Benefits and costs of Leptophlebia (Ephemeroptera) movements between river channels and floodplain wetlands

Linkages between river channels and floodplain wetlands are important for organisms in each habitat, but especially for species that use both habitats. Nymphs of certain mayflies undergo seasonal movements into floodplains. High abundances of leptophlebid nymphs have been observed in Southeastern US floodplains, but how and why they colonize and develop in these temporary habitats has not been established. The benefits and costs of Leptophlebia mayfly movements into temporary floodplain wetlands were studied through descriptive observations and field experiments. While mayflies actively migrated into floodplains, few environmental (i.e. temperature, predation, food quality or abundance) advantages were apparent in wetland compared to river habitats. Despite this, mayflies had higher wetland growth rates and were adapted to tolerate short-term drying typical of floodplain habitats. The reasons why mayflies moved into floodplains remain ambiguous and may be attributed to avoiding swift river flows or an evolutionary relic behavior from more northerly climate conditions.