Invasion Biology

Sunday, June 04, 2006


A neutral terminology to define ‘invasive’ species

The use of simple terms to articulate ecological concepts can confuse ideological debates and undermine management efforts. This problem is particularly acute in studies of non-indigenous species, which alternatively have been called ‘exotic’, ‘introduced’, ‘invasive’ and ‘naturalised’, among others. Attempts to redefine commonly used terminology have proven difficult because authors are often partial to particular definitions. In an attempt to form a consensus on invasion terminology,we synthesize an invasional framework based on current models that break the invasion process into a series of consecutive, obligatory stages. Unlike previous efforts, we propose a neutral terminology based on this framework. This ‘stagebased’ terminology can be used to supplement terms with ambiguous meanings (e.g. invasive, introduced, naturalized, weedy, etc.), and thereby improve clarity of future studies. This approach is based on the concept of ‘propagule pressure’ and has the additional benefit of identifying factors affecting the success of species at each stage. Under this framework, invasions can be more objectively understood as biogeographical, rather than taxonomic, phenomena; and author preferences in the use of existing terminology can be addressed. An example of this recommended protocol might be: ‘We examined distribution data to contrast the characteristics of invasive species (stages IVa and V) and non-invasive species (stages III and IVb)’.


Difficulty C

Dr Richard Knight Co-ordinator: National Information Society Learnerships - Ecological Informatics
Department of Biodiversity and Conservation Biology
University of the Western Cape
Private Bag X17
Bellville 7535

Phone 27 + 21 + 959 3940
Fax 27 + 21 + 959 1237



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