Cross-boundary Subsidy - Relation of Cross-boundary Subsidies To Selected Ecological Concepts - Biotic Interactions and Trophic Structure - Trophic Cascade

Trophic Cascade

In subsidizing top trophic levels, effects may also be felt at all lower trophic levels in a phenomenon known as a trophic cascade. An example of a trophic cascade that also acted as a cross-boundary subsidy is illustrated in a study by Knight et al. (2005) in which changes in the trophic structure of one ecosystem resulted in an effect that cascaded to the adjacent ecosystem. In ponds containing fish, dragonfly larvae were kept to a minimum by fish predation. The resulting low density of adult dragonfly predators led to a high density of bee pollinators. With fish present in adjacent ponds, bees were able to pollinate more flowers in the adjacent upland ecosystem than they were when fish were absent. The dragonfly population could be thought of as subsidized by the absence of fish predation. That subsidy was then transferred across the pond-upland boundary by adult dragonfly movement to affect the interaction between bee pollinators and plants.