Caves and other subterranean habitats with their often strange (even bizarre) inhabitants have long been objects of fascination, curiosity, and debate. The question of how such organisms have evolved, and the relative roles of natural selection and genetic drift, has engaged subterranean biologists for decades. Indeed, these studies continue to inform the more general question of adaptation and evolution. However, interest in subterranean biology is not limited to questions of evolutionary biology. Both the distribution and the apparent ancient age of many subterranean species continue to be of significant interest to biogeographers. Subterranean ecosystems generally exhibit little or no primary productivity and, as