カライワシ類 (Elopomorpha) を中心とした下位真骨類の系統

抄録

Higher-level relationships of the basal teleosts are reviewed, with particular reference to the monophyly and interrelationships of the Elopomorpha.Since Greenwood et al. established in 1966 the Elopomorpha on the basis of eight putative synapomorphies, many authors have discussed validity of their monophyly through comparative observations of osteology, ontogeny, microstructure of spermatozoa, and physiology. Such circumstantial evidence have remained controversial, because none of them have reconstructed their phylogeny using character matrices derived from both morphological and molecular data. The same is true of long-standing controversy over phylogenetic positions of the Elopomorpha among major basal teleostean lineages, many authors simply demonstrating their “views” in the form of cladograms with putative synapomorphies until quite recently. Considering their morphological heterogeneity (from very primitive elopomorphs to highly derived eels) and ancient origins that presumably goes back to over a hundred million years ago, we concluded that corroboration of monophyly and determination of the phylogenetic position of the Elopomorpha should be based on comparisons of longer DNA sequences from many purposefully-chosen species. Recent development of a PCR-based approach for sequencing the fish mitochondrial genomes would be the most promising candidate for providing such data within a short period of time and they have actually resolved the latter problem in a recent study.