Ecogenomic approach to the role of herbivore-induced plant volatiles in community ecology

1 Linking new developments in genomics with ecology provides interesting novel tools to address ecological questions in ways that have not been possible up to now. In this paper we address this issue for the ecology of infochemicals and plant-insect interactions in a food web context. 2 Plants are at the basis of most terrestrial food webs and insects are a dominant animal group interacting with plants. Insect-plant communities are characterized by direct and indirect interactions, many of which are mediated by infochemicals. Plants respond to insect herbivory with the production of volatiles that attract the enemies of the herbivores, such as insect predators and parasitoids. Moreover, the plant volatiles may be exploited by any organism in the environment and this results in many more infochemically mediated interactions. Thus, a food web is overlaid with an infochemical web. 3 In the past, several manipulative tools have been developed to investigate the role of infochemicals. The rapid advancement of molecular genetics and '-omics' technologies results in interesting new tools. A recent development is the use of well-characterized genotypes that are modified in the mechanisms underlying the induced plant volatiles. These genotypes produce precisely manipulated phenotypes that often differ in only a single gene, and can be used to investigate the effect of particular genes on specific interactions. Moreover, these genotypes can be introduced into a natural community to assess the effects of the genetic change and its resulting phenotypic change on interactions with the entire natural community. 4 Furthermore, with the progress in microarray technology it becomes possible to assess the expressed genotype of plants in the field, which can be exploited to investigate expressed genetic variation under field conditions. 5 These developments are expected to be only the beginning of a successful integration of -omics technologies, such as transcriptomics and metabolomics, with community ecology into the new research field of ecogenomics. 6 In this review we present the current status and discuss the prospects for the future of an ecogenomic approach to the role of herbivore-induced plant volatiles in insect-plant community ecology.