Phylogenetic tree showing the relationships between Onchidium individuals based on mitochondrial COI and 16S DNA sequences. Numbers by the nodes are the bootstrap values (Maximum Likelihood analysis) and the posterior probabilities (Bayesian analysis); only significant numbers (> 65% and > 0.9) are indicated. All other sequences serve as outgroups. Information on specimens can be found in the lists of material examined and Table 1. The colors used for each Onchidium species are the same as those used in Figs 2–4.