Plasticity-led evolution- too fast for Neo-Darwinism

Article: "Plasticity-led evolution as an intrinsic property of developmental gene regulatory networks" Nature Journal (11/23) by Eden Tian Hwa Ng and Akira R. Kinjo:

Background

The Modern Evolutionary Synthesis (MES) (aka neo darwinism) is the prevailing framework for understanding evolution, emphasizing the role of genetic variation in driving adaptive changes in populations over time. However, the MES faces limitations in explaining how organisms can adapt to rapid environmental shifts that outpace the accumulation of beneficial mutations. To address this gap, the concept of plasticity-led evolution (PLE) has emerged, proposing that initial phenotypic plasticity in response to environmental cues can be followed by genetic accommodation, enabling organisms to maintain fitness in the face of change.

Study Overview

In their 2023 preprint, Ng and Kinjo delve into the mechanisms underlying PLE by developing computational models of developmental gene regulatory networks (GRNs), the intricate networks of genes that control cellular development and organismal form. Their models demonstrate that these GRNs exhibit PLE, displaying adaptive plastic responses to substantial environmental changes.

Key Findings

The study by Ng and Kinjo uncovers several key aspects of PLE:

1. Universality of PLE: PLE is not limited to specific mutations or environmental scenarios but emerges as an inherent property of complex developmental systems.

2. Plasticity as the Initial Response: Organisms initially respond to environmental changes through phenotypic plasticity, allowing them to adjust their traits without immediate neodarwinian genetic modifications.

3. Genetic Accommodation: Over time, genetic accommodation occurs, where beneficial ‘biased” mutations arise and are incorporated into the genome, reinforcing the adaptive phenotypic changes initially achieved through plasticity.

4. Accelerating Factors: Environmental cues, developmental processes, and hierarchical regulation within GRNs play crucial roles in amplifying PLE, facilitating faster adaptation.

Implications

The findings of Ng and Kinjo's study have significant implications for our understanding of evolutionary adaptation:

1. Broadening Evolutionary Mechanisms: PLE expands our understanding of evolutionary processes beyond the sole reliance on genetic variation.

2. Adapting to Rapid Change: PLE provides a plausible mechanism for organisms to cope with rapid environmental shifts, increasing their resilience and survival chances.

3. Conservation Biology: Understanding PLE can inform conservation strategies by highlighting the importance of maintaining phenotypic plasticity in populations facing environmental threats.

4. Evolutionary Medicine: PLE has implications for understanding human adaptability and the potential role of plasticity in disease progression and treatment.

Future Directions

The study by Ng and Kinjo opens up new avenues for research:

1. Exploring PLE in Diverse Organisms: Investigating the prevalence and mechanisms of PLE across a wider range of organisms.

2. Unveiling Regulatory Mechanisms: Elucidating the specific regulatory mechanisms within GRNs that facilitate PLE.

3. Integrating PLE into Evolutionary Models: Incorporating PLE into evolutionary models to better predict adaptation patterns.

4. Empirical Validation: Conducting empirical studies to validate the predictions made by the computational models.

Ng and Kinjo's work provides a compelling framework for understanding PLE, challenging the traditional view of adaptation solely driven by genetic variation. Their findings underscore the importance of phenotypic plasticity and GRN dynamics in evolutionary processes, particularly in the face of rapid environmental change.

Eden Tian Hwa Ng's paper "Plasticity-led evolution as an intrinsic property of developmental gene regulatory networks" challenges neo-Darwinism in several ways.

Neo-Darwinism is the prevailing theory of evolution, which holds that natural selection acting on random mutations is the primary driving force of evolutionary change. However, Ng's work suggests that plasticity, the ability of organisms to change their phenotypes in response to environmental cues, plays a significant role in evolution.

Plasticity-led evolution is a process in which plasticity first leads to an adaptive phenotype, and then genetic accommodation occurs to fix this phenotype in the population. This process can be much faster than traditional Darwinian evolution, as it does not require the accumulation of beneficial mutations.

Ng's paper provides computational evidence that plasticity-led evolution is an intrinsic property of developmental gene regulatory networks. These networks are responsible for controlling gene expression during development, and they are sensitive to environmental cues. Ng's models show that these networks can exhibit plasticity-led evolution in response to a variety of environmental changes.

The implications of Ng's work are far-reaching. If plasticity-led evolution is a common mechanism, it could help to explain the rapid evolution of many organisms, including humans. Additionally, it could provide a new framework for understanding the relationship between development and evolution.

Here are some specific ways in which Ng's work challenges neo-Darwinism:

• It suggests that plasticity can play a more important role in evolution than previously thought.

• It provides a mechanism for rapid evolution that does not require the accumulation of beneficial mutations.

• It suggests that the relationship between development and evolution is more complex than previously thought.

Ng's work is still in its early stages, but it has the potential to revolutionize our understanding of evolution.

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Article Snippets

The modern evolutionary synthesis fails to explain how a population can survive a large environmental change: the pre-existence of heritable variants adapted to the novel environment is too opportunistic, whereas the search for new adaptive mutations after the environmental change is so slow that the population may go extinct.

Plasticity-led evolution, the initial environmental induction of a novel adaptive phenotype followed by genetic accommodation, has been proposed to solve this problem.

These observations suggest plasticity-led evolution is a universal property of complex developmental systems independent of particular mutations.

According to the modern evolutionary synthesis, the standard theory of evolution, all possible phenotypic variation is almost purely explained by genetic variation, either ignoring environmental contributions or treating them as noise.

In this sense, the standard theory is said to be a theory of mutation-led evolution.

Therefore, the only means for an individual to survive a large environmental change is to possess mutations that produce a phenotype already adapted to the novel environment.

However, natural selection selects adaptive phenotypes in the current environment, making the pre-existence of phenotypes adapted to novel environments highly unlikely.

Suppose instead that adaptive variants only appear after the environmental change. In that case, adaptation requires searching for new adaptive mutations, which is likely too slow for the population to survive.

Phenotypic plasticity, the ability to change the expressed phenotype in response to environmental cues, has been proposed to remedy the above problem because it could produce a phenotype with higher fitness in a novel environment without a change in the genotype.