Phenotypic plasticity in Saxifraga osloensis: comparisons among populations

In a laboratory experiment the variation in plasticity of traits and trait mean values among populations of Saxifraga osloensis was examined. S. osloensis is a winter annual plant of allopolyploid origin, endemic to Scandinavia. Five populations from different parts of the species distribution range were grown in three treatments, differing in temperature and water availability. Most traits were plastic in response to the treatments. The pattern of plasticity varied among the populations, as well as the mean values of the traits. There was some correspondence in differentiation between the trait mean values and the plasticity of the traits. The pattern of differentiation was consistent with geographical distances between the populations. Correlation coefficients between traits were estimated for all populations. The start of flowering was correlated to the initial growth rate. The production of capsules and the number of seeds per capsule were not dependent on any of the other measured traits. There were no indications of buffering of reproductive traits by plasticity in other traits. The results are discussed in relation to local weather conditions at the population sites, but no consistent conclusions about environmental adaptation can be drawn.