Fire Increases Insect Herbivory in a Neotropical Savanna

Fire is an important agent of disturbance in many tropical ecosystems that can potentially influence plant consumers. Nevertheless, there are few reports on whether levels of plant damage change as a result of fire. Here we present the results of a 1-yr study evaluating the effects of fire on rates of herbivory and damage by pathogens in leaves of cerrado (Brazilian savanna) tree species. Damage by leaf chewers was over two times greater in burned than in unburned trees. Levels of damage by leaf miners, leaf scrapers, galling insects, and leaf pathogens were relatively low and increased, remained the same, or even decreased as a result of fire. Nevertheless, in all three plant species studied, total herbivore damage was significantly greater in burned than in unburned trees given the preponderance of damage caused by leaf chewers compared with the other types of damage. Leaf chewers, mainly leaf-cutter ants, caterpillars, and grasshoppers, completely ate over 50 percent of the > 2000 leaves we marked in burned trees. That our results were consistent among different plant species with contrasting leaf phenologies suggests that the observed increase in herbivory is a general phenomenon in our study system. Because herbivore pressure is augmented dramatically in recently burned areas, herbivory may act synergistically with fire in influencing the structure of cerrado vegetation.