Kin Selection & Social Behavior Flashcards
recipient benefits & actor benefits
cooperation (mutualism)
recipient benefits & actor is harmed
alturism
recipient is harmful & actor benefits
selfishness
recipient is harmful & actor is harmed
spite
Darwin suggestions about selection
selection could favor altruistic behavior if those benefitted close relatives
inclusive fitness =
direct fitness + indirect fitness
direct fitness
personal reproduction
indirect fitness
the additional reproduction by relatives that is made possible by an individual’s actions
kin selection
natural selection favoring the spread of alleles that increase indirect fitness
inclusive fitness is mediated by 3 factors
r = relatedness
B = the benefit to the recipient
C= the cost to the actor
Hamilton’s Rule
Br - C > 0 or Br > C
calculating r: sibling to sibling
1/2
calculating r: first cousins
1/8
calculating r: parent to offspring
1/2
calculating r: grandparent to grandparent
1/4
calculating r: aunt/uncle to niece/nephew
1/4
kin selection example: praire dogs
- more likely to give alarms when kin is present
- call as frequent in the presence of parents & full sibs as offspring
kin selection example: squirrels
- 14 yrs, observed 30 natural predator attacks
- squirrels whistle for hawks, but trill for mammals
whistling for hawks =
selfish
trilling for mammals =
altruistic
eusociality describes social systems with:
- overlapping generations between parents & offspring
- cooperative brood care
- specialized casts of non-reproductive individuals
where is eusociality common?
Hymenoptera
is there something that predisposes members of Hymenoptera to be eusocial?
haplodiploidy
haploid
males develop from unfertilized eggs
diploid
females develop from fertilized eggs
hymenoptera are _________________
haploiddiploid
females maximize their inclusive fitness if they ….
raise sisters
consequence of females maximizing their inclusive fitness
because female workers are r=3/4 to sisters & r=1/4 to brothers, they should favor a 3:1 sex ratio
does haploidiploidy explain eusociality?
- calculations assume the queen mates once (1 father). but in honey queens, the queen mates with multiple males. so females are less closely related
- in many species, >1 queen so many workers are related by r=0
- many haploid species are not eusocial and vice versa
eusociality is influenced by ecology & genetics
the evolution of nesting behavior, & the need to supply larvae with food, it makes it difficult for a female to manage a nest by herself
naked mole rats
- live underground in colonies
- dig tunnel systems up to 2 miles long
- ectothermic
naked mole rat natural history
- neither moles or rats
- eusocial, but with XY genetic system
- 1 queen, 2-3 reproductive males
- found in desert regions in the Horn of Africa
- highly inbred groups
how do non-kin cooperate among each other in nature?
individuals can be selected to dispense altruistic acts if equally valuable favors are later returned to the benefactors
in reciprocal altruism, two conditions must be met
- cost to actor must be </= benefit to recipient
- cheaters must be punished
reciprocal altruism most likely to evolve when:
- groups stable & individuals repeatedly interact
- many opportunities for altruism
- individuals have good memories
potential altruists interact in symmetrical situations
vampire bat natural history
- social units of 8-12 adult females & their offspring
- Costa Rica
- roost in tree by day
- average r-0.11 among interacting individuals
- 33% of juveniles & 7% of adults fail to eat each night
