Leopold Schepp Foundation

Previous studies on the muscle lactate dehydrogenase polymorphism of the stichaeid fish Anoplarchus purpurescens in Puget Sound have demonstrated the existence of a clinal pattern of allele frequency. The LDH-A' allele was observed to increase toward the south, with several environmental factors showing correlation with this change in allele frequency. Populations from California were sampled in the present study to determine whether or not gene frequencies along an independent transect near the southern end of the species distribution are consistent with the interpretation that the geographic patterns reflect the influence of environmental factors. In California, the LDH-A' allele decreases in frequency to the south. This observation necessitates the reevaluation of possible environmental influences on the LDH polymorphism. Only one of several proposed hypotheses is completely consistent with the geographic patterns observed along both the Washington and California transects. However, the genetic differentiation along the California coast cannot be unequivically ascribed to the influence of environmental factors; current morphological data indicate the possibility of historical influences on the population genetic structure of California A. purpurescens.