Neverita Risso, 1826

Hollmann, Thomas Huelsken Daniel Tapken Tim Dahlmann Heike Wägele Cynthia Riginos Michael, 2012, Systematics and phylogenetic species delimitation within Polinices s. l. (Caenogastropoda: Naticidae) based on molecular data and shell morphology, Organisms Diversity & Evolution (New York, N. Y.) 12 (4), pp. 349-375 : 372

Neverita Risso, 1826

The genus Neverita was characterized by homogeneous conchological characters such as a depressed shell shape, an ovate aperture, a large parietal callus, a greatly enlarged body whorl and a typical umbilical area containing a large, distinctive funicle (see Cernohorsky 1971; Marincovich 1977; Majima 1989). Its placement as a subgeneric taxon within the genus Polinices , however, was based on the occurrence of several conchological characters that could be assigned to both taxa. For instance, P. albumen , P. peselephanti and P. cumingianus have “ Neverita ”-like depressed to slightly globose shells and thus have often been considered to belong to Neverita , either at the generic level or at the subgeneric level as in Polinices (Neverita) (e.g. Cernohorsky 1971; Majima 1989). The concept of Neverita as a subgenus of Polinices can now be rejected because the taxa Neverita and Polinices each form statistically well-supported monophyletic clades in our analyses. In consequence, similar or even identical shell characters have evolved separately in these two genera.

To our surprise, the widely known and well-investigated (e.g. Bernard 1967; Grey et al. 2007; Cook and Bendell-Young 2010) Northern Pacific species E. lewisii groups within Neverita as sister species to the Australian N. aulacoglossa in the COI tree. This confirms morphology-based cladistics with E. lewisii and E. heros grouping within Neverita ( Aronowsky 2003) . Although our phylogenetic placement is based only on sequence data obtained from the mitochondrial COI gene fragment, we conclude from the data sets of Aronowsky (2003) and this study that E. lewisii (and probably its sister species E. heros ) should definitely be assigned to Neverita (see Table 1).

The existence of a separate (sub)genus Glossaulax Pilsbry, 1929 within Neverita (e.g. Marincovich 1977; Majima 1989) appears doubtful. The (sub)genus Glossaulax is defined by an umbilical callus that covers the umbilicus entirely and is divided into anterior and posterior lobes by a narrow transverse groove ( Majima 1989). In the present study, the type species of the (sub)genus Neverita (Glossaulax) , N. (G.) reclusiana , is grouped together with its nominate sister species N. (G.) didyma but not with the Australian N. (G.) aulacoglossa ( Figs. 2 , 3 and 4 ). The species are in fact separated from each other by species which are distinctly assigned to Neverita s.s. (e.g. N. delessertiana , N. duplicata ) ( Figs. 2 and 3 ).

Our data, albeit somewhat preliminary, supports the proposed validity of N. didyma (Indo-Pacific) and N. aulacoglossa (Eastern Australia) as distinct species and reject their former synonymisation under the name N. didyma ( Kabat 2000) . However, more sequences for N. didyma (presented here by one sequence from Taiwan, AF550509; Strong 2003) are needed for clarification.

Figures

Fig. 2 Phylogram obtained through Bayesian inference based on the concatenated data set (COI, 16S, 18S, 28S, H3) for a reduced number of taxa. Posterior probabilities are indicated at the nodes. Branches supported by values>0.95 are indicated in bold. Polytomies are due to the cut-off value specified for the consensus tree (50 % used as the default value in MrBayes)

Fig. 3 Phylogram obtained through Bayesian inference based on the COI gene fragment. Posterior probabilities are indicated at the nodes. Branches supported by values>0.95 are indicated in bold. Polytomies are due to the cut-off value specified for the consensus tree (50 % used as the default value in MrBayes)

Fig. 4 NeighborNet network based on the concatenated data set (COI, 16S, 18S, 28S, H3). Bootstrap values are indicated