Carbonic anhydrase heterozygosity and F_ST distributions in Kenyan baboon troops

Abstract

Abstract An analysis of the distribution of carbonic anhydrase alleles in troops of olive baboons, Papio cynocephalus , is reported. In an earlier study (Olivier, T. J., J. Buettner‐Janusch and V. Buettner‐Janusch, 1974, Am. J. Phys. Anthrop., 41 : 175–190) the authors found a significant excess of heterozygotes with a large amount of intertroop differentiation at the CA II locus. If balancing selection is acting on the CA II locus and maintaining an excess of heterozygotes, then the degree of local differentiation observed at this locus is unexpected. In this study the analyses of the CA I and CA II data are extended and some idiosyncratic features of baboon population structure are considered. Non‐idealized forms of behavior, such as adult male migration and other age‐specific and sex‐specific behaviors, may affect observed patterns of gene frequency distributions. The analysis reveals that the excess of heterozygotes at the CA II locus is localized in the females only and that the males are highly differentiated among the troops. These findings suggest that a female‐limited heterozygous advantage exists at the CA II locus in this baboon population. A computer simulation model, RAMBLE, further suggests that recurrent male migration between troops may explain the intertroop microdifferentiation found in primate populations.