Dr. Viorel Pâslaru at Midwest Workshop in Philosophy of Science and Philosophy of Mathematics

Ecological Explanation, Mechanisms, and Laws: Biogeography’s Mechanistic Approach

Abstract:
Ecology is currently the stage of a debate on the nature of ecological explanations that parallels and is relevant to the dispute between defenders of nomological, or unificationist accounts, on the one hand, and causal-mechanical accounts, on the other hand. One prominent view in the debate on the nature of ecology and its explanations is that ecology should seek laws and base its explanations on laws either specific to ecology, or supplied by physics and chemistry (Berryman 2003; Lange 2005, 2000). The alternative view is that ecology is rather an historical science, such that it should rely on the methodology of case studies (Shrader-Frechette and McCoy 1993).
In the context of this debate, The Theory of Island Biogeography by Robert MacArthur and E. O. Wilson (1967) is offered as an example of ahistorical thinking concerned with mathematical modeling (Kingsland 1995), whose result is a genuine law of ecology: the area law (Lange 2005). According to this law, the number of species on an island increases with island’s area. Lange articulates the function of this law in securing the autonomy from physics and in providing predictions, yet he fails to show that it satisfies the expectations of ecologists about what counts as explanatory. Recently, Yoichi Ishida (2007) suggests that the models of the theory of biogeography explain the species-area pattern by identifying the underlying mechanisms. However, he does not give an account of these mechanisms or of their explanatory role.
I examine The Theory of Island Biogeography from a mechanistic perspective and argue against the ahistorical interpretation of this canonical work of theoretical ecology. To this end, I assume the analytic and synthetic strategies of experimentation articulated by William Bechtel and Robert C. Richardson (1993), as well as the mechanistic philosophy of Peter Machamer, Lindley Darden and Carl Craver (2000). I argue that the theory of island biogeography employs a mechanistic approach and describes a type mechanism. In particular, I show that the analytical and graphical models that MacArthur and Wilson present are models of a biogeographical mechanism responsible for the orderly relationship between species numbers and island area. These models identify the mechanism components and their organization. Additionally, MacArthur and Wilson give ample attention to the properties of organisms and examine their role in determining the species-area relationship. To establish that the putative components, their properties and organization are the relevant ones, they complementarily use the analytic and synthetic experimental strategies as part of a comprehensive modeling procedure.
In the light of these findings about the mechanistic approach of the theory of island biogeography, I discuss several implications on the nature of ecological explanation. My results help me interpret the claim of Ishida about the mechanisms underlying the species-area pattern. Additionally, I argue against Lange and show that an explanatory account based on the area law does not capture what is explanatorily relevant from ecologists’ standpoint. I show that my mechanistic interpretation furnishes a middle ground between the unificationist and the case study-based, historical views for conceiving of ecological explanation.