Most flowering plants rely on insect pollinators to take care of their reproduction. However, to be able to reproduce plants also need to survive the battle against plant-feeding insects. Plants must, therefore, balance the investments in defences against their attackers with investments in growth/reproduction. The aim of this research was to investigate how plants deal with defences against herbivores, while maintaining interactions with beneficial insects, such as pollinators. Results show that Black Mustard plants (Brassica nigra) can defend themselves against the voracious caterpillars of the Large Cabbage White butterfly, Pieris brassicae, while preserving interactions with carnivores and pollinators. Remarkably, mustard plants sped up reproduction in response to butterfly egg deposition, and compensated for damage caused by the herbivores. This accelerated seed production benefits the plants because caterpillars consume flowers, but not seeds. Seed production could, however, only be sustained when interactions with pollinators and carnivores were maintained. In fact, in the absence of carnivores, plants suffered from herbivory. The data presented in this thesis support the importance of carnivores as a component of a plant’s defence strategy, and revealed the underlying mechanisms that allow this short-lived plant from the cabbage family to balance investments between defence and reproduction.
- Accelerated reproduction in response to insect egg deposition can lead to plant fitness benefit. (this thesis)
- We underestimate the importance of generalist predators in reducing herbivore pressure. (this thesis)
- Loss of biodiversity is as bad as the loss of ecological interactions between species.
- Transgenic food stimulates large monoculture production, and thus poverty.
- Scientists should place the discovery in the centre rather than themselves.
- A key challenge in leadership is to inspire people to perform better than they believe they can do.
- To make progress we should dare to fail.