Interactions between plants and soil microbiota as drivers of plant species coexistence

What drives plant species coexistence? This question has captured the imaginations of ecologists for centuries, but has yet to be comprehensively answered. Plant species coexistence arises from two opposing forces: fitness differences and stabilizing mechanism. Fitness differences between plant species result in ‘successful’ species outcompeting less adapted species. Stabilizing mechanisms reduce the fitness differences between plant species, reducing competitive exclusion and species loss. According to theory, negative interactions between plants and soil microbiota act as a stabilising mechanism by limiting the growth and competitive ability of successful plant species.

Testing this theory is a major challenge due to the sheer complexity and diversity of plant-soil-microbiota interactions and the long time scale at which plant species coexistence takes place. In this lecture I present the theoretical predictions of plant-soil microbiota interactions as drivers of plant species coexistence, and discuss whether theory is in line with findings from long-term experiments.