Phylogenetic hypothesis of Plakobranchus based on COI sequences. Bootstrap values from ML shown above branch and posterior probability (PP) values below branch. Sequences obtained in this study in bold. Missing PP values, or those that support branch placements that deviate from the ML tree are denoted with an asterisk * and are due to the discrepancy between ML and BI topologies (see Suppl. material 1). Tree rooted to Costasiella coronata (not shown).