Characterization and evaluation of microsatellite loci suitable for studies on mating system, parentage, and genetic identity in red titi monkeys (Callicebus discolor) and saki monkeys (Pithecia aequatorialis)

Among the pitheciids (Primates: Platyrrhini), titi (Callicebus) and saki (Pithecia) monkeys are both described as having a monogamous mating system. Titi monkeys live in small groups comprising a male-female pair and their offspring. Males provide a high level of parental care, and pair-mates show a high degree of synchronization and social contact. The composition of saki groups varies, from pair-mate units to small multimale-multifemale groups. Males and females present a much lower degree of social coordination; and among saki males, parental care is relatively absent. The term ‘monogamy’ is currently used to refer to both the male-female pair living arrangement (social monogamy) and the pattern of both males and females mating and breeding with a single member of the opposite sex (genetic monogamy). However, whether social monogamy typically (or ever) reflects genetic monogamy is an important question that arises when studying socially monogamous primates. To evaluate this question, molecular markers capable of being used to assess genetic parentage are critical. Identifying and characterizing polymorphic genetic markers for titi and saki monkeys is thus important for studies of their mating system. In this study, I evaluated the utility of 13 microsatellite marker loci for parentage determination in Callicebus discolor (red titi monkey) and Pithecia aequatorialis (equatorial saki monkey) from the Tiputini Biodiversity Station in Ecuador. Microsatellite parameters and parentage analyses were conducted using the softwares Arlequin v3.11 and Cervus v3.0.3. I successfully identified a panel comprising 10 and 12 polymorphic microsatellite loci for titis and sakis, respectively, by screening these markers in a set of 17 titi and 10 saki individuals from 5 social groups that have been the subjects of behavioral observation in the field for up to 11 years. These panels amplified reliably and provided a combined parentage exclusionary percentage of 96.7% and 98.5% when both parents were unknown, and of 99.7% and 99.9% when one parent was known for titis and sakis, respectively. With these marker panels, I successfully assigned maternity for 4 titi monkeys and 3 saki offspring, and paternity to 8 titis and one saki offspring. All but one of the parentage assignments were consistent with exclusion-based parentage. Additionally, all but two parentage assignments were in accordance with expectations based on observational fieldwork. The genetic parentage results, albeit preliminary, suggest that both panels of loci selected and characterized here will be useful for future studies on mating systems, kin selection, relatedness, and other population genetic studies of both taxa.