Evolutionarily stable strategies

Definition

Evolutionarily stable strategies (ESS) are strategies in game theory that, if adopted by a population, cannot be invaded by any alternative strategy that is initially rare. This concept connects to the broader understanding of how certain behaviors or traits become dominant in populations through natural selection, illustrating the interplay between strategy, stability, and adaptation over time.

5 Must Know Facts For Your Next Test

1. The concept of evolutionarily stable strategies was introduced by John Maynard Smith in the 1970s as a way to explain how certain strategies persist in populations.
2. An ESS is not just stable; it can repel invasions by mutant strategies that might otherwise disrupt the balance.
3. In an ESS, if all individuals adopt the same strategy, no single individual can do better by unilaterally changing their strategy, making it resistant to changes.
4. ESS is often illustrated using examples from biology, such as predator-prey interactions or mating strategies, showing how these concepts apply in natural settings.
5. Evolutionarily stable strategies can change over time due to environmental pressures and interactions with other species, demonstrating the dynamic nature of stability.

Review Questions

• How does the concept of evolutionarily stable strategies relate to natural selection and population dynamics?
  • Evolutionarily stable strategies illustrate how certain traits or behaviors can become prevalent within a population due to natural selection. When a particular strategy offers a competitive advantage, it becomes more common over generations. If this strategy is stable against invasion by alternative strategies, it indicates that the population will favor this behavior, reinforcing its prevalence and contributing to the overall dynamics of the ecosystem.
• What role does the concept of Nash Equilibrium play in understanding evolutionarily stable strategies?
  • Nash Equilibrium and evolutionarily stable strategies are interconnected as both concepts deal with stability in strategic interactions. While Nash Equilibrium focuses on players' best responses to each other's strategies, an evolutionarily stable strategy must also account for biological invasions. An ESS not only represents a Nash Equilibrium but must also be robust enough to resist any new strategies that might arise, which highlights its strength in evolutionary contexts.
• Evaluate how changes in environmental conditions can impact the stability of evolutionarily stable strategies within a population.
  • Changes in environmental conditions can significantly affect the stability of evolutionarily stable strategies as they may alter the payoffs associated with different strategies. For instance, if a sudden change in resource availability favors a previously less common strategy, that strategy may begin to invade the population. As such shifts occur, what was once considered an ESS might become vulnerable, leading to new dynamics and interactions within the population as organisms adapt to the new environment.

Related terms

Nash Equilibrium: A situation in a game where no player can benefit by changing their strategy while the other players keep theirs unchanged.

Payoff Matrix:

A table that describes the payoffs in a strategic interaction between two or more players, used to analyze their optimal strategies.

Cooperation: A strategy where individuals work together for mutual benefit, often analyzed within the framework of game theory to understand social dynamics.