Pre- and post-dispersal seed predation in Tachigali versicolor (Caesalpiniaceae): effects of timing of fruiting and variation among trees

Abstract

Fruiting phenology, habitat types and proximity to conspecific fruiting adults may influence the degree of escape from pre- and post-dispersal seed predators. Successful predator escape by means of satiation is considered to be especially important for selection of masting and monocarpic reproduction in trees, such as exhibited by Tachigali versicolor, a tropical canopy tree. How pre- and post-dispersal predation rates varied with dispersal timing and among trees in T. versicolor was examined in young and old forests on Barro Colorado Island in Panama during a 4-mo period. Seeds were collected from above-ground traps to assess predispersal predation by bruchid beetles, and from quadrats on the ground to record predation and removal by terrestrial mammals. Proportion of seeds aborted varied greatly among trees (range 6–30 %, mean 16 %), and was especially high for trees on the edge of the island with fruiting conspecifics nearby during the early part of fruiting season. The proportion of seeds killed by bruchid beetles varied less among trees (14–25 %, mean 20 %), and remained constant throughout the fruiting season. Seeds on the ground were attacked mostly by rodents, and possibly by deer (26 % of all seeds and 43 % of intact dispersed seeds). The post-dispersal predation level was higher in the young forest than in the old forest (61 and 26 % of intact dispersed seeds, respectively), and was unaffected by the proximity of fruiting conspecifics. Temporal satiation of seed predators was evident only for post-dispersal mammalian predators in the old forest.