Article Title

Morphologic and Genetic Variation Among Six Populations of the Spotted Sand Bass, Paralabrax maculatofasciatus, from Southern California to the Upper Sea of Cortez





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Spotted sand bass, Paralabrax maculatofasciatus, were examined for 19 morphometric and 7 meristic characters to determine the extent of morphologic and genetic variation among six Pacific and Gulf of California populations. Poly- merase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) techniques were used to amplify and cleave the ITS region of the rDNA in order to detect differences among these populations. The morphological and genetic lines of evidence demonstrate that significant differentiation has occurred between the most distant Gulf and Pacific regions. The three Baja California populations share significant morphological and genetic affinity and appear to be different from the three Pacific populations. There is no significant morphologic differentiation between the three Pacific populations although genetically they form two different groups. The northernmost Pacific population of San Diego is significantly different from the two southern-Pacific groups as well as the entire gulf sample. The results of this study indicate that geographically isolated pop- ulations of nearshore marine fishes, under the influence of strong selection pres- sures, do not require long periods of time for divergence. The last 15,000 years may have been sufficient to allow significant divergence to occur between upper Gulf and Pacific groups of the spotted sand bass.