Cooperation Flashcards
What defines cooperativity?
Co-operator pays cost, c
Recipient gets benefit, b
Cooperator specifically evolves to give this benefit (so predation does not count)
How are cooperative behaviours maintained in a population?
Selfish individual = increased individual fitness = spreads through pop = reduced overall fitness
What is the ‘Tragedy of the Commons’?
Arms race of selfishness - no benefit to being fair in a society where no one else is, so each individual becomes increasingly exploitative
Direct benefits of cooperation?
Reproductive success of co-operator increases
Example of direct benefits from reciprocity?
Cleaner wrasse - clean parasites from eels who could just eat the fish, but let them live (and give them a food source) so as to benefit from parasite removal
Indirect benefits of cooperation?
Reproductive success of an individual sharing the cooperators genes is increased
What is altruism?
Behaviours that benefit only the recipient - cannot result in cooperator benefitting later
Reciprocal altruism example?
Vampire bats blood sharing - can regurgitate blood to give to those who have not found any food.
May end up having this returned later, but from a different source
Indirect reciprocity
Often in humans - this is where the cost is repaid much later. It may also contribute to social status e.g. cheaters get no cost or benefit, and may have reduced reputations
What is kin selection?
Favouring of traits because they improve the fitness of others
Hamilton’s rule
rB - C > 0
benefits of cooperating exceed costs, dependant on r = level of relatedness
How can we test Hamilton’s rule?
See if animals can recognise their relatives, and behave differently as a consequence
e.g. tiger salamanders cannibalise, found to have delayed onset of this if raised in groups with relatives
How do animals recognise kin? (3)
Environmental cues
Phenotype - self-reference matching
‘Green-beard’ effects
Environmental cues signalling kin?
Offspring born in the same nest, at the same time are likely to be related
Cues learnt from this environment e.g. acoustic indicators, odour (MHC similarity), appearance
Does not indicate degree of relatedness
Phenotype and self-referent matching?
Essentially if they resemble another - this does allow degree of relatedness to be determined
Unfamiliarity leads to longer time spent investigating; unfamiliar kin are recognised more easily, familiar kin the easiest
Green beard effects
Signal or marker, often leading to increased tendency for co-operative behaviour.
Cheating is observed so it is not always effective, but honesty is maintained by a high cost of cheating
Inclusive fitness? plus example
Cooperation leads to this, where inclusion in a group increases overall fitness.
e.g. mating coalitions in turkeys, where dominant and subordinate males are related and dominant males receive a benefit from them
Inclusive fitness equation?
IF = direct fitness +r(indirect fitness)
When will cooperation evolve?
If it can offer direct and/or indirect fitness benefits
What is cooperative breeding?
Helpers assist in raising another children, at the cost of their own reproduction.
Commonality of cooperative breeding?
3% of birds
2% mammals
0.1% fish
Hypotheses for cooperative breeding? (3)
Kin selection
Life history constrains
Ecological constraints
Kin selection argument for cooperative breeding?
Relatives still possess an individuals genes and so they gain inclusive fitness benefits
Life history constraints argument for cooperative breeding?
Delayed maturity
Low adult mortality (too large a pop. for many breeders)
No/limited dispersal (as above)
Low reproductive rate
Ecological constraints argument for cooperative breeding?
Shortage of territory/mates
-e.g. fairy wrens, loss of male breeder causes helper to move into the position
High dispersal costs
Low independent breeding success (e.g. in harsh environments)
What is the habitat saturation model?
In context of cooperative breeding - occurs when there are insufficient territories.
In warblers introduced to a new island, cooperation only occurred once all territories were full
How do helpers aid breeders?
May supply food, resources, guarding
i.e. increase food delivery rates, as parents can only reach a certain level which may be insufficient with increased offspring numbers
What do helpers directly gain?
Pay-to-stay in group membership (protection, food from group)
Breeding experience
Territory/mate inheritance e.g. fairy wren with removal of breeding male
May attempt to breed
What do reproductive skew models show?
Dynamics between helpers and breeders - where helpers may be allowed to breed as payment for helping (concessions) or because they are large enough to escape risks, or helpers do not breed due to reproductive restraints
Concessions in cooperative breeding?
Breeders offer incentives to induce helpers to remain, e.g. letting them reproduce
Needed with unrelated groups or better territories
Restraints in cooperative breeding?
Helpers opt out of reproduction e.g. in a relative-dominated group to prevent inbreeding, if breeders can punish them, or if surrounding territories are poor
Promiscuity in cooperative breeding?
It decreases relatedness, found to be correlated in nature with reduced cooperativity
What does direct reciprocity depend on?
Repeated interactions to help both cooperator and recipient, relies on memory
