Systematics of the subfamily Aclyvolvinae (Caenogastropoda: Ovulidae) based on molecular and morphometric analyses

摘要

Molecular phylogenetic research on the octocoral-associated gastropod family Ovulidae is still in its infancy and, as a consequence, the relationships between subfamilies and genera are not well defined. Previous research on various ovulid genera has shown that their conchological characters are often too fluid when dealing with species delimitations. For this study, Ovulidae were collected in Indonesia and Malaysia, with some additional specimens obtained from Thailand and the Red Sea. Relationships between the Aclyvolvinae and other ovulid subfamilies were assessed using sequence data from two mitochondrial genes (cytochrome c oxidase subunit I (COI) and 16S rRNA); the dataset contained ovulid species (including type species) from the subfamilies Eocypraeinae, Ovulinae, Pediculariinae and Simniinae. The type species of the subfamilies Eocypraeinae and Sulcocypraeinae are fossils, and hence could not be included in the analyses. The phylogeny and systematics of the subfamily Aclyvolvinae were assessed based on four DNA gene regions (mitochondrial COI and 16S rRNA, and nuclear 28S rRNA and histone H3) and morphometric analyses. Shell morphological characters were analysed to help clarify species delimitations within the Aclyvolvinae. The results from the molecular analyses showed that the subfamilies Aclyvolvinae, Eocypraeinae and Simniinae are polyphyletic, whereas the Ovulinae and Pediculariinae appear to be monophyletic. Within the subfamily Aclyvolvinae, the type species of Hiatavolva, H. depressa, did not form a clade with the other species of Hiatavolva. Instead, H. rugosa and H. coarctata formed a clade that is sister to the clade comprising Aclyvolva lamyi, A. lanceolata and A. nicolamassierae, and are therefore now considered as belonging to the genus Aclyvolva. Aclyvolva lamyi and A. nicolamassierae were shown to be synonyms of A. lanceolata, and A. rugosa (n. comb.) is a synonym of A. coarctata (n. comb.). The genus Kuroshiovolva could not be retrieved in a fixed phylogenetic position within the Aclyvolvinae, nor did it cluster with H. depressa or Aclyvolva spp. Our morphometric analyses are in agreement with the results of the molecular analyses, and furthermore show that juvenile shells are morphologically significantly different from their adult conspecifics. Photographs of the type material of Ovulum lanceolatum, O. coarctatum, Neosimnia lamyi, Hiata rugosa and A. nicolamassierae are provided, and new information is given on the geographical distribution and host species of Aclyvolvinae. The subfamily Aclyvolvinae is redefined and now includes only A. lanceolata and A. coarctata. The genus Hiatavolva is now monotypic, containing only H. depressa, but the subfamily to which this genus belongs remains unclear. Kuroshiovolva is not part of the Aclyvolvinae, but its subfamily level placement is unclear.