Introduction

Abstract

AbstractThe invasion of new habitats by animals and plants represents a basic natural process as well as an anthropogenic phenomenon (Rejmanek 1996). However, the term “Biological Invasion” is used by most authors when species are spreading in a new area mediated by human activities (Auge et al. 2001; Richardson et al. 2000; Kowarik 1995; Pysek 1990). The distribution of species is, among other things, the result of natural dispersal that is limited by geographical or biological barriers. As human trade and transport increase, species can overcome these barriers and invade new areas. Thereby, the transport of species may either occur by accident, for instance in ballast water of ships or in packing material, or deliberately as introduction of cultivated plants or biocontrol species. The number of species that have been translocated has increased dramatically in the last 200 years (Mack et al. 2000; Williamson 1996; Drake et al. 1989). Out of 10 introduced species, one species may establish in the new area, and out of 10 established, one species likely causes problems in the new area (“tens rule”, Williamson and Fitter 1996). Today, biological invasions are considered one of the greatest threats to global biodiversity (Millenium Ecosystem Assessment 2005; Dukes and Mooney 1999). Native species can be suppressed or replaced by invasive species either directly by competition, or indirectly by alterations of the ecosystem as well as by alteration of the relations between organisms (e.g. Sperry et al. 2006; Belnap et al. 2005; Callaway and Aschehoug 2000). The dimension of the threat by invasive foreign species is quite perceptible. For instance in the South African bushland, 80 % of endangered species have become rare as a consequence of invasive species (Armstrong 1995). In addition to ecological problems, invasive species cause considerable economic costs. For the USA alone, Pimental et al. (2000) estimated $137 billion per year for economic loss. Thus, forecasting future invaders will help to arrest those invasions and is essential for maintaining biodiversity as well as saving enormous economic costs. Indeed, forecasting future invasion will not be possible until fundamental research in the field of invasion biology has identified how species become invasive and which processes are important for invasion success.KeywordsInvasive SpeciesLocal AdaptationPhenotypic PlasticityPlant InvasionBiological InvasionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.