Silene Acaulis Research Articles

Growth dynamics and climate sensitivities in alpine cushion plants: insights from Silene acaulis in the Swiss Alps

AbstractUnderstanding alpine plants’ growth dynamics and responses to warming is essential for predicting climate change impacts on mountain ecosystems. Here, we examine growth determinants in the alpine cushion plant Silene acaulis in the Swiss Alps, exploring ontogeny, elevation, and climate influences. We collected 40 Silene individuals and 159 individuals from 38 co-occurring alpine species across 2200–3130 m elevations in the Swiss Alps, analyzing age and growth histories through annual growth rings. While comparing growth rates, we found that Silene was relatively slow-growing. However, Silene exhibited a dual growth strategy, initially rapid and then slowing after ~ 20 years, challenging perceptions of its longevity. Similar ontogenetic trends were observed in other alpine species, albeit with variations based on species and elevation. The consistent unimodal growth-elevation pattern in Silene and other alpine plants, peaking at ~ 2400 m, underscores shared environmental constraints on alpine plant growth. Additionally, cross-dating growth ring series and correlating with daily climate data enabled the precise assessment of warming impacts on growth. Silene’s growth is influenced by year-to-year climate variability, with warming-induced moisture stress and overheating during spring and summer adversely affecting its growth. Despite being low-statured, Silene is not completely decoupled from atmospheric influences. The heat-trapping function of Silene, effective in mature and well-formed cushions, makes it susceptible to adverse effects as temperatures rise. This sensitivity raises concerns about the potential dieback of Silene cushions, as witnessed during recent heatwaves, and emphasizes the broader ecological implications for alpine ecosystems, given Silene’s role as a crucial nurse plant.

From everywhere all at once: Several colonization routes available to Svalbard in the early Holocene.

For many arctic species, the spatial (re-)colonization patterns after the last Pleistocene glaciation have been described. However, the temporal aspects of their colonization are largely missing. Did one route prevail early, while another was more important later? The high Arctic archipelago Svalbard represents a good model system to address timeframe of postglacial plant colonization. Svalbard was almost fully glaciated during last glacial maximum and (re-)colonization of vascular plants began in early Holocene. Early Holocene climatic optimum (HCO) supported an expanded establishment of a partly thermophilic vegetation. Today, we find remnants of this vegetation in sheltered regions referred to as "Arctic biodiversity hotspots". The oldest record of postglacial plant colonization to Svalbard is found in Ringhorndalen-Flatøyrdalen. Even though thermophilic species could establish also later in Holocene, only HCO was favorable for vast colonization, and only hotspots offered stable conditions for thermophilic populations throughout Holocene. Thus, these relic populations may reflect colonization patterns of HCO. We investigate whether the colonization direction of thermophilic plants (Arnica angustifolia, Campanula uniflora, Pinguicula alpina, Tofieldia pusilla, and Vaccinium uliginosum ssp. microphyllum) in Ringhorndalen-Flatøyrdalen was uniform and different from later colonization events in other localities and non-thermophilic plants (Arenaria humifusa, Bistorta vivipara, Juncus biglumis, Oxyria digyna, and Silene acaulis). We analyzed plastid haplotypes of the 10 taxa from Ringhorndalen-Flatøyrdalen, from later-colonized localities in Svalbard, and from putative source regions outside Svalbard. Only rare and thermophilic taxa Campanula uniflora and Vaccinium uliginosum ssp. microphyllum provided results suggesting at least two colonization events from different source regions. Tofieldia pusilla and all the non-thermophilic plants showed no clear phylogeographically differentiation within Svalbard. Two of the thermophilic species showed no sequence variation. Based on the results, a uniform colonization direction to Svalbard in early Holocene is not probable; several source areas and dispersal directions were contemporarily involved.

Dieback of the cushion plant Silene acaulis at its southern limit of distribution in the Apennines

Dieback of the cushion plant Silene acaulis at its southern limit of distribution in the Apennines

Estimating phenological sensitivity in contemporary vs. historical data sets: Effects of climate resolution and spatial scale.

Phenological sensitivity, or the degree to which a species' phenology shifts in response to warming, is an important parameter for comparing and predicting species' responses to climate change. Phenological sensitivity is often measured using herbarium specimens or local studies in natural populations. These approaches differ widely in spatiotemporal scales, yet few studies explicitly consider effects of the geographic extent and resolution of climate data when comparing phenological sensitivities quantified from different data sets for a given species. We compared sensitivity of flowering phenology to growing degree days of the alpine plant Silene acaulis using two data sets: herbarium specimens and a 6 yr observational study in four populations at Niwot Ridge, Colorado, USA. We investigated differences in phenological sensitivity obtained using variable spatial scales and climate data sources. Herbarium specimens underestimated phenological sensitivity compared to observational data, even when herbarium samples were limited geographically or to nearby weather station data. However, when observational data were paired with broader-scale climate data, as is typically used in herbarium data sets, estimates of phenological sensitivity were more similar. This study highlights the potential for variation in data source, geographic scale, and accuracy of macroclimate data to produce very different estimates of phenological responses to climate change. Accurately predicting phenological shifts would benefit from comparisons between methods that estimate climate variables and phenological sensitivity over a variety of spatial scales.

Soil Microbial Communities Associated with Three Arctic Plants in Different Local Environments in Ny-Ålesund, Svalbard.

Understanding soil microbial community structure in the Arctic is essential for predicting the impact of climate change on interactions between organisms living in polar environments. The hypothesis of the present study was that soil microbial communities and soil chemical characteristics would vary depending on their associated plant species and local environments in Arctic mature soils. We analyzed soil bacterial communities and soil chemical characteristics from soil without vegetation (bare soil) and rhizosphere soil of three Arctic plants (Cassiope tetragona [L.] D. Don, Dryas octopetala L. and Silene acaulis [L.] Jacq.) in different local environments (coal-mined site and seashore-adjacent site). We did not observe any clear differences in microbial community structure in samples belonging to different plant rhizospheres; however, samples from different environmental sites had distinct microbial community structure. The samples from coal-mined site had a relatively higher abundance of Bacteroidetes and Firmicutes. On the other hand, Acidobacteria was more prevalent in seashore-adjacent samples. The relative abundance of Proteobacteria and Acidobacteria decreased toward higher soil pH, whereas that of Bacteroidetes and Firmicutes was positively correlated with soil pH. Our results suggest that soil bacterial community dissimilarity can be driven by spatial heterogeneity in deglaciated mature soil. Furthermore, these results indicate that soil microbial composition and relative abundance are more affected by soil pH, an abiotic factor, than plant species, a biotic factor.

Cushion plants act as facilitators for soil microarthropods in high alpine Sweden

Cushion plants can have positive impacts on plant richness in severe environments and possibly across trophic levels on arthropods, an under-studied topic. This study examined whether soil communities under cushions have higher richness and abundance of soil microarthropods than adjacent non-cushion vegetation, and whether differences in collembolan and mite abundance and species richness between cushions and adjacent vegetation increase with elevation. Paired soil samples were taken under cushions of Silene acaulis along the elevation gradient (1000, 1100, 1200, 1300, 1400 m a.s.l.), under cushions of Diapensia lapponica on the exposed ridge above the treeline (1000 m a.s.l.), and under adjacent non-cushion plant vegetation. In total, 5853 individuals of collembolans (n = 1705) and mites (n = 4148) were obtained from soil samples and identified to order/species level. S. acaulis cushions had a positive effect on species richness and abundance of collembolans, with richness effects from 1100 m a.s.l. upwards. Oribatid mite richness and abundance were also higher under cushions compared with adjacent vegetation. Species richness of collembolans and oribatids declined with increasing elevation from 1200 m a.s.l. Collembolan abundance peaked at mid-elevation (1200 m a.s.l.) under cushions and adjacent vegetation, while oribatid mite abundance peaked at 1300 m a.s.l. under both vegetation types. D. lapponica cushions on the exposed ridge had significant positive effects on species richness, abundance and diversity index of collembolans, and abundance of oribatids. Cushion plants play an important role in supporting the biodiversity of soil fauna in severe alpine environments, with the positive effects of cushion plants increasing with environmental severity.

Cushion plant Silene acaulis is a pioneer species at abandoned coal piles in the High Arctic, Svalbard

BackgroundAbandoned coal piles after the closure of mines have a potential negative influence on the environment, such as soil acidification and heavy metal contamination. Therefore, revegetation by efficient species is required. For this, we wanted to identify the role of Silene acaulis in the succession of coal piles as a pioneer and a nurse plant. S. acaulis is a well-studied cushion plant living in the Arctic and alpine environments in the northern hemisphere. It has a highly compact cushion-like form and hosts more plant species under its canopy by ameliorating stressful microhabitats. In this research, we surveyed vegetation cover on open plots and co-occurring species within S. acaulis cushions in coal piles with different slope aspects and a control site where no coal was found. The plant cover and the similarity of communities among sites were compared. Also, the interaction effects of S. acaulis were assessed by rarefaction curves.ResultsS. acaulis was a dominant species with the highest cover (6.7%) on the coal piles and occurred with other well-known pioneer species. Plant communities on the coal piles were significantly different from the control site. We found that the pioneer species S. acaulis showed facilitation, neutral, and competition effect in the north-east facing slope, the south-east facing slope, and the flat ground, respectively. This result was consistent with the stress gradient hypothesis because the facilitation only occurred on the north-east facing slope, which was the most stressed condition, although all the interactions observed were not statistically significant.ConclusionsS. acaulis was a dominant pioneer plant in the succession of coal piles. The interaction effect of S. acaulis on other species depended on the slope and its direction on the coal piles. Overall, it plays an important role in the succession of coal piles in the High Arctic, Svalbard.

Разнообразие лиственничных лесов и редколесий западного макросклона Приполярного и Северного Урала

Разнообразие лиственничных лесов и редколесий западного макросклона Приполярного и Северного Урала

The presence of a foreign microbial community promotes plant growth and reduces filtering of root fungi in the arctic-alpine plant Silene acaulis

ABSTRACT Background Climate change is expected to drive trailing-edge range redistributions of arctic-alpine plant populations, bringing together immigrant plant ecotypes and soil microbial communities associated with already resident ecotypes. Aims The goal of the present study was to assess growth performance and plant–microbe interactions between seedlings and native and foreign microbial communities in ecotypes of the cushion plant Silene acaulis from Europe and North America. Methods Using seed sourced from Colorado, USA, and Ireland we grew Silene seedlings in sterile bulk soil with live inocula added from their own local soil and each other’s soil. We measured above-ground plant growth metrics, and analysed fungal and bacterial community composition using marker gene sequencing and microscopy. Results Seedlings growing in foreign soil inocula showed significantly greater biomass or shoot length compared to growth in home soil inocula. While seedling root microbiomes were overall convergent with each other compared to source soil inocula, significantly lower filtering of fungal taxa from the soil was observed for seedlings growing in foreign compared to home soil inocula. Conclusions Foreign plant ecotypes from distant habitats may experience competitively beneficial effects when growing in local soil communities; however, the nature and generality of these interactions requires further analysis.

Heated rivalries: Phenological variation modifies competition for pollinators among arctic plants.

When plant species compete for pollinators, climate warming may cause directional change in flowering overlap, thereby shifting the strength of pollinator‐mediated plant–plant interactions. Such shifts are likely accentuated in the rapidly warming Arctic. Targeting a plant community in Northeast Greenland, we asked (a) whether the relative phenology of plants is shifting with spatial variation in temperature, (b) whether local plants compete for pollination, and (c) whether shifts in climatic conditions are likely to affect this competition. We first searched for climatic imprints on relative species phenology along an elevational gradient. We then tested for signs of competition with increasing flower densities: reduced pollinator visits, reduced representation of plant species in pollen loads, and reduced seed production. Finally, we evaluated how climate change may affect this competition. Compared to a dominant species, Dryas integrifolia × octopetala, the relative timing of other species shifted along the environmental gradient, with Silene acaulis and Papaver radicatum flowering earlier toward higher elevation. This shift resulted in larger niche overlap, allowing for an increased potential for competition for pollination. Meanwhile, Dryas emerged as a superior competitor by attracting 97.2% of flower visits. Higher Dryas density resulted in reduced insect visits and less pollen of S. acaulis being carried by pollinators, causing reduced seed set by S. acaulis. Our results show that current variation in climate shifts the timing and flowering overlap between dominant and less‐competitive plant species. With climate warming, such shifts in phenology within trophic levels may ultimately affect interactions between them, changing the strength of competition among plants.

Functional composition and diversity of leaf traits in subalpine versus alpine vegetation in the Apennines.

Mediterranean high mountain grasslands are shaped by climatic stress and understanding their functional adaptations can contribute to better understanding ecosystems’ response to global change. The present work analyses the plant functional traits of high-elevation grasslands growing in Mediterranean limestone mountains to explore, at the community level, the presence of different plant strategies for resource use (conservative vs. acquisitive) and functional diversity syndromes (convergent or divergent). Thus, we compared the functional composition and diversity of the above-ground traits related to resource acquisition strategies of subalpine and alpine calcareous grasslands in the central Apennines, a mountain region characterized by a dry-summer Mediterranean climate. We used georeferenced vegetation plots and field-measured plant functional traits (plant maximum height, specific leaf area and leaf dry matter content) for the dominant species of two characteristic vegetation types: the subalpine Sesleria juncifolia community and the alpine Silene acaulis community. Both communities are of particular conservation concern and are rich in endemic species for which plant functional traits are measured here for the first time. We analysed the functional composition and diversity using the community-weighted mean trait index and the functional diversity using Rao’s function, and we assessed how much the observed pattern deviated from a random distribution by calculating the respective standardized effect sizes. The results highlighted that an acquisitive resource use strategy and relatively higher functional diversity of leaf traits prevail in the alpine S. acaulis community, optimizing a rapid carbon gain, which would help overcome the constraints exerted by the short growing season. The divergent functional strategy underlines the co-occurrence of different leaf traits in the alpine grasslands, which shows good adaptation to a microhabitat-rich environment. Conversely, in the subalpine S. juncifolia grassland, a conservative resource use strategy and relatively lower functional diversity of the leaf traits are likely related to a high level resistance to aridity over a longer growing season. Our outcomes indicate the preadaptation strategy of the subalpine S. juncifolia grassland to shift upwards to the alpine zone that will become warmer and drier as a result of anthropogenic climate change.

Incorporating intraspecific variation into species distribution models improves distribution predictions, but cannot predict species traits for a wide‐spread plant species

The most common approach to predicting how species ranges and ecological functions will shift with climate change is to construct correlative species distribution models (SDMs). These models use a species’ climatic distribution to determine currently suitable areas for the species and project its potential distribution under future climate scenarios. A core, rarely tested, assumption of SDMs is that all populations will respond equivalently to climate. Few studies have examined this assumption, and those that have rarely dissect the reasons for intraspecific differences. Focusing on the arctic‐alpine cushion plant Silene acaulis, we compared predictive accuracy from SDMs constructed using the species’ full global distribution with composite predictions from separate SDMs constructed using subpopulations defined either by genetic or habitat differences. This is one of the first studies to compare multiple ways of constructing intraspecific‐level SDMs with a species‐level SDM. We also examine the contested relationship between relative probability of occurrence and species performance or ecological function, testing if SDM output can predict individual performance (plant size) and biotic interactions (facilitation). We found that both genetic‐ and habitat‐informed SDMs are considerably more accurate than a species‐level SDM, and that the genetic model substantially differs from and outperforms the habitat model. While SDMs have been used to infer population performance and possibly even biotic interactions, in our system these relationships were extremely weak. Our results indicate that individual subpopulations may respond differently to climate, although we discuss and explore several alternative explanations for the superior performance of intraspecific‐level SDMs. We emphasize the need to carefully examine how to best define intraspecific‐level SDMs as well as how potential genetic, environmental, or sampling variation within species ranges can critically affect SDM predictions. We urge caution in inferring population performance or biotic interactions from SDM predictions, as these often‐assumed relationships are not supported in our study.

Deinococcus arcticus sp. nov., isolated from Silene acaulis rhizosphere soil of the Arctic tundra.

A Gram-stain-negative, non-motile, aerobic, short rod-shaped bacterium, designated OD32T, was isolated from a soil sample taken from the rhizosphere of Silene acaulis collected from the Arctic tundra. The novel strain, OD32T, was able to grow at 15-37 °C (optimum, 33 °C), pH 6.5-9.5 (pH 7.5-8.0) and 0-0.5 % NaCl (0 %, w/v). A phylogenetic analysis based on 16S rRNA gene sequences revealed that strain OD32T was most closely related to the genus Deinococcus; it shared the highest sequence similarity (95.7 %) with Deinococcus grandis ATCC 43672T. Genomic DNA G+C content of the strain OD32T was 68.2 mol%. The predominant respiratory quinone was menaquinone 8 (MK-8). The major fatty acids were summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c), C15 : 1 ω6c, C17 : 1 ω6c, C17 : 0, C16 : 0 and iso-C17 : 0. Based on phylogenetic inference and genotypic characteristics, strain OD32T represents a novel species of the genus Deinococcus, for which the name Deinococcus arcticus sp. nov. is proposed. The type strain is OD32T (=KCTC 33972T=CICC 24671T).

Litter-driven feedbacks influence plant colonization of a high elevation early successional ecosystem

Plant-microbe interactions are crucial components of ecosystem development but are understudied during early succession. The goal of this study was to investigate species-specific effects of plants on unvegetated soils being colonized by plants as climate changes, and assess how plant-soil feedbacks influence plant succession. We used lab and field litter additions in an early successional unvegetated ecosystem in the Front Range of the Colorado Rocky Mountains to examine litter-driven changes in soil bacterial and fungal communities. We then used plant litter-trained soil as inocula in a greenhouse experiment to test plant-soil feedbacks. We found species-specific effects of litter additions on bacterial and fungal communities in unvegetated soils, which are likely due to both differences in tissue litter chemistry and differences in the litter microbiome. We identified a negative effect of soil trained by litter from the conservative forb Silene acaulis on the growth of the fast-growing bunchgrass Deschampsia cespitosa, likely due to changes in microbial communities that resulted in lowered nitrification rates or to a litter-driven increase in N-immobilization. Our study demonstrates the importance of plant specificity and potential negative litter-driven feedbacks in primary succession, which could lead to patchy distribution of plant colonists as climate change allows colonization of these areas.

Human trampling disturbance exerts different ecological effects at contrasting elevational range limits

Abstract Shifts in species geographic distributions in response to climate change have spurred numerous studies to determine which abiotic (e.g. climatic) and, less commonly, biotic (e.g. competitive) processes determine range limits. However, the impact of disturbances on range limits and their interactions with climatic and biotic effects is not well understood, despite their potential to alter competitive relationships between species or override climatic effects. Disturbance might have differential effects at contrasting range limits, based on Darwin's theory that biotic interactions set abiotically benign range limits and abiotic factors set abiotically stressful range limits. We predicted that plants at lower elevation (abiotically benign) range limits experience a net positive effect of disturbance, whereas those at higher elevation (abiotically stressful) range limits experience a net neutral effect. We examined plant populations along elevational gradients in the Colorado Rocky Mountains, in order to quantify the effects of human trampling disturbance at lower and upper elevational range limits of the common alpine cushion plants Silene acaulis and Minuartia obtusiloba. Our results are consistent with Darwin's theory. A disturbance‐mediated reduction of competitive effects increases the performance of cushion plants at lower elevations, suggesting a range limit set by biotic factors. At higher elevations, where biotic interactions are minimal, disturbance has neutral or negative effects on cushion plants. Synthesis and applications. Human trampling disturbance exerts differential effects on alpine cushion plant populations at contrasting range limits, emphasizing the need to account for the effects of climate change into the management and conservation of disturbed areas. Disturbance can diminish plant–plant competitive interactions at lower elevational range limits, and thus possibly stabilize alpine species populations susceptible to climate change‐mediated encroachment by lower elevation species. Conservation and management approaches should therefore particularly account for the differential effects of disturbance across climatic gradients.

Female advantage? Investigating female frequency and establishment performance in high-Arctic Silene acaulis

Many Arctic plants overcome limited time budgets and energy budgets by selfing, increasing the risk of inbreeding. Gynodioecious breeding systems allows for selfing by hermaphrodites, whereas enforced outcrossing through females lowers risk of inbreeding. Females persist due to female advantage in the system. Using the gynodioecious species Silene acaulis (L.) Jacq., we compared establishment performance and female frequency in 17 populations in open, sparsely vegetated habitats versus closed, denser vegetated habitats, across a regional climate gradient in high-Arctic Svalbard. For two populations, genetics were performed using microsatellites to compare inbreeding levels between habitats. As S. acaulis is a pioneer species, we expected denser vegetation to represent more competitive environments, reducing establishment performance and increasing female frequency due to female advantage. We expected similar responses to harsher regional climate. Establishment performance was reduced in closed habitats and harsher climate, but female frequency was slightly lower in closed habitats and did not differ between regional climates. High inbreeding levels may indicate that female advantage is counteracted by pollen limitation. However, female frequency increased with latitude. Lower sun angle at higher latitudes reduce the heat-trap effect of the cushion growth form, and female advantage might be expressed as response to reduced microclimate amelioration.

Redefining the climate niche of plant species: A novel approach for realistic predictions of species distribution under climate change

Climate change is increasingly affecting plant species distributions, in ways that need to be predicted. Here, in a novel prediction approach, we developed the relevant climate niche (RCN) of plants, based on thorough selection of climate variables and implementation of a non-parametric Bayesian network for climate simulations. The RCN was conditionalized to project the fate of Silene acaulis in North America under moderate (Representative Concentration Pathway 4.5; RCP4.5) and extreme (RCP8.5) short-term (2011–2040) climate scenarios. We identified a three-variable climate hypervolume for S. acaulis. Within 20 years >50% of current locations of the species will be outside the defined climate hypervolume. It could compensate for climate change in 2011–2040 through a poleward shift of 0.97 °C or an upshift of 138 m in the RCP4.5 scenario, and 1.29 °C or 184 m in the RCP8.5 scenario. These results demonstrate the benefits of redefining the climate niche of plant species in the form of a user-defined, data-validated, hierarchical network comprising only variables that are consistent with species distribution. Advantages include realism and interpretability in niche modeling, and new opportunities for predicting future species distributions under climate change.

Синтаксономия луговин тундрового пояса гор Мурманской области

Синтаксономия луговин тундрового пояса гор Мурманской области

Geographic location, local environment, and individual size mediate the effects of climate warming and neighbors on a benefactor plant.

Predictions of plant responses to global warming frequently ignore biotic interactions and intraspecific variation across geographical ranges. Benefactor species play an important role in plant communities by protecting other taxa from harsh environments, but the combined effects of warming and beneficiary species on their performance have been largely unexamined. We analyzed the joint effects of elevated temperature and neighbor removal on the benefactor plant Silene acaulis, in factorial experiments near its low- and high-latitude range limits in Europe. We recorded growth, probability of reproduction and fruit set during 3 years. The effects of enhanced temperature were positive near the northern limit and negative in the south for some performance measures. This pattern was stronger in the presence of neighbors, possibly due to differential thermal tolerances between S. acaulis and beneficiary species in each location. Neighbors generally had a negative or null impact on S. acaulis, in agreement with previous reviews of overall effects of plant-plant interactions on benefactors. However, small S. acaulis individuals in the north showed higher growth when surrounded by neighbors. Finally, the local habitat within each location influenced some effects of experimental treatments. Overall, we show that plant responses to rising temperatures may strongly depend on their position within the geographic range, and on species interactions. Our results also highlight the need to consider features of the interacting taxa, such as whether they are benefactor species, as well as local-scale environmental variation, to predict the joint effects of global warming and biotic interactions on species and communities.

Differences in the fungal communities nursed by two genetic groups of the alpine cushion plant, Silene acaulis.

Foundation plants shape the composition of local biotic communities and abiotic environments, but the impact of a plant's intraspecific variations on these processes is poorly understood. We examined these links in the alpine cushion moss campion (Silene acaulis) on two neighboring mountain ranges in the French Alps. Genotyping of cushion plants revealed two genetic clusters matching known subspecies. The exscapa subspecies was found on both limestone and granite, while the longiscapa one was only found on limestone. Even on similar limestone bedrock, cushion soils from the two S. acaulis subspecies deeply differed in their impact on soil abiotic conditions. They further strikingly differed from each other and from the surrounding bare soils in fungal community composition. Plant genotype variations accounted for a large part of the fungal composition variability in cushion soils, even when considering geography or soil chemistry, and particularly for the dominant molecular operational taxonomic units (MOTUs). Both saprophytic and biotrophic fungal taxa were related to the MOTUs recurrently associated with a single plant genetic cluster. Moreover, the putative phytopathogens were abundant, and within the same genus (Cladosporium) or species (Pyrenopeziza brassicae), MOTUs showing specificity for each plant subspecies were found. Our study highlights the combined influences of bedrock and plant genotype on fungal recruitment into cushion soils and suggests the coexistence of two mechanisms, an indirect selection resulting from the colonization of an engineered soil by free‐living saprobes and a direct selection resulting from direct plant–fungi interactions.