Does Gut Passage Affect Post-dispersal Seed Fate in a Wild Chili, Capsicum annuum?

Seeds of Capsicum spp. (wild chilies ) are coated with capsaicin, which deters mammalian seed predators. During gut passage through frugivorous birds, its presence on seeds likely is greatly reduced, presumably increasing the seeds' susceptibility to postdispersal seed predation by mammals. We tested whether gut passage influences the rate at which dispersed seeds are removed from dispersal sites by different types of seed consumers. We predicted that seeds passed through birds (passed seeds) would be removed at higher rates than seeds taken directly from fruits (non-passed seeds). Removal rates of passed seeds were either lower or no different than removal rates of non-passed seeds, contrary to our prediction. In a second set of trials, we placed caged and exposed (control) seeds in pairs on the ground to determine whether vertebrates or invertebrates were primarily responsible for post-dispersal seed removal. We found an inconsistent effect of caging on frequency of seed removal, indicating that both invertebrates and vertebrates harvest chili seeds at our site. These results suggest that capsaicin's role in mediating interactions with vertebrate seed dispersers and predators is largely restricted to the wild chilles' fruiting stage.

Duke Scholars

Author Clay Noss Environmental Natural Science