PATRICK PAYAN, ANAICK EDEYER, HÉLÈNE DE PONTUAL, GIL BORELLI, GILLES BOEUF, AND NICOLE MAYER-GOSTAN Laboratoire de Physiologie et Toxicologie Environnementales, EA 2138; Laboratoire de Physiologie Cellulaire et Moléculaire, Centre National de la Recherche Scientifique, UMR 6548; Université de Nice-Sophia Antipolis, Faculté des Sciences, 06108 Nice Cedex; and Laboratoire de Sclérochronologie des...

Unregulated river systems are organized in a hierarchy in which large-scale factors (i.e., landscape and segment scales) influence local habitats (i.e., reach, meso-, and microhabitat scales), and both differentially exert selective pressures on biota. Dams, however, create discontinua in these processes and change the hierarchical structure. We examined the relative roles of hydrology and othe...