The ecology of foliar endophytic fungi in tropical plants

Foliar endophytic fungi live inside of leaf tissue without causing apparent harm to their hosts.  While endophytic fungi in some temperate grasses confer defensive benefits to their hosts, it is a subject of current debate whether fungi in woody plants defend plant tissue. Tropical woody plants host a high diversity of endophytic fungi, but little is known about their basic ecology.  We provide an overview of past and ongoing work concerning the interactions of foliar endophytic fungi with their host plants, pathogens, herbivores and decomposers in Panama.  This work has focused on two crop plants, Theobroma cacao Sterculiaceae and Cordia alliodora Boraginaceae, and one non-crop plant, Merremia umbellata Convolvulaceae. We have developed experimental techniques to create leaf tissue with high and low densities of foliar endophytic fungi. We use this system to explore questions such as: Do foliar endophytic fungi defend leaf tissues from infection by pathogens or consumption by herbivores?  Do leaf-cutting ants control which species of endophytic fungi are incorporated into their gardens? Do leaf decomposition rates depend on the densities of foliar endophytic fungi in their tissues?  The answers to these questions may have implications for tropical agriculture (i.e. biological control) as well as our basic understanding of plant-animal-environment interactions in tropical forests.