Predispersal predation of an understory rainforest herb Aphelandra aurantiaca (Acanthaceae) in gaps and mature forest

The opening of a canopy gap at Los Tuxtlas rainforest has an impact on populations of the understory herb Aphelandra aurantiaca: the ratio of recruited seedlings per reproductive individual is 1:17 in mature forest vs. gaps. Predation occurring before seed dispersal seems a plausible explanation for this observed difference. In a field experiment, in which insecticide was applied to plants growing in gaps and mature forest, we evaluated the extent to which herbivore damage to flowers, fruits, and seeds reduces the number of seeds available for seedling establishment. Under natural conditions, ∼30% of the flowers and >70% of the capsules of A. aurantiaca showed herbivore damage, but its impact changed depending on the type of forest habitat. Flower and fruit herbivores caused more damage in closed forest than in gaps, and this difference was even bigger under the insecticide treatment. Insecticide effectiveness varied depending on the type of forest patch. The highest herbivore impact on seeds was found in the mature forest without insecticide treatment, where most seeds were destroyed. The percentages of seed damage reported here show that predispersal predation is limiting seedling recruitment, especially in mature forest. Other possible explanations might be differences in insect composition, densities, and behavior between gaps and mature forest.