Polinices Montfort, 1810

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 : 371

Genus Polinices Montfort, 1810

Based on molecular data, the genus Polinices can be divided in two groups. One group comprises P. sp. 1 (0 P. mammilla ), P. uber and P. mediopacificus , while the second group contains P. albumen , P. cumingianus , P. mellosus , P. flemingianus , P. sp. 2 (0 P. jukesii ), P. sp. 3 (0 P. constanti ), P. sp. 4 (0 P. cf. tawhitirahia ) and P. peselephanti ( Figs. 2 , 3 and 4 , Supplementary Figs. S1–S2). Species in the second Polinices group are related more closely to each other and showed lower intra-specific geographic resolution. This may be largely a consequence of limitations in taxon sampling, as most specimens were sampled in one region only or only one specimen per species was available for sequencing (e.g. P. flemingianus ).

The patterns of genetic variation in the monophyletic P. mammilla (0 P. sp.1) between Egypt (clade 1), Indonesia, New Caledonia (clade 2) and the Great Barrier Reef (clades 2/3) correspond to the phylogeographic category II of Avise (2000) in which it is assumed that the different mitochondrial haplotypes originated either from hitherto unidentified sympatric species or from previously isolated lineages with restricted genetic connectivity (see Thomaz et al. 1996; Avise 2000). Thus, the mtDNAs appear to have diverged in allopatry, with a secondary admixture of populations in the northern Great Barrier Reef. This is supported by the fact that two genetically distinct lineages have been found on Lizard Island (clades 2/3). However, the specimens from Vanuatu and Lizard Island in clade 2 are also clearly separated from clade 3 by the slower evolving protein-coding histone H3 gene fragment (see Supplementary Fig. S2 ). Thus, the apparent genetic divergences between the three P. mammilla lineages support a separation at species level. However, as all specimens are conchologically identical and grouped together in a single monophyletic taxon, more data will be needed to test whether these clades may indeed represent different species.

The phylogenetic separation of the morphologically virtually identical P. constanti and P. jukesii ( Figs. 2 , 3 and 4 ) could either indicate the existence of non-monophyletic species with two mitochondrial lineages caused by incomplete lineage sorting or hybridisation, or indicate the existence of two independent species ( Davison 2000; Funk and Omland 2003; Meyer and Paulay 2005; Huelsken et al. 2011b). The genetic divergence between P. jukesii and P. constanti is identical to, or even higher than, values calculated for conchologically well-separated Polinices species in this group, such as P. mellosus , P. cf. tawhitirahia and P. cumingianus ( Table 4). Additionally, virtually identical mitochondrial and nuclear sequences for P. jukesii were obtained from two independent and not directly connected localities in the Philippines and the Great Barrier Reef indicating strong genetic connectivity. The two taxa are furthermore strictly separated by the slower evolving protein-coding histone H3 gene fragment, with P. jukesii sharing the same genetic information with P. cumingianus , P. mediopacificus and P. peselephanti in this gene fragment (see Supplementary Fig. S2 ). The molecular data in combination with slight differences in protoconch morphology therefore rather reject the hypotheses of hybridisation or incomplete lineage sorting in P. jukesii and P. constanti but support the idea that the two taxa are separated at the species level.

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