Do Successful Invaders Exist? Pre-Adaptations to Novel Environments in Terrestrial Vertebrates

Central in invasion biology is to understand why alien species, whose initial populations are generally small and genetically depleted, can succeed to establish themselves in environments to which they have had no opportunity to adapt (Sax and Brown 2000). This paradox is usually resolved by invoking pre-adaptations of non-indigenous species to novel environments. The idea is that some species are successful invaders because they have attributes that pre-adapt them to survive and reproduce in novel environments (Mayr 1965). However, do we really have evidence that there exist properties of successful invaders?

The goal of this chapter is to evaluate to what extent establishment success of terrestrial vertebrates may be understood by the existence of pre-adaptations of species to novel environments. This implies answering two interrelated questions: (1) do species differ in their invasion potential? And if so, (2) what are the features of the species that identify some as successful invaders? Answering these questions is important not only to fully understand how animals respond to new environmental conditions, but also to help identify and prevent situations where the risk is high that a species becomes established and causes ecological impact when introduced in a novel region.