Assessment of otocephalan and protacanthopterygian concepts in the light of multiple molecular phylogenies.

ABSTRACT

The rise of cladistics in ichthyology has dramatically improved our knowledge of teleostean basal interrelationships. However, some questions have remained open, among them the reliability of the Otocephala, a clade grouping clupeomorphs and ostariophysans, and the relationships of the Esocoidei. These two questions have been investigated in the light of new DNA sequences (from 28S and rhodopsin genes) and sequences from data banks (cytochrome b, 12-16S, 18S, MLL and RAG1). The ability of each of these markers to resolve basal teleostean interrelationships is assessed, and the cytochrome b was not found appropriate. Practical (i.e. different taxonomic samplings) and epistemological grounds led us to perform multiple separated phylogenetic analyses, in order to estimate the reliability of the above clades from their repeatability among trees from independent sequence data. The Otocephala are found monophyletic from most of the datasets; otherwise, they are not significantly contradicted from the others, which exhibit unresolved relationships. We conclude that the evidence provided here favours the sister-group relationship of clupeomorphs and ostariophysans. Morphological evidence including fossils is discussed, concluding that morphological works have not yet provided sufficient data to support this group. Salmonids and esocoids are found sister-groups from every molecular dataset in which these groups were sampled. Based on these convincing results, the Protacanthopterygii of Johnson and Patterson [1] are redefined, including the Esocoidei.