Ch 15 Kin Selection

Cannibalism

- A mechanism of kin recognition - Natural selection should favor the ability to distinguish (not eat) individuals with whom one shares genes - If hunger level is high, eat anyway to survive Ex: Tadpoles more likely to become a cannibal morph if raised with fewer siblings. More likely to cannibalize a cousin than a sibling

Chestnut-Crowned Babblers

- Breeding varies as an asymptomatic function of group size - Due to increased provision of nestlings - New (unrelated) immigrants are less likely to help than natal yearlings - Relatedness has a significant effect on the rate at which immigrant and natal helpers feed young

Associative Learning

- Individuals I interact with are kin; familiarity Ex: As chicks begin to fledge, the parents learn to associate each of their chicks with its own distinct vocalization Ex: After fledging, chicks from flocks with chicks from other broods

Spacial Proximity

- Individuals in my nest are kin - "nest-mate effect" - Altruism directed towards individuals that were raised together - Does not require genetic similarity - Subject to cheating Ex: Adult swallows feed any chick in their nest

Ecological Constraints route of Eusociality

- Many eusocial species build large nests that are difficult to maintain and defend alone - These include paper wasps, termites, snapping shrimp, and naked mole rats - Large individuals become members of the soldier caste and are usually non-reproductive

Mechanisms of Kin Recognition

- Spacial Proximity (indirect cues): Individuals in my nest are kin - Associative Learning (direct cues: learning): Individuals I interact with are kin; familiarity - Phenotype Matching (learning and genes): Individuals that resemble those I interact with are kin - Recognition Alleles (genes): Individuals that have my alleles are kin

Altruistic acts are expected to occur...

- With greater frequency between close relatives than between more distant relatives - With greater frequency between distant relatives when benefits to distant relatives are greater than benefits to close relatives

The 3 Characteristics of Eusociality

1. Parental care of offspring in finite nest 2. Reproductive division of labor 3. Overlapping generations

William D. Hamilton

A British evolutionary biologist widely recognized as one of the greatest evolutionary theorists of the 20th century. Hamilton became famous through his theoretical work expounding a rigorous genetic basis for the existence of kin selection and altruism, an insight that was a key part of the development of a gene-centric view of evolution. He is considered one of the forerunners of sociobiology, as popularized by E. O. Wilson. Hamilton also published important work on sex ratios and the evolution of sex.

Spite

A behavior which is costly to both the actor and to the recipient where cost and benefit are defined on the basis of the lifetime direct fitness consequences of a behavior.

Altruism

A behavior which is costly to the actor and beneficial to the recipient where cost and benefit are defined on the basis of the lifetime direct fitness consequences of a behavior. Helpful behavior that raises the recipient's direct fitness while lowering the actor's direct fitness.

Coefficient of Relatedness (r)

A measure of genetic similarity. The average proportion of genes shared by related individuals

Altruism can evolve if...

A relative of the altruist benefits from the behavior of the altruist. Kin selection works depending on the magnitude of the benefit compared to the cost and if the recipient is closely related

Kin Discrimination

An individual different reaction toward others based on the degree to which they are genetically related

Honeybee colony example

Example of Halpodiploidy route of Eusociality - Since females are more closely related to sisters than brothers, workers will care more for female offspring. Males have higher mortality due to neglect - Queens will manipulate behavior of sterile workers. Emit 36 different pheromones to influence worker behavior

Meerkats Example

Example of Hamilton's Rule - Dominant female does most of the breeding - Helpers are young of previous litters and immigrants - Helpers rarely breed - Helpers engage in: 1. Sentry duty 2. Babysitting pups 3. Provisioning pups

Haplodiploidy route of Eusociality

In honeybees, males are haploid and females are diploid Sister bees are more closely related to each other than their own offfspring Kin selection could favor sterile workers - Since females are more closely related to sisters than brothers, workers will care more for female offspring - Queens will manipulate the behavior of sterile workers. Emit pheromones that manipulate worker behavior

Recognition Alleles

Individuals that have my alleles are kin "Green-Beard" Effect: Help those with similar phenotypic traits/ alleles Altruism is directed toward only those with the same altruism gene The gene must code the behavior, the signal and the recognition Ex: Fire ants accept new queens that have the b allele at the GP-9 locus Ex: Honeybees allow workers to pass based on their genetic relatedness

Phenotype Matching

Individuals that resemble those I interact with are kin Ex: Belding's Ground Squirrels Full siblings fight less and assist each other more than half siblings

Beling's Ground Squirrels Examples

Kin Selection Theory Example - Live in colonies - Females remain close to home. Males disperse - Give alarm calls to: 1. Bird predators- whistle. Alarm whistler is at decreased risk of predation 2. Ground predators- trill. Alarm triller is at increased risk of predation - Females more likely to make alarm calls. - Trill calls are more likely if relatives are in view and vulnerable to attack -

White-Fronted Bee Eaters Example

Kin Selection Theory Example - Live in colonies - Nest sites are limited - Nests have a variable number of non-parental adults (helpers) - Helpers don't breed - Helpers feed nestlings and defend nest against take-overs - Helpers are recruited by breeders through harassment to: 1. younger birds 2. Individuals who are more closely related to at least one of the breeders -Care-giving (provisioning) will improve nestling survival. More food --> higher chick survival - Helpers more likely to act as helpers for siblings over cousins

Eusociality

Non-parents provide care/extra defense Highest level of organization in an animal society

Kin Selection theory

Social interactions create the opportunity for both conflict and cooperation

Hamilton's Rule (definition)

The argument made by W.D. Hamilton that altruism can spread through a population with r*B > C with r being the coefficient of relatedness between the altruist and the individual helped, B being the fitness benefit received by the helped individual, and C being the cost of the altruist in terms of the direct fitness lost by the altruism due to his / her actions.

Kin Recognition

The capacity of an individual to react differently to others based on the degree to which they are genetically related

Indirect Fitness

The component of fitness gained from aiding the reproduction of related individuals

Direct Fitness

The component of fitness gained through the impact of an individual's behavior on the production of offspring

Kin selection

The process by which traits are favored because of their beneficial effects on the fitness of relatives

Inclusive Fitness

The sum of an individual's direct and indirect fitness. The effect of one individual's actions on everybody's number of offspring weighted by the relatedness

When will altruism be favored by natural selection?

When the benefit of helping close kin is greater than the cost to one's self

When should individuals discriminate kin from non-kin?

When performing altruistic behaviors

When are altruistic acts favored? (Hamilton's Rule)

rB-C > 0 r= coefficient of relatedness B= Benefit to recipient C= Cost to the actor