The evolutionary role of dendritic systems in structuring the fish populations of Australia’s northern rivers

Riverine landscapes undergo geographical changes that impact dispersal and gene flow on both temporal and spatial scales. Dendritic structure can often be a major influence on the dispersal of freshwater fish within river catchments. The impacts of dendritic structure and floodplains on dispersal were investigated in populations of Chequered Rainbowfish Melanotaenia splendida inornata, Western Rainbowfish Melanotaenia australis and Sooty Grunter Hephaestus fuliginosus in the Mitchell and Daly Rivers. It is predicted that populations in the Daly River a highly dendritic system will be more genetically structured than populations in the Mitchell River less dendritic, as stream order influences population connectivity. Also, it is expected that populations living in the lowland floodplains will be less structured as a result of flooding events aiding dispersal and gene flow. This paper presents preliminary findings and discusses their implications.