Deciphering the role of specialist and generalist plant–microbial interactions as drivers of plant–soil feedback

Summary

Feedback between plants and soil microbial communities can be a powerful driver of vegetation dynamics. Plants elicit changes in the soil microbiome that either promote or suppress conspecifics at the same location, thereby regulating population density￢ﾀﾐdependence and species co￢ﾀﾐexistence. Such effects are often attributed to the accumulation of host￢ﾀﾐspecific antagonistic or beneficial microbiota in the rhizosphere. However, the identity and host￢ﾀﾐspecificity of the microbial taxa involved are rarely empirically assessed. Here we review the evidence for host￢ﾀﾐspecificity in plant￢ﾀﾐassociated microbes and propose that specific plant￢ﾀﾓsoil feedbacks can also be driven by generalists. We outline the potential mechanisms by which generalist microbial pathogens, mutualists and decomposers can generate differential effects on plant hosts and synthesize existing evidence to predict these effects as a function of plant investments into defence, microbial mutualists and dispersal. Importantly, the capacity of generalist microbiota to drive plant￢ﾀﾓsoil feedbacks depends not only on the traits of individual plants but also on the phylogenetic and functional diversity of plant communities. Identifying factors that promote specialization or generalism in plant￢ﾀﾓmicrobial interactions and thereby modulate the impact of microbiota on plant performance will advance our understanding of the mechanisms underlying plant￢ﾀﾓsoil feedback and the ways it contributes to plant co￢ﾀﾐexistence.