Fire mediated herbivory and plant defense of a neotropical shrub

Abstract

Changes in morphological and physiological features of plants after fire events can modify their attractiveness to herbivorous insects. Our goal was to assess the effects of fire on plant–insect interactions and the development of induced defenses in the shrub Bauhinia brevipes (Fabaceae). We hypothesized that resprouting plants of B. brevipes after a fire occurrence would be more susceptible to herbivory by leaf-chewing and the gall-maker Schizomyia macrocapillata Maia (Diptera: Cecidomyiidae) than non-resprouting plants. We analyzed leaf area, leaf damage caused by chewing insect herbivores and attacks by the gall-midge S. macrocapillata, hypersensitivity response, chlorophyll content and silicon content after a fire event. Resprouting plants presented greater leaf area; higher chlorophyll concentration; hypersensitivity response and greater leaf silicon content. Although these plants experienced a greater number of attacks by S. macrocapillata the greater investment in growth and photosynthetic capacity, and possible leaf nitrogen content, can be determining attractiveness to a range of herbivores specifically galling insects. Leaf silicon content can be related with the lower damage by chewing insects, even with the greater vigor of resprouting plants. Thus, our results are contrary to some previous studies that report increases in leaf herbivory by chewer insects after fire events. Increases in hypersensitive response and silicon content seem to alter herbivorous insect preference and performance after fire occurrence.