Species delimitation is a major quest in biology and is essential for adequate management of the organismal diversity. A challenging example comprises the fish species of red snappers in the Western Atlantic. Red snappers have been traditionally recognized as two separate species based on morphology: Lutjanus campechanus (northern red snapper) and L. purpureus (southern red snapper). Recent genetic studies using mitochondrial markers, however, failed to delineate these nominal species, leading to the current lumping of the northern and southern populations into a single species ( L. campechanus ). This decision carries broad implications for conservation and management as red snappers have been commercially over-exploited across the Western Atlantic and are currently listed as vulnerable. To address this conflict, we examine genome-wide data collected throughout the range of the two species. Population genomics, phylogenetic and coalescent analyses favour the existence of two independent evolutionary lineages, a result that confirms the morphology-based delimitation scenario in agreement with conventional taxonomy. Despite finding evidence of introgression in geographically neighbouring populations in northern South America, our genomic analyses strongly support isolation and differentiation of these species, suggesting that the northern and southern red snappers should be treated as distinct taxonomic entities.

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Prochilodus magdalenae is an endemic freshwater fish that occurs in the Magdalena, Sinú and Atrato hydrographic basins. It has an important economic role and is a food resource for the artisanal fishing communities. Its socioeconomic importance contrasts with the current status of its fisheries, where stocks are being depleted. Considering its importance and lack of information on its genetic structure, we used seven microsatellite markers to assess the genetic structure of wild populations of P. magdalenae. The genetic diversity was assessed and the population genetic structure was estimated through Fst, analysis of molecular variance and Bayesian analysis. A total of 290 alleles were found in all loci throughout all population. The high polymorphism contrasts with the levels of observed heterozygosity (Ho = 0.276), which are the lowest values recorded for the family. We found three populations of bocachico coexisting throughout the studied system, contradicting the hypothesis that freshwater migratory fish form panmictic populations. These results on the genetic structure of P. magdalenae constitute tools for a better understanding of the behavior and biology of this species, contributing to fish management and conservation programs.

The bocachico Prochilodus magdalenae is a freshwater migratory species of great importance for conservation in Colombia. The populations of this fish have been seriously threatened in the last decade, and there is limited knowledge of its genetic conditions.In order to evaluate the genetic structure of P. magdalenae in the Magdalena River basin and some tributaries, the mitochondrial DNA control region was analysed in samples selected from 20 sites.In total, 189 polymorphic sites were detected on a sequence of 500 bp of the control region among 292 individuals, defining 233 haplotypes from which 88.41% were private. Genetic diversity was high (HD = 0.997 and π = 0.0303), neither the analysis of molecular variance, the Φst statistic, nor the Mantel test values revealed significant differences of population subdivision in any of the hierarchical levels. The tests of neutrality and mismatch distribution detected a population expansion in the Middle Pleistocene.Results showed that P. magdalenae forms a large panmictic population in the basin of the Magdalena River. A wide migratory capacity, the absence of geographical barriers and not enough time to accumulate genetic variation are likely reasons for the genetic homogeneity found in this species. Copyright © 2013 John Wiley & Sons, Ltd.