Phenotypic plasticity of growth trajectories in two species of Lobelia in response to nutrient availability

1 Phenotypic plasticity is inherently a developmental and multivariate phenomenon. We examine the responses of growth and fitness components to nutrient availability among genotypes and populations of the phylogenetically closely related but ecologically distinct species Lobelia cardinalis and L. siphilitica. 2 We found evidence of genetic variation for the shape of the growth trajectories of several phenotypic traits at the species, population and genotype levels. The two species were also distinct in the way that their growth patterns responded to differences in nutrient levels. 3 Both phenotypic correlations and estimates of genetic variability were age and environment-dependent, and the patterns of change differed between the two species. Lobelia cardinalis had relatively higher genetic variation in early stages, L. siphilitica in later stages. Selective forces will therefore vary in their effectiveness depending on life stage and environmental conditions. 4 We propose that more investigations using complex data sets such as the one presented here are important for more realistically probing the way plant populations adapt to heterogeneous environmental conditions.