Reflecting on the symmetry of ecosystem tipping points. The influence of trait dissimilarity and environmental driver dynamics in a simple ecosystem model.

Our understanding of the similarity in trajectories of ecosystem changes during different directions of environmental change is limited. For example, do the dominant organisms exhibit the same responses to different directions of environmental change, i.e., do they exhibit symmetric responses? Here, we explore whether such response symmetry is determined and controlled by the symmetry in the features of the underlying biological system (i.e., system symmetry), such as in the network and strength of biotic and abiotic processes, and in symmetry of the environmental change (i.e. environmental symmetry). For this exploration we developed and used a simple mathematical model of a microbial ecosystem driven by mutual inhibition in which we could vary the amount of system and environmental symmetry. Our results show that perfect system and environmental symmetry does indeed produce perfect response symmetry. Moreover, introducing asymmetry in biological system or in the environmental does proportionally increase response asymmetry. This paper suggests using symmetries in ecosystem structures and interaction strength to better understand and predict similarities in degradation and restoration phases of environmental change.