Predicting the long-term effects of hunting on plant species composition and diversity in tropical forests

Hunting can change abundances of vertebrate seed predators and seed dispersers, causing species-specific changes in seed dispersal and seed predation and altering seedling communities. What are the consequences of these changes for the adult plant community in the next generation and beyond ? Here, I derive equations showing how reduced seed dispersal reduces plant reproduction by intensifying kin competition, increasing vulnerability to natural enemies, and reducing the proportion of seeds passing through disperser guts. I parameterize these equations with available empirical data to estimate the likely effects on next-generation abundances. I then consider the indirect effects and longer-term feedbacks of changed seed or adult abundances on reproductive rates due to density-dependent interactions with natural enemies and mutualists, as well as niche differentiation with competitors, and discuss their likely qualitative effects. The factors limiting seed disperser and seed predator populations in natural and hunted forests emerge as critical for determining the long-term effects of hunting on rates of seed dispersal and seed predation. For example, where seed dispersers are held to a constant abundance by hunters, decreases in the availability of their preferred food plants are expected to lead to increased per-seed dispersal probabilities, potentially to the point of compensating for the initial disperser decline. I close by discussing the likely reversibility of hunting-induced changes in tropical forests and key questions and directions for future research.