Lecture 19: Altruism/Kin Identification
What is the definition of direct fitness when using W.D Hamilton's equation?
(personal reproductive output number of offspring) x r
What is the degree of relatedness between children and uncles?
0.25
What is the coefficient of relatedness between parents and offspring?
0.5 because they give 1 allele to offspring
How are individual A and individual B affected by postponed cooperation?
A gains direct fitness (after delay) B gains direct fitness
How are individual A and individual B affected by reciprocity?
A gains direct fitness after delay an B gains direct fitness
How are individual A and B affected by adaptive altruism?
A gains indirect fitness B gains direct fitness
How are individual A and B affected by spite?
A loses inclusive fitness B loses inclusive fitness
How are individual A and B affected by deceit and manipulation?
A loses inclusive fitness B gains inclusive fitness
How are individual A and B affected by maladaptive altruism?
A loses inclusive fitness N gains direct fitness
What is indirect fitness?
A measure of the genetic success of an altruistic individual based on the number of relatives (or genetically similar individuals) that the altruist helps reproduce that would not otherwise have survived to do so
What is Direct Fitness?
A measure of the reproductive or genetic success of an individual based on the number of its offspring that live to produce (for not used simplified measure)
What is spite?
A reduce its reproductive success in order to harm B
What is maladaptive altruism?
A sacrifices its lifetime incluisve fitness in order to help B
How do we see conflict among related individuals in siblings?
Abundant food → More food, mother is feeding both offspring equally Less food → one offspring is going to get the scrap of food, other will not Will there be conflict? Yes Siblings might kill others to get more food
What is altruism?
Actor confers a benefit, but suffers a cost to is direct fitness (or at least no direct benefit)
What is the altruist cost?
Altruist cost < (beneficiary's gain) x (relatedness)
What is reciprocity?
B directly pays back A for its prior aid
Why would there be cooperative courtship of the long-tailed manakin bird?
Better than average chance that a beta male will become alpha male Better chance of mating and raising offspring Previous alpha male and new alpha male both have more copulations and get benefits of having the relationship
What is C in Hamilton's formula?
C = cost to altruist
What is the relationship between C and relatedness?
C<b(r)
How do we see familiarity in kin identification in emperor and king penguins?
Colonies are huge Parents will forage and come back and figure out who their offspring is Young have complex calls and parents will find their own offspring based off of those calls
Whether altruism increases inclusive fitness depends on:
Cost to altruist in reproductive potential Gain in beneficiary in reproductive potential Probability that beneficiary carries same altruism as altruist
What is inclusive fitness?
Direct fitness + indirect fitness EX: If there are three grandchildren and you help one, the only one you've affected is that one
How does reciprocity most likely evolve?
Discrimination against cheaters Likely opportunity for repayment later Individual recognition Stable relationships
What is seen in selfish behavior?
Donor benefits at the expense of the recipient
What does each parent contribute to a gene?
Each parent contributes one allele or copy of a gene
What is an extreme case of altruism?
Eusociality
How do we see helping behavior in birds?
Experimental group and control group vs. number of fledglings Experimental - all helpers but one were removed from group Control - no helpers were removed from these groups Having more helpers made a huge difference in number of young produced
How did we see female house mice using the MHC gene for identification?
Female house mice Prefer males with dissimilar MHC genes, to avoid inbreeding When pregnant or lactating, females form communal nesting and nursing associations with other females that have similar MHC genotypes Presumably such nepotism helps the female mice propagate alleles they share in common with their pregnant relatives
What is a simple example of postponed cooperation?
Female with extra milk will feed other young, in return later when she is low on milk the one that was helped will help her
How do we see indirect selection in ground squirrels?
Females are more likely to give terrestrial alarm calls than males Reproductive females with living relatives nearby are more likely to call than reproductive females with no living relatives nearby
How do we see alarm calls differ in areas with beldings ground squirrels?
Females breed near their natal site (born), whereas males disperse Alarm calls given in response to predators are these likely the result of direct or indirect selection Individually → animal that is alarming is drawing attention to itself Alarm calls may have been selected for Different groups (ages, range between juvenile, 1 year old, and adult) What you would expect them to do vs. observed Adult females give more calls than male, and more than expected Females are giving more alarm calls than males, females have more relatives around Exposing themselves to possible predation (risky behavior)
How do we see humans using the MHC gene for identification?
Females prefer odors males with dissimilar MHC genotypes, except when they are taking birth control, then they prefer odors o males with similar genotypes May be optimal for outbreeding
How did we see selfish behavior in honey pot ants?
Find a colony of ants, bring the eggs to their own colony and use them as slaves for taking care of the young, only species with slavery
What did W.D Hamilton discover about genes?
Genes can be propagated not only by having offspring, but also by helping relatives (genetically similar individuals)
How do we see conflict among related individuals between mothers and babies?
Gestational diabetes in mothers Conflict between baby and mom Baby controls insulin - getting more sugar to grow larger Cost to the mother to get diabetes
What is haplodiploidy and how is it related to bees and eusociality?
Haplodiploidy - unfertilized eggs develop into males and fertilized eggs develop into females (male is haploid, female is diploid) Therefore females are highly related
What is cooperation?
Individual A and B help each other right now
How are individual A and B affected by cooperation?
Individual A gains direct fitness immediately Individual B gains direct fitness
What is an example of selfish behavior?
Infanticide - good for only the one committing the crime
What are the ways that one can identify kin?
Location Familiarity Phenotype Matching Recognition Alleles
How is the MHC gene used in kin selection?
MHC genes now mediate kin recognition in many animals, including tunicates and humans. Because each MHC locus has as many has 50 alleles, each individual often has a unique MHC genotype, however relatives tend to be more similar than non relatives
How does the MHC gene affect the carrier?
MHC somehow affects the odor of its carrier, enabling the other individuals to use small to detect the carrier's genotype
What is the MHC gene?
Major Histocompatibility Complex (MHC Gene) Glycoproteins that reside in cell membranes where their function is to recognize invader organisms (pathogens)
How do we see "family breakups" in family dynamics?
Males often leave their natal group when breeding opportunities open elsewhere Doesn't need to help anymore because he can have more benefits by breeding himself instead of helping
What is phenotype matching in kin identification?
Match a learned family image to a relative through either inherited traits or characteristics related to the family environment such as maternal labeling (scent) while developing in utero or within the same group of eggs
What species shows eusociality the best?
Naked Mole Rat
How do you identify kin by location?
Nest or family sticks around, young are altricial, can't locomote Altruistic deeds oriented towards individuals found in areas where relatives are likely to be located
If a male helps his sister raise four more nieces with a cost of one fewer of his own offspring in addition to helping his sister, what would his genetic gain be then?
Number of extra nieces x r -0.25x4 = 1 Cost: number of fewer offspring x r ----- 0.5x1 = 0.5 There would be a selection because there are more benefits than there is a cost
If a male helps his sister raise four more nieces without a cost to himself than she could have without assistance, the altruist's genetic gain would be:
Number of extra nieces x r 0.25r
What is fitness?
Number of genes contribute to the next generation (individuals with the same genes)
How do we see family dynamics in the white-fronted bee-eater?
Probability of helping vs. coefficient of relatedness More likely to help when they're more related Less likely to help when they aren't related or are barely related This is similar patterns to human
How do we see eusociality in the naked mole rat
Sterile workers labor on behalf of other individuals that are engaged in reproduction Cooperation in the care of the young Overlap of at least two generations
How do we see altruism in honey bees?
Stung = honey bee dies Wants to help relative stay alive by hurting predator
How did we see direct fitness benefits for helping in paper wasps?
Subordinates by inheritance, subordinates with egg laying, solitary foundresses Subordinate by inheritance has a direct correlation
What is postponed cooperation?
The donor and actor will not receive benefits until a later time
What is adaptive altruism?
The initial direct fitness sacrifice made by A leads to indirect fitness gains for A
How do we see tunicates using recognition alleles in kin identification?
Tunicates begin life as planktonic larvae, they form an interconnected colony of genetically identical animals Because large colonies survive better than small ones, colonies other attempt to fuse If sea squirt attempts to join an unrelated colony, however, the colony emits chemicals that repel the unrelated individuals Able to recognize them as unrelated
IS there selection for helping out your own offspring?
Yes, there are different levels of input to offspring
How do you identify kin by familiarity?
Young learn to recognize individuals with which they are raised (i.e nest or burrow)
How do we see eusociality in bees?
females are highly related 25% of alleles in common through their mother 50% of alleles in common through their father 75% of alleles in common between sisters Therefore sister's increase their inclusive fitness more by rearing reproductively capable sisters than if they raised their own offspring
What is r in W.D Hamilton's equations about genes?
fraction of gene copies or alleles shared between two individuals as a result of common descent
What is the definition of indirect fitness when using W.D Hamilton's equation?
genetic gains derived by helping non-descendant relatives (number of relatives that survive because of help) x r
What aspects of a species typically have postponed cooperation?
highly social, good memory, long lifespan, low dispersal rate (stable social group)
What is r in Hamilton's formula?
relatedness of altruist and beneficiary
How do we see familiarity as identifying kin in spiny mice?
spiny mice - prefer to huddle with familiar pups, unrelated individuals raised together treat each other as familiar Thermoregulation is important If you mix up young in a burrow with unrelated individuals, they will treat those animals as similar/kin unlikely to be other individuals in that burrow, learned behavior
How do we see sweat bees show phenotype matching with kin identification?
sweat bees guard the entrance to of their nest so that only relatives enter the nest Degree of genetic similarity between guard and intruder vs. proportion of intruders allowed to pass Greater similarity = more likely they are to pass through to get into the nest What happens if they're raised y unrelated individuals? The unrelated individuals are permitted to enter the nest They allow only what they have encountered before
