Effects of Foliar Endophytic Fungi on the Preference and Performance of the Leaf Beetle<i>Chelymorpha alternans</i>in Panama

ABSTRACT Foliar endophytic fungi live inside healthy plant leaves, and in some cases they confer herbivore resistance to the host. All previous studies of endophyte–herbivore interactions have occurred in temperate areas, and many use correlations rather than experiments. In Panama, Glomerella cingulata is a common endophyte species found in healthy leaves, and Chelymorpha alternans is a common herbivore on Merremia umbellata , a tropical vine. We manipulated the abundance of G. cingulata in the leaves of M. umbellata . We then assessed the effects of high and low endophyte densities on the food choice, development, and reproductive success of the leaf beetle, C. alternans . In ‘choice’ experiments, adult females with a history of feeding on wild plants showed no preference when offered food plants with high and low endophyte densities. Further, in ‘no‐choice’ experiments, C. alternans larvae that were fed high‐ or low‐density endophyte leaves did not differ in development or survivorship. However, when larvae fed on leaves with low endophyte densities became adults, they produced 80 percent more offspring. This suggests high endophyte levels in hosts can have a negative effect on herbivore fecundity. Further experiments are necessary to understand whether the reproductive effects are due to feeding on low‐density endophytes in the larval or adult stages, and whether changes in reproductive success are motivated by the adult's perception of food quality or by physiological constraint due to food quality.