Processes Maintaining the Coexistence of Ectomycorrhizal Fungi at a Fine Spatial Scale

Abstract

Ectomycorrhizal fungi defy classification by scale. As hyphae, they experience heterogeneity in the soil on a micron scale, while individuals can span meters. In this chapter, we seek to identify the most important processes structuring ectomycorrhizal fungal communities at a fine spatial scale, reviewing the current state of the field with respect to ecologically selective processes, the influence of ecological drift or neutrality on fine-scale community structure, the importance of dispersal limitation in this group, and the role of speciation in determining centimeter-scale diversity. We conclude that the spatial scale at which ectomycorrhizal fungi experience resource heterogeneity, competition, and host carbon availability is probably a key factor shaping these communities and has not been adequately studied. The diversity of ectomycorrhizal fungi on a centimeter scale is also likely to be strongly affected by stochastic processes like dispersal limitation and ecological drift, but very little work has addressed these processes specifically. We call for focused research examining these processes to improve our ability to understand and predict patterns of community composition of ectomycorrhizal fungi at a centimeter scale.