What omnivores don't eat Nonconsumptive ecological effects of phytophagy by Macrolophus pygmaeus

It has been shown that omnivorous predators can induce plant defences when feeding on plants, affecting the performance of herbivores. This thesis shows the ecological consequences of plant responses induced by the omnivorous predator Macrolophus pygmaeus in a community of plants, herbivores and their natural enemies. I show that the omnivore induces direct plant defences in sweet pepper plants, which negatively affects the performance of two of three of its prey: spider mites and thrips, but not of aphids. Moreover, I found that spider mites and thrips preferred clean plants over plants previously exposed to the omnivore. Aphids did not show such preference, but a higher proportion of aphids left exposed plants than unexposed plants. Furthermore, plant feeding by the omnivore induced the production of plant volatiles, which attracted a predatory mite even when its prey was absent, showing that the plant response to omnivore feeding may interfere with the searching behaviour of this important natural enemy. Given experience with plants exposed to the omnivore, predatory mites showed equal attractiveness to exposed and unexposed plants, hence, they can learn not to respond to omnivore-induced plants. Lastly, I show that the omnivore affects plant phenology, resulting in a reduced number of flowers, but increased seed production. These changes were not beneficial for the omnivore, whose survival and development was positively related with the number of flowers. Thus, plant responses induced by plant feeding by the omnivorous predator affect interactions among omnivores, plants, herbivores and natural enemies.