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