Figure 2 : Three exotic E populations (A, B, C) experience different levels of enemy pressure relative to native species (N), depending on the product (enemy pressure P = D*I) of proportional differences in both enemy diversity (D) and enemy impact (I), where D = DE/DN, and I = IE/IN. P > 1 indicate enemies have a stronger negative effect on exotic species, P < 1 indicate enemies have a stronger negative effect on natives. Dashed grey lines from each population link to exterior squares that show how those populations would look if only a single process was studied (diversity, a and b; or impact of a few select enemies, c and d). Dashed blue lines indicate equal enemy diversity (richness, abundance or their combination) between natives and exotics (vertical), and equal per-capita impact of those enemies (horizontal). The solid blue line indicates where enemies affect the performance of native and exotic species equally, with support for the ERH below this line. Axes are logged to facilitate symmetrical interpretation (i.e. on the x-axis, 0.1 corresponds to natives having ten times as many enemies as exotics; 10 corresponds to aliens having ten times as many enemies as natives).