PSYO 2160 Lecture Notes - Lecture 8: Eusociality, Haplodiploidy, Fetus
3 May 2018
School
Department
Course
Professor
Kinship
October 19, 2015
Coefficient of Relatedness:
• The probability that 2 related individuals have inherited a particular allele of the single
locus/gene from their common ancestor
• R = (1/2)n
• n=number of steps in genealogy
Hamilton’s Rule:
• an allele associated with some trait will increase frequency when: rB>C
• r=coefficient
• B=benefit to recipients
• C=cost to individual expressing trait
• A trait will increase in frequency in a population if said trait benefits relatives more than it costs
the individual expressing the trait
Family Dynamics: Building Blocks
1. Inclusive Fitness Theory
• Direct – number of viable offspring
• Indirect – reproductive success of genetic relatives
• Inclusive = direct + indirect
2. Ecological constraints theory – dispersal remaining on natal territory
• Availability of habitat – if none available, benefits individuals to remaining in living
group
• Cost of dispersal –survival costs higher than likely reproductive – benefits individual to
remain in group
3. Reproductive Skew Theory
• How reproduction is divided among potential breeders
• High skew (despotic) – one or few breeders dominant
• Low skew (egalitarian) – reproduction shared equally
Family Dynamics: Emlen’s Predictions
1 Family grouping will be unstable, disintegrating when acceptable reproductive opportunities
materialize elsewhere
2 Families that control high-quality resources will be more stable than those with lower-quality
resources
3 Assistance in rearing offspring (cooperatively) will be expressed to the greatest extent between
those family members that are the closest genetic relatives
Haploid-Diploid Sex Determination in Bees
• Queen (diplod) X drone (haploid) = drone (haploid) or workers (diploid)
• Sister workers are 75% related
Eusociality
• All hymenopteran species = haplodiploid
• Some hymenopteran species = eusocial
Conflict in Families:
1. Parent – Offpsring
• All offspring are 50% related to parent
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Document Summary
Coefficient of relatedness: the probability that 2 related individuals have inherited a particular allele of the single locus/gene from their common ancestor, r = (1/2)n, n=number of steps in genealogy. Inclusive = direct + indirect: ecological constraints theory dispersal remaining on natal territory, direct number of viable offspring. 1 family grouping will be unstable, disintegrating when acceptable reproductive opportunities: how reproduction is divided among potential breeders, reproductive skew theory. Family dynamics: emlen"s predictions materialize elsewhere remain in group. 2 families that control high-quality resources will be more stable than those with lower-quality resources. 3 assistance in rearing offspring (cooperatively) will be expressed to the greatest extent between those family members that are the closest genetic relatives. Haploid-diploid sex determination in bees: queen (diplod) x drone (haploid) = drone (haploid) or workers (diploid, sister workers are 75% related. Eusociality: all hymenopteran species = haplodiploid, some hymenopteran species = eusocial. Infanticide: sibling rivalry r=0. 5 limited vs plentiful resources.
