No sex-biased dispersal in a primate with an uncommon social system—cooperative polyandry

Abstract

An influential hypothesis proposed by Greenwood (1980) suggests that different mating systems result in female and male-biased dispersal, respectively, in birds and mammals. However, other aspects of social structure and behavior can also shape sex-biased dispersal. Although sex-specific patterns of kin cooperation are expected to affect the benefits of philopatry and dispersal patterns, empirical evidence is scarce. Unlike many mammals, Saguinus geoffroyi (Geoffroy’s tamarin) has a breeding system in which typically multiple males mate with a single breeding female. Males typically form cooperative reproductive partnerships between relatives, whereas females generally compete for reproductive opportunities. This system of cooperative polyandry is predicted to result in female-biased dispersal, providing an opportunity to test the current hypotheses of sex-biased dispersal. Here we test for evidence of sex-biased dispersal in S. geoffroyi using demographic and genetic data from three populations. We find no sex bias in natal dispersal, contrary to the prediction based on the mating patterns. This pattern was consistent after controlling for the effects of historical population structure. Limited breeding opportunities within social groups likely drive both males and females to disperse, suggesting that dispersal is intimately related to the social context. The integration of genetic and field data revealed that tamarins are another exception to the presumed pattern of male-biased dispersal in mammals. A shift in focus from mating systems to social behavior, which plays a role in most all processes expected to influence sex-bias in dispersal, will be a fruitful target for research both within species and across taxa.

How do rivers, geographic distance, and dispersal behavior influence genetic structure in two sympatric New World monkeys?

“…The limited gene flow between S. midas social groups is consistent with the social organization of tamarins that consist of several breeding‐age males and females within a functionally polyandrous breeding system (Goldizen, ; French et al, ; Goldizen et al, ; Huck et al, ; S. F. Ferrari & Ferrari, ; Sussman & Garber, ). Interestingly, cooperative polyandry and limited individual dispersal distance have been observed to limit gene flow in other Saguinus species (Diaz‐Munoz & Ribeiro, ; Goldizen et al, ; Huck et al, ). Moreover, we found evidence that the level of spatial autocorrelation within social groups was similar and high for both sexes.…”

“…Tamarins, by contrast, tend to live in familial social groups, that consist of several breeding‐age males and females within a functionally polyandrous single female‐breeding system (French, Inglett, & Dethlefs, ; Goldizen, ; Goldizen, Mendelson, vanVlaardingen, & Terborgh, ; Huck, Lottker, Bohle, & Heymann, ; S. F. Ferrari & Ferrari, ; Sussman & Garber, ). Animals of both sexes may disperse (Goldizen & Terborgh, ; Goldizen et al, ; Lottker, Huck, & Heymann, ), and dispersal distances are, overall, relatively short, at least in S. mystax and S. geoffroyi (Diaz‐Munoz & Ribeiro, ; Huck, Roos, & Heymann, ), although sometimes animals remain in their natal groups into adolescence or early adulthood and may breed or attempt to breed in their natal groups. Thus, although dispersal in both Alouatta and Saguinus is characterized as bisexual, dispersal distances seem to be more limited in Saguinus than in Alouatta species.…”