Propagule Pressure: A Null Model for Biological Invasions |
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Authors: | Robert I Colautti Igor A Grigorovich Hugh J MacIsaac |
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Institution: | (1) Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada |
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Abstract: | Invasion ecology has been criticised for its lack of general principles. To explore this criticism, we conducted a meta-analysis
that examined characteristics of invasiveness (i.e. the ability of species to establish in, spread to, or become abundant
in novel communities) and invasibility (i.e. the susceptibility of habitats to the establishment or proliferation of invaders).
There were few consistencies among invasiveness characteristics (3 of 13): established and abundant invaders generally occupy
similar habitats as native species, while abundant species tend to be less affected by enemies; germination success and reproductive
output were significantly positively associated with invasiveness when results from both stages (establishment/spread and
abundance/impact) were combined. Two of six invasibility characteristics were also significant: communities experiencing more
disturbance and with higher resource availability sustained greater establishment and proliferation of invaders. We also found
that even though ‘propagule pressure’ was considered in only ~29% of studies, it was a significant predictor of both invasiveness
and invasibility (55 of 64 total cases). Given that nonindigenous species are likely introduced non-randomly, we contend that
‘propagule biases’ may confound current paradigms in invasion ecology. Examples of patterns that could be confounded by propagule
biases include characteristics of good invaders and susceptible habitats, release from enemies, evolution of ‘invasiveness’,
and invasional meltdown. We conclude that propagule pressure should serve as the basis of a null model for studies of biological
invasions when inferring process from patterns of invasion.
An erratum to this article can be found at |
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Keywords: | establishment exotic introduction invasibility invasion invasive invasiveness nonindigenous species null model propagule pressure |
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