Changes in the dominant pathway subcategories across decades. Cumulative number of documented introduction events (note different scales on y-axes). The 18 pathway subcategories shown are those with most (> 100) introduction events (see Suppl. material 1: Figure S1 for ‘corridors: interconnected waterways/basins/seas’, ‘unaided: natural dispersal across borders’ and ‘unknown’ pathway subcategories not shown).