lecture 9 studyguide - soical behaviours.pdf

1 Evolutionarily Stable Strategies (ESS) are fundamental concepts in evolutionary game theory, originally introduced by John Maynard Smith in his 1982 book "Evolution and the Theory of Games." These strategies represent behaviors or traits within a population that, once adopted by the majority, resi...

1 Evolutionarily Stable Strategies (ESS) are fundamental concepts in evolutionary game theory, originally introduced by John Maynard Smith in his 1982 book "Evolution and the Theory of Games." These strategies represent behaviors or traits within a population that, once adopted by the majority, resist invasion or replacement by any alternative strategy. In simpler terms, an ESS is a strategy that, when most individuals in a population adopt it, cannot be outcompeted by any other strategy. One example of an ESS is protective aggression observed in certain animal populations. For instance, muskoxen form a defensive circle to protect their young from predators. This behavior is successful as long as most individuals within the population participate. However, if only a few individuals engage in protective aggression, its success diminishes significantly. The key characteristic of an ESS is its frequency-dependence, meaning its success depends on its prevalence within the population. If a strategy becomes too rare or too common, it may no longer be evolutionarily stable. Another important aspect of ESS is that the best strategy for an individual depends on what the majority of the population is doing. This highlights the interplay between individual behavior and population dynamics in evolutionary processes. Overall, ESS provide a framework for understanding the stability of certain behaviors or traits within a population and shed light on the dynamics of evolutionary change. 2 Evolutionarily Stable Strategies (ESS) are fundamental concepts in evolutionary game theory, originally introduced by John Maynard Smith and George R. Price in 1973. An ESS is a strategy that, once adopted by the majority of a population, cannot be invaded or replaced by any rare alternative strategy. One key aspect of an ESS is its frequency-dependence, meaning its success depends on its prevalence within the population. For example, protective aggression, such as muskoxen forming a defensive circle to protect their young, is successful when most individuals engage in it. However, if only a few individuals participate, its success diminishes significantly. An important implication of ESS is that the best strategy for an individual depends on what the majority of the population is doing. This highlights the interplay between individual behavior and population dynamics in evolutionary processes. 3 Game theory provides a framework for understanding animal behavior by examining the strategies individuals adopt to maximize their fitness in a given environment. One fundamental question in this field is whether the best strategy for an individual depends on the strategies of others within the population. For instance, individuals may face choices between aggressive and non-aggressive behaviors when competing for limited resources. The decision to engage in aggression depends on various factors, including the likelihood of success and the potential costs involved. Additionally, the presence of alternative strategies, such as cooperation or deception, adds complexity to the decision-making process. An important concept in this context is the notion of evolutionary stable strategies (ESS), where certain behaviors or traits become entrenched within a population due to their success in maximizing individual fitness. These strategies may involve cooperation, competition, or a combination of both, depending on the specific ecological and social dynamics at play. Understanding the interplay between individual behavior and population-level dynamics is crucial for unraveling the evolutionary forces shaping animal behavior. Game theory provides a powerful framework for studying these phenomena and gaining insights into the adaptive strategies employed by different species. 4 4 The Hawks-Doves game is a classic example in game theory used to illustrate the dynamics of aggression and cooperation within populations. In this game, individuals can adopt one of two strategies: "hawk" or "dove." Hawks are aggressive and will fight for resources, while doves are non-aggressive and will retreat from conflicts. When two hawks meet, they engage in a costly fight, which may result in injury or death. If a hawk encounters a dove, it gets the resource without any cost, as the dove retreats. However, if two doves meet, they peacefully share the resource. The outcome of the Hawks-Doves game depends on the frequency of each strategy within the population. If the population consists mostly of doves, hawks have an advantage as they can exploit the non-aggressive behavior of the majority. Conversely, if hawks dominate the population, they engage in frequent and costly fights, which may lead to a decrease in overall fitness. This game illustrates how the prevalence of different strategies within a population affects individual fitness and overall population dynamics. It also highlights the complex trade-offs involved in the evolution of aggression and cooperation in animal behavior. 5 Evolutionarily Stable Strategies (ESS) are fundamental concepts in evolutionary game theory, originally introduced by John Maynard Smith and George R. Price in 1973. An ESS is a strategy that, once adopted by the majority of a population, cannot be invaded or replaced by any rare alternative strategy. One key aspect of an ESS is its frequency-dependence, meaning its success depends on its prevalence within the population. For example, protective aggression, such as muskoxen forming a defensive circle to protect their young, is successful when most individuals engage in it. However, if only a few individuals participate, its success diminishes significantly. An important implication of ESS is that the best strategy for an individual depends on what the majority of the population is doing. This highlights the interplay between individual behavior and population dynamics in evolutionary processes. 6 7 Richard Dawkins popularized the concept of the "selfish gene" in his influential book titled "The Selfish Gene." The term reflects the gene-centered view of evolution, which emphasizes the role of genes in driving evolutionary processes. Dawkins argues that genes are the fundamental units of selection, and their ultimate goal is to propagate themselves through successive generations. From this perspective, individual organisms and even social groups are seen as vehicles or survival machines for genes. The concept of the selfish gene has important implications for understanding altruistic behavior, such as cooperation and selflessness. Dawkins suggests that altruistic behaviors can evolve if they increase the reproductive success of the genes that code for them. This can occur through mechanisms such as kin selection, where individuals help relatives who share their genes, or reciprocal altruism, where individuals cooperate with non-relatives in expectation of future benefits. Overall, Dawkins' concept of the selfish gene revolutionized our understanding of evolution by emphasizing the central role of genes in shaping behavior and driving evolutionary change. 8 Altruistic behavior Altruistic behavior refers to actions that benefit others at a cost to oneself. In the context of evolutionary biology, understanding the evolution of altruism has been a subject of much interest and debate. One mechanism by which altruistic behavior can evolve is through kin selection, where individuals help relatives who share their genes. By promoting the survival and reproduction of genetically similar individuals, genes for altruism can spread through a population, even if they entail personal sacrifice. Another mechanism is reciprocal altruism, where individuals cooperate with nonrelatives in expectation of future benefits. This form of altruism is often observed in social animals, where individuals engage in cooperative behaviors to gain access to resources or support from others. Overall, altruistic behavior presents a fascinating example of how natural selection can favor traits that benefit others, even at a cost to the individual, ultimately contributing to the fitness of the population as a whole. 9 Behavioral adaptations play a crucial role in enabling organisms to thrive in specific environments. These adaptations encompass a wide range of behaviors that are finely tuned to the challenges and opportunities presented by particular ecological niches. One example of behavioral adaptation is observed in black-headed gulls, which ground-nest on grassy sand dunes. By selecting nesting sites that provide camouflage and protection from predators, black-headed gulls increase the likelihood of successfully raising their offspring. Another behavioral adaptation involves the removal of eggshells from nests shortly after hatching. This behavior reduces the risk of predation on nestlings, as predators are less likely to detect the presence of vulnerable chicks without the visual cue of eggshells. 10 11 Kittiwakes, along with other cliff-nesting birds like razorbills and guillemots, exhibit fascinating behavioral adaptations to their environment. Nesting on tiny cliff ledges where predators cannot easily reach them provides these birds with a safe location for raising their offspring. Unlike some other bird species, kittiwakes do not engage in the behavior of throwing out eggshells from their nests. Instead, they have inherited the behavior of leaving eggshells in their nests, which may not offer as significant benefits as it does in other species. The question arises: how did this behavior evolve in kittiwakes? Did they learn it by observing others (cultural transmission of behavior), or was it simply inherited from their ancestors? Evidence suggests that this behavior is inherited rather than learned. Observations and studies indicate that kittiwakes exhibit consistent behavior across populations, suggesting a genetic basis for their nesting habits. Similarly, razorbill behavior is also noteworthy. Razorbills lay their eggs on ledge edges, and the egg's ovoid-pyramidal shape helps prevent it from falling off the ledge when disturbed. This adaptation ensures the safety of the egg, reducing the risk of it rolling off the ledge and being lost. In summary, kittiwakes and razorbills demonstrate remarkable adaptations to their cliff-nesting lifestyle, highlighting the intricate interplay between genetics, behavior, and environmental challenges in shaping the survival strategies of these bird species. 12 12 13 Common guillemots, another species of cliff-nesting birds, exhibit unique reproductive behaviors tailored to their habitat. These birds incubate their single egg on exposed cliff ledges, foregoing the construction of a traditional nest. However, this nesting strategy poses certain risks, as the eggshells can become contaminated with feces, dirt, water, and debris, potentially hindering gas exchange or facilitating microbial infection. To mitigate these risks, guillemots have evolved a mechanism involving the presence of shell accessory material (SAM) on the eggshell surface. SAM largely prevents pore blockages, ensuring optimal gas exchange for the developing embryo. This adaptation reflects the evolutionary fine-tuning of reproductive strategies to suit the specific challenges of cliff-nesting environments. Additionally, male guillemots play an active role in offspring care after the chick hatches. They guide their offspring to the sea and provide support during the early stages of growth. This cooperative parental care contributes to the survival of the population by ensuring the successful development and fledging of offspring. Overall, the reproductive behaviors of common guillemots exemplify the intricate adaptations that enable species to thrive in challenging environments, underscoring the importance of understanding the interplay between behavior, ecology, and evolutionary dynamics in shaping species' survival strategies. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Evolutionarily Stable Strategies (ESS): The objective of understanding evolutionarily stable strategies (ESS) is to explore how certain behaviors or traits persist within a population over time due to their adaptive advantages. In evolutionary biology and game theory, an ESS is a strategy that, when adopted by a majority of individuals in a population, cannot be displaced by any alternative strategy. By studying ESS, researchers aim to elucidate the dynamics of behavior evolution and the factors that contribute to the stability of certain strategies within populations. Game Theory and Animal Behavior: Fishers vs. Pirates and Hawks vs. Doves: The objective here is to apply game theory principles to understand animal behavior, particularly in situations involving competition or cooperation for resources. The examples of "fishers vs. pirates" and "hawks vs. doves" represent classic scenarios in game theory. In these games, individuals must choose between different strategies, each with its own costs and benefits. By analyzing these interactions, researchers aim to identify evolutionary stable strategies and gain insights into the factors influencing the prevalence of certain behaviors within populations. Behavioral Adaptation to Specific Environments: Seabirds: The objective is to investigate how animals adapt their behavior to thrive in specific environmental conditions, with a focus on seabirds as an example. Seabirds face 29 unique challenges related to nesting, foraging, and predator avoidance in marine environments. By studying their behavioral adaptations, researchers seek to understand how natural selection shapes behavior in response to environmental pressures such as food availability, predation risk, and nesting opportunities. Sexual Selection: The objective of studying sexual selection is to explore the evolutionary mechanisms driving mate choice and competition for mates within animal populations. Sexual selection encompasses both intra- and intersexual selection processes, where individuals compete for mating opportunities or are chosen as mates based on specific traits or behaviors. By investigating sexual selection, researchers aim to understand the evolution of elaborate mating displays, ornaments, and behaviors, as well as their implications for population dynamics and species diversification. Male-Male Competitions: The Four Types: The objective here is to categorize and understand the different forms of competition that occur between males within animal populations. Male-male competition plays a crucial role in sexual selection and mate acquisition. The four types typically include physical combat, mate guarding, coalition formation, and frequency of copulation. By studying these types of competitions, researchers aim to elucidate the selective pressures driving the evolution of male traits and behaviors involved in securing reproductive success. Alternative Reproductive Tactics: The objective is to explore the diversity of reproductive strategies exhibited by individuals within a population, particularly when traditional mating strategies are not feasible or effective. Alternative reproductive tactics (ARTs) encompass a range of behaviors and strategies that individuals employ to maximize their reproductive success in different contexts. By studying ARTs, researchers aim to understand the adaptive significance of these strategies and their implications for population dynamics, genetic diversity, and species evolution. 29