Dampier 300, biodiversity in Australia 1699-1999 and beyond, Perth, Australia, December 1999.

Biogeography of Australian freshwater fishes.

P.J. Unmack

Biogeographic patterns of obligate freshwater fishes of Australia were investigated. Similarity indices, parsimony analysis, and drainage-based plots of speciesí ranges were used to identify patterns. Relationships among regions were deduced largely by concordance between methodologies, then summarized into a proposed series of faunal provinces. The most striking pattern was in the incidence of endemism across the continent. Provinces in southern, central, and western Australia have high numbers of endemic fishes, presumably resulting from isolation by aridity and drainage divides. With exception of one region, northern and eastern Australia provinces have few endemics, likely explained in the north by high drainage connectivity during times of lowered sea levels. This does not account for low endemism in the east since drainages appear to have remained isolated during lowered sea levels and patterns suggest an absence of distinct barriers of other kinds. By default, climate again seems the most likely cause of speciesí distributional limits. Whatever the case, most patterns were almost certainly established in the distant past, perhaps as early as Miocene. Influences of Plio-Pleistocene events on broad patterns of freshwater fish distributions seem minimal.