Getting from “here” to “there” in a complex environment. Addressing context dependence and extrapolation in ecology
Dr. Robert Frühstückl (doctoral project)
This project is a conceptual and epistemological investigation into the problem of context dependence in ecology. When ecologists speak of context dependence, they usually refer to situations where the sign or magnitude of an ecological relationship varies depending on the biotic or abiotic context under which it is observed. A classic example of context dependence is mutualistic interactions between plants and mycorrhizal fungi, where the plant receives phosphorous and other nutrients from the fungus, while the fungus receives sugars from the plant in return. However, the outcome of this interaction is not independent of environmental context but crucially depends on the levels of phosphorous in the soil such that under high phosphorous concentrations, the interaction between plants and fungi ceases to be mutualistic and can even become parasitic (Bronstein 1994). Context dependence has many implications, but the most important is that it limits the extent to which knowledge of ecological relationships can be extrapolated from one context to another.
The problem of context dependence has received growing attention in the ecological literature of recent years as observational and experimental studies frequently report various context-dependent results (Chamberlain et al. 2014). Because of this, some ecologists have expressed concerns that the increasing use of context dependence to merely describe variation in the outcome of experimental and observational results does little to contribute to our theoretical understanding of ecological processes and might even create the false impression that ecological relationships are generally unstable (Catford et al. 2022).
In this project, I provide a novel conceptual understanding of “context” and “context dependence” and analyze their epistemic consequences for establishing causal relationships on the one hand and transferring knowledge of these relationships across systems and locations on the other.
The first part of this thesis suggests an explication of the concepts of “context” and “context dependence” that clarifies their relation to similar concepts, such as “location” and “environment”. Furthermore, the more precise and fruitful concept of context dependence that emerges also helps distinguish context dependence from other sources of variation, such as disruptions, indirect effects, confounding, and the function of normal background conditions.
The second part investigates the problem of extrapolation in ecology. Although the philosophical literature has offered several analyses of extrapolation and its difficulties (Guala 2005; Steel 2008; Khosrowi 2019), I argue that understanding the problem as it manifests in ecology requires expanding our concept of heterogeneity between source and target system.
The third part applies the position of evidential pluralism to the case of biological invasions. I argue that both mechanistic and correlative evidence is required for causal claims in invasion biology, and then explain what form mechanistic evidence can take in ecology.