Number of alien species recorded (a,b) in South Africa (S=2,108) and (c,d) in Chile (S=950, including Juan Fernandez and Easter Islands) by (a,c) environment and (b,d) taxonomic group. Grey bars represent species with evidence of impact (Table 2, Fig. 2). Black bars indicate species with no evidence of impact. Note that ‘no evidence of impact’ does not mean that a species does not have any impact, rather that there is currently no evidence that it does.