Re-evaluating the environment in developmental evolution

Abstract

This manuscript reviews our growing understanding of the role of environmental conditions in shaping development and developmental evolution. It then discusses how this enhanced understanding increasingly questions our intuitive notions of the environment as separable from-and external to-organisms, as a selective force that is passive rather than generative, and as an external agent that organisms respond to, rather than one that organisms actively modify to suit their responses. Throughout I highlight examples of case studies in evo devo and beyond that-by integrating a revised evaluation of the environment into their research programs-have been able to advance long-standing and critical questions in the biological sciences. I end by summarizing several theoretical frameworks that are already well in place to guide a more systemic re-integration of the role of environmental conditions in evo devo.

Towards a Truly Developmental Epigenetics

“…These then modify how individuals respond to conspecifics and their environment, bringing about changes at higher levels of biological organization. (p. 394) In keeping with this expanded approach, a growing number of investigators are broadening the focus of their research attention to include not only internal factors (genes, proteins, cells, hormones) at play in phenotypic development, but also the contributions of the varied physical, biological, and social resources available to an organism in its developmental context [i.e., Gilbert, 2005;Gilbert & Epel, 2009;Moczek, 2015]. This approach has provided convincing evidence that developmental outcomes simply cannot be prescribed at the molecular level of analysis -the course of development emerges from the regulatory dynamics of the gene-in-a-cell-in-an-organism-in-an-environment system [Lickliter & Honeycutt, 2015;Oyama, 1985;Robert, 2004].…”

Temperature Shift Alters DNA Methylation and Histone Modification Patterns in Gonadal Aromatase (cyp19a1) Gene in Species with Temperature-Dependent Sex Determination

“…Epigenetic mechanisms, such as DNA methylation and histone modifications have been implicated as an important mediator in the process of phenotypic plasticity [18,19]. Recent studies suggest that temperature-specific expression of the aromatase during gonad determination is also directed by epigenetic mechanisms, especially DNA methylation.…”

The Semiosis of “Side Effects” in Genetic Interventions

“…While this has been partially recognized by traditionally non-biosemiotics scientists, (including Moczek (2015), Laland et al (2008), Chiu and Gilbert (2015)), the most important integrating insights have been made by those in the community. In particular, the dynamic nature of semiosis (as opposed to the mechanism of computation and signalling) (Kull 2015), the concept of semiotic scaffolding (Hoffmeyer 2008, 2015), and multilevel semiosis (Bruni 2003, 2007) seem to particularly fruitful.…”

“…However, the point can be made more strongly as much of this “inner” plasticity is itself the outcome of various niche constructing semiotic activities occurring on the intercellular level (both by host cells and symbionts (Chiu and Gilbert 2015)). Laland et al (2014a, 2014b) have suggested a strong “parallel” between internal and external constructive processes in development and evolution, while Moczek (2015) has discussed how niche construction can refer to the construction not only of external environments but internal environments as well, with the only difference being of scale. In fact, phenotypic accommodation, inner and outer niche construction always occur simultaneously because external and internal events are co-emergent and mutually implicated.…”

“…For example, Moczek (2015: 1) has recently described how niche construction can be used to make sense of gene regulation in the following way: whatever transcriptional and translational events take place in a given cell are influenced by the specific cellular environments that cell finds itself in, characterized for instance by the presence or absence of key resources such as microRNAs, transcription factors, nutrients, signals from neighboring cells, and other signatures of past developmental events. While many of these components of the nuclear and cellular environment involved the earlier expression of specific genes, at any given developmental time they collectively make up an environment that defines the developmental context within which a given cell finds itself and to which it responds by altering its transcriptional or translational activity, thereby again shaping the environmental conditions in which the same cell will find itself later in development.…”