With the contraction of their main range, relictual species are hypothesised to have evolved different characteristics from their original stock, leading to the high levels of endemism (the frequency of species with restricted distributions) in isolated GAB artesian spring groups.Brown and Gibson 1983 Hence artesian springs provide the localised habitat requirements for a suite of endemic (restricted to one or more GAB spring) fish and aquatic invertebrate species which include hydrobiid molluscs, isopods, ostracods, amphipods, copepods and flatworms.Morton et al, 1995, p.11, p.119 & p.134
