Genetic determination of paternity and variation in male reproductive success in two populations of rhesus macaques.

The fundamental framework for uncovering factors affecting the evolution of social behavior rests upon analyses of variation in reproductive success. In species where females mate with multiple males, paternity is invisible in the absence of genetic data. We determined paternity in two populations of rhesus macaques, Macaca mulatta, using both single locus and multilocus techniques. One troop, Group R, is one of four troops living on a 15 ha island (Cayo Santiago) off the coast of Puerto Rico, while the other troop, Group M, was translocated from Cayo Santiago to the Sabana Seca Field Station (Puerto Rico) in 1984. About a dozen human-derived short tandem repeat (STR) markers have been found to be polymorphic in the study of populations and provide the initial paternity determination. Final evaluation of paternity is then confirmed by multilocus DNA fingerprinting using synthetic oligonucleotide probes. Body condition, age, and dominance rank have an impact on male progeny production, while canine size does not. We suggest that nonagonistic competition in the form of sperm competition and endurance rivalry will modulate male reproductive success. A large body size among males provides them with an advantage in both sperm competition and endurance rivalry. Comparison of the two populations indicated that demographic, social, ecological, and morphological factors interact to regulate variation in reproductive success among male nonhuman primates.