Population Differentiation for Phenotypic Plasticity in the Stellaria Longipes Complex

Population differentiation for phenotypic plasticity of 12 morphological and reproductive traits was investigated in five populations of the Stellaria longipes complex including a population of the sand dune endemic S. arenicola. Population differentiation was detected for the mean (genotypic) value, amount of plasticity, and pattern of plasticity of traits. Average amount of plasticity was not related to degree of isozyme variability in the populations. Differentiation for pattern of plasticity was much more common than for amount. The direction and extent of divergence among populations was dependent on which of the three trait aspects was under consideration (mean, amount of plasticity, pattern of plasticity) and did not reflect their similarity as revealed by enzyme electrophoretic data. It was concluded that trait means, amounts of plasticity, and patterns of plasticity are independent of one another during evolutionary divergence and may be influenced by mosaic selection.