Genetic evidence of population structuring in the neotropical freshwater fish Brycon hilarii (Valenciennes, 1850)

Abstract

Brycon hilarii is a migratory fish widely distributed throughout the Paraguay River Basin. It is appreciated in sport fishing and for its superior meat quality. It is also the main species for tourist attraction in the Bonito region (State of Mato Grosso do Sul, Brazil). Considering the lack of information on the genetic structure of the fish of this species, the aim of the present study was to detect the genetic variability of Brycon hilarii through RAPD markers. A total of eighty specimens collected in different seasons at four sites of the Miranda River sub-basin (Paraguay River Basin, Brazil) were used for analysis. The results of genetic similarity, Shannon diversity, and AMOVA revealed differences between the sampling sites. Through AMOVA, differences between populations were more evident among the animals collected during the non-reproductive season, corresponding to a time of less movement of these fish. A population structuring model in which B. hilarii appears organized into genetically differentiated reproductive units that coexist and co-migrate through the studied system was suggested, contrasting the currently accepted idea that freshwater migratory fish form large panmictic populations in a determined hydrographic system. Despite the lack of a complete picture regarding the distribution of B. hilarii in the studied region, this initial idea on its population genetic structure could be an important contribution to providing aid for management and conservation programs of these fish.Keywords: Bryconinae, Characidae, conservation genetics, population genetics. Evidência genética de estruturação populacional do peixe neotropical de água doce Brycon hilarii ResumoBrycon hilarii é uma espécie de peixe migrador, distribuída por toda a Bacia do Paraguai, bastante apreciada tanto pela qualidade da carne quanto para a pesca esportiva, além de ser a principal espécie de interesse turístico da região de Bonito (MS, Brasil). Considerando a ausência de informações sobre a estrutura genética dos peixes desta espécie, o presente trabalho visou detectar a variabilidade genética de Brycon hilarii através de marcadores RAPD. Foi estudado um total de 80 exemplares amostrados em diferentes períodos do ano, em 4 localidades da sub-bacia do Rio Miranda (Bacia do Rio Paraguai, Brasil). Os resultados de similaridade genética, de diversidade de Shanon e AMOVA evidenciaram diferenças entre as localidades amostradas. Através da AMOVA, a diferenciação populacional foi mais evidente entre os peixes coletados no período não-reprodutivo, que representa a época de menor deslocamento desses peixes. Desta forma, ao contrário da idéia até então aceita de que os peixes migradores de água doce formam grandes populações panmíticas em um dado sistema hidrográfico, sugere-se a ocorrência de um modelo de sub-estruturação populacional onde os indivíduos de B. hilarii se organizam em unidades reprodutivas geneticamente diferenciadas e mantêm sua integridade co-existindo e co-migrando através do sistema estudado. Apesar da falta de u...

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

“…Population structuring has also been found in B. hilarii from the Paraguay River Basin (Sanches & Galetti, 2007). Significant genetic differences were detected between populations and the authors assumed that the spawning schools may organize themselves in such way as to maintain the integrity of each subunit residing in the system.…”

“…In recent years, the number of genetic studies on Neotropical freshwater fish have indicated structuring of their populations within a same hydrographic basin (for a review, see Piorski et al, 2008), including migratory species (Machado et al, 2005;Sanches & Galetti, 2007). The present study revealed different results for both migratory fish species studied.…”

“…In recent years, a number of genetic investigations have revealed that Neotropical freshwater migratory fish can exhibit population structuring, with different genetic populations within a single hydrographic system (Wasko & Galetti, 2002;Hatanaka et al, 2006;Sanches & Galetti, 2007). It has been claimed that during the spawning season fish schools may exhibit behavior that enables the maintenance of the genetic integrity of such populations Sanches & Galetti, 2007).…”

“…It has been claimed that during the spawning season fish schools may exhibit behavior that enables the maintenance of the genetic integrity of such populations Sanches & Galetti, 2007). Knowledge on the genetic diversity within and between wild populations is crucial to the conservation of species (Haig, 1998).…”

Population genetic structuring in pacu (Piaractus mesopotamicus) across the Paraná-Paraguay basin: evidence from microsatellites

“…Sanches & Galetti Jr. (2007) used RAPDs to assess the genetic variability of 80 individuals of the migratory characin Brycon hilarii at four sites of the rio Miranda subbasin (Paraná-Paraguay basin) and found significant population differences. Those differences, however, were more evident during the dry season when fish movement is limited.…”