ABSTRACT
Subterranean amphipods are interesting biogeographically because of their taxonomic diversity, limited dispersal ability, and significant geographic isolation and restriction to groundwater aquifers. Isolation and restriction to groundwater aquifers has, in turn, apparently contributed significantly to the evolution of a large number of locally endemic species, which are common in large genera such as Bogidiella, Niphargus, Pseudoniphargus, and Stygobromus. Moreover, many taxa probably represent old phylogenetic lineages that have persisted in well-buffered groundwater habitats for long periods of time and are genuine relicts, both phylogenetic and distributional. However, not all stygobitic amphipods are old relicts. Some are apparently morphologically closely
similar to epigean forms, suggesting a rather recent invasion and colonization of subterranean waters by the ancestors of these species.
