Dispersal of Melastome Seeds by Fruit-Eating Birds of Tropical Forest Understory

Birds directly affect seed dispersal through (1) the number of seeds they remove and (2) where and in what condition those seeds are deposited. Dispersal effectiveness is a composite of these quality and quantity components of seed dispersal. In this study, number of seeds removed and patterns of seed deposition by six bird species were determined for four shrubs in the Melastomataceae. Bird species differed in both quantity and quality components of seed dispersal. Bird species that contributed most to the quantity component of seed dispersal were not always the same as those that contributed most to the quality component. Thus, to evaluate the ecological roles of frugivores and their effectiveness as seed dispersers requires integration across various processes involved in seed dispersal (removal, deposition, etc.). In contrast to canopy trees, shrubs apparently have a relatively small set of seed dispersers, which makes them more vulnerable to the extinction of a seed disperser.