Chapter nineteen Biomonotony: definition and assessment for macroinvertebrates in European running waters Jean-Nicolas Beisel and Simon Devin INTRODUCTION Emerging evidence shows that most species are declining as a result of human activity and are being replaced by a much smaller number of expanding species that are successful in human-altered environments (McKinney and Lockwood 1999). The process by which the genetic, taxonomic, or functional similarities of regional biota increase over time is called biotic homogenization (Olden and Rooney 2006). Some researchers view homogenization as a form of community globalization (Lockwood and McKinney 2001, Mooney and Cleland 2001) that causes the ‘‘McDonaldization’’ of the biosphere (Ritzer 1996, Lo ¨vei 1997) or the setting of global ‘‘McEcosystems’’ (Enserink 1999). Many studies report on this phenomenon across and within continents, such as the homogenization of the fish fauna across the North America (Rahel 2000, Taylor 2004, Olden et al. 2006), and biotic homogenization is now recognized as an important component of the modern biodiversity crisis (Olden et al. 2006). Aquatic ecosystems are not spared this rampant homogenization of the earth’s ecosystems, but on the contrary they have some sensitive features that lead to heightened vulnerability (Beisel 2001, Rahel 2002). Several recent 369 Francesca Gherardi, Biological invaders in inland waters: Profiles, distribution, and threats, 369–379. ß 2007 Springer.