Potential Effects of Host Height and Phenology on Adult Susceptibility to Foliar Attack in Tropical Dry Forest Grass

Identifying the sources of variation in plant susceptibility to herbivore and pathogen attack is critical to understand ecological processes determining species abundance and diversity in tropical forests. We assessed the potential effect of tiller height and phenology on standing levels of herbivore and pathogen damage on adults of the woody perennial grass Lasiacis ruscifolia in the tropical dry forest of Chamela, Mexico. Analyses revealed that adult susceptibility to pathogens was greater in small and fruiting tillers than in taller and leaf flushing tillers. Adult susceptibility to herbivores, on the other hand, varied greatly among plants and had no relationship with tiller height and phenology. Our findings suggest that adults highly susceptible to pathogen attack could augment the negative density and distance dependence effects predicted by the Janzen-Connell hypothesis, with potential consequences for the local distribution of the studied species in the forest.