Altruism, Kin Selection, and Inclusive Fitness
relatedness
r coefficient r = probability that a gene in one indiv is an identical copy, by descent, of a gene in another indiv as r increases, prob that genes are shared increases path method
inclusive fitness using the gene equivalents method
an indiv's offspring production devalued by relatedness to offspring + summed offspring of all same gen relatives devalued by r to the relatives offspring (avoids double accounting over generations) confused?? ya. use the equation on the notecard i think thats all u may need to know hehe
ground squirrel example
calling is costly, but allows for genes to be passed on (one sacrificed themself for greater good of gene pool)
holmes and sherman sibling recognition in ground squirrels
created 4 groups -sibs reared together -sibs reared apart by different mothers -non-sibs reared together in a single litter -non-sibs reared apart animals reared together rarely fought regardless of genetic relatedness when sibs were reared apart were less aggressive to each other than to unrelated individuals
examples of r for diploid organisms
full sibs - .5 half sibs - .25 parent/offspring - .5 grandparent/grandchild - .25 uncle/nephew - .25 first cousins - .125 (.5^4 + .5^4)
calculating inclusive fitness when helping a relative
for an altruistic act to spread by kin selection gene causing the altruistic act will spread if : B*r>C - Hamilton's rule or B r of donor to own offspring -- > ------------------------------- C r to donor to recipients of offspring b - benefit realized by helping relative c - cost of giving help
green beard effect
may be recognition alleles which express their effects phenotypically enabling bearers to recognize these alleles in others and causing bearers to behave altruistically towards others with the phenotype ex. gene for green beard - be nice to others w green beard
inclusive fitness
measure of fitness including genes passed on via relatives as well as via offspring two components: -direct component (ur offspring) -indirect component (component from helping kin)
conditions under which altruism will evolve via kin selection
relatedness is high (full siblings less aggressive) benefit to relatives is high (alarm calls) cost is low (donor in control of abundant resource)
assumptions of kin selection model
relatives also possess altruistic gene relatives have mechanism of recognizing e/o
calculating r
sum over all possible pathways between the two individuals
kin selection
the process by which characteristics are favored due to their beneficial effects on the survival of close relatives
