Molecular phylogeny of the Mediterranean Flabellinidae (Heterobranchia, Nudibranchia, Aeolidida): preliminary results based on mitochondrial and nuclear markers

The Flabellinidae Bergh, 1889 is one of the largest families of aeolid nudibranchs, but its systematics is far from being completely elucidated. Morphological analyses have been carried out to assess the evolutionary history of flabellinids (Gosliner & Kuzirian, 1990; Gosliner & Willan, 1991), while molecular analyses have mainly focused on a few species in the frame of more general systematic and phylogenetic works on other aeolids groups (Carmona et al., 2011; 2013). We inferred the phylogeny of Flabellinidae based on DNA sequence data from two mitochondrial (COI and 16S) and two nuclear (H3 and ITS2) genes. While several studies on mollusks suggest that the nuclear marker ITS2 (ribosomal RNA internal transcribed spacer 2) is promising for phylogenetic and taxonomic inference (Oliverio et al., 2002; Salvi et al., 2012), this DNA region has never been used in nudibranch studies. Overall, results from molecular data analyses, suggest that the use of some morphological characters for Flabellinidae diagnosis needs to be re-evaluated. In fact, data support that two Piseinotecidae species are better relocated within Flabellinidae. In addition molecular analysis also revealed the occurrence of two taxonomic units within Flabellina ischitana. Finally, the combined information of sequence and secondary structure of the ITS2 region revealed to be a powerful tool for DNA barcoding. This work may be an important basis for future research on Flabellinidae phylogenetics and systematics.