Flower color polymorphism with geographical patterns is likely driven by some combination of abiotic and biotic factors. Campanula punctata, the spotted bellflower (hotarubukuro in Japanese) displays regional flower polymorphism with either white or pigmented flowers, and the factors driving these patterns remain unclear. Here, we investigate the relationships between flower color distribution, environmental factors, and population genetic structure. We first determined that the geographical patterns in polymorphism are not random using spatial autocorrelation analyses. Mantel tests further showed strong correlations between genetic distance and both geographic and environmental distances for pigmented populations. Species distribution models indicated that suitable environments for pigmented populations are mainly high elevation hotter, drier areas, whereas suitable environments for white populations were more widespread, coastal areas with fertile soils and stable climates. These results suggest that pigmented populations may have adapted to stressful environments and become geographically isolated, establishing genetic clines. Reduced cost of pigment production may be invested in reproduction for white populations, providing a reproductive advantage in stable environments. Thus, pigmented populations may be adapted for stress tolerance, while white populations may be optimized for reproductive efficiency. Future steps for this research include investigating relationships with pollinators and conducting experiments with varying soil conditions.