Ess

Definition

An evolutionary stable strategy (ess) is a strategy in a population that, if adopted by a majority of individuals, cannot be invaded by any alternative strategy. It represents a form of equilibrium where any small fraction of the population adopting a different strategy will not thrive or reproduce effectively, ensuring that the original strategy remains prevalent. This concept connects to broader ideas of stability and adaptation in populations, where strategies evolve over time through interactions among individuals.

5 Must Know Facts For Your Next Test

1. An ess is characterized by its resistance to invasion; if a small group of individuals adopts an alternative strategy, they will not succeed against the majority using the ess.
2. In order for a strategy to qualify as an ess, it must not only be stable against invasion but also provide a greater payoff when played against itself compared to when played against an alternative strategy.
3. The concept of ess extends to various contexts, including animal behavior, economics, and social sciences, illustrating its broad applicability in understanding strategic interactions.
4. In evolutionary terms, ess can be seen as a form of natural selection, where certain behaviors or strategies are favored and persist within populations over time.
5. Ess can be identified using mathematical models and simulations, which help researchers predict how different strategies will evolve in response to environmental changes or competitor behaviors.

Review Questions

• How does the concept of an evolutionary stable strategy (ess) relate to the stability of population dynamics?
  • An evolutionary stable strategy (ess) provides a framework for understanding stability in population dynamics because it defines conditions under which a particular strategy persists in a population. If most individuals adopt this strategy, it becomes resistant to invasion by alternative strategies. This relationship highlights how certain behaviors or traits become fixed within a population due to their effectiveness in ensuring survival and reproduction, thus influencing overall population dynamics.
• Analyze how replicator dynamics can be used to illustrate the evolution of an ess in a population.
  • Replicator dynamics mathematically captures how strategies within a population change based on their relative success. By modeling the fitness payoffs associated with different strategies, researchers can show how an ess emerges over time. As more individuals adopt the successful strategy, its frequency increases, while less effective strategies decline. This dynamic illustrates the process through which certain strategies become dominant and highlights the role of competition and adaptation in shaping evolutionary outcomes.
• Evaluate the implications of an evolutionary stable strategy for understanding behavioral ecology and animal interactions.
  • The concept of an evolutionary stable strategy has significant implications for behavioral ecology as it helps explain why certain behaviors persist within animal populations. An ess indicates that specific behaviors confer advantages under competitive conditions, leading to greater reproductive success. By evaluating various strategies within animal interactions—such as foraging methods or mating displays—researchers can better understand how these behaviors evolve and stabilize over time in response to environmental pressures and social dynamics. This evaluation furthers our understanding of adaptability and survival in diverse ecological contexts.

Related terms

Nash Equilibrium: A situation in game theory where no player can benefit from changing their strategy while others keep theirs unchanged, often associated with the stability of strategies.

Replicator Dynamics: A mathematical framework used to describe how the proportion of different strategies in a population changes over time based on their relative fitness.

Fitness Landscape: A representation of how different strategies or genotypes are favored by the environment, where peaks correspond to high fitness and valleys to low fitness.