Population genetic structure and history of the long-tailed hake, Macruronus magellanicus, in the SW Atlantic as revealed by mtDNA RFLP analysis

The long-tailed hake, Macruronus magellanicus, is widely distributed in the SW Atlantic, and although it is commercially exploited, the extent of genetic structuring remains unclear. The hypothesis of a separate inshore stock as suggested by past biological data in northern Patagonia was tested with RFLP profiles of the mtDNA region ND5/6, in a total of 160 animals from eight locations. Sequence divergence between populations was nil, and all diversity is contained within populations. Despite the lack of geographic structuring in the distribution of haplotypes, the inference of population homogeneity should be taken cautiously owing to the skewed frequency distribution of haplotypes, with one allele accounting for 63% of individuals. A phylogenetic analysis of haplotypes reveals a star-shaped pattern with the presence of two lineages that may represent a population expansion. A rapid turnover of lineages, sweepstake recruitment, rapid expansion, or vulnerability to environmental conditions is not only suggested by the network pattern, but also by the departure from neutrality expectations. However, the role of selection cannot be ruled out until more loci or markers are examined. (C) 2004 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All tights reserved.