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The emission of herbivore induced phytochemicals and their effect on the insect community of Nicotiana attenuata in natural populations.
Kessler, André*,1, Baldwin, Ian*,1, 1 Max-Planck-Institute for Chemical Ecology, Jena, Thuringia, Germany
ABSTRACT- Herbivore attack causes plants to release volatile phytochemicals that can function as attractants for predators or parasitoids of herbivores and potentially influence plant fitness. However, while a majority of the previous work has focused on genetically uniform crop plants and genetic variation in the volatile organic compound (VOC) emission is well described, the ecological relevance of induced emissions for natural plant populations remains unclear. We present a repeatable, quantitative method for the collection of VOCs from the headspace of Nicotiana attenuata plants growing in natural populations. Different natural herbivores were used to elicit VOC emission to evaluate the signaling function of that emission for natural enemies of the herbivores. On wild growing N. attenuata we tested the attractiveness of singly applied VOCs for natural occurring predators and found that the 5 to 10 fold higher emission of certain compounds (cis-3-hexene-1-ol, cis-3-hexenyl butyrate, linalool, bergamotene) and the application of methyl jasmonate (MeJA) can increase predation of Manduca sexta eggs and 1st instar larvae by Geocoris spec.(Heteroptera). Moreover we tested the effect of "doping" plants with single VOCs for their effect on ovipositing adult Manduca quinquemaculata. The moths avoided ovipositing on plants with increased linalool emission and on plants treated with MeJA or attacked previously by caterpillars. The plant not only mediates the described tritrophic interactions but also competitive interactions between the leaf bug Tupiocoris notatus and M. quinquemaculata. Our results demonstrate how induced VOCs are used by both the herbivore and its generalist predator and hence are capable of influencing the composition of N. attenuata's herbivore community.
Key words: predator-prey-interaction, plant-herbivore interaction, plant induced responses, Nicotiana attenuata