Zoo 4513 Chapter 9 Kinship/ Relatedness

Kinship

A connection by blood or common origin

It influences cooperation, social structure, and survival strategies

Observation

Females give alarm calls more often then males when predators approach

Reasons:

Males leave natal groups to find mates

Females stay in natal area

Females alarm calls protect genetic kin (kin selection in action)

What is kinship in evolutionary biology?

Definition: relationship through common ancestry or shared genes

Maynard Smith & Hamilton’s theories:

Kin selection: traits that help relatives survive are favored by natural selection.

Inclusive fitness: the total genetic success from personal reproduction plus aiding to reproduce.

Altruism

A behavior that decreases individual fitness but increases others fitness (warning calls, helping raise others offsprings)

Inclusive fitness equation

Personal reproduction + helping relatives produce= total genetic success

Related and genetic connection

Definition: the probability that two individuals share genes identical by descent

Examples:

• Parent-child or full sibling: 0.5

• Grandparent-grandchild: 0.25

• Aunt/Uncle- Niece/Nephew: 0.25

• Cousins: 0.125

Hamiltons Rule (1964)

Rb>c

Where:

• R= coefficient

• B= benefit to recipient

• C= cost to altruist

Hamiltons rule interpretation

Natural selection favors altruism when the benefit to kin (weighed by relatedness) exceeds the cost to the actor.

Hamilton’s rule limitation

Hard to measure b and c in wild populations

Jerram Brown’s “offspring rule” reformulated the equation using offspring number as a measurable fitness unit

Reciprocal Altrusim

Definition: helping non-relatives with the expectation of future help

Evolutionary Theory of Family (Steve Emlen)

Based on:

1. Kin selection theory

2. Ecological constraints theory- limits to dispersal

3. Reproductive skew theory- predicts conflict or cooperation in reproduction

Predictions from family evolution models

1. Prediction 1- family instability

   families disintegrate when reproductive opportunities arise elsewhere

2. Prediction 2- resource quality

   Families with high- quality territories/ resources are more stable

3. Prediction 4- cooperation among relatives

   cooperative breeding highest among closely related individuals (high r)

4. Prediction 9- step parent investment

   step parent (r=0) invest less in stepchildren than biological parents (r=65)

   basis of Cinderella effect

   stepchildren more likely to suffer neglect or leave early

5. Prediction 13- shared reproduction

   as dominance differences lessen, reproduction is more equally shared

Family conflicts

Parent- offspring conflict

• Conflict over how much care parents should give vs. how much offspring want

• Reasons:

• Parent wants to balance care among all offspring

• Offspring value its own survival more (r=1) than its siblings (r=0.5)

Sibling Rivalry

• Aries when resources are limited

• Each sibling value its survival more→ competition or aggression may occur

Kin Recognition

Question: how do animals recognize relatives?

Mechanisms:

• Internal template: memory or sensory recognition (scent, voice, facial cues)

• Rule of thumb models: “if it lives in your nest or territory, treat it like kin” ( not true recognition- just a heuristic)