Top-down cascading effects of seed-feeding beetles and their parasitoids on plants and leaf herbivores

When feeding on a plant, herbivorous insects alter the quality of the plant as a food source. This affects other organisms interacting with the same plant. These so-called ‘plant-mediated interactions’ can be altered by parasitoids that attack the herbivores. So far, this research area has mainly focused on interactions at the leaf level, and very little is known about plant-mediated interactions via seeds. It is still poorly understood if seeds that survive insect damage have fewer resources to allocate to plant growth and defence against leaf herbivores, and whether parasitoids that kill seed-feeding insects mitigate such negative effects.
Using seeds of wild lima bean plants (Phaseolus lunatus) we studied the effect of the intensity of infestation by seed beetles (Zabrotes subfasciatus) and their parasitoids (Stenocorse bruchivora) on the following parameters under lab conditions: seed mass and germination, plant growth and defensive compounds (cyanogenic glycosides and flavonoids) a...