Population life-history differences and their correlates across a regional spatial scale in largemouth bass (Micropterus nigricans)

Abstract

Isolation and limited migration among populations and differences in the environments they inhabit set up conditions for population differentiation of life-history traits, even across a regional spatial scale, such as a statewide landscape of lakes and reservoirs. Our objective was to understand how largemouth bass (Micropterus nigricans) life histories differ across a regional spatial scale (Ohio, USA) and whether environmental differences are influencing this variation. To address this, we (1) described spatial variation in largemouth bass life-history traits, with a specific interest in potential correlations between early-life growth and later-life traits and (2) tested whether life-history traits can be predicted by reservoir characteristics. We found two groups of correlated population traits: the inverse relationship of early-life growth rate with population density and asymptotic length and the positive relationship between adult size and asymptotic length. Early-life growth had a positive relationship (and population density and asymptotic length had a negative relationship) with littoral habitat availability and other environmental conditions expected to enhance early growth. Despite the strong influence of reservoir characteristics on life-history traits in our analysis, the most plausible model could not give precise predictions of these life-history traits, suggesting that the availability of data on other aspects of the populations and environments may improve our ability to understand life-history differences. Overall, our results suggest that, even among recently separated populations, we should expect differences in growth patterns and that we cannot understand drivers of these differences without considering possible correlations in growth patterns across the lifespan.