"The guppy, Poecilia reticulata, is one of the world's most widely distributed tropical fish. It is found in every continent apart from Antarctica and its range continues to be extended, both through the pet trade and as a means of controlling malarial mosquitoes. Guppies occur in some unlikely locations, such as the Moscow sewage works (Zhuikov 1993) and the in Essex in England (Maitland and Campbell 1992; but see Wheeler et al. 2004), where they can survive because heated effluent maintains the water temperature at tropical levels. Guppies were even sent into space aboard the . This spectacular dispersal, much of it human assisted and not all of it beneficial to the native fish communities into which guppies are introduced ..., illustrates the adaptability of the species. However, it is the ability of guppies to thrive in different ecological communities and environmental conditions within their natural range of NE , and in in particular, that has proved particularly fruitful in testing key evolutionary theories."