Data and code from: The functional form of specialized predation affects whether Janzen-Connell effects can prevent competitive exclusion

Janzen-Connell Effects (JCEs), specialized predation of seeds and
seedlings near conspecific trees, are hypothesized to maintain species
richness. While previous studies show JCEs can maintain high richness
relative to neutral communities, recent theoretical work indicates JCEs
may weakly inhibit competitive exclusion when species exhibit
inter-specific fitness variation. However, recent models make somewhat
restrictive assumptions about the functional form of specialized predation
-- that JCEs occur at a fixed rate when offspring are within a fixed
distance of a conspecific tree. Using a theoretical model, I show that the
functional form of JCEs largely impacts their ability to maintain
coexistence. If predation pressure increases additively with adult tree
density and decays exponentially with distance, JCEs maintain considerably
higher species richness than predicted by recent models. Loosely
parameterizing the model with data from a Panamanian tree community, I
elucidate the conditions under which JCEs are capable of maintaining high
species richness.