Genetics of Kin Selection: The Role of Behavioral Inclusive Fitness

A framework is developed for understanding the equilibria and dynamics of diploid sib-sib kin selection in terms of behavioral inclusive fitness functions, in analogy with how behavioral fitness functions control selection in general two-phenotype frequency-dependent selection, where interactions are assumed to occur at random. This approach is used to clarify the difference between exact and approximate models of kin selection, which differ in their treatment of relatedness. Various forms of relatedness are explored, and their relation to Hamilton's rule and individual and behavioral inclusive fitness is discussed. Numerical simulations are used to quantify the limits on changes in relatedness during selection, which is the only force that can cause a decrease in mean inclusive fitness