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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]