# Comparative Genomic and Mitochondrial Phylogenetic Relationships of Ovulidae (Mollusca: Gastropoda) Along the Chinese Coast

## TL;DR

This study uses mitochondrial genomes to clarify the evolutionary relationships and classification of Ovulidae snails along China's coast, revealing new phylogenetic insights and genomic patterns.

## Contribution

The study provides new mitochondrial genomic data and phylogenetic insights for Ovulidae, supporting taxonomic reclassifications and highlighting unique evolutionary patterns.

## Key findings

- Mitochondrial phylogenetic analysis supports reclassifying Naviculavolva and Contrasimnia into Prionovolvinae.
- Ovulidae species show higher Ka/Ks ratios than Cypraeidae, indicating distinct selective pressures.
- Mitochondrial gene rearrangements occurred after divergence of Prionovolvinae and Ovulinae.

## Abstract

The family Ovulidae, closely related to Cypraeidae (cowries), comprises approximately 260–280 species predominantly inhabiting tropical and subtropical shallow marine environments. Unlike cowries, ovulids have a more specialized diet, with most species feeding on soft corals, leather corals, or black corals. Given their proximity in distribution and close phylogenetic relationship, dietary specialization may have played a crucial role in the evolutionary divergence of cowries and ovulids. However, unlike cowries, the traditional morphological classification of Ovulidae has proven challenging due to substantial variability influenced by their host organisms, leading to ongoing debates regarding species delimitation and taxonomy. In this study, we collected 15 Ovulidae species from China's offshore waters, including the first regional record of Habuprionovolva aenigma (M. Azuma & C. N. Cate, 1971). We successfully obtained mitochondrial genomes for 14 of these species and found that, with the exception of
H. aenigma
, they exhibit the typical mitochondrial genome structure of Caenogastropoda. Our phylogenetic analyses based on mitochondrial genome data, along with the discovery of a unique mitochondrial tRNA gene order in the subfamily Prionovolvinae, support recent studies suggesting that the genera Naviculavolva and Contrasimnia should be reclassified from the Simniinae to the Prionovolvinae. Additionally, our results do not support the monophyly of the genus Cuspivolva. Furthermore, our findings indicate that mitochondrial gene rearrangements occurred after the divergence of the subfamilies Prionovolvinae and Ovulinae. Additionally, we found that Ovulidae species display significantly higher Ka/Ks ratios compared to Cypraeidae, indicating different selective pressures, possibly linked to their unique feeding habits. This research enhances the understanding of Ovulidae phylogeny and provides genomic resources for future studies.

This study explores the phylogeny and mitochondrial genomics of Ovulidae, a family of marine gastropods related to Cypraeidae, by analyzing mitochondrial genomes from 14 of 15 species collected off China's coast. Key findings include the reclassification of genera Naviculavolva and Contrasimnia to the subfamily Prionovolvinae, evidence against the monophyly of Cuspivolva, and insights into mitochondrial gene rearrangements and higher Ka/Ks ratios in Ovulidae compared to Cypraeidae, suggesting distinct selective pressures tied to their specialized diets. These results deepen our understanding of Ovulidae evolution and offer valuable mitochondrial genomic resources for future research.