Biological Journal of the Linnean Society, 2006, 87, 457–467. With 3 figures © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 457–467 457 Blackwell Publishing LtdOxford, UKBIJBiological Journal of the Linnean Society0024-4066The Linnean Society of London, 2006? 2006 873 457467 Original Article GENE FLOW IN EEL-TAILED CATFISH J. A. HUEY ET AL . *Corresponding author. E-mail: j.huey@griffith.edu.au Patterns of gene flow in two species of eel-tailed catfish, Neosilurus hyrtlii and Porochilus argenteus (Siluriformes: Plotosidae), in western Queensland’s dryland rivers JOEL A. HUEY*, JANE M. HUGHES and ANDREW M. BAKER CRC for Freshwater Ecology and the Centre for Riverine Landscapes, Australian School of Environmental Studies, Griffith University, Nathan, Queensland, 4111, Australia Received 18 June 2004; accepted for publication 29 April 2005 Using genetic techniques (mtDNA, microsatellites and allozymes), this study investigated patterns of gene flow in two plotosid catfish species (Neosilurus hyrtlii and Porochilus argenteus), at various hierarchical scales in the dry- land rivers of western Queensland, Australia. The study area constituted two major catchments, Cooper and Darling, representing arid and semiarid systems, respectively. Results generally conformed to expectations, with high levels of gene flow observed within catchments and limited contemporary gene flow evident across catchment boundaries. However, the isolation between catchments was more recent than expected, occurring approximately 40 000– 72 000 years ago. Also contrary to predictions, genetic structure within the Cooper catchment did not fit the stream hierarchy model of genetic differentiation, which there was evidence of in the Darling catchment. This was hypoth- esized to relate to the different climatic regimes and hydrological inputs in each system, leading to a more genetically homogeneous system in the Cooper than in the Darling system. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87, 457–467. ADDITIONAL KEYWORDS: allozymes - Cooper Creek – fish - genetic structuring - Lake Eyre Basin – microsatellites - mitochondrial DNA - Warrego River. INTRODUCTION Understanding patterns of connectivity among popu- lations is essential, as gene flow affects population via- bility through the recolonization of locally extinct areas and the maintenance of genetic diversity (Vrijenhoek, 1996; Moran, 2002). In riverine environ- ments, connectivity is a complex relationship between river architecture, flow regime, and the dispersal abil- ity of the organism in question (Amoros & Bornette, 2002). In the dryland rivers of western Queensland, river architecture is complex, owing to low catchment gradients and the dominance of refugial waterholes, periodically connected via an anastomosing channel system of primary and secondary channels, floodways and backswamps (Kotwicki, 1986; Knighton & Nan- son, 2002). Large flood events that connect waterholes across large spatial scales are typically infrequent, occurring approximately once every 100 years (Pickup, 1991). As these waterholes are the only per- manent water bodies within this environment, they are often important to the surrounding biota, present- ing a reliable source of water and/or habitat (Puck- ridge, Walker & Costelloe, 2000). The frequency and degree of connectivity between waterholes via these channels is determined by the highly variable flow regime that exists in the region, primarily influenced by the El Niño Southern Oscilla- tion System, generating monsoonal inputs for the Lake Eyre Basin and most of northern Australia (Simpson et al., 1993; Knighton & Nanson, 1994, 1997). In less arid regions, such as those dryland riv- ers associated with the Murray-Darling Basin, local precipitation and sources from coastal ranges may also contribute to hydrological inputs, leading to a more hydrologically stable system (Young, 1999). Species in this environment exhibit a range of dif- ferent dispersal tactics and capabilities. For example, in two crustacean species (Cherax destructor and Macrobrachium australiense) from the dryland rivers Downloaded from https://academic.oup.com/biolinnean/article-abstract/87/3/457/2691563 by guest on 21 May 2020