Seed mass, seedling herbivory and the reserve effect in tropical rainforest seedlings

1. The seedlings of larger-seeded species typically perform better than those of smaller-seeded species in the face of a variety of hazards. One mechanism that might explain this general pattern is the reserve effect, where larger-seeded species commit a smaller proportion of their initial seed reserves to seedling construction, keeping a greater proportion in reserve to sustain seedlings during times of resource deficit or imposed hazards. 2. This study tested two hypotheses: (1) that seedlings of larger-seeded rainforest species can resprout more often, following simulated herbivory, than those of smaller-seeded species; and (2) that any such correlation is consistent with the reserve effect. 3. To test these hypotheses we grew the seedlings of 15 rainforest species with hypogeal storage cotyledons in a shade house, excised the initial shoot, and sequentially clipped each resprout. Previous work had demonstrated a reserve effect among these species. 4. The first hypothesis was proved true: seedlings of larger-seeded species resprouted significantly more often than those of smaller-seeded species. 5. The second hypothesis was proved false: although large-seeded species resprouted more often, the total mass invested in resprouts scaled isometrically with seed mass across species. The reserve effect predicted that total resprout mass should have scaled more than proportionately with seed mass. 6. This study adds to a growing body of work demonstrating that the seedlings of larger-seeded species often perform better than those of their smaller-seeded counterparts. However, the results presented here are at odds with the view that the reserve effect might be a common mechanism explaining this pattern.