Why Do Introduced Species Appear to Devastate Islands More Than Mainland Areas?

Abstract

Island biotas are viewed popularly as much more fragile than those of mainland areas and much more prone to damage from invaders. There are far too few data to assess this view thoroughly; for example, failed invasions are often unrecorded, and claims that an introduced species has displaced a native one are often based on correlated population changes rather than experiment and/or detailed field observations. If there is a tendency for invasions to affect island communities more than mainland ones, it is far from universal; virtually every kind of damage wrought by invaders on islands has also been wrought in mainland areas. It is unlikely that, by virtue of their reduced species richness alone, island communities pose less "biotic resistance" to invaders than mainland communities do. Rather, certain entire groups of species, like terrestrial mammals, are often missing from islands, and these absences can predispose certain invaders to be especially likely to survive and to produce particular impacts.