A phylogeny of freshwater eels inferred from mitochondrial genes

The genus Anguilla Shaw of Family Anguillidae consists entirely of freshwat er eels, including 15 species and 2 subspecies. Conventionally, variegated markings and the length of the dorsal fin are the major morphological featu res used for reconstruction of phylogenetic relationships. The evolutionary history of these species remains unclear, especially for the Atlantic eels , whose habitats are far from the Metropolis in the Indo-Pacific region. Th is study reexamined the phylogenetic relationships of 12 Anguilla species b y sequencing of the cytochrome b and 12S rRNA genes. In our analysis, speci es bearing similar coloration patterns or dorsal fin morphology are not nec essarily clustered in the same Glade, indicating that these morphological f eatures might be unstable or might have occurred independently in different lineages during evolution. Combining our molecular data and geographical e vidence, we speculate that (1) Anguilla first radiated about 20 million yea rs ago, (2) the ancestors of Atlantic eels did not migrate by drifting thro ugh the Tethys Seaway at the leptocephali stage but instead trekked across the Central American Isthmus to the Sargasso Sea for spawning at the adult stage, and (3) multiple radiation events had occurred at the Metropolis dur ing Anguilla evolution. (C) 2001 Academic Press.