Evolution of floral size in Campanula rotundifolia (Campanulaceae) - effects of selection by pollinators and gene flow

Campanula rotundifolia is a widespread plant that exhibits a clinal variation in flower size along altitudinal gradients. Generally, lowland populations exhibits plants with many small flowers and alpine populations exhibits plants with few large flowers. This variation also seems to covary with the size of the local pollinator fauna. The fact that local pollinators can drive the floral evolution lead us to think that there could have been selection towards large flower size in high altitudes because of l arger body size of pollinators. Differentiation is most likely if gene flow is low and/or selection is strong. With this project we intend to look at many of the mechanism that are important for floral evolution in flowering plants. To find out how much o f the variation in flower size is a response to environmental factors and to selection mediated by pollinators we will perform a series of experiments both in field and greenhouse. We will plant seedlings of high and low altitude origin in different envir onments both in field and greenhouse to se the plastic response of characters. In the field, we will estimate selection on morphological characters mediated by pollinators in reciprocal transplant populations. We will also estimate heritability of charact ers to be able to predict response to phenotypic selection. To investigate floral evolution in C. rotundifolia in a selection – gene flow balance perspective we will study the genetic structure of populations and compare with morphology (Qst-Fst analysis) . Generally, if populations are genetically similar but morphologically different and morphology is not only a plastic response to environmental factors, gene flow has not counteracted the effects of selection.