Abundance and Diversity of Adult Flying Insects in Two Altamaha River Floodplains with Differing Hydrology

Large rivers are characterized by predictive flood pulses that link floodplains to river channels. In recent years this flow regime in the Altamaha River floodplain has been interrupted by droughts. To determine the influence of flooding on adult insect abundance and diversity, insects were collected by light traps in two sites (flooded vs. non-flooded) in October 2012. Ten insect orders accounting for 1,259 individuals were collected at the flooded site while only seven insect orders accounting for 244 individuals were collected at the non-flooded site. Among the orders represented Lepidoptera, Coleoptera, and Diptera, in decreasing order of abundance, accounted for most of the insect community. There were also differences in the abundance of insects with an aquatic life stage between the two sites. These differences were highlighted by Lepidoptera (37 individuals in flooded vs. 1 individual non-flooded) and Tricoptera (73 individuals in flooded vs. 7 individuals non-flooded). Our findings suggest that drought events can impact the abundance and diversity of adult insects in southeastern floodplains. Furthermore, these effects can negatively impact aquatic-terrestrial linkages.