Nevertheless, our knowledge of the effects of alien marine species on biodiversity and ecosystem services is mainly qualitative and largely based on weak evidence. The lack of precise knowledge about the life history traits of alien species and their invasive strategies constitutes a big obstacle to understanding their functional roles in the prevailing ecosystems and their impacts. An additional constraint to quantifying and mapping the impact of alien marine species is the lack of coverage and resolution in the available data (such as spatial distribution of native and alien species, habitat mapping), especially in data-poor regions such as the eastern Mediterranean.