Flood-mediated dispersal versus hatching: early recolonisation strategies of copepods in floodplain ponds

1. We explored the quantitative contribution of two alternative recolonisation strategies by a combination of experimental and field data from the Little Tallahatchie floodplain (Mississippi, U.S.A.). In this area, several floods of short duration occur in winter and spring. During floods, lentic and lotic waterbodies of different size are connected for a limited period. 2. Shortly before the onset of the flood season we collected sediment samples from six temporary ponds. The emergence of seven cyclopoid species was recorded from the experimentally flooded sediments and was quantified over a 4-week period. Water samples were taken in the same ponds after flooding, from which eight further species were recorded and quantified. 3. The contribution of flood-dispersed individuals was variable among flooded ponds (between 38 and 94%), but numbers of flood-dispersed colonists did not differ significantly from those of hatching individuals in flooded ponds. Our results demonstrate the equal importance of both hydrological connections and hatching from dormant stages as pathways for recolonisation by copepods if ponds are hydrologically connected. 4. The significance of recolonisation by hatching individuals in disconnected waterbodies was apparent in an isolated temporary pond that was exclusively recolonised by cyclopoid copepods emerging from the sediment.