Plant-Herbivores

Plant-herbivore interactions have been implicated in shaping both the maintenance and origin of the high diversity of plants and the insects that feed on them. Our work on Inga has shown that leaves are well defended chemically, with each leaf containing 50% DW in hundreds of secondary metabolites. They also have extrafloral nectaries to attract predaceous ants, trichomes, and phenological defenses. As a consequence of this battery of defenses, insect herbivores are extremely specialized with most species only being able to feed on 1-3 Inga hosts. There is no phylogenetic signal for defenses, suggesting that there has been strong selection for closely related species to have evolved divergent defenses so that they will not share herbivores. Furthermore, because herbivores are specialized, they reduce the growth and survival of an Ingaspecies if it becomes dominant. As a consequence, neighbors are different in defenses, and local diversity is enhanced. We also are studying several species swarms with apparent insipient speciation to understand the role of herbivores in driving speciation and local habitat preferences. To address these questions, we monitor marked plants for Lepidopteran herbivores and plant growth and survival. All caterpillars are bar-coded. We use untargeted metabolomics (UPLC-MS/MS) to characterize secondary metabolites.