Evolutionary Biology Chapter 17: The Evolution of Sociality

For signals to remain constant over time, what is needed?

*Honest* signaling

In one-shot games (played once) what is the Nash equilibrium?

*Testifying/Defection* because it will be either 0 years or 3 years. Not testifying will be either 1 year or *5 years*

However, what is the Nash equilibrium in iterative rounds with *uncertain* end point?

*Tit-for-tat strategy* i.e Reciprocal altruism seen in animals

What are the 3 empirical predictions by the costly signaling explanation of begging?

1. Begging is costly 2. Begging intensity equates hunger 3. Parents feed loudest beggar

Selection can also select for dishonest signaling. Describe an example.

1. Cue observer (receiver) acts in response to un-intentional cues from signaler. 2. Signaler throws off false signals which cue observer soon realizes 3. Coevolutionary arms race happens

Why is information well-suited for sharing?

1. Easily transported 2. Like a instantly regrowing starfish

Name the order of highest fitness in trait-group selection models.

1. Free-riders in Cooperative groups 2. Cooperatorative groups 3. Non-cooperative groups

Why do stalk cells forfeit their own reproductive opportunity?

1. Genetically close with reproductive spore cells so their reproductive success are essentially same 2. Taller stalks means greater spore dispersal and competition reduction

How did cooperation come about i.e evolutionary "paths" to cooperation?

1. Group selection 2. Reciprocity 3. Kinship

What are 2 important characters of bees to take into account for understanding eusociality?

1. Haplodiploid (males: haploid and females: diploid) 2. Monandrous (single mate)

Where can conflicts happen?

1. Nonkin 2. Families 3. Genomes

What traits did Edwards believe were group-level adaptations?

1. Reproductive restraint (overpopulation would lead to resource depletion) 2. Defending unnecessarily large territories

What are the 2 types of Conflict within Genome?

1. SD: Segration distortion 2. POCGI: Parent-of-Origin *Conflict* and Genomic Imprinting

What are the 3 types of conflicts in families?

1. Sexual conflict 2. Parent- offspring conflict 3. Sib - sib conflict

What were Williams' counter-arguments to Edwards statements?

1. Simply due to unusually poor environmental conditions(or insurance for future ones) 2. Eventually unrestrained mutants (thus higher fitness) will take over whole population *Analogy is cancer cells taking over*

What can explain how natural selection select for evolution of reciprocity?

A game theory model called the Prisoner's dilemma (shows how cooperation results in higher fitness for all)

What solves the problem of the *Free-rider problem* and *Altruism*?

Again, 1. Group selection 2. Reciprocity 3. Kinship

What is an important point to note in Mixed Nash Equilibrium?

At a mixed Nash equilibrium, the payoff from playing hawk must equal the payoff from playing dove.

What does natural selection select for in chicks then?

Chicks that squawk when truly hungry and that keep quiet once satiated.

What did Hughes et al correctly hypothesized?

Common ancestor of each eusocial clade is monandrous.

When studying evolution of animal interactions, what kind of behaviors is studied more?

Conflict-associated behaviors

What is one theory that supports the prior statement?

Costly signaling theory

Which famous scientists believed that animals sometimes practiced group-selection i.e. had adaptations that minimized chances that the species or populations would go extinct as a whole?

Darwin, Lorenz, Edward

In bird nests, why doesn't natural selection select for chicks that squawk for food even when satiated i.e dishonesty?

Dishonest chicks that squawk for food even when satiated will not have higher fitness because predators will find them (Cost outweighs benefit).

What happens when neither players know which role to take e.g no idea who territory owner is?

Each player will play hawk p=v/c Each player will play dove 1-p = 1- v/c v = payoff c = cost

What did Sherman discover in ground squirrels?

Females stay in same nest all their lives and they make more alarm calls because their benefits to fitness still outweighs the cost. Males join the nests and do not make alarm calls because the cost is bigger than the benefit to fitness.

What is this chapter about?

Fitness effects of interactions among genetically related individuals.

Evolution of aggression in non-kin can be explained by what game theory model?

Hawk-dove game

How can natural selection maintain honest signaling?

Honest signals results in higher fitness than dishonest signals

How does a cell decide to either become a reproductive spore or stalk cell?

If it is large and well-nourished, it becomes a reproductive spore. It is less well nourished, it becomes a stalk cell.

What is the Nash equilibrium?

In game theory, the Nash equilibrium is a *solution* concept of a non-cooperative game involving two or more players in which each player is assumed to know the equilibrium strategies of the other players, and no player has anything to gain by changing only his or her own strategy. Stated simply, Amy and Phil are in Nash equilibrium if Amy is making the best decision she can, taking into account Phil's decision while Phil's decision remains unchanged, and Phil is making the best decision he can, taking into account Amy's decision while Amy's decision remains unchanged.

What is 1 type of non-kin conflict?

Intrasexual selection: Fighting for territory, food, and mates.

Why were eggs with MM chromosomes or PP chromosomes not viable?

M and P express different genes and both are needed for survival i.e MP eggs

What kind of genes are MI (Maternally imprinted) and why?

M for Matermal, M for Max Growth Igf2r, a growth factor hormone Natural selection: "Next batch will not be my offspring, so must maximize this batch's growth"

What are Maternally imprinted genes?

MI P X ✓ Silenced in maternal chromosomes but expressed in paternal chromosomes

Generally, why are normal sized offsprings produced?

MI and PI genes cancel each other out. "Normal" is defined as what is seen in general.

What is Hamilton's rule?

Natural selection favors indirect fitness Allele X (f increases) when rb >>> c r: Coefficient of relatedness b: Benefits c: Cost

In a scenario where the players *know* whether they are going to either *always* play the Hawk or Dove, how is the Nash equilibrium achieved?

One player must always be a *Hawk* and one must always be a *Dove*. Either one changing would only be extra cost to the player.

What kind of genes are PI (paternally imprinted) and why?

P for Paternal, P for Puny Igf2r causes "puniness" by inhibiting Igf2r Natural selection: "Future offspring needs resources too, so will save some for them"

What are Paternally imprinted genes?

PI M X ✓ Silenced in paternal chromosomes but expressed in maternal chromosomes

In *parent-offspring conflict*, explain the reason behind the conflict.

Parents want to equally invest in both children but each child wants greater investment because it is less related to its sibling (the cost it incurs if its sibling gets less investment is less compared to the parent).

What is the cause of the "tug-of-war" model between the mother and father for the evolution of genomic imprinting?

Polygamous mating system, where the next batch of offspring will not belong to the same father.

What is r (Coefficient of Relatedness between 2 individuals)?

R = PAIDD Probability alleles are identical by descent

The mobile slugs produce fruiting bodies. What are they?

Reproductive structures where some cells make up the stalk and some cells become the reproductive spores in the capsule.

Why is conflict easier to understand?

Resources are usually limited and so they are worth contesting.

If slug cells are not close genetic relatives, what happens?

Selection will favor cheater cells that suppress other cells from differentiating into spores and increase their own probability of ending up a spore cells.

Why can natural selection select for signaling?

Signaler will benefit and the receiver will also benefit. (Honey guide will guide humans to beehives)

Even in a decided *fixed* number of rounds, what is the Nash equilibrium?

Still *Defection*

What is the inclusive fitness (term coined by Hamilton) of a person?

Sum of Direct fitness + Indirect fitness Direct fitness: No. of viable offspring it produces Indirect fitness: Incremental effect towards genetic kin's direct fitness

Do free-riders (receiving benefits without cost) have lower or higher fitness eventually and why?

They have lower fitness because others will not exhibit reciprocal altruism towards them.

Why are slimes molds cells "social"?

They join together to form mobile slugs.

What is the eventual fate of signals in dishonest signaling?

They will disappear over time.

If a set of individuals affect one another's fitness, what is this set called?

Trait group

Why is Coefficient of Relatedness between bee sister workers 0.75?

r = 1/2 * 1/2 (Mother) + 1/2 (Dad) = 0.75

*Conflict*

x

*Cooperation*

x

*Information and Communication*

x