American Society of Ichthyologists and Herpetologists, Guelph, Ontario, June 1998.

Biogeography of Australian freshwater fishes: patterns of faunal occurrence in southeastern Australia.

P.J. Unmack

This presentation is part of a wider study of the biogeography of Australian freshwater fishes. Southeastern Australia is hereby defined as coastal drainages from the Fitzroy River through Gulf of St. Vincent, including the inland Murray system separated from coastal drainages by the Great Dividing Range. It has the following biogeographic relationships of fishes restricted to freshwater: 1) 5 of 8 species from southern Victoria also occur in the Murray system; and 2) 18 of 27 species (or species pairs) co-occur between coastal Queensland drainages and the Murray system. The relationships of an additional 6 species endemic to the Murray system are more obscure. Biogeographic connectivity between the Murray and surrounding drainages thus appears high. Past biogeographic explanations for these relationships have relied heavily upon river captures, making faunal distributions easily explained. However, the last 15 years have seen a paradigm shift in the proposed evolution of the Great Dividing Range including evidence that river captures are either non-existent or very old (> 30-60 mba). Most patterns are congruent with present geological scenarios although exceptions exist. The new geologic conclusions are assessed on the basis of biological evidence and new hypotheses are provided to explain present distribution patterns.