Jasmonate-mediated induced plant resistance affects a community of herbivores

1. The negative effect of induced plant resistance on the preference and pe rformance of herbivores is a well-documented ecological phenomenon that is thought to be important for both plants and herbivores. This study links th e well-developed mechanistic understanding of the biochemistry of induced p lant resistance in the tomato system with an examination of how these mecha nisms affect the community of herbivores in the field. 2. Several proteins that are induced in tomato foliage following herbivore damage have been linked causally to reductions in herbivore performance und er laboratory conditions. Application of jasmonic acid, a natural elicitor of these defensive proteins, to tomato foliage stimulates induced responses to herbivory. 3. Jasmonic acid was sprayed on plants in three doses to generate plants wi th varying levels of induced responses, which were measured as increases in the activities of proteinase inhibitors and polyphenol oxidase. 4. Field experiments conducted over 3 years indicated that induction of the se defensive proteins is associated with decreases in the abundance of all four naturally abundant herbivores, including insects in three feeding guil ds, caterpillars, flea beetles, aphids, and thrips. Induced resistance kill ed early instars of noctuid caterpillars. Adult flea beetles strongly prefe rred control plants over induced plants, and this effect on host plant pref erence probably contributed to differences in the natural abundance of flea beetles. 5. The general nature of the effects observed in this study suggests that i nduced resistance will suppress many members of the herbivore community. By linking plant biochemistry, insect preference, performance, and abundance, tools can be developed to manipulate plant resistance sensibly and to pred ict its outcome under field conditions.