Historical interdrainage dispersal of eastern rainbowfish from the Atherton Tableland, north-eastern Australia

The widespread distribution of the eastern rainbowfish Melanotaenia splendida splendida throughout the isolated headwaters of the: rivers on the Atherton Tableland. north-eastern Australia. suggests multiple colonization events from the eastern lowlands via each respective river channel, or a single colonization event on to the tableland with subsequent dispersal between the headwaters. To explore the likely processes that resulted in the current distribution on the tableland, two models of gene flow were tested. (a) the hierarchical gene flow model that tests the hypothesis for contemporary gene flow via stream channels and (b) the stepping stone model that tests for dispersal between streams. Neither of these models explained the observed genetic structure, adequately. However. there is support for extensive historical dispersal across the headwaters of the isolated drainages. If this dispersal followed a single colonization event. the subsequent range expansion could have facilitated a rapid rise in population size due to an increase in suitable habitat. The genetic data indicates an eight-fold increase in population size c. 100 thousand years ago. (C) 2001 The Fisheries Society of the British Isles.