ABSTRACT 96-15374 O'Brien Invasion of an exotic Cladoceran into North American Reservoirs Invasions of non-native species can cause profound problems by displacing or dominating indigenous species. One such recent invasion is that of Daphnia lumholtzi, a crustacean zooplankter that is invading the reservoirs of southeastern and south central North America. During the last five years D. lumholtzi has invaded 124 reservoirs in 21 states, including 29 reservoirs in Missouri and 5 in Kansas. Daphnia lumholtzi has an unusually large head and tail spines. These features would be expected to reduce predation and increase their competitive advantage compared with other daphnids lacking similar structures. The invasion of this species thus may dramatically alter freshwater food webs, where daphnids are often keystone species. In this project we will investigate the zoogeographic distribution of D. lumholtzi in Kansas and Missouri reservoirs, and will carry out extensive parallel limnological measurements. We will learn (1) what conditions affect the likelihood of invasions, and (2) the ecological effects on invaded food webs.
