HABITAT SIZE AND ISOLATION AFFECT COLONIZATION OF SEASONAL WETLANDS BY PREDATORY AQUATIC INSECTS

Abstract

Despite the evidence for the importance of predation in structuring ephemeral aquatic communities, there is relatively little information on what controls predator species and their densities in these systems. Most predators do not complete their life cycle in ephemeral aquatic systems, thus colonization processes may have a strong effect on the patterns of predation in these communities. I used an artificial pond experiment and surveys of vertebrate and invertebrate species in a system of natural ephemeral pools to study the effect of habitat size and isolation on the colonization patterns of predatory aquatic insects. Artificial pond experiments demonstrated that the two main predatory aquatic insect taxa in ponds were affected by the size and isolation of the pond from semipermanent wetlands. The effect of pond size was nonlinear, fitting a saturating function with size, and it interacted with isolation in determining predator density. These effects of size and isolation may explain some of the invertebrate community differences that are not explained by hydroperiod or food resources. However, data from surveys of natural pools point to the complexity of factors controlling the density of predators in seasonal aquatic habitats. The final pattern of predator density may represent a combination of dispersal patterns, life history limitations, prey abundance, and predation pressure.