1 Citation 318 Views 32 Downloads
Many predatory insects that prey on herbivores also feed on the plant, but
it is unknown whether plants affect the performance of herbivores by
responding to this phytophagy with defence induction. We investigate
whether the prior presence of the omnivorous predator Macrolophus pygmaeus
(Rambur) on tomato plants affects plant resistance against two different
herbivore species. Besides plant-mediated effects of M. pygmaeus on
herbivore performance, we examined whether a plant defence trait that is
known to be inducible by herbivory, proteinase inhibitors (PI), may also
be activated in response to the interactions of this predator with the
tomato plant. We show that exposing tomato plants to the omnivorous
predator M. pygmaeus reduced performance of a subsequently infesting
herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not
of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The
spider-mite infested tomato plants experience a lower herbivore load,
i.e., number of eggs deposited and individuals present, when previously
exposed to the zoophytophagous predator. This effect is not restricted to
the exposed leaf and persists on exposed plants for at least two weeks
after the removal of the predators. The decreased performance of spider
mites as a result of prior exposure of the plant to M. pygmaeus is
accompanied by a locally and systemically increased accumulation of
transcripts and activity of proteinase inhibitors that are known to be
involved in plant defence. Our results demonstrate that zoophytophagous
predators can induce plant defence responses and reduce herbivore
performance. Hence, the suppression of populations of certain herbivores
via consumption may be strengthened by the induction of plant defences by
zoophytophagous predators.
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