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Abstract
Gaining a greater understanding of how aquatic invertebrates are environmentally controlled has proven challenging. Batzer (2013) examined invertebrate ecology in freshwater wetlands across North America and concluded that assemblage controls are commonly weak or operate inconsistently. It is vital that we better understand those factors affecting aquatic invertebrates so that we can anticipate how these organisms are likely to respond to climate change. Wetland researchers frequently attribute invertebrate assemblage variation to spatial or temporal factors (location, hydrology, water quality, plant communities, and predation). When I partitioned the variation of three large wetland datasets (North Dakota prairie potholes, California rock pools, and Georgia Carolina bay wetlands) into spatial, temporal, and unexplained components, variation that was explained by spatial and temporal factors and unexplained variation were of comparable magnitudes (i.e., similar R2 values of ~ 50%). To understand what might contribute to the currently unexplained variation, that is unrelated to spatial and temporal controls, I focused on the Georgia Carolina bay wetland data and assessed patterns of secondary succession. I found that non-successional wetlands tended to be smaller and drier, while successional wetlands were larger and wetter. I found that in those wetlands where annual variation was significant, assemblages changed individualistically following unique trajectories rather than changing in similar ways. However, assemblages in all successional wetlands appeared to reach a compositional threshold that, once reached, resulted in a return towards a regional central tendency in assemblage composition. This range standard may serve as a useful guide when using invertebrate assemblages to assess wetland condition and potential non-natural changes, i.e., assemblages developing outside this natural range of variation are likely aberrant.