Molecular phylogeny and evolution of the freshwater eel, genus Anguilla

A molecular phylogenetic analysis was conducted on all of the known catadro mous eel species of the genus Anguilla to assess their relationships and ev olutionary history. The analyses of a total of 1427 bp of the mitochondrial 16S ribosomal RNA and 1140 bp of the complete cytochrome b gene sequences suggested that the genus Anguilla was monophyletic in origin, with A. borne ensis as the most basal species. Four clades/species groups that correspond to their geographical ranges were indicated, Indo-Atlantic (three species) , Oceania (two species), tropical Pacific (two species), and Indo-Pacific ( five species), with ambiguous positions for A. japonica and A reinhardti. T his grouping conflicts with that of a previous morphological study, since t he broad undivided maxillary and short-fin type, which were thought to be p hylogenetically important, were paraphyletic in the molecular analysis. How ever, the molecular phylogeny and the present geographic distribution of sp ecies suggested historical dispersion of the genus Anguilla according to th e Tethys corridor hypothesis, which proposed that anguillid eels originated near present-day Indonesia and dispersed westward along paleo-circumglobal equatorial currents. The westward-moving strain entered the paleo-Atlantic thyough the Tethys Sea and was ancestral to present-day European and Ameri can species. (C) 2001 Academic Press.