L18 inclusive fitness controversy examples

Question 1

What is the goal of this lecture?

Answer 1

To delve into why relatedness (r) isn’t always the sole driver of cooperation, emphasizing the roles of benefit (b) and cost (C).

Question 2

What balance does this week’s lecture strike compared to last week?

Answer 2

While last week showcased examples where relatedness is paramount, this week highlights cases where relatedness plays a minor role.

Question 3

What “easy trap” are we warned against in applying Hamilton’s rule?

Answer 3

Overfocusing on relatedness at the expense of the benefit (b) and cost (C) terms.

Question 4

Is high relatedness required for altruism to evolve?

Answer 4

No. Cooperation can evolve even when r = 0, as long as b > C.

Question 5

Does relatedness always matter most in Hamilton’s rule?

Answer 5

No. In some scenarios, benefit or cost can dominate the outcome.

Question 6

Will kin discrimination inevitably evolve according to Hamilton’s rule?

Answer 6

No. Discrimination arises only when the combination of r, b, and C favors it.

Question 7

What is the model answer to the relatedness question?

Answer 7

The strength of selection for cooperation is positively correlated with r b, assuming constant C.

Question 8

What are the key requirements for testing kin discrimination?

Answer 8

Choosing a suitable system, using experimental vs. observational approaches, accurately measuring r, and quantifying cooperation.

Question 9

Why are cooperative breeding species ideal for kin discrimination studies?

Answer 9

They have clear helper–recipient relationships, natural variation in relatedness, and allow comparative analyses.

Question 10

Describe the meerkat field system and relatedness variation.

Answer 10

Meerkats have dominant breeders and subordinate helpers; male immigration creates variation—including negative r—measured via microsatellite markers.

Question 11

What surprising result was found in meerkat helping behavior?

Answer 11

No significant correlation between relatedness and which pups helpers feed or how much help they provide.

Question 12

What ecological factor drives helpers to assist other nests in long-tailed tits?

Answer 12

High nest predation (~76% failure rate).

Question 13

How was kin recognition via vocal cues tested in long-tailed tits?

Answer 13

Researchers recorded calls, generated sonograms, and used a call-similarity metric to show helpers assist nests with closely matching calls.

Question 14

What did the battle-arena study of ground squirrels reveal about aggression?

Answer 14

Both relatedness and familiarity influence aggression: siblings housed together show low aggression, non-siblings apart show very high aggression.

Question 15

How do familiarity and relatedness influence helping in ground squirrels?

Answer 15

Full sisters receive more aid and fight less than half sisters, indicating both co-rearing and r matter.

Question 16

What three factors does Hamilton’s rule incorporate?

Answer 16

Relatedness (r), benefit (b), and cost (C).

Question 17

Can cooperation evolve when r = 0 or negative? Under what condition?

Answer 17

Yes—as long as the benefit (b) to the recipient exceeds the cost (C) to the actor.

Question 18

What are two proximate mechanisms for kin recognition discussed?

Answer 18

Vocal cues (in long-tailed tits) and familiarity (in ground squirrels).

Question 19

What do empirical findings like those in meerkats demonstrate about cooperation?

Answer 19

That relatedness sometimes doesn’t predict helping behavior, highlighting the need to consider the full Hamiltonian framework.

Question 20

What is unique about banded mongoose breeding?

Answer 20

Multiple females breed simultaneously with synchronized birthing, creating communal pup cohorts.

Question 21

What is eviction as reproductive competition in banded mongooses?

Answer 21

Dominant females expel subordinate females to reduce competition for resources and breeding.

Question 22

What research question was posed about eviction and kin discrimination?

Answer 22

Do dominant females preferentially evict non kin as predicted by standard kin discrimination theories?

Question 23

What was the predicted eviction pattern under standard kin discrimination?

Answer 23

Dominants would target non-kin for eviction, sparing close relatives.

Question 24

What actual pattern was observed in eviction events?

Answer 24

Dominant females evicted closest relatives first, showing higher eviction risk with higher r.

Question 25

What term describes this inversion of expected kin discrimination?

Answer 25

Negative kin discrimination.

Question 26

In the game theory model of eviction, who are the players and possible actions?

Answer 26

Player 1: dominant (evict or refrain); Player 2: subordinate (submit or resist).

Question 27

What payoff factors influence a subordinate’s decision to resist eviction?

Answer 27

Resistance cost (risk of injury C₂) versus benefit of group membership (B₂).

Question 28

What indirect cost affects the dominant’s decision regarding kin eviction?

Answer 28

Lost benefit r B₁ when evicting a relative who could aid the group.

Question 29

How does the equilibrium of the model explain targeting close kin?

Answer 29

High-r subordinates submit rather than resist, lowering cost to dominants, so dominants target kin.

Question 30

How was the model’s prediction tested empirically?

Answer 30

Comparing eviction correlation with r between older (can resist) and younger (cannot resist) subordinates.

Question 31

What did the age-based test reveal?

Answer 31

Negative kin discrimination in older subordinates, but no r effect in younger subordinates.

Question 32

What did a comparative meta-analysis across 18 species show?

Answer 32

~50% of species exhibit strong kin discrimination; the rest show weak or no discrimination.

Question 33

How does benefit (b) correlate with kin discrimination strength?

Answer 33

Species with larger helper benefits show stronger kin discrimination.

Question 34

What outlier pattern was seen in stripe-backed tanagers?

Answer 34

Despite very high b, they show negligible kin discrimination.

Question 35

What are the necessary conditions for kin discrimination to evolve?

Answer 35

Kin cues, within-group r variation, heritable discrimination strategies, and fitness gains from discrimination.

Question 36

How does variation in average relatedness among recipients affect discrimination?

Answer 36

Low average r (mix of kin and non-kin) → strong discrimination; high average r → indiscriminate help.

Question 37

Summarize why negative kin discrimination occurs in eviction contexts.

Answer 37

Dominants exploit close kin’s tendency to submit, reducing resistance costs and optimizing reproductive success.

Question 38

What does the 2024 review by Liddell, Green, Pike, Milo et al. synthesize?

Answer 38

Kin recognition mechanisms across taxa, exploring when genetic versus environmental/familiarity cues are used.

Question 39

What is Local Mate Competition (LMC) theory in fig wasps?

Answer 39

When mating occurs among related males on a patch, foundresses bias offspring sex ratio female to reduce brother–brother competition.

Question 40

Why do solitary foundresses in LMC theory bias the sex ratio toward females?

Answer 40

To avoid male–male competition among related sons and maximize inclusive fitness.

Question 41

How does the predicted offspring sex ratio change when there are multiple foundresses?

Answer 41

It approaches 50:50 because competition among related males is reduced.

Question 42

What did empirical data show for Species A fig wasps?

Answer 42

Sex ratios matched LMC predictions at all levels of foundress number.

Question 43

What pattern was observed in Species B fig wasps?

Answer 43

Accurate female bias with single foundresses but deviations under multiple, though multiple events are rare (~10%).

Question 44

What pattern was observed in Species C fig wasps?

Answer 44

Accurate bias with multiple foundresses but deviations under single, though single foundress events are rare (~5%).

Question 45

How is the fig wasp sex allocation strategy interpreted in light of ecological context?

Answer 45

Selection tunes sex allocation to the frequency of real ecological scenarios rather than all possible contexts equally.

Question 46

What is the hypothesis linking male parental investment to paternity certainty?

Answer 46

Male care should increase with certainty of paternity.

Question 47

Describe an experimental manipulation used to reduce male paternity certainty in birds.

Answer 47

Removing the social male during the female’s fertile window to lower his paternity share.

Question 48

What did a comparative meta-analysis of 40 species reveal about paternal care adjustment?

Answer 48

Some species reduce care under paternity doubt, while others show no change or even increased care.

Question 49

Which two factors explain variation in paternal adjustment to paternity uncertainty?

Answer 49

The cost of care (C) and the natural rate of extra-pair paternity.

Question 50

When do males most strongly reduce care in response to paternity uncertainty?

Answer 50

When both the cost of care is high and the risk of extra-pair paternity is high.

Question 51

What metric assesses inbreeding avoidance across species?

Answer 51

Comparing average relatedness among all potential mates to the relatedness of actual breeding pairs.

Question 52

In the inbreeding plot, what does a point below the 1:1 line indicate?

Answer 52

Breeding pairs are less related than expected by chance, showing inbreeding avoidance.

Question 53

In which species does inbreeding avoidance typically occur?

Answer 53

Only in species where inbreeding has been shown to impose severe fitness costs.

Question 54

What does context dependence mean for social strategies?

Answer 54

Optimal helping, sex allocation, care, and mate choice reflect the frequency and cost–benefit landscape of real ecological scenarios.

Question 55

Why is kin discrimination not inevitable?

Answer 55

It requires interactions among relatedness (r), benefit (b), cost (C), cue mechanisms, and r variation to produce observable discrimination.

Question 56

How can game-theoretic reversals like negative kin discrimination arise?

Answer 56

When resistance costs and inclusive fitness trade-offs invert the expected patterns of discrimination.

Question 57

What do comparative analyses reveal about behavioral variation across species?

Answer 57

Variation is often explained by interaction effects (e.g., cost × uncertainty) rather than single factors alone.

Question 58

What is needed beyond strong directional selection for a trait like discrimination to evolve?

Answer 58

Sufficient genetic variance and variable relatedness contexts (selective opportunity).