Mycorrhizae regulate elemental and energy flows in terrestrial ecosystems.We understand much of how mycorrhizae work, but integrating all possiblemechanisms into a whole has proven elusive. Multiple evolutionary events andthe long evolutionary history mean that different plants and fungi bringindependent characteristics to the symbiosis. This variety results in extensivephysiological variation. How do we integrate functional responses withdiversity to understand the role of mycorrhizae in ecosystems? We reviewecophysiological mechanisms of mycorrhizae and organize these into functionalgroups. Species-area relationships are not curvilinear, but resemble the“broken stick” model. We coupled functional groups with ametacommunity analysis to show how complex behavior can be generated using asimple matrix model of resource exchange. This approach provides insights intohow we might integrate diversity and function across landscapes.