SEED REMOVAL AND SEED FATE IN GUSTAVIA-SUPERBA (LECYTHIDACEAE)

The fate of the large (mean 12.6 g) seeds of Gustavia superba, an understory tree, was analyzed on Barro Colorado Island (BCI), Panama. Eight hundred thread-marked seeds were placed on the ground at two contrasting 1-ha forest sites (Gustavia-rich vs Gustavia-poor) during two periods (June and July) of the fruiting season of G. superba. These months correspond to maximum food availability on BCI. On average, 85.5 percent of the seeds were removed within 28 days, 47.5 percent and 3.8 percent of them being found scatterhoarded (buried) by agouti (Dasyprocta punctata) and gnawed by rodents, respectively, within 10 m of their origins. The effect of site and the interaction of site with month significantly affected seed removal rates, but not scatterhoarding rates. Proportions of seeds removed were greater where G. superba trees were rare. Because freshly fallen seeds were not infested by bruchid weevils, unburied and germinating seeds provide an abundant short-term food supply for terrestrial mammals. Burying seeds allowed agoutis to later consume cotyledons of germinating seeds from mid-August throughout October, when food is scarce on BCI. Overall seed dispersal effectiveness (% seed dispersal multiplied by % seedling survival) contrasts dramatically between forest sites, being 10. 1 percent and 0.75 percent at Gustavia-rich and Gustavia-poor areas, respectively. This result suggests that predator-disperser satiation occurred, maybe due to greater G. superba seed availability and other alternative food supply, allowing greater G. superba seedling survival at the Gustavia-rich area.