Selection and the transferrin polymorphism in rhesus monkeys (Macaca mulatta).

Rates of survival, infant growth and fertility of rhesus monkeys with two, one and no C allele(s) at the transferrin locus are compared. Infants with no C allele experience slower growth rates than animals with either one or two C allele(s). While heterozygous females exhibit the highest infant growth rates among females, their fertility is lower and incidence of abortions and stillbirths is higher than for females with two or no C alleles. It is hypothesized that opposing directions of selection at different life-cycle stages maintain a stable equilibrium at the transferrin locus.