Fitness

Inclusive fitness

• Hamilton (1964)

Coefficient of Relatedness

• Chance of two individuals possessin an indentical allele
• 100% chance , r=1
• 50% chance, r=0.5
• 0% chance, r=0
• We inherit half of our chromosomes from our mother and half from our father (parents - gametes - embryo).

Parent - Offspring

• in a sexually -reproducing species, diploid offspring produce haploid gametes.
• A given individual will pass on 50% of its genes to each offspring
• Therefore, the coefficient of relatedness between parents and offspring is 0.5

Grandparent - Grandchild

• 50% chance between grandparent and parent (0.5), multipled by 50% chance between parent and child (0.5).
• Coefficient of relatedness between grandparent and grandchild is 0.25

Coefficient of Relatedness

• coefficient of relatedness r=0.5^L
• L = the number of generation links between the two individuals concerned (Campbell (1993))
• E.g. grandparent - grandchild is 2 generations so r = 0.5² = 0.25
• What is the coefficient of relatedness between Full siblings? 
• Generation links - identical genes by descent can be inherited by two pathways, either the mother or the father.
• What is the coefficient of relatedness between Half siblings?
• Identical twins: r=1
• Unrelated individuals: r=0
• Parent & offspring: r=0.5
• Full siblings: r=0.5
• Half siblings: r=0.25
• Uncles/aunts and nieces/nephews: r=0.25
• Cousins: r=0.125

Inclusive Fitness

• Incorporates the potential costs and benefits of performing a given act to an individual and any of its genetic relatives.
• From an inclusive fitness point of view an individual is…