A Comparison of Dipterans from Ten Created and Ten Natural Wetlands

This study compares densities of common larval dipterans collected from areas dominated by Pontederia cordata in 10 natural and 10 created freshwater herbaceous wetlands in central Florida. At each wetland, 7 core. samples were collected from each of 5 stations during summer 1993. In addition, stem densities, vegetation areal coverage, pH, dissolved oxygen, water temperature, water depth, conductivity, sediment quality, and leaf litter were measured at 3 locations near each of the 5 stations in each wetland. Of the 57 dipteran taxa collected, 20 occurred with sufficient abundance to justify statistical comparison. Despite a large sampling effort, there were no significant differences in densities of 20 commonly occurring taxa found in created and natural wetlands after considering the effect of multiple univariate tests. Comparison of environmental variables showed significant differences in stem densities for vegetation other than P. cordata,, pH, conductivity, and sediment quality. Canonical correspondence analysis, used to relate environmental and biological variables, suggests that pH, conductivity, and sediment quality are only weakly related to dipteran community structure. Despite differences in environmental conditions, there is no convincing evidence of differences in natural and created wetland dipteran communities

Chironomidae (Diptera) and Vegetation in a Created Wetland and Implications for Sampling

Although invertebrate communities are used in the evaluation of created freshwater wetlands, spatial patterns of invertebrate community structure are frequently ignored. Invertebrate distributions are generally associated with plant community distribution in natural aquatic ecosystems. In this study, 180 core samples were collected to examine associations between chironomid (Diptera) genera and emergent vegetation communities in a single created freshwater herbaceous wetland in central Florida. Three of the five common genera were significantly more abundant (p \u3c 0.05, Wilcoxon Rank Sum Test) in areas with greater than 50% cover by emergent vegetation than in open water, but no differences were found between areas dominated by Pontederia cordata and areas dominated by mixed emergent vegetation. Samples from an area of open water and an area with over 80% cover by P. cordata showed significant differences in abundances of all common chironomid genera (P \u3c 0.05, Wilcoxon Rank Sum Test). Results suggest that sampling designs for studies comparing benthic invertebrate communities from natural and created wetlands should consider the possible associations between vegetation and invertebrate communities