Abstract
Invasions by non-indigenous species are one of the largest threats to biodiversity today and the ecological and economical costs associated with species invasions are enormous. Identifying the underlying mechanisms of invasions is a vital step in developing the highly needed predictive tools to prevent invasions. High levels of biodiversity have long been believed to hamper invasions and the escape from ones old enemies is still a common explanation for successful invasions of new regions. However, while these theories are still being supported, outcomes that oppose the predictions are reported from an increasing number of studies (a.k.a. the *invasion paradox*). I will use a novel multi-factorial approach where I investigate the interactive effects of diversity, resource availability and ecological disturbance on species invasions. Such an approach has not been used before and has the advantage of revealing underlying mechanisms of invasion that cannot be found by the more common single-factor studies. Because unconfounded manipulations of diversity require a high degree of experimenter control, the studies on three-factor interactions will be performed in mesocosms. In addition, I will conduct field experiments at a larger scale on the interactive effects of disturbance and resources on the invasibility of natural marine communities. Thus, my aim is to solve the *invasion paradox* and identify the mechanisms behind successful invasions by non-indigenous species.
Sweden