Mitochondrial DNA differentiation in North Atlantic eels: Population genetic consequences of an unusual life history pattern.

A survey of restriction site polymorphism in the mitochondrial DNA (mtDNA) of the American eel Anguilla rostrata showed no genetic divergence among samples from a 4000-km stretch of North America coastline. Lack of geographic differentiation in mtDNA over such a large area contrasts sharply with results for terrestrial and freshwater vertebrates and is most likely attributable to the extraordinary life history of these catadromous fishes, which involves perhaps a single spawning population in the western tropical mid-Atlantic Ocean and subsequent widespread dispersal of larvae by ocean currents. However, samples of the European eel (nominally Anguilla anguilla) are highly distinct from A. rostrata in mtDNA genotype (distinguishable by 11 of 14 restriction endonucleases), contradicting some previous suggestions that the two forms belong to the same panmictic population. Results of this study emphasize the importance of life history in shaping population genetic structure.