Multiscale patterns and drivers of arbuscular mycorrhizal fungal communities in the roots and root‐associated soil of a wild perennial herb

Abstract

Summary Arbuscular mycorrhizal (AM) fungi form diverse communities and are known to influence above‐ground community dynamics and biodiversity. However, the multiscale patterns and drivers of AM fungal composition and diversity are still poorly understood.We sequenced DNA markers from roots and root‐associated soil from Plantago lanceolata plants collected across multiple spatial scales to allow comparison of AM fungal communities among neighbouring plants, plant subpopulations, nearby plant populations, and regions. We also measured soil nutrients, temperature, humidity, and community composition of neighbouring plants and nonAM root‐associated fungi.AM fungal communities were already highly dissimilar among neighbouring plants (c. 30 cm apart), albeit with a high variation in the degree of similarity at this small spatial scale. AM fungal communities were increasingly, and more consistently, dissimilar at larger spatial scales. Spatial structure and environmental drivers explained a similar percentage of the variation, from 7% to 25%. A large fraction of the variation remained unexplained, which may be a result of unmeasured environmental variables, species interactions and stochastic processes.We conclude that AM fungal communities are highly variable among nearby plants. AM fungi may therefore play a major role in maintaining small‐scale variation in community dynamics and biodiversity.

Disentangling the factors shaping arbuscular mycorrhizal fungal communities across multiple spatial scales

“…In general, the closer any two sampling sites are the more similar they will tend to be in terms of species co‐occurence and abundance of individual species. However, while Rasmussen et al . confirm this result both for root and soil AMF communities they also highlight that variation at a very small scale (i.e. among neighbourhood plants) was very high, indeed the highest across the scales analysed in their study, which ranged from the neighbourhood (30 cm) and subpopulation scale (10 m), to the population (10 km) and regional scale (30 km).…”

“…The implication is that while AMF communities are very much spatially structured at the smallest scale, they are also least predictable in terms of taxonomic composition and diversity at this scale. This result is particularly intriguing because Rasmussen et al . kept the focus plant constant across spatial scales, while most previous studies either sampled AMF associated to a mixture of plant species (Mummey & Rillig, ) or focused on one plant species but within a much shorter range of scales (Horn et al ., ). Which factors can explain both spatial structure and high variance at small spatial scales?…”

“…(), have typically found significant correlations between variables such as pH and AMF community variation across small to medium scales. However, a very interesting point made by Rasmussen et al . is that different soil variables showed their highest level of variation at different scales, with variables such as pH that showed the highest variability at the smallest scales. Differences in the scale at which the highest variance is observed may thus point to the factors that play the major role in structuring AMF communities.…”

“…But what is the potential role of other groups of soil biota, especially other root symbionts? Rasmussen et al . offer one important example of the analysis of covariation between AM and non‐AM fungi in plant roots across spatial scales. The authors convincingly show that non‐AM fungi, too, display higher variation at the smallest scales of analysis, correlating very well with AMF.…”

“…Yet, there are still significant gaps of knowledge about the relative roles of these factors and how these roles change across multiple scales. In this issue of New Phytologist , Rasmussen et al . (pp. 1248–1261) provide a novel and very detailed analysis of the multiscale patterns that characterize both root and soil AMF communities of Plantago lanceolata .…”