Abstract
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.
Highlights
We previously reported that the presence of a cushion affects soil chemical parameters on two bedrocks and that this shift in abi‐ otic properties comes along with a shift in the fungal community; in particular, the fungal turnover from bare soil to cushion soil in‐ creased with environmental stress
The longiscapa genetic cluster only occurred on calcare‐ ous bedrock, except for one population found on quartz‐ ite (CIIIQ, Figure 2a) for which the abiotic environment was close to that of the calcareous environments (Supporting Information Table S1; Figure 3a)
We have studied the fungal communities of a foundation cushion plant in a microevolutionary context across contrasting environmen‐ tal conditions, such as different bedrocks
Summary
Terrestrial plants interact with aboveground and belowground fungal communities (Buée et al, 2009; Jumpponen & Jones, 2009) whose as‐ semblage is influenced both by abiotic factors and by the plant commu‐ nity. Alpine cushion plants offer an interesting system to study fungal community assembly and to assess the role of intraspe‐ cific plant genetic variation These foundation plants locally mod‐ ify their physicochemical environment (Badano, Jones, Cavieres, & Wright, 2006) and the soil biotic community (Roy et al, 2013), both defining ecological engineering effects (see Jones, Lawton, & Shachak, 1994). We first established that the two plant subspecies corresponded to distinct genotypic clusters, which allowed us to assess the correlation between plant ge‐ netic distances and fungal beta diversity To disentangle this genetic effect from those of the local environment (geology, elevation), and to measure abiotic soil engineering by the plant, we sampled soils both beneath cushions and in neighboring bare soils.
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