Population genetics of the speckled peacock bass (Cichla temensis), South America's most important inland sport fishery

The Neotropics harbor the world's most diverse freshwater fish fauna, with many of these species supporting major commercial, subsistence, or sport fisheries. Knowledge of population genetic structure is available for very few Neotropical fishes, thereby restricting management. To address this need, we examined population genetic variation in mtDNA control region sequences and twelve microsatellite loci in the speckled or barred peacock bass, Cichla temensis. Moderate and statistically significant genetic divergence among localities indicates that migration is low in this species, implying that populations inhabiting tributaries or even smaller spatial units should constitute management units. Analysis of molecular variance of mtDNA sequences identified six areas with largely exclusive haplotype clades, and a seventh area of high admixture, but major drainage basins harbored non-monophyletic haplotype groups. On the other hand, molecular variation in the microsatellite data was best explained by drainage basin and, subsequently, by the seven areas. Populations in these seven areas could be considered evolutionarily significant units (ESUs), and, therefore, we tested hypotheses explaining the discordant signal of mtDNA and microsatellite data using approximate Bayesian computation. This analysis indicated that the divergence of mtDNA clades preceded the divergence of contemporary ESUs across basins, with subsequent lineage sorting among ESUs due to reduced gene flow. Available genetic and ecological information indicates that C. temensis populations of major tributary rivers should be managed as separate stocks that likely are adapted to local environmental conditions.