Population Connectivity of Two Australian Freshwater Fishes in a Large Tropical Dendritic River Network

Abstract

Freshwater fishes are often characterized by extensive population genetic subdivision and low genetic diversity and are ideal subjects for investigating contemporary patterns of dispersal and subsequent gene flow. In lotic systems, different riverine architecture, variable hydrology and species biology influence genetic diversity and population structure in resident species. Stream-dwelling species often display greater levels of gene flow within drainages or catchments or sub-catchments than between them due to complexity of stream order and the isolating nature of these systems by land or sea. However, the relative importance of these attributes in driving population structure at spatial scales remains poorly understood for many freshwater species. Study on the effects of riverscape in shaping population structure is very important to identify management or conservation units and to undertake habitat restoration measures. The Daly River is one of the largest river networks in the wet-dry tropics of Northern Australia and shows variability in hydrology. This river has a complex arrangement of habitats and heterogeneous landscape features (e.g. slope, elevation) across the catchment area. There are also instream physical barriers like waterfalls, cliffs, road crossings etc. that may hinder dispersal and subsequent gene flow.