Subindividual variation and genetic versus environmental effects on seed traits in a European Aquilegia

Abstract

Repetitive plant parts such as seeds can be characterized at the within-individual level not only by average values but also by higher moments of their distributions, such as the standard deviation, skewness, and kurtosis. These parameters can potentially be adaptive and shaped by selection like any other individual trait, but tend to be understudied. We present an example of how within-individual variation might be studied. We used a diallel crossing design to investigate the sources of phenotypic variance of among- and within-individual variation in seed and germination traits of the endemic columbine Aquilegia pyrenaica subsp. cazorlensis (Heywood) Galiano & Rivas Martínez. Individual plants and even fruits have their characteristic mean, standard deviation, skewness, and kurtosis and therefore these parameters could potentially respond to selection. However, we only found evidence of genetic variance in mean within-fruit seed mass, mean time to seedling emergence, and number of seeds: these effects were attributable to maternal effects. Variance in higher moments of the within-fruit distributions in this species could instead reflect developmental instability or plastic responses to localized environmental conditions as fruits develop. Large sample sizes are required to make final conclusions in this case, but this study illustrates how the novel approach of considering high moments of intra-individual variation will enhance our view of plant trait evolution.