Studying organism-environment interactions

The complex interactions between organisms and their environments are a topic at the heart of both evolutionary biology and ecology. In this special issue we bring together papers addressing two central aspects of the organism-environment relation: the concept of the ecological niche and the question of how to understand niche-related ecological and evolutionary mechanisms such as niche construction.

Since its coining in the early twentieth century, the concept of the ecological niche has been used and debated by ecologists and more recently also by evolutionary biologists. The ecological niche has been defined in various ways: as the functional role in an ecosystem, the aspects of the physical environment relevant to the species, or the abstract n-dimensional space of those biotic and abiotic factors required for the establishment or persistence of a species (see Pocheville 2015). In evolutionary biology niches are defined in terms of fitness-relevant aspects of the environment (Odling-Smee et al. 2003).

The sheer multiplicity of definitions and applications, as well as the contested nature of their usefulness or practicability, makes the philosophical investigation into concepts of the niche both pressing and highly interesting. Reflecting on the niche, however, forces us to scrutinize ecological and evolutionary mechanisms: Niche construction theory, models of species invasions, and explanations of species persistence and ecosystem composition all call on mechanisms involving niche concepts (Chase and Leibold 2003; Odling-Smee et al. 2003; Holt 2009). More generally, an understanding of the mechanisms relevant to organism-environment interactions is requisite to achieve the explanatory goals of ecology and evolutionary biology. What are these mechanisms and how are they linked to each other? What form do mechanisms take in ecology and evolution, and how do they compare to mechanisms in other parts of biology such as molecular biology and neuroscience? The answers to these questions have real explanatory value and practical consequences for biologists working in the field and lab. They also bear theoretical value for philosophers studying the ontology of mechanisms and the structure of evolutionary and ecological theory.

Therefore, there is a crucial need for exploring, sharpening and perhaps reconsidering or redefining our notions of mechanisms and niches in ecology and evolution. For doing so, a collaborative, interdisciplinary approach is required: although some work has already appeared on both niches and mechanisms in ecology and evolution, there has been little contact between these closely related debates. As a step to creating this dialogue, we have designed a special issue gathering papers from philosophers and ecologists on the topics of niches and mechanisms. The combination of topics and approaches will stimulate debates around the notions of niche and eco-evo mechanisms and their explanatory significance.

Contextualizing the special issue

The special issue includes papers by philosophers and biologists and covers topics across ecology and evolutionary biology. Many of the authors originally presented their works at a pair of interdisciplinary workshops, one on ecological niches and the other on niche construction and other mechanisms in ecology and evolution. Further authors were invited for the special issue to complement and expand the discussion. The papers we collect therefore reflect the outcome of a growing dialogue across and between disciplines.

The workshops that formed the basis of this special issue were organized within the context of the DFG-funded Collaborative Research Centre TRR-212 “A Novel Synthesis of Individualisation Across Behaviour, Ecology and Evolution: Niche Choice, Niche Conformance, and Niche Construction (NC3)”, or CRC for short (for further details, see www.uni-bielefeld.de/biologie/crc212). This is a large, interdisciplinary group spread across three German universities and covering fields such as behavioral biology, behavioral ecology, chemical ecology, evolutionary ecology, theoretical ecology, evolutionary biology, and philosophy of biology.

Our workshops drew out two central themes of the CRC. The first one looked at the concept of the ecological niche and how it features in ecological and evolutionary theory, and what it might mean to talk about an individualized niche. Discussing these topics is central to current developments in behavioral ecology and related fields, where individual differences are theorized in terms of individual niche variation that can have ecological and evolutionary consequences (Bolnick et al. 2011; Dall et al. 2012; Wolf and Weissing 2012).

In the second workshop, we took the cue from the CRC’s mechanistic framework, in which niche construction is seen as one of three individual-level ecological-evolutionary mechanisms, the others being niche choice and niche construction (Kaiser and Trappes forthcoming; Trappes et al. 2022). Here, we took a broader look at niche construction and at other ecological and evolutionary mechanisms. Specific questions concerned causal relations and distinctions in niche construction theory, types of evolutionary and ecological mechanisms, and mechanism discovery in ecology.

Both workshops were exercises in interdisciplinarity, with biologists and philosophers amongst both speakers and audience members. This variety of backgrounds generated many new insights on methods and content, helped to expose hidden assumptions, and led to very interesting and fruitful discussions. We carried this diversity through to the special issue, including by having many papers reviewed by both ecologists and philosophers.

Overview of contributions

The papers of this special issue collect a variety of approaches, including ethnographic case studies, historical studies, conceptual analysis and practice-based approaches. Overall, the special issue presents a snapshot of current philosophical theorizing and contemporary debates concerning the scientific study of organism-environment relations. Contributions are arranged roughly according to their topic: niche construction and evolutionary theory, niches, and ecological and evolutionary mechanisms.

Niche construction & evolutionary theory

The first three papers in our special issue examine theories and concepts that describe, scrutinize and explain organism-environment interactions and their evolutionary significance. This includes the debates around the proximate-ultimate distinction, niche construction theory and the concept of ecological fitness.

In their paper “The proximate-ultimate distinction and the active role of the organism in evolution” Grant Ramsey and Bendik Aaby discuss the proximate-ultimate distinction, due originally to Ernst Mayr (1961). On Mayr’s account, proximate causes explain how something works by invoking underlying mechanisms, whereas ultimate causes explain why the trait exists via evolution. Opponents of the distinction fear that it rules out individual-level organismic processes such as niche construction from evolutionary explanations. Ramsey and Aaby offer an ontological interpretation of the distinction in terms of the difference between structuring and triggering causes. They argue that this distinction allows us to account for the active role of organisms in evolution.

Jan Baedke, Alejandro Fábregas-Tejeda and Guido I. Prieto in “Unknotting reciprocal causation between organism and environment” take up another debate concerning niche construction. The problem of reciprocal causation concerns the explanatory circle that supposedly arises as a result of feedback loops, whereby organisms change their environment and the changed environment in turn applies selection pressures on organisms, causing them to change their environment, and so on. After a detailed analysis of the debates around this problem, Baedke et al. develop a conceptual and visual model to solve different aspects of the problem.

Ulrich Krohs considers another aspect to organism-environment relations by scrutinizing how an organism’s match to the environment relates to its reproductive success. In “Darwin’s empirical claim and the janiform character of fitness proxies,” he shows that Darwin claims an empirically established, rather than conceptual, connection between match and reproductive success. Fitness proxies in today’s evolutionary biology, being at the same time measures of match and predictors of reproductive success, are empirically linked to both relata. Krohs argues that this perspective not only resolves the so-called tautology problem of fitness, but also helps to straighten out the dispute between the Modern Synthesis and Extended Evolutionary Synthesis.

Niches

Four contributions scrutinize the concept of the ecological niche in the context of recent developments of ecology.

Rose Trappes analyzes the niche concept in niche construction theory. In her “Defining the niche for niche construction: evolutionary and ecological niches”, she demonstrates that the evolutionary concept of a niche, defined basically as a selective environment, differs from standard definitions of the ecological niche. She shows that not only the intensions but also the extensions of both concepts differ, by discussing three cases in which evolutionary niche dimensions and ecological niche dimensions do not coincide. The way in which niche construction theory relates to ecology therefore needs to be reconsidered.

Elina Takola and Holger Schielzeth develop a concept of an individualized niche in line with Hutchinson’s concepts of fundamental and realized niche. In “Hutchinson’s ecological niche for individuals”, they identify challenges to this project and present their solutions. One challenge is that individuals differ among each other—the very motivation for the individualized niche concept—so that the description of the niche cannot be based on measurements of groups. Based on the consideration that organisms’ individuality is grounded in their unique combinations of traits, Takola and Schielzeth propose to map the fitness effects for each trait and reconstruct the individual niche from the trait combination. They present a fivefold differentiation of the niche concept, including a time-slice individualized niche.

In his paper “Does the study of facilitation require a reform of the Hutchinsonian niche concept?”, Antoine Dussault takes up a recent debate in niche theory. Facilitation seems to require that the realized niche extends beyond the fundamental niche, contrary to standard niche theory. Dussault proposes as a solution to incorporate the concept of a potential niche from Jackson and Overpeck (2000). The potential niche covers that part of the parameter space that allows for (indefinite) survival of a population in the presence of facilitators. It is larger than the realized niche, but does not extend beyond the fundamental niche.

While the three papers introduced so far aim at refining the niche concept, Samantha Wakil and James Justus deny the usefulness of the niche concept altogether. In “The ‘niche’ in niche-based theorizing: Much ado about nothing” they argue that prominent attempts to define the ecological niche have failed. They also show how the explanatory burden in ecological models was never carried by the niche concept, but only by particular niche dimensions. Wakil and Justus close their paper with the provocative claim that this deficit is not restricted to the examples they present, but is a general one: the niche concept is neither adequately definable, nor theoretically important.

Ecological and evolutionary mechanisms

Finally, two papers consider mechanisms and mechanism discovery in ecology and evolution.

In her paper “What are ecological mechanisms? Suggestions for a fine-grained description of causal mechanisms in invasion ecology”, Tina Heger argues that recent philosophical discussions of mechanisms can help practicing ecologists like herself. She reasons that mechanisms in ecology are generally recurrent, multi-step causal processes. This understanding encourages the use of causal network diagrams to explore intervening steps. Using the example of the enemy release hypothesis in invasion biology, Heger illustrates how a mechanistic approach helps with opening up black boxes, identifying inconsistencies, and indicating where further evidence and experimentation is needed.

A detailed case study of ecological mechanism discovery is found in the paper “Philosophy of science in practice in ecological model building: an analysis of mechanism discovery in ecological research” by Luana Poliseli, Jeferson Gabriel da Encarnação Coutinho, Blandina Viana, Federica Russo, and Charbel El-Hani. In an intensive collaboration between an ecologist and one of the authors, ideas from the new mechanistic philosophy of science were developed into a heuristic set to guide the creation of a mechanistic ecological model. The heuristic set included tasks such as characterizing the phenomenon, identifying levels, and distinguishing enabling conditions. The heuristic set proved helpful for understanding complex ecological systems, bringing to light new hypotheses and points needing further evidence.

We would like to close this introduction by thanking all who participated in the workshops we conducted. The discussions we had at these two events contributed essentially to the papers collected here, and we hope that such discussions continue into the future. We also acknowledge the speakers who were in the end unable to submit a paper, including Alan Love, Alkistis Elliott-Graves, Viorel Pâslaru, Lynn Chiu, Joachim Kurtz, and Etienne Roux. Their contributions on niche concepts, ecological mechanisms, and niche construction shaped our discussions and are present in spirit, if not in print, in this special issue. Finally, our thanks go to Marie I. Kaiser for working together with us to organize and run the workshops.