Investigating the evolution and development of biological complexity under the framework of epigenetics

Abstract

Biological complexity is a key component of evolvability, yet its study has been hampered by a focus on evolutionary trends of complexification and inconsistent definitions. Here, we demonstrate the utility of bringing complexity into the framework of epigenetics to better investigate its utility as a concept in evolutionary biology. We first analyze the existing metrics of complexity and explore the link between complexity and adaptation. Although recently developed metrics allow for a unified framework, they omit developmental mechanisms. We argue that a better approach to the empirical study of complexity and its evolution includes developmental mechanisms. We then consider epigenetic mechanisms and their role in shaping developmental and evolutionary trajectories, as well as the development and organization of complexity. We argue that epigenetics itself could have emerged from complexity because of a need to self‐regulate. Finally, we explore hybridization complexes and hybrid organisms as potential models for studying the association between epigenetics and complexity. Our goal is not to explain trends in biological complexity but to help develop and elucidate novel questions in the investigation of biological complexity and its evolution.

Temporal instability of lake charr phenotypes: synchronicity of growth rates and morphology linked to environmental variables?

“…The degree of phenotypic variation that occurs within an ecotype theoretically depends on the relative strength and time of mechanisms that drive phenotypic change (Wood et al 2020), the environment is not necessary constant across cohorts (Johnson et al 2014). Heim et al 2017;Duclos et al 2019). In this study, a decline in annual growth increment for lean and huronicus ecotypes occurred at the same time as a consistent phenotypic shift in morphology and these changes occurred within the time frame of a decade.…”

“…This low genetic diversity and divergence favor the hypothesis that phenotypic variation is the result of phenotypic plasticity rather than genetic adaptations (although rapid genetic change cannot be excluded). Epigenetically mediated biological complexity is known to be an important process to tailor phenotypic reaction norms (e.g., linear and nonlinear) to selective environmental pressures (Crozier & Hutchings 2014;Ramler et al 2014;Duclos et al 2019). A rapid change in the environment can also induce changes in the phenotypic variance within an ecotype by exposing previously hidden cryptic genetic variation or by inducing new epigenetic changes (O'Dea et al 2016).…”

Arctic charr phenotypic responses to abrupt temperature change: an insight into how cold water fish could respond to extreme climatic events

“…The thermal history experienced by an individual during early development is known to be a key factor defining adult phenotype (Georga & Koumoundouros, 2010;Angilletta, Steury & Sears, 2004;Ramler et al, 2014). It is particularly during early development that environmental signals can influence developmental processes through epigenetic mechanisms, influencing the expressed phenotype (Duclos, Hendrikse & Jamniczky, 2019). This observed effect on the phenotype in this study was cumulative, with divergence between treatment groups increasing over time.…”

From the individual to the colony: Marine invertebrates as models to understand levels of biological organization

“…30,000 genes in humans) or number of cells in an organism (e.g., ca. 1000 cells in Caenorhabditis elegans )– are represented by quantifiable units (Duclos et al, 2019), and consequently represent easy characters to assess for change during evolutionary transitions, the processes acting on the evolution of vertical complexity have only recently started to gather empirical evidence (McShea, 2017). For example, a recent hypothesis suggests the existence of a complexity ratchet mechanism that may be allowing more complex phenotypes to irreversibly evolve, resulting in the evolution of complex solutions to natural selection, which under some circumstances, are favored over simpler ones (Liard et al, 2020; Simpson, 2020, in this issue)⁠.…”