A molecular phylogeny of the family Chromodorididae (Gastropoda: Nudibranchia) based on 16S rDNA and 18S rDNA data

This study investigated the phylogeny of the nudibranch family Chromodorididae by comparing the partial sequences of the mitochondrial 16S rDNA of 53 species and nuclear 18S rDNA of 41 species. Representatives from the Actinocyclidae, Bathydorididae, Onchidorididae and Phyllidiidae were used as outgroups. Several tests were applied to the dataset to investigate relative evolutionary rates of the taxa, saturation of substitution, base composition and amount of phylogenetic information. Maximum-parsimony, maximum-likelihood and distance methods of tree construction were used. The mitochondrial 16S rDNA and nuclear 18S rDNA genes usefulness for inferring molecular phylogeny at family level is discussed. The taxonomic positioning of the basal genera Cadlina, Cadlinella and Tyrinna is investigated. Evidence is provided for the potential reclassification of Cadlinella. The chromodorid genera Chromodoris, Hypselodoris and Mexichromis were found to be paraphyletic, with the potential for paraphyly identified in other genera of the Chromodorididae. The results of the molecular phylogeny recovered were compared to previous molecular phylogenetic work and published cladistic analyses based on morphological data. Possible revisions of the current generic classification of the Chromodorididae are suggested and discussed