Reconsiderando a tipologia das águas de Wallace: escolha de água de igarapé e maior sucesso de desova em um peixe amazônico

Abstract

Following Alfred Russel Wallace, Amazonian freshwaters have been classified into three main types: black, white and clear. Adaptation to water types has been demonstrated to affect gene flow, making it an important source for diversification of the Amazonian fish fauna. However, this classification focuses on large rivers and fails to acknowledge the importance of small forest streams that flow through non-flooded forest, known as igarapés. As compared to large river channels, igarapés cover a much greater area than the Amazon River and have a distinct hydrochemistry, mostly due to soil and vegetation. We assessed the importance of water type on habitat choice and spawning in Crenuchus spilurus, a small fish that inhabits igarapés inserted within blackwater and whitewater river basins. Lineages from the Rio Negro (blackwater) and Amazon River (whitewater) basins showed active selection of igarapé water in habitat choice trials and had greater spawning success in igarapé water when compared to water from their respective flooded forest basin. Due to the hydrochemical conditions of igarapés acting to shape reproduction and behavior of C. spilurus, our results expand Wallace’s intuition that water types influence diversity by providing evidence that igarapés represent an important habitat driving adaptation in Amazonian fishes.