Diagram to help visualize pairwise genetic distances between COI sequences within and between Onchidium species (Table 2). Ranges of minimum to maximum distances are indicated (in percentages). For instance, the intra-specific divergences within O. typhae are between 0.1 and 0.4%, while the inter-specific divergences between O. typhae and the three other species are between 10.9 and 14.3%. Overall, the distance gap between all four Onchidium species is between 3.2 and 8.6%. The colors used for each Onchidium species are the same as those used in Figs 1, 2, and 4.