The impact of vertebrate predators on wetland macroinvertebrate communities

The influence of fish on aquatic invertebrate communities through the mechanism of trophic cascades has been well documented. Wellborn et al. (1996) described a permanence/predator model where lentic waters were divided into three habitat categories. The first category is reserved for temporary water habitats which exclude fish, leaving invertebrates or amphibians as the top predators. The invertebrate community is dominated by members that have fast development times or drought-resistant capabilities. The second category involves permanent water habitats that exclude fish, leading to a large, active invertebrate community with invertebrates as the top predators. The final category includes permanent waters with fish, whose presence drives the invertebrate community to consist of morphologically smaller, relatively inactive members who are able to escape detection by fish. Large invertebrate predators are generally absent from these habitats. Batzer et al. (2006) added a fourth habitat called temporary waters with fish, referring to tidal salt marshes and riverine floodplains where fish are occasionally present. This invertebrate community would have members that are drought-resistant or able to disperse via flood waters. Fish used for control of mosquitoes can have negative impacts on non-target invertebrates. Many of the fish species that dominate wetlands are smaller in body size and coexist with large invertebrate predators. This pattern has been shown to occur in the Okefenokee Swamp, but it has not been tested elsewhere. Furthermore, studies have shown that the amphibian predators may have significant effects on invertebrate communities in the absence of fish. The impacts of vertebrate predators on wetland invertebrate community structure are varied and require further investigation.