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

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