Family mean correlations among fitness components in wild radish: controlling for maternal effects on seed weight

Abstract

Qualitative estimates of genetic associations among life-history and fitness components are reported for 30 sibships (or families) in a common garden population of Raphanus raphanistrum L. (Brassicaceae: wild radish). Genetic associations are detected in a qualitative way when correlation coefficients among family means are highly significant. In this study, correlation coefficients among family means are compared with phenotypic correlation coefficients and to each other to address three questions: (i) Do strong genetic trade-offs among fitness components exist in wild radish under experimental conditions? (ii) Do qualitative estimates of genetic associations differ from phenotypic correlations? and (iii) Since seed weight is strongly phenotypically correlated with many components of plant performance and since families differ in seed weight because of strong maternal environmental (nongenetic) effects, does controlling for seed weight affect the correlations among family means? Many heritable fitness components were positively correlated among families; however, strong positive phenotypic correlation coefficients were much more common than strong positive family-mean correlation coefficients. No strong negative genetic associations were detected. The tendency for phenotypic correlations to be more positive than family mean correlations is consistent with the expectation that environmental variation generates positive correlations among characters, masking genetically based trade-offs. Partitioning out the effect of seed weight had only a small effect on the magnitude of the among-family correlation coefficients.