This post was originally published on BioDiverse Perspectives – a research blog aimed at fostering communication about biodiversity.
I want to preface this post by saying that I am not a theoretician. In fact, I often find long presentations full of complex equations and zero-growth isoclines dizzying. But lacking an inclination (or even possessing a slight aversion) towards theoretical models should not ever keep someone away from reading Peter Chesson’s 2000 Mechanisms of Maintenance of Species Diversity.
I’m hesitant to provide too thorough of an overview of the paper because in essence, the theme is very simple and I don’t want to dissuade you from actually reading it. Species coexist despite competition due to two categories of mechanisms. There are mechanisms that are equalizing, because they minimize fitness differences between species. For example a predator the primarily consumes a competitively dominant species, may equalize fitness differences between that species and it’s inferior competitor. And there are mechanisms that are stabilizing, because they increase negative intraspecific interactions relative to interspecific interactions (think Lotka-Volterra competition models). For instance, if two species have strong requirements for different resources, then the effect of intraspecific competition for those resources will limit population growth even if they share some other common resource.
That’s it. Chesson, 2000 in a nutshell.*
So yes, this paper is foundational because Chesson provides a simple mechanism to explain species coexistence. And yes, his simplification of coexistence mechanisms has contributed substantially to the idea that we can use phylogenetic and functional diversity to infer community assembly. In fact, I think an argument can be made that in a period of time when niche-based assembly models were falling out of vogue, this paper brought them back into the limelight. But, like so many papers highlighted on this website, Chesson’s simplification of ecological theory is only a small part of why this paper was so influential. Here is another paper that takes an extraordinarily complex field, integrates research in many systems, and uses a (relatively) straightforward model to simplify the field of ecology. The message of this paper is important, but how Chesson conveys that message is equally important, so read this paper.
* Sort of.