INVASION OF THE EXOTIC CLADOCERAN DAPHNIA-LUMHOLTZI INTO NORTH-AMERICAN RESERVOIRS

Daphnia lumholtzi, a large cladoceran native to Africa, Asia, and Aust ralia, has recently invaded reservoirs of the southern United States. We examined its distribution, history of invasion, and population dyna mics in Missouri reservoirs. Surveys detected the species in 7 of 112 reservoirs in 1992 and 11 of 119 reservoirs in 1993. Analysis of quant itative zooplankton samples from two reservoirs over a 7-year period i ndicated that D. lumholtzi first reached detectable densities in 1990 and persisted during 1991-1993. Population maxima typically occurred i n late summer, with the species absent from the plankton during winter and spring. Based on its current distributional patterns, D. lumholtz i appears to be capable of colonizing most reservoirs in the southern regions of North America.