Genetic population structure of two migratory freshwater fish species (Brycon orthotaenia and Prochilodus argenteus) from the Sao Francisco River in Brazil and its significance for conservation

Abstract

ABSTRACT. Previous genetic studies conducted with migratory fish populations from downstream of the Três Marias dam in the São Francisco River Basin (Brazil) have documented the occurrence of population structuring, as reported for Brycon orthotaenia and Prochilodus argenteus, two commercially important species in this basin. We revisited the genetic structure of these species using microsatellites. B. orthotaenia was sampled during the spawning season and was analyzed using five heterologous microsatellites. P. argenteus was collected in the non-reproductive season and genetic analysis was conducted using ten speciesspecific microsatellites. For both species, genetic diversity between collection sites was similar. Considering B. orthotaenia, F ST and R ST estimates and the Bayesian analysis demonstrated significant differences between sites. Two well-defined populations were identified in the study area, indicating population structuring for this species. No significant differences were found for P. argenteus. These data provide information for knowledge regarding genetic structure of migratory fish species, which may contribute toward the conservation besides the understanding the biology and ecology of these important fishery resources. Keywords: migratory fish, freshwater fish, genetic structure, Characidae, Prochilodontidae, microsatallite, Brazil.Estructura genética poblacional de dos especies de peces migratorios de agua dulce (Brycon orthotaenia y Prochilodus argenteus) en la cuenca del Río San Francisco (Brasil) y su importancia para la conservación RESUMEN. Estudios genéticos anteriores realizados con poblaciones de peces migratorios de aguas abajo de la represa de las Tres Marías en la cuenca del río San Francisco (Brasil) han documentado casos de estructuración genética, como se ha descrito para Brycon orthotaenia y Prochilodus argenteus, dos especies de importancia comercial. Se revisó la estructura genética de estas especies utilizando microsatélites. Se obtuvieron muestras de B. orthotaenia durante la temporada de desove y se analizaron mediante cinco microsatélites heterólogos. Muestras de P. argenteus fueron recogidas en la temporada no reproductiva y el análisis genético se realizó utilizando diez microsatélites específicos para P. argenteus. Para ambas especies, la diversidad genética entre los sitios de recolección fue similar. Considerando a B. orthotaenia, las estimaciones F ST y R ST y el análisis Bayesiano demostraron diferencias significativas entre los sitios. Se identificaron dos poblaciones bien definidas en el área de estudio, indicando una estructuración de la población de esta especie. No se encontraron diferencias significativas para P. argenteus. Estos datos proporcionan información para el conocimiento sobre la estructura genética de las especies de peces migratorios, que puede contribuir a la conservación, además de la comprensión de la biología y ecología de estos importantes recursos pesqueros. Palabras clave: peces migratorios, peces de agua dulce, estructura genética, Chara...

The roles of marginal lagoons in the maintenance of genetic diversity in the Brazilian migratory fishes Prochilodus argenteus and P. costatus

“…The migration behavior, which is common in prochilodontids (Castro & Vari, 2004) likely plays an important role in the continuous gene flow in these species, keeping them as a single unit in the studied area. Variability levels in microsatellites with a mean number of 9.6 alleles per locus in Prochilodus argenteus and 12.9 alleles per locus in P. costatus were similar to those reported in freshwater fish with an average of 9.1 alleles per locus (DeWoody & Avise, 2000) and were similar to or higher than previous studies with both Prochilodus species (Hatanaka et al, 2006;Carvalho-Costa et al, 2008;Sanches et al, 2012). High genetic diversity was previously identified in P. lineatus (Sivasundar et al, 2001), which can be explained by the capacity of Prochilodus species to perform great migrations and by their large occurrence along the rivers.…”

“…The population differentiation indexes F ST and R ST , the chord genetic distance associated to a high gene flow and previous studies (Carvalho-Costa et al, 2008;Sanches et al, 2012) corroborate the panmictic unit model for both species. The migration behavior, which is common in prochilodontids (Castro & Vari, 2004) likely plays an important role in the continuous gene flow in these species, keeping them as a single unit in the studied area.…”

“…The R ST values under the SMM are expected to be greater than the F ST values under the IAM (Slatkin, 1995), although the inverse has been observed in some fish species (e.g., Pereira et al, 2009). Low indexes of F ST have been observed in other studies with characiforms, such as in Colossoma macropomum (Santos et al, 2007), Piaractus mesopotamicus (Calcagnotto & DeSalle, 2009;Iervolino et al, 2010), Prochilodus argenteus (Hatanaka et al, 2006;Sanches et al, 2012), Prochilodus costatus (Carvalho-Costa et al, 2008), Prochilodus lineatus (Revaldaves et al, 1997) and Salminus brasiliensis (Lopes et al, 2007).…”

“…Microsatellites are abundantly distributed along genomes and demonstrate high levels of allelic polymorphism (DeWoody & Avise, 2000). The molecular structure and genetic variability of microsatellites are extensively exploited in evolutionary studies of a wide variety of fish species (see Chistiakov et al, 2006), including some from Neotropical freshwater (Hrbek et al, 2007;Abreu et al, 2009;Calcagnotto & DeSalle, 2009;Matsumoto & Hilsdorf, 2009;Pereira et al, 2009;Sanches et al, 2012).…”

“…Population genetic studies have been performed with both Prochilodus species from the rio São Francisco basin using Random Amplified Polymorphic DNA (RAPD) technique (Hatanaka & Galetti, 2003) and microsatellites (Hatanaka et al, 2006;Carvalho-Costa et al 2008;Sanches et al, 2012;Barroca et al, 2012). However, there is no knowledge about the main nursery areas of the populations of either species or the importance of the marginal lagoons in the maintenance of the genetic variability of these or other migratory species.…”