Quantitative variation for metabolic traits among brook trout populations inhabiting different environments

Abstract

AbstractEcologically relevant traits can change over short time scales if they vary among populations and if they are heritable. Comparisons of quantitative variation for phenotypic characters and molecular traits can be used to indicate whether phenotypic traits are under directional or stabilizing selection, or are changing as a result of drift. Many studies have shown that population differentiation in life history and morphological traits differ from null expectations, suggesting the action of diversifying selection. Very few studies have examined quantitative variation for metabolic traits. In this study, we examine variation for enzymatic activities in 181 brook trout inhabiting different environments (rivers, streams and lakes). Different environments may exert different selective pressures in fish locomotor performance and in underlying metabolic pathways. Our objectives were to determine (1) if metabolic traits of whole axial muscle exhibited variation among closely located populations of brook trout exploiting different habitats and (2) assess if these divergences could be associated with genetic structure. No significant differences were found in citrate synthase, cytochrome oxidase (CCO), pyruvate kinase (PK), amino acid transferase (AAT) activities among fish from different habitats but sampling location had a significant effect on CCO, PK and AAT activities. Measures of quantitative divergence for metabolic traits were higher than population genetic divergence values for both allozymes and microsatellites revealing significant plasticity of these metabolic traits upon which selection may act.