Summary and conclusions: characteristics and consequences of biological invasions

Abstract

The mechanisms of colonization, competition and extinction have fascinated biologists since they began to appreciate that ecological patterns, however stable they might appear, are the outcome of complex dynamic interactions. The pioneer naturalists who recorded the similarities and differences between floras and faunas in different regions were often confronted by the question of whether todays patterns were the relict consequence of processes that operated in the past but no longer did no, or could be explained by the dispersal capacity of species in a world with todays geography. Darwin and Hooker corresponded over the cause of the floristic and faunistic similarities between widely separated temperate lands in the southern hemisphere, and Darwin once wrote to Hooker about one widely dispersed island tree ‘I believe you are afraid to send me a ripe Edwardsia pod lest I should float it from New Zealand to Chile’. The study of the disjunct and distinctive biotas of oceanic islands has always involved assumptions (if not calculations) about the isolating influence of ocean barriers and about the rates of colonization as a source of new genes diluting the pool already present and moderating the trend towards endemism.