Lecture 5 - Sociality Flashcards
What are the four main types of social behaviour?
Mutualism
Selfish
Altruism
Spite (Harms both)
Why does kin selection work?
Most important means of cooperation
r = P(relatives sharing copy of same gene by descent)
Evolution doesn’t distinguishbetween copies from offspring vs sibing’s offspring
What are the types of fitness?
Direct fitness - fitness via personal reproduction
Indirect fitness - Fitness due to aiding relatives
Inclusive fitness = direct + indirect fitness
What is Hamilton’s rule?
Conditions under which an altruistic act will spread by kin selection
(B/C) > (1/r) or rB - C > 0
B = benefit to recipient C = cost to donor r = relatedness
How does competition influence altruism?
Competition between relatives may reduce altruism spread
Must be considered
For cooperative/altruistic behaviour to evolve:
(rxyb) - C - (rxed) > 0
rxy = relatedness between donor and recipient rxe = relatedness between donor and individuals who differ due to competition from donor d = reduction in fitness due to altruistic act
Do animals treat their kin differently? Provide examples
Yes
Beldings ground squirrels more likely to produce a costly alarm call in presence of close relatives (Sherman, 1977)
Fewer tiger salamander cannibals in kin groups
Cannibalism occurs later in kin groups
In mixed litters of mice, young gain more weight proportionally (Hager and Johnstone, 2005)
How do animals recognize relatives?
Shared environment so familiarity eg. birdsong
Only teaches who SHOULD be a relative
Self-referent matching - graded response to strangers based on comparison of phenotype and of self and relatives
Green beard effect - identify those with same distinctive genetic marker
What cristicisms have there been of kin selection?
Its a mathematical construct
Pairwise and additive interactions assumed which ingores impacts of multiple interactions
Only describes static interactions - dynamic populations need constant updating
No empirical tests
Only works for small subset of species when standard natural selection works for all
How have people responded to criticisms of inclusicve fitnes theory?
Incorrect distinction between natural selection and inclusive fitness
Natural selection explains appearance, inclusive fitness explains why
Only full sibling families evolved eusociality, so r is important
Hamilton: individual fitness isn’t maximised, inclusive fitness is
If benefit high enough, altruism will evolve
What is direct reciprocity?
Cooperation between individuals
C < B and reciprocation from recipient in future meeting
Cheats are a problem
Evolutionarily stable reciprocity depends on the uncertainty of repeated interactions
How do you win prisoner’s dilemma?
Tit for tat
Cooperate on first move
Do what opponent did on previous move
ESS if W is large enough
What is an ESS?
E(I,I) > E(J,I)
I = stable strategy J = possible mutant E = evolution
How does tit for tat evolve?
All defect are also ESS
Kin selected cooperation can create clusters in which tit for tat can enjoy benefits of mutual cooperation
Cooperation based on reciprocity can evolve if individuals can retaliate W high
Donors must be able to recognize cheaters and refuse to aid
Must be high probability for a given individual to be a donor or recipent
Vampire bats
What is indirect reciprocity?
Interactions often inbetween individuals who won’t meet again
Image scoring: if you help others to increase their reputation they may be more likely to help you
Bystanders gain benefits from this
eg. cleaner fish
How does spite evolve?
rB - C > 0
Requires negative relatedness
Costly action to unrelated individual may benefit related individual
Found where kin and non kin interact in competitive environments
eg. bacteria
Describe spite in the parasitoid wasp
Lay one male and one female egg into moth eggs
Each produces 1000s of larvae asexually
Some females become sterile soldiers and kill less related brothers
Find relatedness with extraembryonic membrane to discover who is related
Summarise West et al, 2007`
If assistance gives greater benefits, more kin discrimination
Haplodiploid hypothsesis is false so cooperation in Hymenoptera due to high cost to benefit ratio
Punsishment can favour cooperative behaviour
Need more integration between empirical and theory
Summarise Nowark et al 2010
Inclusive fitness theory requires assumptions that aren’t required by natural selection and are unrealistic in a real system
Inclusive fitness says cooperative behaviour is a result of relatedness, but authors believe it is the other way around eg. nest and food
Summarise Abbot et al, 2011
Response to Nowark et al, 2010
Assumptions are not required for inclusive fitness, general as natural selection, just for specific species
Biological progress has been made with inclusive fitness theory eg. explaining gender ratios
Summarise Wilson and Wilson, 2007
A trait which disadvantages total fitness of an individual but benefits the group will evolve, therefore group selection must be ~real~
Group selection is not always ineffective across generations eg. when predators introduced
Group selection abandoned based on theory only, while some empirical evidence suggests it might be a thing
All evolutionary behaviour models share key points
Altruistic traits are detrimental to individual.so must be group selection (ever heard of inclusive fitness pal????)
