Seed traits, not density or distance from parent, determine seed predation and establishment in an Afrotropical forest

Abstract

AbstractSeed predators drive patterns in seed mortality and seedling establishment and are posited to contribute to the maintenance of plant species diversity through several mechanisms. Negative density dependence and spatially restricted recruitment are apparently widespread in Neotropical forests, but are little studied in Afrotropical forests, where generalist vertebrates may contribute more to seed mortality than do specialized invertebrates and fungi. We experimentally assessed the roles of seed density and distance from the parent tree for ten tree species in a forest in northeastern Gabon, using exclosures to isolate the effects of different seed predator types. Vertebrates caused greater seed losses than all other mortality agents combined. Unexpectedly, seeds under fruiting conspecific trees had significantly lower removal and higher seedling establishment than those under heterospecific trees or in neutral non‐fruiting locations. Seed density did not significantly affect seedling establishment. Vertebrate seed removal ranged from 0 percent to 100 percent among focal species and was positively correlated with seed mass but had no relationship with species commonness (adult tree density). Seed traits strongly affected patterns of seed removal and seedling establishment and may contribute more to the likelihood of success for an individual seed than do its density or distance from parent. Our results highlight an apparent divergence in patterns of seed mortality and seedling establishment between tropical forest regions and emphasize the need for further comparative study.