American Society of Ichthyologists and Herpetologists, State College, Pennsylvania, June 1999.

Biogeography of Australian freshwater fishes.

P.J. Unmack

Australia is unusual due to its quiescent Tertiary geological history. The last major orogeny was ~90 Ma and present day river basins were by and large established in Paleocene. Furthermore, likely due to its isolation since separating from Antarctica 95 Ma, its fish fauna mostly consists of secondarily derived freshwater families. This has resulted in a belief the fauna is relatively young, despite a fossil records of three secondary families going back ~40 Ma.

The present paper investigated detailed biogeographic patterns of the freshwater fish fauna within Australia. Museum records were collected at a river basin scale and summarized into 31 regions for ease of examination. Any marine tolerant species were excluded, leaving 167 species for consideration. Similarity indices and parsimony analysis were used to identify clustering patterns among regions. Relationships between regions were largely deduced by concordance between techniques. Two broad patterns were apparent. Not surprisingly, a gradient of high species diversity occurred from north to south. Of more interest is a line of endemism, from the northwest to the southeast, with high endemism occurring almost exclusively in the southwestern half. These broader patterns will be presented and interpreted based upon possible historical geological and climatic changes.