Natal dispersal in rhesus macaques is related to serotonin transporter gene promoter variation

VNTR polymorphism previously characterized in the promoter region of the hu man serotonin transporter (SLC6A4) gene was also found to segregate two maj or alleles (l and s) among the free-ranging rhesus macaques of Cayo Santiag o, Puerto Rico. When VNTR genotypes were related to age at male natal dispe rsal on Cayo Santiago, ss homozygotes (43 of 532 males tested) were found t o have left their natal groups significantly earlier (age 57.1 +/- 2.6 mont hs) than carriers of the l allele (ll age, 71.5 +/- 2.1 months; Is age, 63. 5 +/- 1.5 months; P = 0.0001). Since migration implies reproductive costs a nd benefits that change with age at dispersal, migration at an intermediate age might have conferred a heterozygote advantage serving to maintain the VNTR polymorphism via overdominant selection.