Genetic variability and historic stability of the California spiny lobster Panulirus interruptus in the Gulf of California

• Population genetic structure of the California Spiny lobster in California and Mexico was investigated.
• Similar diversity among locations and overall weak genetic structure was found.
• Genetic diversity within the Gulf of California was higher than anticipated.
• An older and more stable population is present in the Gulf of California.
• The lack of significant differences between the gulf and the Pacific does not imply present geneflow.

The California spiny lobster Panulirus interruptus ranges from California into the Gulf of California in Mexico. In Mexico, the lobster supports an economically important fishery. Lobsters in the Gulf of California may belong to a small and genetically distinct population. We determined the genetic diversity and population structure of P. interruptus, using mitochondrial DNA sequences of the control region and the 16SrRNA gene. Samples were collected in the Gulf of California, the west central and southwest coast of the Baja California Peninsula, and the United States. We found a slightly higher genetic diversity in the Gulf of California populations than in the Pacific, but no significant genetic differentiation was shown by an analysis of molecular variance. Using a spatial clustering model and Bayesian methods, the weak population structure was consistent with the absence of a phylogeographic pattern and genetic admixture analysis. However, mismatch distribution analysis suggests that lobster from the gulf represents a more stable and older population than the Pacific, which fitted a model of sudden population expansion. The clinal trend in several genetic parameters between the Gulf of California and the Pacific suggests a historical separation that has not yet resulted in a significant genetic differentiation by genetic drift, mainly because of the large size of the population. Implementation of independent fisheries management practices between these regions could be justified; however, biological and ecological information should be used to support genetic data.