Root Tragedy of the Commons: What is it and Where Might it Occur?

Understanding how plants change their root foraging strategy in the presence of neighbors is of paramount importance for plant ecology and agriculture. The root tragedy of the common (RToC) is a plant behavior predicted by game theory models in which competing plants forage for soil resources inefficiently. The RToC is generally assumed to be induced by non-self root recognition, and researchers consider root overproliferation and reduced fitness with respect to a plant growing solo as the trace left by plants engaging in an RToC in experiments and model results. Herein, I first challenge both notions, and argue that the RToC is a suboptimal phenotypically plastic response of plants that is based in soil resource information exclusively. Second, I discuss how this new perspective carries important implications for the design of experiments investigating the physiological mechanisms underlying observable plant root responses. Finally, I discuss why placing the RToC theory in the context of more general root research is fundamental: The RToC represents a mechanistic foundation for understanding the belowground behavior of plants interacting with neighbors, and a spatially explicit approach to RToC may produce more comprehensive results.