Biological Constraints and Diversity Stability

Gellner et al's research builds on influential early ecologists like Robert May who applied approaches from economics to ecology

There has been a longstanding interest in the relationship between organismal diversity and the stability of complex ecosystems. In a famous piece of work (May 1972,2001), Robert May used a mathematical approach to attack this complex problem. His simplification was seminal and borrowed from a similar mathematical approach used in economics. The approach assumed the ecosystem was at an equilibrium state and then could a similar linear approach to estimate how fast a system returned to equilibrium from a small perturbation.  

This approach is a beautiful reduction of complexity to a doable stability problem, the type that shows the creativity of science. Not surprisingly, it does so at a cost. The classic approach draws from a statistical universe that may or may not produce a real equilibrium. Further, and following this, it is effectively unconstrained by biology except that it replicated the network structure of a food web.

Recently, Gellner et al. 2023 drew from a well-known inverse approach that flips this problem on its head and starts by assuming an actual equilibrium biomass and then back calculating to ask what interaction strengths (the linearization of May 21) that yields this equilibrium. In this way, the inverse method ensures that Mays approach only includes realistic interaction strengths (not a statistical universe but rather now a biologically plausible universe). Further, Gellner et al. 2023 inverse method allows one to back calculate by adding more and more realistic biological constraints. More constraints alter the plausible set of solutions and thus the outcome of diversity-stability results.  

When they then asked how increasing diversity altered stability under different levels of biological constraints they found that the answer changed relative to the longstanding results of May. As an example, making the system feasible and energetically constrained (predators lose energy through assimilation of prey) they found that diversity no longer really destabilized complex food webs. This result is only the tip of the iceberg for this approach and really merely an example of its potential. The future holds application to real management situations seeking to understand how we alter resilience and further theoretical work that seeks to understand how different constrains alter stability.

To read the article under discussion, check out the following link.