Two Genetically Distinct Forms of Rougheye Rockfish Are Different Species

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Abstract
The variation in mitochondrial DNA (mtDNA) and at eight microsatellite loci was analyzed in 700 rougheye rockfish Sebastes aleutianus sampled along the Pacific Rim from the Oregon coast to the western Aleutian Islands and Bering Sea. The program STRUCTURE was used to analyze the microsatellite genotypes and determine that the samples probably came from two genetically distinct sources (type I and type II) by minimizing the strong Hardy−Weinberg and gametic disequilibria observed in the total sample. The two types had nearly fixed differences at one microsatellite locus (μSma 6), which corresponded to divergent mtDNA haplotype clusters. We conclude that these two types are distinct species. The ranges of the two types overlapped but were not coincident; in some areas, one or the other predominated. For example, most of the Aleutian Island samples were type I fish. Although both types were caught in the same hauls in some regions, often one or the other species was predominant in a haul. The differences in distributions suggest a historic vicariant or ecological basis for their divergence. No phenotypic characteristics have been confirmed that can be used to distinguish the two species visually. Rougheye rockfish have high commercial value and their incidental catch has the potential to greatly affect larger fisheries. The discovery of cryptic speciation in a commercially important species underscores our need to learn more about the distribution and biology of these and other groundfish species.

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