Chemical ecological characteristics of herbivory of Siparuna guianensis seeds by buffy-headed marmosets (callithrix flaviceps) in the Atlantic forestof southeastern Brazil

The buffy-hraded marmoset (Callithrix flaviceps) is apparently the only pre disperal herbivore of the seeds of Siparuna guianensis at the Caratinga Bio logical Station in southeastern Brazil. Both the Fruit receptacles and the frutioies (seeds) of S. guianensis are relatively rich in nutrients such as carbohydrates. proteins, and lipids, but the receptacles contain high conc entrations of benzylisoquinoline alkaloids. The latter presumably act as a qualitative chemical defense, impeding the access of potential predators to the alkaloid-poor frutioles. However, on ripening, the receptacle splits o pen, exposing the frutioles, which enables C. flaviceps to avoid the plant' s chemical defenses effectively. Taking care to avoid contact with the rece ptacle. the marmosets pluck out the frutioles and ingest the seeds. Qualita tive and quantitative changes tin particular a significant reduction in dai ly ranging) in the marmosets' behavior during the period when S. guianensis frutioles were accessible indicate that this was a preferred plant resourc e. This is the first record of the consumption of S. guianensis seeds by ca llitrichine monkeys (which are not known to be systematic seed eaters), des pite the fact that both are widely distributed in the Neotropics. It is thu s possible that the behavioral strategy observed here is a unique phenomeno n resulting from a specific combination of factors. including the abundance of S. guianensis within the study area. The lack of other records may neve rtheless be a result of insufficient sampling effort. in which case, the fe eding strategies of callitrichines may have an important influence on the r eproductive biology of S. guainensis in many areas.