Floral color change has been suggested to benefit plants by manipulating pollinators, but this trait appears hardly prevalent among angiosperms. One possible explanation for this discrepancy is that the strategy of color changing plants may be favored under specific conditions. My preliminary survey shows that floral color change yield a benefit of attracting bees that return preferentially to more easily exploitable plants. Under conditions where benefits of enhancing exploitability cannot outweigh the costs of doing so, however, noncolor changing plants may be more advantageous.

In this study, to explore such possibilities, I compared visitor frequencies and taxa for individual plants between a color changing and a noncolor changing species in Weigera which grow in different habitats in Japan. Moreover, to examine whether color changers receive more return visits by bees than noncolor changers, I glued numbered tags on thoraxes of foraging bumble bees on the plants, and measured the individual visitation rates for each focal plant for three days after the gluing. Based on the data derived from these observations, I will discuss the difference in pollination conditions where floral color change could be selected for and against.