One claim made by niche construction theory is that it provides additional conceptual tools with which to integrate evolution and ecology more effectively (Odling-Smee et al. 1996, 2003, 2013, Matthews et al. 2014). This is particularly relevant to the integration of evolutionary biology with ecosystem science, which historically has made little use of evolutionary principles and methodologies (O’Neill et al. 1986; Matthews et al. 2011).

Physiologist Scott Turner (this volume) identifies organismal agency as the key distinction between traditional evolutionary perspectives and niche construction theory. For Turner, agency in living systems is an expression of a fundamental property of life— homeostasis. In order to stay alive and maintain order in their bodies and immediate surrounds, organisms must act on their environment, and change it in a directional manner. The physiology of organisms, at various levels of organization from the cell to the colony, extends beyond its immediate boundaries—what Turner calls an “extended physiology” (Turner 2000). Organisms can thus be viewed as actively maintaining a nested series of adaptive boundaries to ensure suitable homeostatic relations. Turner emphasizes how the maintenance of extended homeostasis requires active agency on the part of the organism, and this must be informed—it is inherently purposive and demands some kind of ‘cognition’.

The bacterium Pseudomonas fluorescens is widely used as a model system for studying experimental evolution, including the evolution of niche construction (Callahan et al. 2014). Claire-Marie Loudon, Blake Matthews, Duygu Sevgi Sevilgen and Bas Ibelings (this volume) argue that it may also provide an opportunity to test predictions from both niche construction theory and dissipative systems theory. These authors examine how manipulating two aspects of niche construction by Pseudomonas affected the development of diversity of the bacterial community and its ability to dissipate the oxygen gradient (and thereby increase entropy). As predicted, system diversity increased because of evolution by niche construction, and along with it the rate of oxygen dissipation increased. This Pseudomonas system is also the inspiration for a model of the origins of developmental programs by Emma Wolinsky & Eric Libby (this volume), who show how genotypes can evolve sensitivities to the environmental conditions that they construct.

While theory suggests that niche construction can affect the accumulation and release of cryptic genetic variation (Laland et al. 1996, 1999; Odling-Smee et al. 2003; Laland and Sterelny 2006), few experimental studies have tested this hypothesis. Emilie Snell-Rood, Melissa Burger, Quinton Hutton, and Armin Moczek (this volume) suggest that parental niche construction can buffer offspring from environmental stress, for instance, by providing food or shelter, ameliorating the negative effects on fitness of new mutations, and resulting in the accumulation of cryptic genetic variation. They discuss this idea using the case of Onthophagus horned beetles, adult females of which construct a benign developmental niche for their offspring by constructing a brood ball of dung in which they oviposit a single egg, which provides the food that larvae need to complete larval development and metamorphosis. Snell-Rood and colleagues consider whether natural variation in parental behaviour is tied to the release of cryptic genetic variation when reared under scenarios that mimic the removal of parental investment. They illustrate how it would be possible to induce novel mutations experimentally and test the extent to which parental investment buffers selection on new mutations. Provisional data provide partial support for the behavioral buffering hypothesis, but also suggest that such buffering may vary in complex ways with specific mutations and traits.

Julia Saltz and her colleagues (this volume) note that while the terms ‘social niche’ and ‘social niche construction’ are starting to be deployed there is considerable variation in their usage. Saltz et al. bring clarity to these issues by proposing working definitions. They characterize the social niche as the set of social environments in which the focal individual has non-zero inclusive fitness. Only where a focal individual’s phenotype, as expressed in its social environment, results in the focal individual having non-zero inclusive fitness in that social environment, is the social environment part of the focal individual’s social niche. Social niche construction describes the situation in which individuals, singly or collectively, influence the composition and dynamics of their social environments, for instance, by choosing whom they associate with or by acting in such a way as to change the composition of their social environment. This focus raises a number of questions that historically have received little attention.

A longstanding challenge for evolutionary biology is to understand the mechanisms that support the evolution of cooperation. Brian Connelly, Katherine Dickinson, Sarah Hammarlund, and Benjamin Kerr (this volume) demonstrate that cooperation can persist by hitchhiking with beneficial non-social adaptations. Cooperators play an active role in this process. In spatially structured environments, clustered cooperator populations reach greater densities, creating mutational opportunities to gain beneficial non-social adaptations, and allowing cooperation to increase. However, once adaptive opportunities have been exhausted, the opportunity to spread ends, and cooperators are displaced by adapted defectors. Using an agent-based model, Connelly et al. demonstrate that the selective feedbacks, which are created as populations construct their local niches, can maintain cooperation indefinitely.

Nicole Creanza, Laurel Fogarty, and Marcus Feldman (this volume) propose that selection pressure on the size and complexity of birdsong repertoires may have facilitated the construction of a niche in which learning, sexual selection, and song-based homophily co-evolve. Creanza et al. analyze the relationship between the number of syllables in a species-typical repertoire and the length of the song-learning program, finding significantly larger repertoire sizes in open-ended compared to closed-ended learners. They go on to use a mathematical model to examine the interactions between the culturally transmitted trait of song repertoire size, the evolved capacity for song learning in adulthood, and mating preference for a song heard early in life. Underpinning the correlation between open-ended or closed-ended learning and repertoire size is a form of cultural niche construction in which a costly biological trait (open-ended learning) can spread in a population (or be lost) as a result of direct selection on an associated cultural trait (song repertoire size). Culturally transmitted song can be an important niche-constructing trait, influencing the spread of other traits that are likely to have genetic underpinnings, such as those that affect neural development and mating preferences.

This special edition ends with two articles on human niche construction. Archaeologist Bruce Smith (this volume) suggests that the human transition from hunting and gathering to food production economies provides an excellent opportunity to compare the relative strength of explanatory frameworks for domestication based on standard evolutionary theory with an alternative derived from niche construction theory. He shows how archaeological and paleo-environmental records from both eastern North America and northern South America contradict the assumption of traditional explanatory frameworks that environments change and species adapt. Conversely, explanations based on niche construction theory are well supported in both regions. Smith sees initial domestication as a lengthy evolutionary process that involves the complex interplay of a diverse array of environmental and cultural variables. He shows that initial domestication took place in settings where climatic fluctuation was limited enough, and biotic communities were rich and varied enough, to allow human societies to maintain sustainable settlements, which afforded the time and resources to experiment with domesticating plants and animals.

Melinda Zeder (this volume) proposes domestication as an excellent model system for testing predictions from niche construction theory. Like Smith (this volume), Zeder sees advantages to niche-construction theory over explanatory frameworks grounded in more traditional neo-Darwinian theory, for understanding initial domestication. These advantages stem from niche-construction theory’s focus on reciprocal causation, and the capacity of niche-constructing species to modify the niches of other species that share constructed environments. For Zeder, this provides a useful framework within which to understand the co-evolutionary mechanisms that lead to domestication, and the role of human intentionality. She concludes that domestication provides a valuable model system for niche-construction theory, and that data are consistent with predictions from the niche construction literature.

Collectively, the articles illustrate the diverse research programs that niche construction theory is starting to influence, and provide concrete evidence that the perspective is proving useful within evolutionary ecology.