Evolutionary game theory (DONE)

Question 1

How is game theory used in evolutionary biology?

Answer 1

used to analyze behaviors where an individual’s fitness depends on the actions of others in the population, especially for strategic traits like cooperation or aggression.

Question 2

What’s the difference between a strategy and a tactic in game theory?

Answer 2

A strategy is a general plan for behavior in different situations, while a tactic is the specific action used in a particular situation.

Question 3

What is an Evolutionarily Stable Strategy (ESS)?

Answer 3

An ESS is a strategy that, if everyone in the population adopts it, cannot be overtaken by a new mutant strategy.

Question 4

What is frequency dependence in the context of an ESS?

Answer 4

Frequency dependence means that the fitness of a strategy depends on how common or rare it is relative to others in the population.

Question 5

How does game theory differ from group selection?

Answer 5

assumes individuals behave selfishly, and outcomes are shaped by individual strategies, not by selection acting on groups.

Question 6

What is the Hawk-Dove game?

Answer 6

The Hawk-Dove game models conflicts over a resource, with individuals adopting aggressive (Hawk) or non-aggressive (Dove) strategies. It explores how aggression evolves in populations.

Question 7

What are the strategies in the Hawk-Dove game?

Answer 7

2 different strategies =
Hawk: fight aggressively for the resource, retreat only if injured.
Dove: display but retreat if the opponent escalates.

Question 8

What are the tactics in the hawk dove game?

Answer 8

Display
Escalate
Retreat

Question 9

What is the key idea behind the Hawk-Dove game?

Answer 9

shows how aggression and cooperation evolve based on the frequency of aggressive and non-aggressive individuals in the population.

Question 10

What happens in a Dove vs. Hawk interaction in the Hawk-Dove game?

Answer 10

The Dove always loses but avoids injury, so the payoff is 0 for the Dove.
The Hawk always wins and gets the full resource (V)

Question 11

What happens in a Dove vs. Dove interaction in the Hawk-Dove game?

Answer 11

The two Doves share the resource (V/2) or might randomly win or lose.

Question 12

What happens in a Hawk vs. Hawk interaction in the Hawk-Dove game?

Answer 12

One Hawk wins, one loses. On average, the payoff is ½(V-C), where C is the cost of injury

Question 13

What does E represent in the Hawk-Dove game?

Answer 13

the expected payoff in an interaction. It depends on the combination of strategies (Hawk or Dove) in the interaction, such as E(H,D) for a Hawk vs. Dove, or E(D,D) for Dove vs. Dove

Question 14

How is the Evolutionarily Stable Strategy (ESS) determined in the Hawk-Dove game?

Answer 14

To determine the ESS, compare the payoffs of different strategies

Question 15

When is a strategy (Hawk or Dove) considered an Evolutionarily Stable Strategy (ESS) in the Hawk-Dove game?

Answer 15

• Dove is not an ESS because if a population is all Doves, a single Hawk (mutant) can invade and will have a higher fitness by always winning against Doves
• Hawk is an ESS if the value of the resource (V) is greater than the cost of fighting (C), i.e., V > C. In this case, Hawks always win, and Doves cannot invade.

Question 16

What happens when V < C in the Hawk-Dove game?

Answer 16

neither Hawk nor Dove is an ESS. The result is a mixed strategy, where both strategies coexist in the population with equal fitness, and the strategies cannot be eliminated by one another.

Question 17

What is the equation for fitness in the Hawk-Dove game when both strategies coexist?

Answer 17

p × ½(V - C) (pay off to hawks fighting other hawks) + (1 - p) × V (pay off to hawks fighting doves) = p × 0 (pay off to doves against hawks) + (1 - p) × V/2 (pay off to doves fighting other doves)
where p is the probability of playing Hawk. The equation simplifies to p = V/C.

Question 18

What does the Hawk-Dove game show about aggression?

Answer 18

aggression involves a trade-off between costs and benefits. Selfish evolution doesn’t always lead to pure aggression, as the costs (like injury) usually limit aggressive behavior.

Question 19

What does stable polymorphism require in evolutionary strategies?

Answer 19

For stable polymorphism to occur, strategies must have equal fitness, or one will be eliminated. Both strategies must have the same fitness for them to coexist over time.

Question 20

How is game theory useful in understanding reproductive strategies?

Answer 20

Game theory helps explain the variation in mating strategies commonly seen in animal populations.

Question 21

What are the three types of reproductive strategies in game theory + describe them?

Answer 21

1. Alternative strategies: genetic polymorphism with equal fitness, but rare.
2. Mixed strategies: probabilistic (=behaving in a random way), equal fitness, and rarest (no good examples).
3. Conditional strategies: common, best-of-a-bad-job strategies (changing behaviour based on the situation)- adapt to bad circumstances, doing what they can to survive, with unequal fitness.

Question 22

What types of strategies are common in reproductive behavior across animals?

Answer 22

Common strategies include alternative phenotypes like more aggressive vs. less aggressive or more sneaky vs. less sneaky individuals, each with different advantages for survival and reproduction.

Question 23

What does the game theory matrix for Rock-Paper-Scissors reveal about reproductive strategies?

Answer 23

In Rock-Paper-Scissors, the best strategy is to play each of the three options one-third of the time, leading to no pure ESS and an unstable polymorphism, where no single strategy dominates.

Question 24

What does the example of the side-blotched lizard demonstrate about alternative reproductive strategies?

Answer 24

The side-blotched lizard exhibits three alternative reproductive strategies (aggressive, territorial orange; less aggressive, small territory blue; and sneaky, non-territorial yellow), showing how different strategies coexist and impact reproductive success.

Question 25

How is the polymorphism of the side-blotched lizard related to genetics?

Answer 25

The variation in throat color (orange, blue, yellow) in the side-blotched lizard appears to have a genetic basis, suggesting that these reproductive strategies are heritable.

Question 26

Why is there no Evolutionary Stable Strategy (ESS) in the side-blotched lizard example?

Answer 26

No ESS exists because each morph has advantages and disadvantages depending on the frequency of the others: yellow morphs can sneak matings when orange is common, but are countered by the blue morph, which holds smaller territories and prevents sneaky matings.

Question 27

What does modeling the side-blotched lizard’s reproductive strategies over time reveal?

Answer 27

Over time, the different morphs fluctuate in frequency, creating a cycle where the population shifts between more orange, yellow, or blue individuals, demonstrating a dynamic, unstable polymorphism rather than a stable strategy- no morph reaches stability

Question 28

What does the long-tailed tit example show about conditional reproductive strategies?

Answer 28

The long-tailed tit uses conditional strategies, where birds choose between breeding and helping based on timing and success, adjusting their strategy depending on the season and environmental pressures.

Question 29

What options do long-tailed tits have when they lose their nest?

Answer 29

can either build a new nest and lay eggs (which takes time) or help a pair with an existing nest, feeding their chicks without the time cost, often helping relatives.

Question 30

How does timing influence whether long-tailed tits breed or help?

Answer 30

Early in the season, it’s better to breed, but later in the season, when breeding success declines, it’s more beneficial to help others, as the time cost of breeding outweighs the benefits.

Question 31

How does predation affect the breeding and helping strategies in long-tailed tits?

Answer 31

Predation reduces the success of both breeding and helping strategies, with both strategies showing lower fitness, especially when predation risk is high later in the season.

Question 32

How does the probability of re-nesting change over the breeding season in long-tailed tits?

Answer 32

Early in the season, birds are more likely to try breeding again if they fail, but as the season progresses, this probability decreases, and they are more likely to help another pair instead.

Question 33

What general conclusions can be drawn from the long-tailed tit study on breeding vs. helping?

Answer 33

study shows that breeding offers higher fitness when successful, but as the season progresses and breeding opportunities decline, helping others becomes a better strategy. This highlights the flexibility of conditional reproductive strategies based on timing and available opportunities.

Question 34

What does sex ratio theory predict about the sex ratio in most species?

Answer 34

Sex ratio theory predicts that natural selection favors a 50:50 sex ratio at conception, as it ensures equal genetic contribution from both males and females, optimizing reproductive success = 1st example of ESS

Question 35

Why must the total genetic contribution from males and females be equal in most organisms?

Answer 35

Since each individual has one mother and one father, the total genetic contribution from both sexes must balance to maintain equal average fitness between males and females- so natural selection favours this

Question 36

What happens when the sex ratio deviates from 50:50?

Answer 36

If the sex ratio is unequal, individuals of the rarer sex will have more mating opportunities and leave more offspring than the more common sex, as they are more “in demand.”

Question 37

What is the role of frequency-dependent selection in sex ratio evolution?

Answer 37

Frequency-dependent selection explains that producing more of the rarer sex increases fitness, and this advantage continues until a balanced 50:50 sex ratio is achieved.

Question 38

Why is a 50:50 sex ratio considered an Evolutionary Stable State (ESS)?

Answer 38

A 50:50 sex ratio is an ESS because it maximizes reproductive success, balancing the genetic contribution of both sexes, and is stable over time due to frequency-dependent selection.

Question 39

What is the evidence for sex ratio evolution in most organisms?

Answer 39

Most organisms exhibit a 50:50 sex ratio, suggesting that this balance has been strongly selected for. The lack of variation in sex determination in many species implies this ratio may have been a result of strong evolutionary pressure.

Question 40

What are the key caveats for expecting a 50:50 sex ratio in a population?

Answer 40

A 50:50 sex ratio is expected when the species is diploid, the nucleus controls sex determination, and the costs and benefits of each sex are equal.

Question 41

How do haplodiploid wasps manipulate their sex ratio?

Answer 41

control their sex ratio by adjusting the number of fertilized (female) and unfertilized (male) eggs they lay, influenced by factors like parasitism on the host.

Question 42

Why do haplodiploid wasps produce more females under certain conditions?

Answer 42

Wasps produce more females in response to parasitism because more females are needed to reproduce, while males (produced from unfertilized eggs) are only useful when there is competition for mates.

Question 43

How does local mate competition impact the sex ratio of haplodiploid wasps?

Answer 43

Local mate competition favors producing more females, as males only compete within a limited area (host), making it more beneficial to have more females who can mate with males from other hosts.

Question 44

How does the Seychelles warbler sex ratio deviate from the typical 50:50 pattern?

Answer 44

adjust their sex ratio based on territory quality, with females on low-quality territories producing more males (77%) and on high-quality territories, producing more females (87%).

Question 45

Why do Seychelles warblers produce more males on low-quality territories?

Answer 45

On low-quality territories, males are more likely to disperse and reduce competition for resources, whereas helpers (often males) lower reproductive success, making it beneficial to produce more sons who leave.

Question 46

What is the effect of helpers on the sex ratio in Seychelles warblers?

Answer 46

On high-quality territories, helpers increase reproductive success, so females are more likely to produce females (13% sons), who stay and help, enhancing survival chances for offspring.

Question 47

How does the presence of helpers affect the reproductive strategy of Seychelles warblers?

Answer 47

The sex ratio manipulation ensures that females produce offspring that maximize the effectiveness of helpers. On high-quality territories, producing females ensures help, while on low-quality territories, males are produced to disperse and reduce competition.

Question 48

What is the Prisoner’s Dilemma, and why is it important in understanding cooperation?

Answer 48

The Prisoner’s Dilemma demonstrates a situation where two individuals can either cooperate or defect, with the best individual outcome being to defect. Despite this, cooperation can still evolve in certain contexts, such as repeated interactions.

Question 49

How does the Prisoner’s Dilemma describe the decision-making process between two individuals?

Answer 49

Each individual can either cooperate (remain silent) or defect (blame the other). If both cooperate, they get a moderate sentence. If both defect, they both get a heavier sentence. Defection is the dominant strategy, as it always leads to a better individual outcome, regardless of the other’s choice.

Question 50

Why is defection the stable strategy in a one-shot Prisoner’s Dilemma?

Answer 50

In a one-time interaction, defection provides the best individual outcome, regardless of what the other person does. Since cooperation doesn’t offer a higher payoff, defection becomes the stable strategy.

Question 51

What is the global optimum in the Prisoner’s Dilemma, and why is it unstable?

Answer 51

The global optimum occurs when both players cooperate, leading to the best collective outcome (moderate sentences). However, it is unstable because each player is tempted to defect for a personal gain, which results in both defecting and a worse outcome for both.

Question 52

How does iterated interaction (repeated rounds of the Prisoner’s Dilemma) change the dynamics of cooperation?

Answer 52

When the Prisoner’s Dilemma is played repeatedly, individuals have the chance to respond to each other’s previous actions. Cooperation can evolve because individuals learn to reciprocate cooperation and punish defection, making cooperation more stable over time.

Question 53

What is the Tit-for-Tat strategy in the Iterated Prisoner’s Dilemma, and why is it successful?

Answer 53

Tit-for-Tat is a strategy where the player starts by cooperating and then repeats whatever the opponent did in the previous round. It’s successful because it’s simple, generous, and forgiving, promoting mutual cooperation by rewarding cooperation and punishing defection.

Question 54

Why is Tit-for-Tat considered the most successful strategy in the Iterated Prisoner’s Dilemma?

Answer 54

Tit-for-Tat is the most successful because it is easy to understand, encourages cooperation, and punishes defection. It’s effective in promoting long-term cooperation, as it’s both forgiving (if the opponent cooperates later) and punishing (if the opponent defects).

Question 55

How do evolutionary game theory and the Prisoner’s Dilemma relate to cooperation between species?

Answer 55

Evolutionary game theory shows that cooperation can evolve between non-relatives if the individuals interact multiple times, allowing strategies like Tit-for-Tat to emerge. It applies to both within-species cooperation (e.g., kin selection) and between-species cooperation (e.g., mutualistic interactions like cleaner fish and clients).

Question 56

What are some examples of cooperation between species that can be understood through game theory?

Answer 56

include figs and fig wasps, cleaner fish and clients, and ants and acacia trees. These interactions involve mutual benefits and can be modeled through the Prisoner’s Dilemma, where each species cooperates because it leads to better outcomes over time

Question 57

What is the overall conclusion of game theory in relation to outcomes and its application in nature?

Answer 57

Game theory provides models that are useful when outcomes depend on the actions of others, are frequency-dependent, and help us understand strategic decisions. While not always strictly applicable in nature, it serves as a heuristic tool for understanding complex interactions.