Alpine Botany最新文献

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.

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.

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.

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.

The role of Pleistocene climate change in shaping patterns of genetic and species diversity has been widely demonstrated. However, tropical mountains remain less explored. In the northern Andes, distributional shifts of the vegetation during the Pleistocene are believed to have promoted plant diversification. In this regard, the role of gene flow and geographic isolation has been intensively debated. Here, we use a population genetic approach, microsatellite markers, and Bayesian statistics to assess the impact of Pleistocene climate change on intraspecific patterns of gene flow and genetic variation, and on the demographic history of the populations. We study Lupinus microphyllus, which belongs to a clade of Andean Lupinus species that has emerged as a model group in studies of plant diversification. We detect signatures of historical gene flow and negligible contemporary gene flow between populations. We find very low within-population genetic diversity and signals of an ancient decline in population size that may be lasting until today. We conclude that, in spite of periods of increased connectivity and gene flow, intraspecific genetic differentiation is mainly driven by periods of geographic isolation, restricted gene flow, and genetic drift. The intraspecific genetic pattern of high-elevation Andean plant species has been also shaped by local environmental factors, such as volcanic activity or glacier coverage, and by species-specific traits, such as the reproductive and dispersal strategies.

Studies in alpine environments indicate that nurse plants can facilitate other species mainly through direct mechanisms (i.e., improvements in local abiotic conditions). However, far fewer studies consider indirect facilitation, including the effect on plant–plant interactions of symbiosis with soil fungi. We asked whether the nurse shrub Hypericum laricifolium affected the colonization and activity of fungal symbionts of plants showing contrasting patterns of local spatial association with this nurse in four sites between 4100 and 4400 m in the tropical Andes. We selected three abundant herb species (Senecio wedglacialis, Castilleja fissifolia, and Agrostis tolucensis) which showed positive spatial associations with the shrub, and two herbs (Agrostis breviculmis and the exotic Rumex acetosella), which showed predominantly negative associations. We collected roots of these species from individuals under the shrub’s crown and outside, and measured colonization and activity of arbuscular mycorrhizal fungi (AMF) and colonization of dark septate fungi (DSE), as well as glomalin content in soil samples from both study situations. We found no consistent effect of the nurse across species or elevations on the degree of AMF and DSE colonization, but there was a consistent increase in AMF phosphatase activity in plants positively associated with the shrub, as well as an increase in the content of easily extractable glomalin in soils under its influence across elevations. Thus, our results suggest that an increased AMF metabolic activity and soil stabilization mediated by the increase in extractable glomalin could be linked with an indirect facilitation effect of this nurse shrub on its beneficiary plants.

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 (N_mass), 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 N_mass significantly declined. Further analysis indicated that N_mass and total phenolics mainly explained the variation of frequency of herbivory, while N_mass 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.

Bacterial communities in the phyllosphere are shaped by host genotype and phenotype and spatio-temporal variation of the environment. In turn, bacteria have the potential for altering the plant phenotype. Field experiments can help to estimate bacterial effects on plant functional traits under natural conditions. We used a transplantation approach of culturable bacterial communities to explore how manipulation of leaf-associated microbial communities in two different successional stages within a glacier foreland can influence microbial composition and functional plant traits. Our study documents successional stage-specific variations in the composition of foliar bacterial communities and shifts therein throughout a season and between years. We show that cultured bacteria transferred between plant communities can alter diversity and composition of the microbiome on plant community level as well as species-specific functional plant traits of two selected plant species within one growing season. Furthermore, our results demonstrate a strong resilience of plant-associated bacterial communities and of plants in response to bacterial invaders. Our study illustrates that inoculation experiments in the field with naturally occurring microbial communities of wild plants are suited to investigate complex interactions between microbial communities, the environment, and plant traits.

Páramo, the most species-rich tropical mountain ecosystem, is relatively well-researched in terms of the diversity and evolutionary sources of its flora, yet we know very little about the diversification within this environment. This study aims to unravel the evolutionary history of Oritrophium, an endemic genus of alpine habitats in North and South America, with a disjunct and bi-modal distribution of its species diversity. We aim to disentangle the center of origin and radiation of the genus, and mechanisms structuring its genetic diversity at inter- and intra-specific level. We sampled 19 species (85% from the total) and extended the sampling at population level for the two widely distributed species, O. limnophilum and O. peruvianum, comprising 19 and 24 populations, respectively. Using nuclear ribosomal internal transcribed spacer (ITS) and trnL-trnF chloroplast DNA region, we reconstructed dated phylogenies to test the monophyly of the genus and unravel possible historical forces underlying its diversification. We also performed an ancestral area estimation to reconstruct the biogeographic history of the genus. At the population level, we constructed haplotype networks and run spatial analyses of molecular variance to explore possible mechanisms that operate on structuring the diversity at intraspecific level. Oritrophium resulted polyphyletic, with two species being closely related to Erigeron and three other species ambiguously related to Erigeron, Diplostephium, Linochilus, and/or Hinterhubera. The remaining 14 species formed a clade, Oritrophium s.s., that likely originated during the Early Pliocene in the Andes of northwestern Bolivia to southern Ecuador, the center of the genus' diversity. The group likely diversified with the emergence of the Páramo during the Late Pliocene and further dispersed mainly from South-to-North in the Pleistocene. This migration involved both, long-distance dispersal from the Central Andes to Mexico and gradual migration of the species along the Andes. Accordingly, Oritrophium s.s. appears as the first record of a long-distance dispersal from the Páramo of South America to North America. The dispersal pattern within South America was mirrored by the intraspecific population diversity and structure of the investigated species.