Predator-prey body size relationship in temporary wetlands: effect of predatory insects on prey size spectra and survival

The effect of predators on prey size structure in aquatic communities has been well studied in lentic permanent habits, but less attention has been placed on temporary environments. The biota of seasonal Andean wetlands in Patagonia is basically formed by crustaceans, insects and pond-breeding amphibians. The dominant predators in these wetlands are macroinvertebrates, mostly aquatic insects. The main objectives of this study were to examine the seasonal and interannual variation in the body size of prey and predators in two temporary wetlands located in northwest Patagonia, during two consecutive hydroperiods and to evaluate the effect of different insect predators over different prey sizes and different ontogenetic stages of invertebrate and vertebrate prey. Prey size structure and predator size structure were affected by the wetland type and the sampling months and predator body size was not correlated with prey size structure. The experiments showed that small prey were the most impacted by predaceous insects and all predators showed size-limited predation. Although aquatic insects significantly reduced the number of prey in the predation experiments, they did not significantly affect the body size structure of prey in nature. In this sense, the diversity of aquatic insects with different predatory strategies could maintain the heterogeneity in prey size structure in the wetlands studied.