Tetraploidy and the Evolution of Salmonid Fishes

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Abstract

Polyploidy has long been recognized to have played an important role in the evolution of plant species (Lewis, 1980). However, polyploidy has only recently been recognized as a potentially important process in the evolution of vertebrates (Ohno, 1974; Fisher et al.,1980; Bogart, 1980; Schultz, 1980). Mammals and birds generally possess more DNA per cell than do fish and other chordates. This observation and the existence of many duplicated gene loci have led Ohno and co-workers (Ohno,1967, 1970a, 1974; Ohno et al., 1968) to propose that genome doubling has taken place at least once in the evolution of vertebrates. One tetraploid event apparently took place about 500 million years (Myr) ago in a common ancestor of all vertebrates. Fisher et al. (1980) describe isozyme studies that are consistent with this idea. Other tetraploid events may have taken place in major lineages of vertebrate evolution, possibly including a genome doubling in a reptilian ancestor of mammals (Ohno, 1967; Comings, 1972).