A Mycorrhizal Revolution

It has long been postulated that symbiotic fungi facilitated plant migrations onto land through enhancing the scavenging of mineral nutrients and exchanging these for photosynthetically-fixed organic carbon. Today land plant-fungal symbioses are both widespread and diverse. Recent discoveries have shown that a variety of potential fungal associates was likely available to the earliest land plants, and that these early partnerships were most likely affected by changing atmospheric CO2 concentrations. Here, we evaluate current hypotheses and knowledge gaps regarding early plant-fungal partnerships in the context of newly discovered fungal mutualists of early and more recently evolved land plants and the rapidly changing views on the roles of plant-fungal symbioses in the evolution and ecology of the biosphere.