SREL Reprint #3843

An epigenomic threshold hypothesis for integrating dynamic environmental signals into functional models of developmental polyphenisms

Benjamin B. Parrott1,2 and Samantha L. Bock1,2,3

1Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, USA
2Eugene P. Odum School of Ecology, University of Georgia, Athens, Georgia, USA
3Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA

Abstract:
1. Interactions between developing embryos and a multitude of environmental factors (e.g. climate, nutrition, social cues, stress and anthropogenic contaminants) underlie adaptive and non-adaptive developmental plasticity and carry broad implications across ecological, evolutionary and biomedical science.
2. At its core, developmental plasticity entails an environmental signal, a biological pathway capable of sensing and transducing the signal and an epigenetic response that directs alternative developmental trajectories from a single genotype. In recent years, our collective understanding of these processes has advanced in meaningful ways—the instructive environmental factors have been identified in many systems and in some cases, even the molecular cascades connecting environmental cues to developmental outcomes have been revealed.
3. Yet, environmental signals that induce plastic responses are often transient and co-occur with opposing cues in nature, and how molecular hierarchical pathways integrate temporal variation in environmental conditions across environmentally and biologically relevant timescales has received relatively little attention. For example, predator cues, nutritional quality, density, temperature and almost any other environmental signal dictating plastic responses are dynamic across time.
4. This leads to a fundamental, yet unanswered question: How is the strength, stability and frequency of inductive cues integrated into genomic responses that ultimately trigger robust and stable developmental outcomes?
5. Here we develop an epigenomic threshold hypothesis for integrating ecologically and biologically relevant timescales into a mechanistic model, highlighting temperature-dependent sex determination in reptiles as a timely case study. We further define several key questions stemming from the epigenomic threshold hypothesis and suggest experimental and methodological considerations for future investigations of these questions across diverse polyphenic systems.

Keywords: developmental plasticity, environmental fluctuations, environmental sex determination, epigenetics, temperature-dependent sex determination, threshold effects

SREL Reprint #3843

Parrott, B. B., and S. L. Bock. 2025. An epigenomic threshold hypothesis for integrating dynamic environmental signals into functional models of developmental polyphenisms. Functional Ecology (39): 3050-3060.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).