Understanding the mechanisms that determine community structure is fundamental to predicting the consequences of species loss and introductions. For example, egg-laying females must decide where to oviposit across a gradient of habitats with varying quality. This decision is crucial to both the resultant community structure of a habitat, and to the female’s realized fitness.
The presence of predators, native and introduced, is a key factor driving community assembly, often by reducing population sizes of prey through deterrence (i.e. indirect predation effects). But not all predator-free habitats are the same. Deterrence in one habitat may extend to nearby habitats that are predator-free, and thus “high fitness”, but which are close enough to habitats with predators that they are avoided by ovipositing insects (i.e. spatial contagion of predation).
We are testing whether proximity to predator habitats affects colonization of aquatic mesocosms. We are manipulating monocultures and polycultures of native (gomphid dragonflies) and non-native (brown trout) predators, which allows us to examine both landscape effects of predator location, and interactive effects of single vs. multiple predators on community assembly.