Concordant estimates of countergradient growth variation in striped bass (Morone saxatilis) using comparative life-history data

Latitudinal growth compensation (i.e., countergradient growth) is increasingly suspected to be pervasive across diverse taxa. However, a major challenge limiting wider exploration of this topic lies in the difficulty of quantifying these relationships. Common garden experiments, and ideally genetics, remain the only true methods for understanding the genetic basis for compensatory growth. However, previous research suggests that comparative life-history data might produce concomitant, albeit nonconfirmatory, results on countergradient growth variations. However, there have been no evaluations of the precision of such estimates against those that are experimentally derived. I examined countergradient growth variations using comparative size-at-age data for striped bass ( Morone saxatilis ), a species for which experiments have already quantified countergradient growth patterns, and compared results derived from both techniques. The slope of the growth–latitude relationship for striped bass in eastern North America as measured with comparative data was virtually identical to that produced from experiments. Furthermore, comparative estimates of countergradient growth variations developed using a variety of metrics produced highly concordant results with one another. Comparative life-history data are not a replacement for experiments, but do provide valuable information on countergradient growth variations, especially for species and hypotheses not amenable to experimentation.