Studying invasion: have we missed the boat?

Invasive species, and the ensuing homogenization of the world's biota, form a global problem with consequences ranging from the decline and extirpation of native species to threats to human health. The magnitude of this issue demands a thorough understanding of the invasion process, which consists of three main stages: initial dispersal, establishment of self-sustaining populations, and spread. To assess the relative distribution of research effort among these stages, we conducted a literature review using 873 articles published in 23 major journals over the past 10 years. Of the 873 papers, only 96 (11.0%) studied initial dispersal, and only half of these (6.2% of the total) were empirical. As the first stage in a contingent process, we argue that initial dispersal is the best stage during which to direct management efforts. In addition, initial dispersal has direct relevance for fundamental ecological questions regarding community assembly and metacommunity dynamics. In so far that answering these questions and preventing invasion are goals of ecologists, the disparity in research effort noted here suggests that ecologists need to expand their efforts to include more research on initial dispersal.