The Contributions of Microbial Interactions to Abrupt Ecosystem Changes during the Late Quaternary

AbstractAbrupt ecosystem shifts during the Late Quaternary coincided with major climatic changes and intensified human activities, but the precise causes of these shifts remain debated. Here, building on previous hypotheses and work, we propose a new hypothesis that both plant beneficial and antagonistic soil microorganisms were the proximate drivers of Late Quaternary change. We synthesized evidence from paleoecological studies and contemporary ecosystems to understand how microbes and their interactions with plants shift ecosystem function. Because relevant paleoecological data are nonexistent, we reanalyzed a contemporary survey from grasslands and woodlands across Europe to test the general role of microbial diversity versus climate in controlling ecosystem function. Our models found that the richness of different microbial groups, including Proteobacteria, mycorrhizas, and plant fungal pathogens, were more strongly associated with the magnitude of direct effects on net primary productivity than temperature and precipitation. The richness of most of these groups was also influenced by climate, supporting our hypothesis that climate change may have indirectly caused past ecosystem shifts by changing microbial composition and function. We end by highlighting the potential of environmental DNA to reconstruct the biota and conditions of past ecosystems. Ultimately, improving our understanding of how microbes drove past ecosystem shifts may improve our ability to respond to future environmental changes.