Abstract

PLANT AND ANIMAL SCIENCES BY FRANCISCO J. AYALA Department of Ecology and Evolutionary Biology University of California Irvine, Calif. " The great lakes of Africa each contain a unique radiation of cichlids. Lake Tanganyika has more than 140 endemic species, Lake Victoria more than 200, and Lake Malawi about 500. Around 1960, the Nile perch, a piscivorous fish, was introduced in Lake Victoria in order to improve the fisheries, but it has eaten its way through much of the lake and caused a dramatic decrease in the number of species and fish biomass in the lake. This should provide a clear warning against the proposed introduction of exotic fish in Lake Malawi. DJ. Miller, “Introductions and extinction of fish in the African great lakes,” Trends in Ecology and Evolution, 4,56-8, February 1989. " Genetic diversity is very high among natural clones of the soil bacterium Pseudomonas cepacia, higher than it has been reported for any bacterial species. Amount and pattern of genetic diversity are correlated with variability of the habitat from which the bacterial clones are isolated. This suggests that the source of bacterial strains used in genetic engineering will affect the success of planned releases into the