In tropical regions, vertebrate seed dispersal largely determines the distributions of many plant species, and the diversity of the local disperser community plays a major role in this relationship. We investigated seed removal of seven rainforest species on the island of Dominica, which has a low diversity of seed dispersers, as well as assessed the relative importance of the red-rumped agouti, Dasyprocta leporina, an introduced scatterhoarder, to seed removal rates. We recorded removal rates from 168 experimentally placed seed piles of six canopy tree species and one liana species that were either available to the entire seed remover community or placed within D. leporina exclosures designed to allow access to all seed removers except D. leporina. A model was constructed to test the fixed effects of exclosure treatment, island region, seed species, and proximity to forest edge on the predicted probability of a seed being removed from the forest floor.
Results/Conclusions
We found natural seed removal in Dominican rainforests after 13 days to be 47.3%, with 25.8% of removed seeds being taken by D. leporina. The predicted probability of a seed being removed was significantly higher for seeds available to the entire seed remover community than for those placed within agouti exclosures. Significant species preferences were found for all seed removers, and these species preferences were found to be significantly different between D. leporina and the rest of the seed remover community. Species preferences of D. leporina were likely due largely to seed mass, with D. leporina accounting for a larger proportion of the removal of species with large mean seed mass than species with smaller seeds. The removal rates presented here provide a novel insight into seed removal patterns in oceanic island systems with low seed-disperser diversity, and the influence of D. leporina on these removal rates provides evidence of an introduced scatterhoarder making a substantial contribution to the removal of seeds too large for much of the native seed remover community.
