Invasion Biology Terminology - Introduction

Introduction

Definitions of "invasive non-indigenous species have been inconsistent", which has led to confusion both in literature and in popular publications (Williams and Meffe 2005). Also, many scientists and managers feel that there is no firm definition of non-indigenous species, native species, exotic species, "and so on, and ecologists do not use the terms consistently." (Shrader-Frechette 2001) Another question asked is whether current language is likely to promote "effective and appropriate action" towards invasive species through cohesive language (Larson 2005). Biologists today spend more time and effort on invasive species work because of the rapid spread, economic cost, and effects on ecological systems, so the importance of effective communication about invasive species is clear. (Larson 2005)

Controversy in invasion biology terms exists because of past usage and because of preferences for certain terms. Even for biologists, defining a species as native may be far from being a straightforward matter of biological classification based on the location or the discipline a biologist is working in (Helmreich 2005). Questions often arise as to what exactly makes a species native as opposed to non-native, because some non-native species have no known negative effects (Woods and Moriarty 2001). Natural biological invasions, generally considered range expansions, and introductions involving human activities are important and could be considered a normal ecological process (Vermeij 2005). Non-native and native species may be sometimes considered invasive, and these invasions often follow human-induced landscape changes, with subsequent damage to existing landscapes a value judgment (Foster and Sandberg 2004). As a result, many important terms relevant to invasion biology, such as invasive, weed, or transient, include qualities that are "open to subjective interpretation" (Colautti and MacIsaac 2004). Sometimes one species can have both beneficial and detrimental effects, such as the Mosquito fish (Gambusia affinis), which has been widely introduced because of its suppression of larval mosquitoes, although it also has negative impacts on native species of insects, fish and amphibians (Colautti and MacIsaac 2004).

The large number and current complexity of terms makes interpretation of some of the invasion biology literature challenging and intimidating. Exotic, alien, transplanted, introduced, non-indigenous, and invasive are all words that have been used to describe plants and animals that have been moved beyond their native ranges by humans (Williams and Meffe 2005), along with other terms such as foreign, injurious, aquatic nuisance, pest, non-native, all with a particular implication. Even the use of what seem to be simple, basic terms to articulate ecological concepts "can confuse ideological debates and undermine management efforts" (Colautti and MacIsaac 2004). Attempts to redefine commonly used terms in invasion biology have been difficult because many authors and biologists are particular to a favorite definition (Colautti and MacIsaac 2004). Also, the status and identification of any species as an invader, a weed, or an exotic are "conditioned by cultural and political circumstances." (Robbins 2004)