Scientia Marina, Vol 67, No 4 (2003)

Microsatellite variation in the Mexican rockfish Sebastes macdonaldi


https://doi.org/10.3989/scimar.2003.67n4451

Axayácatl Rocha-Olivares
Centro de Investigación Científica y Educación Superior de Ensenada, Departamento de Oceanografía Biológica, Mexico

Raul A. Leal-Navarro
Universidad Autónoma de Baja California, Facultad de Ciencias Marinas - Universidad Autónoma de Baja California, Facultad de Ciencias Marinas, Mexico

Karol Kimbrell
National Oceanic and Atmospheric Administration, Southwest Fisheries Science Center, United States

Eric A. Lynn
National Oceanic and Atmospheric Administration, Southwest Fisheries Science Center, United States

Russell D. Vetter
National Oceanic and Atmospheric Administration, Southwest Fisheries Science Center, United States

Abstract


The Mexican rockfish Sebastes macdonaldi is the Northeast Pacific rockfish with the southernmost distribution, featuring isolated populations in the Gulf of California. We analysed seven microsatellite loci in 111 organisms collected throughout most of its geographical range to test long-standing hypotheses regarding its disjunct distribution. One locus was fixed and the number of alleles in polymorphic loci ranged from 2 to 24 (average 13.5). We found very high levels of polymorphism (overall He = 0.75) comparable to other congeneric species but no significant differences in genetic diversity among localities or between Pacific and Gulf of California populations (p > 0.1). Significant shifts in allelic and genotypic frequencies were detected at three loci, which resulted in a small but significant partitioning of genetic variance among California, Baja California and Gulf of California populations (FST = 0.007, p = 0.03) and between Gulf and Pacific populations (FST = 0.01, p = 0.004). The latter but not the former result was corroborated by analyses of molecular variance (AMOVA) using the number of distinct alleles (FST) and the sum of square differences of allele sizes (RST) as Euclidean distances. The evidence argues against contemporary gene flow between the gulf and the Pacific ocean and against an ancient invasion of the gulf with a founder effect. The small level of divergence favours a recent dispersal but a larger data set including DNA sequences amenable to phylogenetic analyses will help to test alternative hypotheses of dispersal versus vicariance.

Keywords


Mexican rockfish; disjunct distribution; microsatellites; genetic structure; Baja California; México

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