Size-selective dispersal of Daphnia resting eggs by backswimmers ( Notonecta maculata )

Freshwater zooplankton is increasingly used to study effects of dispersal on community and metacommunity structure. Yet, it remains unclear how zooplankton disperses. Clearly, birds and wind play a significant role as zooplankton dispersal agents, but they may not always be the main vectors. This experimental study shows that a cosmopolitan aquatic insect, Notonecta , can be an important vector of cladoceran resting eggs (ephippia). Dispersing Notonecta frequently transported ephippia during flight, with a bias towards smaller ephippia in two species. A similar trend was present at the species level: Daphnia species with smaller ephippia were more often dispersed, suggesting that Notonecta could generate specific colonist communities. In addition, buoyancy appeared a critical trait, as non-floating ephippia of Daphnia magna were never dispersed. Our data suggest that Notonecta could be important dispersers of Daphnia , and that knowledge of dispersal dynamics of Notonecta may be used to predict Daphnia dispersal, colonization and resilience to disturbance.