Native insects colonizing introduced tree species-patterns and potential risks

Abstract

Biological invasions are today considered to be among the greatest threat to biodiversity on earth (Gurevitch & Padilla 2004). The many examples of introduced plant species that have spread and appear to out-compete native plants illustrate the severity of this problem (Crawley 1997, Vitousek et al. 1997, Richardson & Higgins 1998). One commonly accepted mechanism behind plant invasions is that the plants experience decreased regulation by herbivorous insects and other enemies in the new environment. This is often referred to as the enemy-release hypothesis (Keane & Crawley 2002) or the escape-from-enemy hypothesis (Wolfe 2002). However, not all introduced plant populations have spread and become invasive (Grotkopp et al. 2002, Louda & Rand 2003). For example, some plants might be rapidly colonized by herbivorous insects (Strong 1974, Strong et al. 1977, Auerbach & Simberloff 1988), which may in turn limit the spread of the species (Maron & Vilà 2001, Louda & Rand 2003). The control of exotic plant species by the native biota is often referred to as the biotic resistance hypothesis (Elton 1958, Maron & Vilà 2001) which, similar to the enemy-release hypothesis, assumes that herbivorous insects can be participants in the regulation of plant populations. This suggests that the ability and the rate at which native insects can shift to feed on introduced plants might determine the plants' success in the new environment. © Springer Science+Business Media B.V. 2008.