Abstract

Marine mussels in Mytiloidea Rafinesque, 1815, are ecologically and commercially significant, but their phylogenetic relationships and taxonomic classification remain controversial. In this study, we aimed to clarify the phylogenetic relationships within Mytiloidea and provide new molecular evidence for the taxonomy of problematic taxa. Complete mitochondrial genomes and five gene fragments, including cox1, 16S rRNA, 18S rRNA, 28S rRNA, and the histone H3 gene, were newly obtained for nine species representing four subfamilies: Mytilinae, Brachidontinae, Septiferinae, and Mytiliseptinae. All mitogenomes are double-stranded circular molecules characterized by a high A + T content and significantly variable gene arrangements. Phylogenetic analysis recovered Mytiloidea as two major clades. The monophyly of Mytilinae and Crenellinae were well supported, based on nuclear and mitochondrial gene fragments, and further analysis is required to determine the monophyly of Brachidontinae. Our results support the placement of Perna within the Crenellinae and provide molecular evidence for revising the taxonomic status of Trichomya hirsuta and Dentimodiolus species. The estimation of divergence time suggested that Mytiloidea originated during the Silurian, with major subfamily divergences occurring during the Mesozoic. Overall, this study provides new molecular evidence and advances the understanding of the complex phylogenetic relationships within Mytiloidea.