The Complete Mitogenome of the Estuarine Clam <i>Potamocorbula amurensis</i> (Corbulidae, Myida) and Its Implications for Phylogeny and Adaptation

ABSTRACT Potamocorbula amurensis is a euryhaline bivalve of considerable ecological and economic importance in estuarine ecosystems of the North Pacific. However, the absence of a well‐characterized mitogenome has limited a comprehensive understanding of phylogenetic relationships within order Myida, as well as the genomic mechanisms underlying its adaptation to estuarine environments. In this study, the complete mitogenome of P. amurensis was sequenced and assembled, which consists of a 21,044 bp circular molecule encoding 13 protein‐coding genes, 2 rRNA genes, and 23 tRNA genes, and exhibits a pronounced A + T bias (68.18%). Notably, the otherwise frequently undetected ATP synthase F0 subunit 8 ( atp8 ) gene was successfully identified and annotated, confirming its presence in the family Corbulidae. Phylogenetic analyses revealed that Corbulidae, represented by P. amurensis , forms a sister clade to the Myidae–Dreissenidae lineage with strong nodal support. The estimation of divergence times indicated that P. amurensis diverged during the Middle Jurassic, coinciding with major marine diversification events. Furthermore, signatures of positive selection were detected in nad5 along the P. amurensis lineage, suggesting mitochondrial adaptation in oxidative phosphorylation pathways in response to osmotic and thermal variability in estuarine environments. Collectively, these findings provide key insights into the mitogenomic evolution and estuarine adaptation of P. amurensis , and may inform future conservation strategies for this ecologically and economically important species.