River Flow Regime Predicts Life History Traits in Poeciliid Fish

Abstract

Life history theory seeks to explain how the environment shapes life history traits. Based on this theory, we expected that Poecilia vivipara in rivers with intermittent and perennial flow regimes would show differences in maturation and reproductive investment. We sampled specimens from two rivers in the Brazilian semi-arid region with these contrasting river flow regimes. One is intermittent, where the flow ceases during the dry season and fish populations become confined to isolated pools on the riverbed, and the other is artificially perennial with continuous flow. We predicted that females would mature earlier and invest more in reproduction in the intermittent river than in the perennial river. Our findings supported the predictions; river intermittency apparently has shaped the traits of P. vivipara in natural environments as contrasted with those affected by anthropogenic alterations. Further study is needed to investigate whether these traits reflect genetic differences or phenotypic plasticity.