Freshwater snails in competition: alien Physa acuta (Physidae) and native Glyptophysa gibbosa (Planorbidae) in the River Murray, South Australia

摘要: Physa acuta (Draparnaud), an invasive species from Europe, is the most abundant freshwater snail in Lower River Murray. Its ascendancy follows a general decline of native species, including morphologically and ecologically similar Glyptophysa gibbosa (Gould). We began with two hypotheses. The first required comparisons salinity temperature tolerances other attributes eggs, juveniles adults to reveal differences that might account for relative abundances species. As anticipated, P. proved have higher fecundity, shorter hatching time than G. gibbosa. second hypothesis concerned possible competitive interaction between This was confirmed, as when were kept together, under laboratory conditions, growth rate increased decreased (with some mortality). suggest apparent Murray may reflect its sensitivity vulnerability interactions acuta. global concern has spread also North America, Japan South Africa, there been reports impacts on local