Figure 2: Adoptions increase inclusive fitness, consistent with Hamilton's rule.
From: Adopting kin enhances inclusive fitness in asocial red squirrels
Predicted fitness cost (solid line) of adoption to the surrogate dam increases, while fitness benefit (dash line) to the adopted juvenile decreases with litter size. Dashed lines represent three different degrees of relatedness calculated from a maternal pedigree or microsatellite allele frequencies and multiplied by the benefit to the juvenile (rb). Adoptions (closed circles) increased inclusive fitness, whereas unadopted litters (open circles) would have reduced inclusive fitness if adopted.
