THE CONSEQUENCES OF GLOBAL WARMING FOR STREAM INVERTEBRATES - A FIELDSIMULATION

1. We manipulated the thermal regime of a stream and analyzed the popu lation genetics of constituent species to examine the effects of globa l warming on stream invertebrates. 2. Increased temperature resulted i n significantly lower total densities of invertebrates and altered gro wth patterns for two target species. 3. Hyalella azteca showed the gre atest change in growth and also exhibited high levels of genetic diffe rentiation among populations. Nemoura trispinosa showed only small shi fts in growth and phenology and exhibited little genetic differentiati on among populations. 4. The potential impacts of global warming may d epend critically on the dispersal abilities and genetic structure of l otic populations.