The stability-diversity-complexity (SDC) debate has persisted as a central focus of theoretical ecology for half a century. The debate concerns the deceptively simple question of whether there is a relationship between the complexity and/or diversity of a biological community and its stability. From 1955, when Robert MacArthur initiated the debate, to the early 1970s, the prevailing view among ecologists was that diversity and complexity were important, if not the principal, causes of community stability. Robert May, a physicist turned mathematical ecologist, confounded this view with analyses of mathematical models of communities that seemed to confirm the opposite, that increased complexity jeopardizes stability. The praise May’s work received for its mathematical rigor and the criticisms it received for its seeming biological irrelevance thrust the SDC debate into the ecological limelight, but subsequent analyses have failed to resolve it. Different analyses seem to support conflicting claims and indicate an underlying lack of conceptual clarity about ecological stability, diversity, and complexity.
Results/Conclusions
To understand what the SDC debate is about and the conceptual and methodological issues it raises, this paper traces its history. I begin by analyzing the seminal works by Robert MacArthur, Charles Elton, David Pimentel, and others that elevated the previously poorly formulated question of whether more complicated biological communities are more “balanced” to the status of a scientific debate. Part of what this analysis reveals are the formidable theoretical and empirical challenges involved in evaluating stability-diversity-complexity relationships. Next I examine some technical attempts to define the concepts of the debate more precisely in the 1960s and 1970s, the most important of which were Lewontin’s analysis of the relationship between the concept of ecological stability and mathematical concepts of stability and Hurlbert’s incisive critique of the concept of ecological diversity. These attempts to define ecological concepts more precisely were part of a general trend towards greater emphasis on theoretical development and mathematical modeling in ecology in the late 1950s and 1960s. Robert May’s analysis of mathematical models of biological communities epitomized this approach, and it brought greater mathematical rigor and sophistication to the SDC debate. I conclude by discussing his influential work and how it upended the popular belief among ecologists that “diversity begets stability.”
