Collaborative Research: Dimensions US-Biota Sao Paulo: Chemically mediated multi-trophic interaction diversity across tropical gradients

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This research will examine the diversity and ecological complexity of plants and associated insects in forests across a variable landscape in Brazil. Plants, insects, and their predators make up over half of all known organisms, and their interactions are essential to ecosystem health. This is especially true for tropical forests, where ecologists are only beginning to understand the nature and complexity of these interactions. In particular, little is known about: 1) the diversity of plant chemicals that deter insect herbivory and affect other plants and animals, 2) how diversity of these plant chemicals varies within and between plant species, and 3) how plant chemistry can affect the diversity and productivity of entire forests. Recent advances in chemistry and molecular biology provide the opportunity to understand the diversity of plant-insect interactions at three different levels (chemical, genetic, and taxonomic) with unprecedented scope and depth. These new methods will be integrated and enhanced by a unique team of U.S. and Brazilian scientists to investigate the diversity of insect-plant food webs, how they are shaped by plant chemical defenses and environmental gradients, and how this diversity affects forest stability and productivity. The research will contribute to understanding how large global changes in biodiversity and climate will affect plant-insect-predator interactions, how plant genetic and chemical diversity influences plant-feeding, and how taxonomic and genetic diversity of insect predators can affect control of harmful insects. The comprehensive sampling and methods used in this project will result in the discovery of new species of plants and insects, new biologically active molecules, and are likely to deliver new tools and approaches that have powerful applications in agriculture and medicine. This international and multi-disciplinary research project will have broad impacts by involving K-12 students, science teachers, and citizen scientists. Discoveries will be widely communicated to the public via websites, and scientific and popular publications. This project is focused on a highly diverse system involving plants in the genus Piper (Piperaceae), associated herbivores, and parasitic wasps and flies. The research will utilize cutting edge approaches to studying biodiversity that link measures of interaction diversity to genetic diversity, population genetic structure, and plant chemical diversity involving the following components: 1) Large scale sampling of herbivores and their parasitoids on diverse Piper species across an array of sites to assess effects of abiotic gradients on community structure and ecosystem processes, and to acquire specimens for taxonomic, genomic, and phytochemical analysis. 2) Field experiments where taxonomic, genetic, and functional diversity will be manipulated along with abiotic factors to strengthen inferences from statistical analysis of field surveys, community genetics, and measures of metabolite diversity. 3) Taxonomic and systematic analysis of plants, herbivores, and parasitoids using traditional and novel methods (genomics) to document and describe new taxa, understand their relationships, and reveal cryptic diversity. 4) Population genomic analyses of plants, herbivores, and parasitoids to understand how geography, plant phylogeny and chemistry influence population structure and genetic differentiation across trophic levels. 5) Characterization of metabolite diversity of Piper species; how metabolite diversity varies with phylogeny, ecology, and herbivore pressure; and the effect of phytochemical diversity on higher trophic levels. The combination of quantitative sampling along elevational gradients, newly developed metabolomics methods, population genomics, and a large scale experiment will make possible tests of emerging hypotheses about relationships between plant chemistry, and different dimensions of diversity, and will represent the first large scale, among-site plant-herbivore-parasitoid food-web comparison in the tropics.