Alpine Botany最新文献

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.

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.

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.

Throughout the last centuries, the structure and genetic composition of forests have been strongly affected by forest management. Over 30% of European forests are artificially regenerated, very often using translocated forest reproductive material, among these species the Swiss stone pine (Pinus cembra L.). In the late nineteenth and early twentieth centuries, the species was largely used for artificial afforestation in the northern Alps. However, only a few planted trees have survived. Therefore, we aimed to evaluate if the historical afforestation of P. cembra in the northwestern Swiss Alps relied on allochthonous material. We sampled 12 sites, genotyping 11 nuclear microsatellites, to infer the spatial genetic structure of regional populations, to test for genetic differences between natural and planted stands, and to infer potential source regions of planted stands using reference samples covering the entire Alps. Population genetic structure analysis allowed us to distinguish planted from natural stands and to determine that forest reproductive material used for plantations was not of regional origin. We found similar levels of genetic diversity between natural and planted stands. Assignment tests revealed that reproductive material for planting was translocated to the study area from two source regions, i.e., near the border of Switzerland and Austria, and further to the East, between Austria and Italy. Our study shows how genetic tools may inform about historical transfer of forest reproductive material, which still may affect the population genetic make-up of regional occurrences, e.g., because of reduced natural regeneration.

In high mountain environments, the availability of pollinators may decrease as elevation increases, affecting plant reproductive success. Floral volatile organic compounds (VOCs) are relevant to pollinator attraction; however, few studies have explored the variation of floral VOCs at different elevational sites. We analyzed the floral VOCs, flower size and nectar volume in Bidens triplinervia (a species with a generalized pollination system) and Penstemon roseus (with bee and bird pollination system) at three elevations (2800, 3300, and 3700 m) in the Nevado de Colima Volcano in Mexico. We recorded visitation rate and the identity of pollinators and explored the relationships between floral traits and pollinator visitation. The floral scent profile (composition and relative amounts of VOCs) of B. triplinervia and P. roseus differed between the three elevations. The highest number of VOCs and the largest flowers were found at high elevation, which had the lower visitation rate. Nectar volume was higher at low elevation and nectar concentration was lower at middle elevation. In B. triplinervia, Bombus ephippiatus was the main pollinator at low and middle elevation, while Musca domestica predominated at the highest elevation. Penstemon roseus was visited by hummingbirds and bumblebees, which were the most frequent pollinators at all three elevations. The floral traits (i.e., flower size, floral VOCs and nectar) were significantly associated with pollinator visitation. This study provides evidence of floral VOCs variation at different elevations, which was correlated with the visitation rate of local pollinators. The larger flowers at higher elevations may increase the attraction of pollinators where the environment is more extreme and erratic.

Deciphering how plants interact with each other across environmental gradients is important to understand plant community assembly, as well as potential future plant responses to environmental change. Plant−plant interactions are expected to shift from predominantly negative (i.e. competition) to predominantly positive (i.e. facilitation) along gradients of environmental severity. However, most experiments examine the net effects of interactions by growing plants in either the presence or absence of neighbours, thereby neglecting the interplay of both negative and positive effects acting simultaneously within communities. To partially unravel these effects, we tested how the seedling establishment of 10 mountain grassland plants varied in the presence versus absence of plant communities at two sites along an elevation gradient. We created a third experimental treatment (using plastic plant mats to mimic surrounding vegetation) that retained the main hypothesised benefits of plant neighbours (microsite amelioration), while reducing a key negative effect (competition for soil resources). In contrast to our expectations, we found evidence for net positive effects of vegetation at the low elevation site, and net negative effects at the high elevation site. Interestingly, the negative effects of plant neighbours at high elevation were driven by high establishment rates of low elevation grasses in bare soil plots. At both sites, establishment rates were highest in artificial vegetation (after excluding two low elevation grasses at the high elevation site), indicating that positive effects of above-ground vegetation are partially offset by their negative effects. Our results demonstrate that both competition and facilitation act jointly to affect community structure across environmental gradients, while emphasising that competition can be strong also at higher elevations in temperate mountain regions. Consequently, plant−plant interactions are likely to influence the establishment of new, and persistence of resident, species in mountain plant communities as environments change.

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.