Eastern freshwater cod are a species of cod that is descended from the Murray cod, "Maccullochella peelii", present in tributaries of the Murray-Darling Basin on the western side of the Great Dividing Range. Murray cod entered an east coast river system, likely the Clarence, via a natural event somewhere between 0.62 and 1.62 million years ago (mean estimate 1.1 mya), as estimated by DNA divergence rates. Subsequent isolation from Murray cod populations, the founder effect, genetic drift, and natural selection lead to allopatric speciation.