Phylogenetic analysis of the family Pectinidae (Bivalvia) based on mitochondrial cytochrome C oxidase subunit I

Abstract

A molecular phylogenetic study of the Pectinidae (Mollusca: Bivalvia) was carried out based on the amino acid sequences of mitochondrial cytochrome c oxidase subunit I (COI) in 17 species of this family. Interestingly, the obtained phylogenetic tree is almost completely consistent with Waller's classification system of the Pectinoidea, which was proposed mainly on the basis of shell microstructure and early dissoconch morphology. The recognized clades of various levels in the present tree correspond well to the families, subfamilies or tribes defined by him. It indicates not only the adequacy of his method in the evaluation of taxonomic characters but also the possibility that a thoughtful analytical study of uniquely derived morphologic characters also could approach true phylogenetic relationship. On the other hand, the present tree is evidently inconsistent with the systems by many other authors which are merely based on the macroscopic morphology of adult shells. They seem to have overlooked convergence which arises from similar life habit between independent lineages. Although the object of phylogenetics and taxonomy should be discriminated, molecular phylogenetic studies thus provide criteria to see through convergence at various levels and will contribute much to improve existing classification systems.