Are islands the end of the colonization road?

Abstract

Ecologists have, up to now, widely regarded colonization of islands from continents as a one-way journey, mainly because of widely accepted assertions that less diverse island communities are easier to invade. However, continents present large targets and island species should be capable of making the reverse journey, considering they are the direct descendants of successful colonists and provided that they have not lost their dispersal abilities. Recent mapping of geography onto molecular phylogenies has revealed several cases of 'reverse colonization' (from islands to continents). We suggest this phenomenon warrants closer attention in ecology and biogeography. Assessing its significance will contribute to understanding the role of dispersal and establishment in biogeographic distributions and the assembly of natural biotas.