Fish Out of Water: Evolutionary and Ecological Issues in the Conservation of Fishes in Water-Altered Environments: Introduction to the Symposium: Eco-Evolutionary Change and the Conundrum of Darwinian Debt

Human impacts on aquatic systems are pervasive and often extreme worldwide, resulting in numerous fish species, as well as other aquatic organisms, being at risk of extinction. Until recently, however, species targeted in conservation efforts have been treated as static units, rather than as locally evolving populations. The intent of the ASIH 2013 symposium, Fish Out of Water: Evolutionary and Ecological Issues in the Conservation of Fishes in Water-Altered Environments, was to examine fish assemblage responses to anthropogenic impacts and the potential for altered evolutionary trajectories. The recent realization that feedback between ecology and evolution can occur on ecological time scales emphasizes that ecological studies cannot assume evolutionary stasis. The cyclical interaction of ecology and evolution, termed eco-evolution, suggests that both directions of effect, ecology to evolution and evolution to ecology, are substantial. Such interactions seem to be particularly likely in many impoundments. For instance, various species of fishes show shifts in morphology in reservoir compared to stream environments, although the changes are generally species-specific or system-specific. In general, conservation efforts to recover populations that have changed in response to human-altered habitats could be compromised if systems are returned to quasi-normal states because of Darwinian debt, the situation where evolutionary recovery from genetic changes caused by anthropogenic impacts can take longer than the time required to induce the changes, resulting in evolutionary costs for future generations.