Foliar Pathogen Incidence on Woody Seedlings Across a Tropical Forest Chronosequence

ABSTRACT Fungal pathogens affect seedling performance and mediate plant species coexistence in mature tropical forests. Yet the role of pathogens in driving tropical forest community dynamics during secondary succession has received little attention. To assess how pathogen incidence affects plant community assembly during tropical forest recovery, we recorded foliar fungal pathogen incidence on 6010 seedlings (5–200 cm tall) of 176 tree and 71 liana species along a chronosequence of 10 forest sites in Panama ranging in age from 9 to 129 years. We tested the hypotheses that pathogen incidence (a) increases with forest successional age, (b) increases with local species seedling abundance, (c) is greater for liana than tree seedlings, and (d) varies with tree species' life‐history strategy. Contrary to expectations, pathogen incidence was greatest in the youngest sites and decreased with increasing forest age. There was a positive relationship between pathogen incidence and site‐level seedling abundance, with this relationship being stronger in younger compared to older forest sites. Liana and tree seedlings experienced similar levels of pathogen incidence. Within tree species, pathogen incidence varied with species' position along the growth‐survival and stature‐recruitment trade‐offs. Fast‐growing species had lower pathogen incidence than slow‐growing species in the earliest successional sites. This trend reversed with increasing forest age. Our results highlight the need to consider both trade‐off axes of plant life‐history strategies when assessing biotic interactions. We suggest that pathogen pressure may contribute to successional seedling dynamics by providing a rare‐species advantage and by reinforcing ecological niches.