Molecular data reveal cryptic lineages within the northeastern A tlantic and M editerranean small mussel drills of the O cinebrina edwardsii complex ( M ollusca: G astropoda: M uricidae)

We used a molecular phylogenetic approach to investigate species delimitations and diversification in the mussel drills of the O cinebrina edwardsii complex by means of a combination of nuclear (internal transcribed spacer 2, ITS2 ) and mitochondrial [cytochrome oxidase subunit I ( COI ) and 16S ] sequences. Our sample included 243 specimens ascribed to seven currently accepted species from 51 sites. Five of the samples were from either the type locality of a nominal species or a close nearby locality ( O . edwardsii from C orsica, O . carmelae and O . piantonii from the K erkennah Islands, O . hispidula from the G ulf of G abès and O . leukos from the C anary I slands), one from the inferred original locality ( O . ingloria from V enice L agoon), and specimens assigned in the recent literature to O . nicolai . We used a combination of distance‐ and tree‐based species delimitation methods to identify M olecular O perational T axonomic U nits ( MOTU s) to compare with the a priori species identifications. The consensus tree obtained by BEAST on the COI alignment allows the recognition of several distinct clades supported by the three species delimitation methods employed. The eight‐ MOTUs scenario, shared by the A utomatic B arcode G ap D iscovery ( ABGD ) and G eneralized M ixed Y ule‐ C oalescent ( GMYC ) methods, comprises the following major clades: clade A contains the south Tunisian species O cinebrina piantonii   C ecalupo, B uzzurro & M ariani from which the sympatric taxon O . carmelae   C ecalupo, B uzzurro & M ariani (new synonym) cannot be separated; clades B and C bring together all populations from the A egean S ea and some from the I onian S ea, respectively; clade D groups, on the one hand, the south Tunisian samples morphologically assigned to O . hispidula   P allary and, on the other, A tlantic and A lboran S ea samples (including the C anarian taxon O . leukos   H ouart); clade E includes a sample from the type locality of O . edwardsii and several samples from the T yrrhenian S ea; clades F and G correspond to a few samples from the V enice L agoon and the T yrrhenian S ea, respectively; clade H groups the bulk of samples from the A driatic S ea, including samples from the V enice L agoon morphologically identified as O cinebrina ingloria ( C rosse), and some from the I onian S ea. No final conclusions could be reached to reconcile the currently recognized morphological taxa with the clades suggested by the COI data. The geographical structure proposed by the mitochondrial markers is similar to that found in other marine invertebrates and partially corresponds to the species defined by shell characters. We propose here a framework for the revision of the O cinebrina edwardsii species complex, suggesting a geographical pattern for the diversification of this group in the studied area. © 2013 The Linnean Society of London