The number of a invasive species in each taxonomic group investigated across all papers in this review [two papers each investigated one charophyte species, (see Nyberg and Wallentinus (2005); Sahlin et al. (2011)) which are not shown], b the number of papers that investigated the ten most studied invasive species found in this review and c the total number of orders for each taxonomic group and the number of orders which contain non-native species with data taken from Schaffelke et al. (2006). Drawings are courtesy of Tracey Saxby and the Integration and Application Network (ian.umces.edu/symbols/).