イタヤガイ類の系統分類と分類形質の評価

抄録

Current suprageneric classification systems of scallops (superfamily Pectinoidea), which were proposed by several authors mainly on the basis of adult shell morphology, are critically reviewed, and some important characters for the macrotaxonomy are evaluated. In recent years T. R. Waller has been establishing a new classification system of this superfamily in view of the fossil records, shell microstructure and some derived characters in the early dissoconch. Because the shell morphology in early byssate stage is not related to the subsequent change of life habit and resultant convergence, Waller's system may be logically regarded as more adequate than previous ones, possibly better reflecting true phylogenetic relationship. This inference was preliminarily but successfully tested by our mitochondrial DNA phylogenetic analyses of seven pectinids from Japanese waters; for example, the molecular phylogenetic tree using cytochrome oxidase subunit I surprisingly agrees well with Waller's system. Although the results of molecular phylogenetic analyses may not directly indicate Linnean hierarchial systems, they must greatly contribute to the improvement of classification and adequate evaluation of taxonomic characters.