Biological Invasions Riskier than Thought

A new paper Invasion success of vertebrates in Europe and North America by Jonathan Jeschke and David Strayer from IES was published online in PNAS April 222.

Their paper examined patterns in to the introduction, establishment and spread of freshwater fish, mammals, and birds between Europe or North America.

Their paper produces a number of interesting results. First it suggests that risks from invasive species are much higher than previously thought. The 10:10 rule of thumb proposes that in the steps of establishment, spread only 1:100 introduced species should spread. This paper suggests it is 25X greater at 1/4.

This result is supported by their examination of other patterns shown below.

Graph from Paper

Figure 2. Proportions of introduced animals that establish themselves (establishment success) and of established animals that spread or are pests (spread success). The tens rule predicts a 10% success for either step (vertical dotted line). Planarians, alien terrestrial planarians established in the U.K.; insects, biocontrol insects, symbols denote different diets and propagule pressures; island mammals, mammals introduced to Ireland and Newfoundland ; Australian mammals; island birds, symbols denote different islands; continental birds, birds introduced to continental USA and Australia; world parrots, worldwide parrot introductions; E, NA vertebrates, European North American vertebrates according to Table 1 (this study); British animals, symbols denote different taxa; Austrian animals, symbols denote different taxa; German animals, symbols denote different native continents.

They also show that species movement between Canada and the USA and Europe is roughly equal, rather than it being mostly a Europe->N. America pattern.

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