produced on seed longevity. p50 varied between 7.77 and 18.49 days. There was no relationship between length of time in storage or seed mass on seed longevity. p50 was higher in years with increased temperature and lower precipitation during the growing season, with precipitation having more impact than temperature. The results suggest that seeds of alpine species are suitable for genebank storage, and inter-annual variation in precipitation induces a plastic response in seed longevity. Using genebank stored seeds provides insights into how alpine species may respond to future climate changes and could have implications for genebank storage. [ABSTRACT FROM AUTHOR]

Refugia will be important to the response of alpine vegetation to climate change. Potential refugia exist at multiple scales, including a range-wide mesoscale. The climates of alpine grasslands of 23 mountain ranges of southern and central Europe were evaluated to assess whether each range would support potential refugia in projected future climates. The mean temperature the warmest month and quarter with the precipitation of the warmest quarter, derived from gridded global climate data at ~ 1 km resolution, were examined range-wide and for areas identified as alpine grassland to identify limits within each range. The overlap of current grassland climate and future range-wide climates, the latter calculated using regional projections from three global models with three socioeconomic driving scenarios, were assessed as potential refugia. Among the nine projections, three had none of the current grassland climates in any of the 23 ranges by 2100, while two retained more than 20% in more than half of the ranges. Most of the potential mesoscale refugia were in the Alps. Micro-refugia and warmer and drier fundamental climatic niches for alpine grassland species could mitigate these bleak results, but otherwise they are extremely threatened. [ABSTRACT FROM AUTHOR]

Mesoscale heterogeneity of alpine landscapes generates snowmelt gradients resulting in a distinct vegetation zonation from almost snow-free fellfields to long-lasting snowbeds. Although the vegetative trait variation along such gradients has been intensively studied, little is known about whether and how seed germination is adapted to the variable snowpack duration. Here, we compare the seed germination niches of 18 characteristic plant species occurring in four distinct plant communities (alpine lichen heath—Festuca varia grassland—Geranium-Hedysarum meadow—snowbed) along an alpine snowmelt gradient in the North Caucasus (Russia). In a fully factorial experiment, we tested seed germination responses to temperature (10/2, 14/6, 18/10, 22/14, 26/18 and 30/22 °C) and water potential (0, − 0.2, − 0.4, − 0.6 and − 0.8 MPa) gradients, reflecting the full spectrum of seedling establishment conditions in the study system. Community-specific germination niches were identified by generalised mixed model with Bayesian estimation. Our study revealed that the species from the four focal communities significantly differed in their temperature requirements for germination, whereas soil moisture was found to be a limiting factor for seedling establishment along the entire gradient. The snowbed germination was constrained to comparatively high temperatures above 10 °C, whereas seed germination in alpine lichen heaths occurred under a wide range of experimental conditions. The seed germination patterns of species from Festuca varia grasslands and Geranium-Hedysarum meadows reflected their intermediate position along the snowmelt gradient. We conclude that seed germination niche is affected by the environmental filtering along the snowmelt gradient thus departing from the general alpine germination syndrome. [ABSTRACT FROM AUTHOR]

Climate change, such as warming, is a threat to mountain ecosystems in the forest-line ecotone. This influence could seriously affect bryophytes, because they easily lose their internal water at high temperatures. We conducted experimental warming using open-top chambers (OTCs) in a forest-line ecotone in central Japan and examined its influence on bryophyte cover. Six years after the experiment was initiated, the total bryophyte cover was not significantly different between the control and OTC treatments. However, the two dominant bryophyte species (Pogonatum japonicum and Dicranum majus) responded differently to the OTC treatment. The cover of P. japonicum significantly increased under the OTC treatment, while that of D. majus decreased to approximately 14% of the initial cover under the OTC treatment. These results could be explained by D. majus being better adapted to high-elevation climates than P. japonicum. The decline of D. majus cover was potentially further enhanced by the decrease in rainfall and fog within the OTCs. These are important water sources for D. majus because the species lacks water-conducting systems that enable mosses to absorb water from their substrates. As the OTCs in this study were tall (210 cm high), they may have blocked slanting rain and fog from reaching the plants, increasing water stress in D. majus. In contrast, P. japonicum develops water-conducting systems and may be less susceptible to the decrease in rainfall and fog. These results can aid future experimental studies in the mountains to elucidate the mechanisms underlying bryophyte responses to warming. [ABSTRACT FROM AUTHOR]

Pollination-induced flower senescence is expected in species of dry habitats with large long-lived water-demanding flowers as means for reducing floral maintenance costs. We investigated this hypothesis in Alstroemeria umbellata, an alpine species of the semiarid central Chilean Andes. Pollinator-excluded flowers were submitted to hand cross-pollination and manual pollen removal and monitored twice daily to assess the time spans of four floral stages and two expressions of flower longevity. Wilting and floral stage duration responses in open-pollinated flowers were studied. Ramet-level floral and leaf water content were quantified. Pollen removal had no effect on any floral trait analyzed. Hand cross-pollination reduced the functional flower lifespan from 7.5 to 6.7 days and the female stage from 3.4 to 1.6 days, but did not have a clear effect on the total flower lifespan (9.3 days). Counterintuitively, the length of the dehydration stage increased following pollination. No effect of pollination was detected in naturally pollinated flowers. Inflorescences contained > 3.5 g of water, > 3 times more than the ramet leaves, with > 50% of floral water housed in the turgid tepals. Although inflorescences contain much more water than the leaves, based on the open-pollination results, the amount of tepal water saved through pollination-associated floral senescence under natural circumstances is likely to be far less than the ~ 11% predicted by the manipulative experiment. Knowledge of tepal and leaf transpiration rates and the water content of underground plant parts is desirable to arrive at a more precise assessment of the impact of pollination-associated floral senescence on the water balance in A. umbellata. [ABSTRACT FROM AUTHOR]

Uncertainty still exists on the directions and intensity of changes in leaf herbivory under scenarios of global warming. We, therefore, conducted an investigation on insect herbivory along an elevational gradient to explore how leaf herbivory may respond to future climate warming using a space-for-time substitution approach. We hypothesize that the leaf herbivory for alpine woody species should decline with elevation. We also guess the leaf herbivory may not differ between different leaf-age groups, for the old leaves are less attractive to insect due to their lower nutrients. To approve these assertions, we measured different aspects of leaf herbivory, i.e., the intensity (leaf area consumed per damaged leaf), frequency (percentage of leaves damaged), and rate (percentage of consumed leaf area over the total number of leaves), across different leaf-age groups for Rhododendron aganniphum var. schizopeplum along an elevational gradient (4280–4640 m) in the Sergymla Mountains, southeast Tibet. Related leaf traits of leaf mass per area (LMA) and nitrogen (Nmass), as well as total phenolics for 1-year-old leaves, were also investigated. In contrast with our expectation, the rate of herbivory did not vary with elevation, while the frequency and intensity reflected increasing and declining patterns, respectively. LMA and total phenolics tended to increase with elevation, while Nmass significantly declined. Further analysis indicated that Nmass and total phenolics mainly explained the variation of frequency of herbivory, while Nmass reflected a significant effect on the variation of intensity. No differences in herbivory were found between the leaf-age groups. Our results suggest that the lower intensity of leaf herbivory at higher elevations is mainly associated with the declined nutritional levels, while the higher frequency might be related to the higher costly anti-herbivore defenses like phenolics and the lower nutritional levels. Although the older leaves are exposed to herbivore attacks for a longer time, they possessed the same herbivory levels as current-year leaves partly due to their lower nitrogen concentrations. Both supporting the nutrient limitation hypothesis, i.e., plants with lower leaf nutrient levels possess less leaf herbivory. In all, the herbivory on the alpine Rhododendron is small in magnitude, but given the higher herbivory (for intensity at least) under persistent warming conditions and its potential impacts on mediating plant–insect interactions, insect herbivory should be included in predictions of climate change impacts on alpine ecosystems. [ABSTRACT FROM AUTHOR]

In alpine plants, the temporal variation in the concentrations of non-structural carbohydrates (NSC) is closely related to the growth phenology, which is largely controlled by annual variations in temperature. However, in alpine areas of Mediterranean-type climate regions, plants growing at low elevations are also exposed to seasonal drought. Given the influence of drought on growth phenology and gas exchange, we hypothesize that the seasonal dynamics of growth and NSC concentrations in alpine plants of Mediterranean biomes is co-controlled by elevational gradients of temperature and soil moisture. If so, the end of the growing season and the maximum NSC concentrations at lower elevations should coincide with the occurrence of drought. We characterized the seasonal dynamics of photosynthesis capacity, growth and NSC concentrations, in an alpine plant species of the Andes of central Chile (Phacelia secunda Gmel.) at 1600 and 3600 m. We found that the length of the growing season was similar between elevations, but the timings differed. Whilst at 3600 m, the number of leaves and the mean leaf length progressively increased from December to February, at 1600 m, in contrast, they increased from the October to December. Likewise, maximum NSC concentrations at 3600 were observed at autumn along with growth cessation. Conversely, at 1600 m, the highest NSC concentration and the growth cessation were found towards mid-summer, and coincided with a drastic drop in both stomatal conductance and photosynthesis which were not observed at 3600 m. These results demonstrate that temperature alone does not control the growth phenology and the seasonal dynamics of NSC concentrations in alpine plants of Mediterranean biomes. Rather, summer drought also exerts a significant influence in the timing of the growing season and the NSC dynamics. [ABSTRACT FROM AUTHOR]

Global warming is expected to have large impacts on high alpine and Arctic ecosystems in the future. Here we report effects of 18 years of experimental warming on two contrasting high alpine plant communities in subarctic Sweden. Using open-top chambers, we analysed effects of long-term passive experimental warming on a heath and a meadow. We determined the impact on species composition, species diversity (at the level of rare, common and dominant species), and phylogenetic and functional diversity. Long-term warming drove differentiation in species composition in both communities; warmed plots, but not control plots, had distinctly different species composition in 2013 compared with 1995. Beta diversity increased in the meadow, while it decreased in the heath. Long-term warming had significant negative effects on the three orders of phylogenetic Hill diversity in the meadow. There was a similar tendency in the heath, but only phylogenetic diversity of dominant species was significantly affected. Long-term warming caused reductions in forbs in the heath, while evergreen shrubs increased. In the meadow, deciduous and evergreen shrubs showed increased abundance from 2001 to 2013 in warmed plots. Responses in species and phylogenetic diversity to experimental warming varied over both time (medium (7 years) vs long-term (18 years)) and space (between two neighbouring plant communities). The meadow community was more negatively affected in terms of species and phylogenetic diversity than the heath community. A potential driver for the changes in the meadow may be decreased soil moisture caused by long-term warming. [ABSTRACT FROM AUTHOR]

Mountaineering, since the beginning of its history, has played an inconspicuous but key role in the collection of species samples at the highest elevations. During two historical expeditions undertaken to reach the summit of Mount Everest in 1935 and 1952, mountaineers collected five species of vascular plants from both the north and south sides of the mountain, at ca. 6400 m a.s.l. Only one of these specimens was determined immediately following the expedition (Saussurea gnaphalodes), and the remaining four were not identified until quite recently. In 2000, the second specimen from the 1935 expedition was described as a new species for science (Lepidostemon everestianus), endemic to Tibet. In this paper, the remaining three specimens from the 1952 Everest expedition are reviewed and analysed, bringing the number of species sharing the title of “highest known vascular plant” from two to five. I identify one of the 1952 specimens as Arenaria bryophylla, and describe two novel taxa based on analysis of the herbarium records: Saxifraga lychnitis var. everestianus and Androsace khumbuensis. Although elevation records on their own do not inform us about the ecological conditions and physiological capacity of plants at the upper limit of their distribution, this taxonomic investigation contributes to our knowledge of the biogeography of Himalayan flora and opens the way for future field-based investigations of mechanisms limiting plant growth on the roof of the world. [ABSTRACT FROM AUTHOR]

Mountain ecosystems are becoming increasingly threatened by non-native plant invasions. In this paper, the occurrence of non-native plant species was examined in a protected area (Laojun Mountain Area) in the eastern Himalayas, China. Sampling plots were systematically set up along elevation from 1950 to 3500 m a.s.l. Sixty-one non-natives were recorded that account for 24% of the roadside flora. The number of non-native species decreased continuously with increasing elevation and significant nestedness was found between the low- and high-elevation plots. Moreover, all non-native species distributed at high elevation were also found at low elevation and mountain specialists were not found among non-natives. These results indicate that the eastern Himalayan ecosystem is not immune to invasion and most of the non-natives spread from lowland areas upward to the highlands. Future efforts to manage plant invasions in this region should concentrate on low-elevation areas where agriculture and disturbances by tourism are increasing rapidly. [ABSTRACT FROM AUTHOR]

This special issue of the journal Alpine Botany brings together syntheses, macroecological and taxon-specific studies of patterns and processes of plant evolution in major mountain ranges across Europe, Africa, the Americas and Asia. Apart from reflecting current conceptual and methodological perspectives in the field, it contributes to our understanding of the interplay between factors determining the evolution and distribution of plant variation across topographically complex areas, and will help to identify the components necessary for building an integrative model of the origin and distribution of diversity in mountain areas. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Climatic changes threaten the diverse and highly endemic páramo flora of the equatorial Andes with species loss and reduction of plant community diversity. Edward Whymper's findings in his botanical exploration of the Ecuadorian Andes in 1880 offer an opportunity to examine the impact of climate changes on species distribution over time. To achieve these goals, we revised Whymper's historical plant species collections, recorded elevational distribution of the same species along his 1880 sampling routes on two volcanoes, Chimborazo and Antisana, and applied to them ecological indicator values. Of the species recorded by Whymper, 24 on Antisana and 21 on Chimborazo, we resampled 21 and 14 of those species, respectively, in 2020. The highest record we found on Chimborazo was at 5385 m, seven meters above the zero-richness elevation predicted from Whymper's distribution data, and at 4937 m on Antisana, 113 m below it. Mean upper range limits of species have shifted upward by 91.7 m on Chimborazo and by 27.1 m on Antisana, suggesting mean shift rates of 6.6 m and 1.9 m per decade, respectively. This rate of upslope migration ranks among the slowest reported worldwide. Humidity ecological indicator values suggest that species composition of páramo plant communities changed since 1880 in response not only to rising temperature, but also increasing dryness. Rather than a uniform upslope migration, the response of páramo plants to climate changes in the equatorial Andes has been species-specific, likely driven, among other factors, by coupled effects of increasing temperature and declining humidity. [ABSTRACT FROM AUTHOR]

Seed germination and seedling recruitment are key processes in the life cycle of plants. They enable populations to grow, migrate, or persist. Both processes are under environmental control and influenced by site conditions and plant–plant interactions. Here, we present the results of a seed-sowing experiment performed along an elevation gradient (2000–2900 m a.s.l.) in the European eastern Alps. We monitored the germination of seeds and seedling recruitment for 2 years. Three effects were investigated: effects of sites and home sites (seed origin), effects of gaps, and plant–plant interactions. Seeds of eight species originating from two home sites were transplanted to four sites (home site and ± in elevation). Seed sowing was performed in experimentally created gaps. These gap types ('gap + roots', 'neighbor + roots', and 'no-comp') provided different plant–plant interactions and competition intensities. We observed decreasing germination with increasing elevation, independent of the species home sites. Competition-released gaps favored recruitment, pointing out the important role of belowground competition and soil components in recruitment. In gaps with one neighboring species, neutral plant–plant interactions occurred (with one exception). However, considering the relative vegetation cover of each experimental site, high vegetation cover resulted in positive effects on recruitment at higher sites and neutral effects at lower sites. All tested species showed intraspecific variability when responding to the experimental conditions. We discuss our findings considering novel site and climatic conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

While the high elevation limit of trees is commonly related to low temperature, the rear edge of their distribution is often associated with drought. Here we explore phenology traits that contribute to a mechanistic explanation of both these edges of the fundamental niche in the broad leaved evergreen Quercus pannosa s.l. Populations of this species reach a drought limit (DL) at 2510 m in the semi-arid upper Yangtze valley, and a cold limit (CL) at 4270 m, very close to the conifer treeline, within a short geographical distance. Trees reach a height of only 4–7 m at both climatic limits, and > 30 m height at optimum site (OS) at 3440 m. At OS, flushing starts in mid-May and at the summer solstice at CL (after late frosts end), suggesting a photoperiod control. At DL, oak phenology tracks the (irregular) arrival of the monsoon. Shoots and leaves grew fastest and for the shortest period at DL, and slowest at CL, in both cases forming 4–7 cm long new shoots per year, contrasted by 12–13 cm a−1 at OS. Maturation of leaves (length and specific leaf area, SLA) was again fastest at DL, followed by CL and slowest at OS, with a much longer shoot growth duration per year and bigger leaves. We conclude that the period favorable for growth and maturation was more than halved at both range limits (by frost or drought) compared to the optimum site, pointing at a common range restriction by the duration of the growing season. [ABSTRACT FROM AUTHOR]

Global warming may pose a serious threat to seed germination and establishment in alpine ecosystems, given that temperature is a primary factor in stimulating seed germination and regulating changes in seed dormancy. However, to date, little is known about the relative importance of temperatures experienced by parents versus by the seeds (after dispersal). In this study, we tested the effects of warming at different stages on germination success and timing in the Australian alpine herb Wahlenbergia ceracea. To decouple the effect of parental warming from that of offspring warming, we raised parental plants (in both outcrossed and selfed lines) in both current (benign, cool) and future (warm) temperature conditions, and then sowed the seeds they produced back in either current or future conditions. We quantified (1) the effects of parental and/or offspring warming on (i) the percentage of germination and (ii) the season of germination (i.e. effects on dormancy); (2) whether the season of germination affected seedling growth; and (3) the effects of inbreeding and its interaction with temperature. We found that the percentage of germination decreased slightly with parental warming, but increased greatly with offspring warming. Parental warming also increased the fraction of dormant seeds, indicating a shift from predominately autumn to spring emergence. Spring-emerged seedlings grew slower than autumn-emerged seedlings, but the growth rate of spring-emerged seedlings were not detrimentally affected by warm offspring temperatures. In this facultatively autogamous species, inbreeding magnified the negative effects of both parental and offspring warming. Our results illustrate the value of tests of the effects of warming across generations and on multiple life stages for improving our understanding of the ecological processes behind plant germination and establishment, and of plant responses to climate warming. [ABSTRACT FROM AUTHOR]

Elevation gradients provide an ideal setting to infer species' functional trait responses to predicted future climate change. In plants, leaf functional traits help assess their capacity to cope with varying resources. Variation in abiotic conditions over short vertical distances can influence plant phenology, particularly leafing and flowering durations, and leaf functional traits at both inter- and intra-specific levels. However, studies examining relationships between leaf functional traits and phenology duration along elevation gradients are limited. We tested the relationship between leaf size, leaf thickness, specific leaf area, and leafing durations in 10 Rhododendron species in the Sikkim Himalaya. All the investigated traits varied significantly across species, but intra-specific variation in functional traits was observed only among a few. Leaf size and thickness showed significant negative relationships with elevation and a comparative phylogenetic method exhibited a strong relationship between leaf traits and leafing duration. We observed higher leaf thickness and size in species with longer leafing durations and less overlap in leafing and flowering durations. In contrast, species with shorter leafing durations and relatively more overlap in their flowering and leafing durations showed lower leaf thickness and leaf size. Leaf traits such as leaf thickness and leaf size also exhibited a strong phylogenetic signal across 10 Rhododendron species. Overall, from our findings, we infer that along an elevation gradient, the magnitude of leaf trait responses to future increases in temperature may vary depending on species phenology durations and phylogeny. [ABSTRACT FROM AUTHOR]

This study examined the morphological variation in Senecio subalpinus W.D.J. Koch. (Asteraceae) along a 950-m elevation gradient in the Tatra Mountains, Central Europe, with emphasis on floral allocation patterns. Fifteen morphological traits were measured in 200 plants collected in the field from 20 sites then the findings were modelled by elevation using linear mixed-effects models. Plant aboveground biomass and height decreased steadily with increasing elevation; however, the most distinctive feature was the elevational shift in floral allocation patterns. Low-elevation plants had greater numbers of smaller flower heads with a lower overall number of flowers, while high-elevation plants had smaller numbers of bigger flower heads and a greater overall number of flowers. Accordingly, the mean individual flower mass increased significantly with increasing elevation. Interestingly, the width of the outer ligulate flowers also increased considerably with increasing elevation, increasing the fill of the overall circumference of the flower head. Results of this study confirmed that elevation is an important ecological gradient driving variation in vegetative and floral traits of S. subalpinus. Possible causes of the observed variations are subsequently discussed, including the varying effects of both abiotic and biotic factors with elevation gradients. [ABSTRACT FROM AUTHOR]

Climatic oscillations of the Quaternary rapidly compelled plant species to shift their geographical range. How alpine plant species responded to climate change, however, remains elusive and remnants of the cold-adapted flora that currently strive in restricted ranges as small, isolated populations have been particularly overlooked. To address the evolutionary history of such a 'glacial relict', we here sampled and genotyped all known native populations of a narrow endemic species from the northwestern Alps, Papaver occidentale, as well as closely related taxa with double digest restriction-site Associated DNA (ddRAD) sequencing. Spatial patterns of genetic variation across populations coupled with insights from climatic niche modelling through time address underpinings of the long-term persistence of the species in face of climate changes. Evidence from population genetics and ecological modelling indicates that P. occidentale likely persisted through the last glacial maximum outside of the Western Prealps and that a major lineage recolonized the area from lower elevation, external regions. Differentiated lineages at the Northern margins of the species distribution range highlight highly divergent and geographically restricted populations that include considerable share of private markers and may indicate local glacial survival in isolated conditions. Our data thus imply that processes having shaped intraspecific spatial genetic structure within the Alps can be complex and lead to mosaic of populations with a mixed-history of local survival and immigration. A better understanding of spatio-temporal aspects of range contraction–expansion is crucial to shed light on processes underlying the evolution of remnant populations of such endemic species and set conservation priorities considering current climate changes. [ABSTRACT FROM AUTHOR]

In high-mountain habitats, summer frosts have negative consequences for plant fitness, therefore high-mountain plants have developed mechanisms of avoidance and tolerance to cope with freezing temperatures. Various hypotheses have been proposed to explain the prevalence of one freezing-resistance mechanism over another, focusing on thermal conditions without a consensus. We hypothesize that the prevalence of a freezing-resistance mechanism depends on the life-history strategy of the species, and is probably the consequence of a trade-off between growth/reproduction and the cost of the mechanism. Specifically, short-lived annual species should be freezing avoidant, whereas perennial long-lived species should be freezing tolerant. We used thermal analysis to determine the mechanism of freezing resistance of leaves and flowers for 10 annual and 14 perennial herb species from an alpine ecosystem in the Central Chilean Andes. We found that 70% of the annual species, their flowers and leaves were freezing avoidant, indicating that avoidance was their predominant freezing-resistance mechanism. In the case of perennial species, both mechanisms were almost equally represented in flowers and leaves. Overall, our results showed that a species freezing-resistance mechanism depends on its life-history strategy, and that leaves and flowers of single species exhibit the same freezing resistance mechanism, suggesting a common whole plant strategy. Further, freezing resistance strategies were not found to be mutually exclusive. In some cases, a specific combination of phenological, structural, and functional strategies may determine how freezing resistant vegetative and reproductive organs are to freezing during the growing season. [ABSTRACT FROM AUTHOR]

Ongoing changes in temperature and precipitation regime may have a strong impact on vulnerable life-history stages such as germination, especially in alpine regions. Differences in germination patterns among species and populations may reflect their adaptation to conditions of their origin or may be determined by the phylogenetic constraints. These two effects are, however, rarely separated. All the germination patterns may also be modified by seed mass. We studied 40 populations of 14 species of Impatiens coming from different elevations in the Himalayas. Three home site temperatures were simulated and one warmer temperature according to a climate change scenario were used. We also studied the combined effect of shorter stratification and warmer temperature as another possible effect of climate change. Interactions of home site and germination conditions affected total germination and germination speed, but not seed dormancy. Seed mass and home site conditions' interaction indicated different germination strategies in light and heavy seeds. Only seed mass was affected by phylogenetic relationships among the species, while germination response (except T30) was driven primarily by home site conditions. This study is the first to show that the effect of seed mass interacts with home site conditions in determining species' germination patterns under changing climate. The differences in seed mass are thus likely crucial for species' ability to adapt to novel conditions since seed mass, unlike seed germination patterns, is strongly phylogenetically constrained. Further studies exploring how seed mass modifies species' germination under changing climate are needed to confirm generalisability of these findings. [ABSTRACT FROM AUTHOR]

Abandonment of pastures and successional shrub expansion are widespread in European mountain regions. Moderate shrub encroachment is perceived beneficial for plant diversity by adding new species without outcompeting existing ones, yet systematic evidence is missing. We surveyed vegetation along 24 transects from open pasture into shrubland across the Swiss Alps using a new protocol distinguishing different spatial scales, shrub cover of each plot (2 × 2 m) and larger-scale zonal cover along the transect. Data were analysed using generalized linear models of shrub cover, shrub species and environmental conditions, such as geology, aspect or soil. Most shrub communities were dominated by Alnus viridis (62% of transects) and Pinus mugo (25%), and the rest by other shrub species (13%). These dominant shrub species explained vegetation response to shrub cover well, without need of environmental variables in the model. Compared to open pasture, A. viridis resulted in an immediate linear decline in plant species richness and a marginal increase in beta-diversity (maximally + 10% at 35% cover). Dense A. viridis hosted 62% less species than open pasture. In P. mugo, species richness remained stable until 40% shrub cover and dropped thereafter; beta-diversity peaked at 35% cover. Hence, scattered P. mugo increases beta-diversity without impairing species richness. In transects dominated by other shrubs, species richness and beta-diversity peaked at 40–60% shrub cover (+ 23% both). A. viridis reduced species richness in a larger area around the shrubs than P. mugo. Therefore, effects of shrub encroachment on plant diversity cannot be generalized and depend on dominant shrub species. [ABSTRACT FROM AUTHOR]

In contrast to adult plants, little is known about the frost-tolerance of seedlings of alpine species, despite the fact that frost has been considered as one of the main factors limiting plant recruitment in high elevation. Here we report the results of a comparative study on seedling frost-tolerance of nine congeneric species pairs with lowland (0–900 m a.s.l.) and alpine (1800–2700 m a.s.l.) distribution. Similarly to adult alpine plants, we expected seedlings of alpine species to be more frost-tolerant than their lowland counterparts. Frost-tolerance was estimated under laboratory conditions by exposing seedlings to frost events from − 1 to − 9 °C, calculated as the temperature at which 50% of the seedlings were lethally damaged by frost (LT50). The LT50 values varied between − 1.95 and − 6.11 °C suggesting that seedling of all tested species could potentially survive mild and/or short frosts, but might be lethally damaged by severe and/or continuous frost events. The LT50 values for lowland and alpine species did not differ statistically and were on average − 3.96 ± 0.18 °C and − 4.16 ± 0.43 °C, respectively. These findings did not confirm our hypothesis that seedlings of alpine species have higher frost-tolerance than seedlings of lowland species. Four possible reasons could explain this pattern. They include (1) comparable levels of negative-stress in both lowland and alpine habitats, (2) opportunistic seed germination strategy in alpine plants, (3) peculiarities of our experimental set up and (4) potentially stronger effects of drought on alpine seedling survival than frost. [ABSTRACT FROM AUTHOR]

In high-mountain habitats, summer frost events can have negative consequences for plant fitness. Despite this, most studies have evaluated the consequences of frosts for vegetative structures of perennial plants, and neither for leaves nor for flowers of annual plants. We hypothesize that the degree of freezing resistance of flowers and leaves of a species depends on its life-history strategy (LHS), and is probably the consequence of a trade-off between growth/reproduction and the cost of the freezing resistance. Specifically, flowers and leaves of short-lived annual species should be less freezing resistant than those of perennial plant species. We compared the freezing resistance of flowers and leaves of 10 annual and 12 perennial plant species from the Andes of central Chile using the electrolyte leakage method. Temperature damage for 50% tissue (LT50) of annual species was − 9.6 °C in flowers and − 11.9 °C in leaves. In perennial species, LT50 was similar in flowers (− 12.3 °C) and leaves (− 12.5 °C). Despite that, these differences were not significant (except the flowers of annual species), we found remarkable differences between LHS when freezing resistance was analyzed species by species. Like this, 58% and 83% of perennial species resist temperatures ≤ − 10 °C in their flowers and leaves, respectively, compared with only 30% and 40% of annual species. Additionally, in most of the species, the freezing resistance of leaves was greater than that of flowers, with this proportion being greater in annual (58%) than in perennial species (43%). Thus, we concluded that the degree of freezing resistance depends on the LHS, such that annual species, which are less freezing resistant than perennial species, have an infrequent occurrence and a distribution restricted to low elevation in high-mountain habitats. [ABSTRACT FROM AUTHOR]

Ecological interactions play a fundamental role in determining the genetic structure of plant species in time and space. The demography of the Andean Puya hamata has been linked to fire regimes and hummingbird behaviour, which might modify the plant's population genetic structure. Naturally, poor dispersal results in patches of genetically related plants, a pattern intensified further by burning which promotes seedling germination around parent plants. Later, when these plants flower, large patches are attractive to territorial hummingbirds which prevent visits by traplining hummingbird species, carrying pollen from likely unrelated plants. To explore this hypothesis, a genetic study of P. hamata using microsatellite markers was conducted with (i) isolated and grouped adults in two size categories of patches, and (ii) seeds collected from the same patches and isolated individuals. Isolated individual plants presented a higher observed heterozygosity with close to zero inbreeding. Adult plants from large patches showed a lower observed heterozygosity and higher inbreeding than plants from other spatial contexts. Seed genetic structure displayed a gradient of diversity: lower at patch centres but higher at patch edges, in small patches, and for isolated infructescences. The spatial context of these plants, especially the contrast between large patch centres and other situations, determines the genetic diversity of their seeds via hummingbird foraging behaviour. Territorial hummingbirds restrict gene flow in and out of large patches, but traplining hummingbirds maintain genetic diversity among isolated plants, small patches, and plants at the edges of large patches. Our study illustrates the need to consider interactions between land use, plants, and their pollinators when considering genetic diversity at the landscape scale. [ABSTRACT FROM AUTHOR]

Treeline isotherms are used in comparative and modelling studies to predict treeline positions. However, how representative local short-term temperature records are for a given region remains poorly understood. Furthermore, the predictive value of on-site temperatures for explaining tree growth requires further validation. Here we present temperature records and tree growth datasets from treeline ecotone sites differing in elevation and slope direction in the High Sudetes (Czechia and Poland). The goal was to determine the spatial and temporal variability of soil and air temperatures and to describe the relationship of various temperature metrics with tree growth. Our results demonstrate that, because of spatial and temporal variability, major temperature metrics used in comparative studies should be provided with an uncertainty range between 0.6 and 0.8 K for seasonal mean soil and air temperature. While soil temperatures exhibit high spatial variability, air temperatures vary more with time. Elevation is the most important driver of temperature patterns in treeline ecotones. Differences related to slope direction were important mainly for soil temperatures in lower parts of treeline ecotones. Tree growth is tightly related to June–September air temperature, with a modulating role of the onset date of soil temperature-defined growing season. In this study, we describe patterns of temperature variation in the treeline ecotones of two mountain ranges and demonstrate the extremely strong dependence of tree stem growth on air temperature, with very limited remaining space for other potentially limiting factors. [ABSTRACT FROM AUTHOR]

The Alps played an important role in the biogeography of European plants and acted as a refugium for numerous species during the interglacial cycles. We investigated Nuphar pumila, one of the most emblematic glacial relicts of the Alps, by carrying out exhaustive literature and field surveys to collect relevant data on its distribution and threats. We further evaluated the level of introgression with the closely related N. lutea based on microsatellite data from natural populations across the Alps as well as from all ex situ collections and reintroductions in Switzerland. According to our results, more than 60% of the known N. pumila populations went extinct, and the species currently presents 37 natural populations in the investigated area. A large number of populations were affected by eutrophication (69%) and hybridization with N. lutea (53%). Priority should be given to the in situ conservation of genetically pure populations, while ex situ cultures should be applied to nearly extinct populations and the genetically pure individuals still present in hybrid populations. N. pumila is an excellent representative of the wetland/aquatic glacial relicts that are particularly affected by the combination of climate change and habitat degradation. International integration of research and conservation programs is needed to limit the decline of such rare species in the Alps. [ABSTRACT FROM AUTHOR]

The largest alpine–nival vegetation permanent plot site in the Alps, the GLORIA mastersite Schrankogel (Tirol, Austria), provided evidence of warming-driven vegetation changes already 10 years after its establishment in 1994. Another decade later, in 2014, substantial compositional changes with increasing ratios of warmth-demanding to cold-adapted species have been found. The current study deals with species-specific responses involved in an ongoing vegetation transformation across the alpine–nival ecotone on Schrankogel by using presence/absence as well as cover data from permanent plots, situated between 2900 and 3400 masl. The number of occupied plots per species remained constant or even increased during the first decade, whereas disappearance events became more frequent during the second one, especially for cold-adapted specialists (subnival–nival species). Remarkably, the latter was accompanied by continued strong losses in cover of all subnival–nival species. These losses were more frequent in plots with a more thermophilous species composition, suggesting an increasing maladaptation of subnival–nival species to warmer habitat conditions and a successive trailing-edge decline. Several species with a distribution centre at lower elevations (alpine–subnival) markedly increased in cover, comparatively more so in colder plots, indicating a leading-edge expansion. Moreover, our findings show an increase in occupied plots and cover of almost all snowbed species, suggesting that areas previously with a too long snowpack period are now becoming suitable snowbed habitats. Vegetation gaps arising from population dieback of cold-adapted species, however, could only be partly filled by advancing species, indicating that species declines have occurred already before the onset of strong competition pressure. [ABSTRACT FROM AUTHOR]

Diversity patterns of tropical alpine vegetation is poorly studied. We estimated vascular plant floristic richness for two typical afro-alpine communities in Mount Kenya using a series of nested plots sized from 25 to 100 m2. The α-diversity was low for all plot sizes (4.8–7.8 and 12.8 species per one and 100 m2, respectively). Comparative analysis of α-, β- and γ-diversity across 22 plant communities from five Mountain regions (Mount Kenya, European Alps, Caucasus, Tibet, New Zealand Alps) revealed that area of mountain system was the only significant variable shaping the local richness; this effect became stronger with increasing spatial scale. Beta-diversity, by contrast, showed neither latitudinal trends nor significant correlation with other geographical or climatic variables. We conclude that the total area of mountain system is one of the main factors determining the regional species pool and, ultimately, the local diversity of alpine plant communities (the "echo-effect"). Small area and isolation of Mt. Kenya are considered as the main reasons for low local richness of its afro-alpine vegetation. [ABSTRACT FROM AUTHOR]

In the southern side of the Alps, many relic species with Mediterranean and sub-Mediterranean distribution were described in mild-winter, fire-prone areas. Very few studies have modeled the importance of environmental factors on their distribution. In this paper, we assessed the effect of fire on the occurrence of euri- and steno-Mediterranean (ESM) species in Pinus sylvestris forests of Aosta Valley (Italy), by analyzing vegetation in a chronosequence of six stand-replacing fires (1962-2006). We analyzed species richness along the chronosequence, and modeled it as a function of time since fire, environment, and stand structure. We observed a strong positive association between ESM and total species richness. Temporal vegetation dynamics did not follow the direct succession pattern that is commonly observed in Mediterranean ecosystems. Two distinct maxima of ESM species richness were observed: (1) short lived, ruderal species (32 % of all ESM species) in the early post-fire stages, and (2) dry grassland species (54 %) in intermediate stages. The first were facilitated by the consumption of canopy and litter during fire, while the second by delayed tree canopy closure. In multivariate models of ESM species richness, light and elevation were the only significant predictors. Contrary to expectations, time since fire was not significant. Our study suggests that stand-replacing fires play an important role in preserving Mediterranean species in the study area by maintaining an open canopy, and promote local species diversity. [ABSTRACT FROM AUTHOR]

Arenaria bernensis (Caryophyllaceae), traditionally placed within the Arenaria ciliata aggregate and discovered only in 1955, is a poorly studied endemic taxon of western Prealps in Switzerland. In this study, we aimed to deliver the first detailed appraisal on morphology, distribution and ecology of A. bernensis accompanied by first molecular insights into the A. ciliata aggregate using chloroplast (cp) DNA markers. Altogether 18 populations attributed morphologically to A. bernensis were found during our field surveys. The distribution area of A. bernensis forms an irregular line of ca. 50 km from the south-west (Dent de Lys, FR) to the north-east (Stockhorn, BE). The taxon counts globally ca. 4,000 individuals and the majority of populations are small (<100 individuals). Furthermore, our study demonstrates clear ecological and phytosociological differentiation between A. bernensis and Arenaria multicaulis, another member of the A. ciliata complex growing in the same geographic area. Arenaria bernensis grows exclusively on shady, cool and steep slopes with northern exposition in the alpine zone above 1,900-2,000 m a.s.l. Results of our chloroplast DNA analyses suggest that the A. ciliata aggregate is a monophyletic group (including A. ciliata s.str., A. multicaulis, A. gothica and A. bernensis). Additionally, A. bernensis is genetically closer to A. multicaulis than to A. ciliata s.str. However, our data also suggest that A. bernensis has a complex evolutionary history. Future investigation of nuclear genomic DNA is needed to clarify the phylogenetic status of A. bernensis. The present paper also delivers a first scientific drawing of A. bernensis and a detailed English description of its morphology. The here documented narrow endemic character of A. bernensis emphasizes the role of the western Prealps as a peripheral refugia during Quaternary glaciations. [ABSTRACT FROM AUTHOR]

Leaf shape variations and developmental instability were examined for the first time in natural populations of Prunus avium (L.) L. in the central Balkan region (Bosnia and Herzegovina) at different elevational points, from 230 to 1177 m. above sea level. Geometric morphometric tools were applied to assess the variability of leaf shapes and sizes, while a fluctuating asymmetry leaf index was used as a measure of leaf developmental instability. According to the results of canonical variate analysis for the symmetric component of shape variation and hierarchical analysis of variance for centroid size, the studied populations could be partially differentiated into three groups. The co-variation between leaf form (shape and size) and climate variables was significant, estimated by two-block partial least square analysis. Climate variables (the sum of precipitation in May and the De Martonne aridity index) mostly influenced leaf shape and size. A population situated at the highest elevation had the highest value for fluctuating asymmetry leaf index, which was an indication of developmental instability. High natural variability and interpopulation differences were observed for all studied leaf traits (leaf shape, centroid size, fluctuating asymmetry leaf index, leaf area, leaf length and width, petiole length). For well-known traditional morphometric measures (leaf area, leaf length, leaf width, and petiole length) in accordance with previous studies, intrapopulation variability was greater than interpopulation variability. For centroid size and the fluctuating asymmetry leaf index (measures used in geometric morphometrics) variability was higher among populations than within them. This indicates that geometric morphometrics could give new insights into infra-specific variability. [ABSTRACT FROM AUTHOR]

Pleistocene climatic changes affected the current distribution and genetic structure of alpine plants. Some refugial areas for the high elevation species have been proposed in the Alps, but whether they could survive on nunataks, is still controversial. Here, the spatial genetic structure in Salix serpillifolia revealed by chloroplast (cpSSR) and nuclear (nSSR) microsatellites was compared with the MaxEnt-modelled geographic distributions under current and past (Last Glacial Maximum) climate conditions. Our results suggest that the genetic pattern of differentiation detected in S. serpillifolia may be explained by the existence of Pleistocene refugia, including nunataks. The geographical patterns of variation obtained from the chloroplast and nuclear markers were not fully congruent. The spatial genetic structure that was based on nSSRs was more homogenous, while the cpSSR-based pattern pointed at strong genetic structure along the Alps. Five populations from the Central Alps had a combination of local and unique cpSSR clusters and admixture of those occurring in the Western and Eastern Alps. These findings may indicate the local survival of small populations of S. serpillifolia that were subsequently populated by new colonists in the postglacial period. [ABSTRACT FROM AUTHOR]

All plant species reach a low temperature range limit when either low temperature extremes exceed their freezing tolerance or when their metabolism becomes too restricted. In this study, we explore the ultimate thermal limit of plant tissue formation exemplified by a plant species that seemingly grows through snow. By a combination of studies in alpine snowbeds and under controlled environmental conditions, we demonstrate and quantify that the clonal herb Soldanella pusilla (Primulaceae) does indeed grow its entire flowering shoot at 0 °C. We show that plants resume growth under 2–3 m of snow in mid-winter, following an internal clock, with the remaining period under snow until snow melt (mostly in July) sufficient to produce a flowering shoot that is ready for pollination. When snow pack gets thin, the flowering shoot intercepts and re-radiates long-wave solar radiation, so that snow and ice gently melt around the fragile shoot and the flowers emerge without any mechanical interaction. We evidence bud preformation in the previous season and enormous non-structural carbohydrate reserves in tissues (mainly below ground) in the form of soluble sugars (largely stachyose) that would support basic metabolism for more than 2 entire years under snow. However, cell-wall formation at 0 °C appears to lack unknown strengthening factors, including lignification (assessed by confocal Raman spectroscopy imaging) that require between a few hours or a day of warmth after snow melt to complete tissue strengthening. Complemented with a suite of anatomical data, the work opens a window towards understanding low temperature limits of plant growth in general, with potential relevance for winter crops and trees at the natural climatic treeline. [ABSTRACT FROM AUTHOR]

Dioecious plants often exhibit deviations from expected 1:1 sex ratios. Genus Salix is a notable example of the female-biased sex ratio. Quite surprisingly, there are very few studies retesting observed bias patterns from the different parts of the species range. We have determined whether isolated subalpine populations of Salix lapponum exhibit a biased secondary sex ratio, measured the size of the plants, and tested the spatial and ecological correlations of the bias at fine and broad scales. Males were generally taller than females, suggesting that a different allocation of resources may occur in both sexes. Despite this, we found consistent female bias with females on average twice as common as males in most populations studied. No correlations of sex ratio with elevation as a proxy of environmental harshness and proportion of non-flowering individuals were found. Additionally, no differences in spatial sex segregation and microhabitat preferences were found between males and females at a fine scale within the studied populations. Our results suggest that the biased sex ratio in S. lapponum is not environment-dependent and probably originates during early stages of ontogenetic development (seeds). [ABSTRACT FROM AUTHOR]

Phenotypic variation may be genetically determined or reflect phenotypic plasticity. More common plants are expected to be less differentiated between and within regions and more adapted than less common ones. However, such differences might not develop in hybridizing species which cannot evolve completely independently. We collected 311 genets of Carex flava, 215 of C. viridula and 46 of their hybrid C. × subviridula from 42 natural populations in cold temperate Estonia, mild temperate Lowland Switzerland and alpine Highland Switzerland. Three plantlets from each genet were planted to three experimental gardens, one in each region. We measured survival, growth, reproduction and morphological traits. The experimental transplants showed strong plasticity and grew smallest in the alpine garden. The less common C. viridula was slightly more differentiated between regions of origin than the more common C. flava and the hybrid. However, this depended on the experimental garden. Significant origin-by-garden-by-taxon and taxon-by-garden interactions suggest differential adaptation among populations and taxa. Regional differed from non-regional plants in several traits indicating both adaptations and, especially for C. viridula, maladaptations to the home regions. For C. flava, plant seed production was higher when mean annual temperature and precipitation were more similar between population of origin and garden, suggesting local adaptation to climate. Hybrids were intermediate between parental taxa or more similar to one of them, which was retained across gardens. We conclude that plasticity, genetic variation and genotype-environment interactions all contributed to regional differentiation of the closely related species. Hybridization did not completely align evolutionary patterns, and the less common species showed slightly more genetic differentiation between populations and more maladapted traits than the more common one. [ABSTRACT FROM AUTHOR]

Phenotypic changes conferred by polyploidisation likely alter the ecological niche of polyploids, coming along with differences in performance compared to their diploid ancestors. However, it is largely unknown whether these performance differences remain constant during the life history of plants. Diploid Senecio noricus, tetraploid S. disjunctus, and hexaploid Senecio carniolicus s. str. of the autopolyploid species complex of S. carniolicus (Asteraceae) from the easternmost Alps were reciprocally transplanted to address the following questions: Are there differences in species performances indicating niche differentiation? If so, does the resident or the higher ploid species—which is taller growing and possibly more tolerant against challenging abiotic and biotic conditions—show higher performance? Are performance differences consistent between the early and late life-history stages? Our data suggest that the hierarchy of species performance depends on the life-history stage. For early life-history stages (seeds and seedlings), we mainly observed superior performance of S. carniolicus s. str. even on resident sites of the two other species. In contrast, vital rates of adults were predominantly highest for the resident species. The resident site of S. carniolicus s. str., which was expected to be environmentally least stressful (i.e., longest growing period, least affected by frost), turned out to be the most selective one, with high mortality and (nearly) no reproduction of the foreign species most likely due to top soil desiccation. Our study illustrates that there may be no clear-cut answer to the question if the resident or the higher ploid species shows superior performance in polyploid complexes, but rather suggests that relative performance may depend on life-history stage. [ABSTRACT FROM AUTHOR]

The occurrence of triploid hybrids in nature is scarce due to the so-called triploid block representing formation of nonviable progeny after mating diploid with tetraploid. Here we describe frequent presence of triploids originating from hybridization of diploid Festuca pratensis with tetraploid F. apennina in the Swiss Alps. F. pratensis is a forage grass grown in lowlands and up to 1800 m a.s.l., while F. apennina is a mountain grass found in elevations from 1100 to 2000 m a.s.l. In the overlapping zone these species often grow sympatrically and triploid hybrids have been observed. We show that elevation is the main factor in the distribution of plants with various ploidy levels. Diploids occupy lower elevations, while triploids predominate in the mid-elevation zones and tetraploids are the most frequent in higher elevations. Other factors, such as topography and soil composition probably have only marginal effects on the distribution of the plants with different ploidy levels. Triploids seem to be frequently formed in the Swiss Alps and crosses in both directions are involved in the formation of triploid hybrids. As shown by chloroplast DNA analysis, F. apennina more frequently serves as female. Our analysis suggests that in the mid-elevation zones, triploids have a higher level of competitiveness than both parents. Triploids can overgrow microhabitats to a much higher extent than tetraploids. Such frequent occurrence and local dominance of triploids can at least be partially explained by asexual reproduction. Using DNA markers, we show that triploids can disperse ramets of a single clone over a distance of at least 14.4 m. [ABSTRACT FROM AUTHOR]

Alpine plants growing along wide elevational gradients experience very different abiotic and biotic conditions across elevations. As a result of genetic differentiation and/or plastic response, conspecific plants growing in high elevations, as compared to low elevations, generally have shorter stems and lower number of flowers, but larger flower size. However, most often, detailed models of elevational variations were not examined. To reveal the pattern of elevational changes in a set of fitness-related morphological traits, tests of linear and unimodal models were performed based on measurements of 1047 Solidago minuta plants collected from 47 sites distributed along a 1000 m elevational gradient in the Tatra Mountains. Nearly all of the investigated floral traits, i.e. inflorescence and flower heads size, and number and size of individual flowers, expressed unimodal relationships with elevation having their maxima in the centre of the elevation range. This pattern suggests the existence of a local optimum with respect to sexual reproduction at the centre of the elevational range. Possible explanations of observed elevational variations are discussed in the context of pollinator selection and the ‘resource-cost compromise’ hypothesis. Best floral performance in the centre of the elevational range of S. minuta may also support the idea that the favourability of habitat conditions declines from the centre to the margin of the distribution, and species are expected to be more abundant, increase reproduction and perform better in the centre of the range. [ABSTRACT FROM AUTHOR]