• anthropogenic disturbance ;
  • freshwater ;
  • genetic diversity ;
  • habitat connectivity ;
  • mitochondrial DNA ;
  • phylogeography

The distribution of genetic variation in Texas stream fishes has been shaped by a complex mix of historical and anthropogenic factors. Although Texas was not glaciated during the Pleistocene, the rise in sea level following this epoch isolated formerly connected drainages. More recently, the construction of dams, modifications of stream systems, and the release of commercially raised fish have influenced the patterns of genetic diversity. To examine how these different factors have impacted Texas stream fishes, we compared the genetic structure of five species of fish spanning two families and inhabiting two adjacent drainages: Lepomis megalotis, Lepomis cyanellus, Cyprinella lutrensis, Cyprinella venusta, and Campostoma anomalum. Our analyses of the mitochondrial D-Loop show that genetic patterns differ strongly across species. A phylogeographical split between the Brazos and Trinity drainages was seen in conspecific populations of Lepomis species and is probably the result of the historical separation of these river systems. In contrast, contemporary ecological and anthropogenic factors, such as the desiccation of streams during summer, and the translocation of bait fish, appear to have a stronger influence on the genetic patterns in the remaining species. The contrasting results demonstrate the importance of using a multi-species, comparative approach for landscape genetic studies as single species patterns may not be representative of others and thus may obscure differential effects of historical versus recent events as well as natural versus anthropogenic forces. By comparing closely related species that differ in their life history and economic importance it may be possible to disentangle the relative roles of historical, intrinsic, and anthropogenic influences on different organisms within a region. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••–••.