Demographic components of gene frequency change in free‐ranging macaques on Cayo Santiago

Abstract

Gene frequency profiles from January 1973 to January 1977 for three polymorphic loci were examined in Cayo Santiago rhesus social groups. The effects of demographic components (i.e., births, deaths, immigrations, emigrations, and group fission and fusion) on total change in gene frequencies are assessed. Allelic frequencies at the carbonic anhydrase II, 6-phosphogluconate dehydrogenase, and transferrin loci were analyzed in four social groups. In the two groups that underwent fission and fusion during the study period, the timing of these processes was related to the largest short-term changes in gene frequences. However, immigration and emigration had the greatest effect on total change in gene frequency in all groups during the study period. The relative importance of births and deaths in producing gene frequency change varied among the social groups. These results suggest that the relative importance of the demographic components of gene frequency change in primate populations is determined by behavioral patterns and ecological conditions specific to the population considered.

Potential mates analysis and the study of human population structure

“…It may well be commonplace among "primitive" societies in which kinship is so important, as was the case for most of human history. Indeed, kin-structured migration has been observed (Koyama, 1970) and associated with gene-frequency changes (Ober et al, 1984) in nonhuman primates. Perhaps there has been a general shift during the course of human evolution: a decline in importance of kin-structured migration and an increase in the importance of the factors that make the isolation by distance model an accurate description of the structure of many sedentary populations.…”

Untitled

“…structure. Many species have populations which undergo fission and fusion (see Fix, 1978;Ober et al, 1984 for reviews), yet no formal theory of fission/fusion population structure is available (Fix, 1978). The analysis we present begins to fill this gap: fission is formally equivalent to the extinction of one poulation and the recolonization oftwo (or more) new populations, and fusion can be represented as the founding ofa new population (Long et al, 1987).…”

An autocorrelation analysis of genetic variation due to lineal fission in social groups of rhesus macaques

“…However, this common model will not always be appropriate for interpreting the genetic distances among the subdivisions of a regional population. Lineal fission, a process of population formation in which relatives nonrandomly assort into the new daughter groups (Neel and Ward, 1970;Chagnon, 1975;Chepko-Sade and Sade, 1979), can cause rather large differences between groups, instantaneously, at the time of their formation (Neel and Ward, 1970;Duggleby, 1977;Cheverud et al, 1978;Cheverud, 1981;Fix, 1978;Olivier et al, 1981;Smouse et al, 1981;Buettner-Janusch et al, 1983;Ober et al, 1984). This may alter the usual correlation between time since divergence and genetic distance among related populations.…”

“…where lineal fission of groups [is] common, biological distances among social groups may not reliably reflect recent historical, phyletic relations" (p. 352). If the original difference generated by lineal fission is large enough, it may produce levels of divergence equal to the average divergence represented in a set of subpopulations connected through migration I I I (Cheverud et al, 1978;Cheverud, 1981;Smouse et al, 1981;Buettner-Janusch et al, 1983;Ober et al, 1984). Thus lineal fission may seriously disrupt the theoretical relationship between genetic divergence and time since formation from a common ancestral group.…”

“…O'Rourke and Bach En-cis0 (1982) have recently analyzed allelic variation among social groups on Cay0 Santiago and interpreted the degree of genetic divergence among groups in terms of the geographical distance separating them on the 40-acre island and the recency of group fission, although there is no evidence for the effects of geographical separation of migration between groups in the Cay0 Santiago colony. Previous genetic research on this island population has concentrated on the genetical analysis of individual fission events (Duggleby, 1977;Cheverud et al, 1978;Cheverud, 1981;Buettner-Janusch et al, 1983;Ober et al, 1984). This research has indicated that lineal fission is an important source of genetic variation between social groups, generally producing moderate to high levels of differentiation at the time of group formation, but the overall importance of lineal fission for understanding diversity between social groups has not been measured.…”