Evidence for insect seed predator dynamics mediated by vertebrate frugivores
Vertebrate frugivores have been suggested to reduce seed predation, indirectly controlling populations of insect seed predators (ISP) by means of consuming many individuals when feeding on fruits. The possibility has not been explored, however, that this 'frugivore predation' may differentially affect ISP according to species-specific differences in larval development time within the fruit. In the dry tropical forest trees Acacia pennatula and Guazuma ulmifolia we compared seed predation and the absolute and relative abundances of bruchid beetle species (Bruchinae) in two sites, one with large frugivores (cattle) and the other cattle-free for a considerable time. In the site with cattle we found a notable overall reduction in the proportion of seeds predated (ca. 15 %) with respect to cattle-free site, and changes in the ISP community as well, in particular a reduced absolute and relative abundance of the bruchid species with the longest larval development time. Our results suggest that the interplay between evolutionary processes (resulting in variation in insect life-histories) and complex ecological interactions (inadvertent consumption by larger animals) may contribute to the coexistence of different insect species feeding upon the same host plant.