Week 6 Flashcards
kinds of social behaviour
mutual benefit, selfishness, altruism, spite
mutual benefit
Genetically unrelated cuckoo couples nest together and all the adults work together
Communal breeding can have mutual benefit
Fitness benefit explains this
selfishness
ane toad tadpoles that cannibalise cane toad eggs achieve higher fitness
alturism
Ground squirrels that raise an alarm when a hawk is seen risk their own fitness for the fitness of others
spite
Bacteria develop more slowly so that they can produce toxins to kill off neighbouring populations that get too close but this decreases their own fitness
Hamilton’s rule
Hamilton’s rule: Br - C > 0
B benefit to recipient
C cost to actor
R is relatedness
Personally costly behaviour can evolve if the benefit to kin is sufficiently high
Fitness has both direct and indirect components and inclusive fitness is the sum of both
direct fitness
results from reproduction an individual achieves on its own
indirect fitness
results from additional reproduction by relatives that is made possible by individual’s actions
inclusive fitness
sum of direct and indirect
kin selection
natural selection leading to the spread of alleles that increase the indirect component of fitness
measuring costs and benefits
Female red squirrels adopt related kittens when the result is a net gain in the mother’s inclusive fitness
kin selection and human behaviour
Natural selection in our ancestors left us with a tendency to feel more generous to closely related kin
Only measured in one culture though
cooperative breeding
evolves most readily in birds in which potential helpers and beneficiaries tend to be more closely related to each other
greenbeard alleles
Most alleles favoured by kin selection rise to high frequency inducing altruism toward individuals likely to be carrying copies of the same allele
Greenbeard alleles would rise to high frequency by inducing altruism towards individuals certain to be carrying the same allele
kin selection and spite: negative relatedness
Spite towards individuals less closely related to the actor than the average member of the population may increase the actor’s inclusive fitness
multilevel selection and cooperation
If cooperators provide sufficient benefit to their social groups, cooperation may increase in the population at large even if it decreases in frequency within groups
This is Simpson’s paradox
parent-offspring conflict
Conflict over provisioning offspring
Siblicide
cooperation and conflict among non-kin
Reciprocity - trading favours
Punishment
eusocial
animals that have overlapping adult generations in which non-productive individuals participate in cooperative care of young
haplodiploidy hypothesis
Predisposed to eusociality by unusual sex determination
Female ants, bees and wasps are more closely related to sisters than their own offspring
Not all eusocial animals are haplodiploidy though
the monogamy hypothesis
Lifelong monogamy facilitates evolution of eusociality
But not required for eusociality
the ecology and life history hypothesis
Eusocial species present extreme examples of altruistic behaviour
Hinges on ecological and life-history factors
phylogeny
how to calculate r in Hamilton’s rule
½ chance parents will pass down an allele - 0.5 relation to each parent
R = (0.5)(0.5) + (0.5)(0.5) in full siblings
R = (0.5)(0.5) in half siblings
Average r is 0.32
reciprocal altruism
Cooperation cannot evolve if you only interact once
Tit for tat - cooperate if they cooperate and retaliate if they retaliate
Organisms are not expected to weight up options - more instinctual
Must repeat interactions, must have possible win-wins and must have low miscommunication for cooperation to evolve
forgiving copy-cat behaviour
Tamarins could pull a pole to give their friend food
Paired always pull with never pull partner
Then reversed roles
Expected reciprocal altruism
blood sharing vampire bats
One bat pesters and get other bat to regurgitate
Need to feed every 60 hours
Close to starving individuals pester
Donor moves closer to starvation zone but helps starving bat
Donor loses less time before next feed than what hungry bat gains
Expect a reciprocal relationship
There is a kin-selection effect but there is also an effect of frequency of association between bats (reciprocal altruism) - both strong
Bats that groom others and have frequent interactions are more likely to give a lot of blood
group selection
Selection on groups of organisms favouring some groups over others leading to group-advantageous traits
Selection on the individual is stronger than selection on the group
multilevel selection
Population with cooperative individuals and selfish individuals
Randomly reproduce in groups of three and then die
Mixed groups - pays to be selfish
But not all groups are mixed so cooperative can still build up
Highest reproductive success amongst cooperative groups
Simpson’s paradox: trends at one level do not match those at another
