How do different empirically derived patterns of natural enemy attack and seed dispersal affect patterns of seedling recruitment?

Seed dispersal and mortality due to natural enemies are important in determining the pattern of seedling recruitment. Seed dispersal establishes the spatial template that determines future local interactions; natural enemies alter this initial pattern. Seed deposition patterns vary with dispersal mode and fecundity. Natural enemies, such as mammals, insects, and pathogens, vary in their distribution from source plants and in their functional and numerical responses. We use models parameterized from literature data to investigate how seed dispersal and natural enemy attack together affect patterns of seedling recruitment around a parent plant. Seeds first disperse from a parent tree according to dispersal kernels that represent dispersal by animals, wind, or gravity. Mortality due to mammals, insects, and/or pathogens then follows with patterns of enemy spread, attack, and increase varying depending on the type of enemy. For example, seed mortality due to mammalian and insect seed predators depends on the number of predators relative to the number of seeds, while mortality due to pathogens depends on the absolute density of pathogen propagules. The seedling recruitment patterns observed in the model reproduce the range of patterns observed empirically. We find that recruitment patterns are very sensitive to the type of natural enemy attack and the movement distances of natural enemies, as well as to seed dispersal modes and distances. We discuss the importance of accurately describing seed dispersal and natural enemy attack to develop a better understanding of recruitment patterns and the mechanisms that structure plant communities.