Prey (Moina macrocopa) population density drives emigration rate of its predator (Trichocorixa verticalis) in a rock-pool metacommunity

Dispersal connects spatially separated local food webs at a larger, metacommunity scale, and as a result, dispersal may both influence and be influenced by local food-web dynamics. Here, I focused on a rock-pool metacommunity and used a combination of observational, experimental, and theoretical approaches to explore the role of local prey (Moina macrocopa) density on the rate of emigration by their predator (Trichocorixa verticalis) and in turn, the effect of predator emigration on the per capita predation rate experienced by local prey populations. A lab feeding experiment quantified predation rates, demonstrating that indeed adult T. verticalis are voracious predators of M. macrocopa. M. macrocopa densities vary over five orders of magnitude across both space and time in rock pools, and a mesocosm experiment showed that this variation significantly influences T. verticalis emigration: predators emigrated more rapidly when prey were in lower densities. Finally, computer simulations demonstrated that this pattern of dispersal by T. verticalis has the potential to relieve local M. macrocopa populations from predation when the prey are at low densities, thereby reducing the likelihood that local M. macrocopa populations will be driven extinct by predation from T. verticalis.