EFFECT OF DISTANCE, AGGREGATION, AND HABITAT ON LEVELS OF SEED PREDATION FOR 2 MAMMAL-DISPERSED NEOTROPICAL RAIN FOREST TREE SPECIES

The effect of seed aggregation and distance from conspecific trees on seed predation was experimentally examined for two neotropical tree sp ecies, Macoubea guianensis (Apocynaceae) and Pourteria sp. (Sapotaceae ) in a lowland tropical rain forest in northeastern Peru. Results of t hese experiments are discussed in the context of the Janzen-Connell mo del (Janzen 1970; Connell 1971), which predicts decreased seed surviva l near parent trees due to either density- or distance-responsive mort ality, and Howe's model (Howe 1989) which predicts that trees with see ds dispersed in clumps (aggregated) will not suffer density-dependent predation, and will have higher survival of seeds near the parent tree than other trees. We also examined whether predation on seeds of thes e species was affected by seed placement in or near 30-m-wide strips r egenerating after clear-cutting. Both species appeared to be mammal-di spersed but differed in how frugivores handled seeds, seed size, overa ll fruit crop size, and gemination time. Neither of the two species st udied appeared to suffer seed predation in a manner predicted by the J anzen-Connell model, and patterns of seed predation for only one of th e species was similar to predictions of Howe's model. For neither spec ies did seed predation along the edge of, or in the center of, regener ating clear cuts differ from predation 15 m into the primary forest. F or Pouteria, seed predation in and near regnerating strips was signifi cantly greater than around forest trees, but the opposite pattern held for Macouben. Overall, seed predation was much greater on Macouben. T he difference in seed predation for these two species was most likely a result of differences in the types of seed predators that attacked t hese two species.