Intraspecific floral colour variation in three Pedicularis species.

Flower constancy describes the phenomenon that pollinators tend to successively visit flowers of a single species during foraging, reducing reproductive interference in natural communities. The extent of flower constancy is largely determined by the floral traits of co-flowering species. Both higher inter-specific and lower intraspecific differences of floral traits should contribute to a higher level of flower constancy. However, previous studies mainly focused on interspecific difference, and the intraspecific variation (consistency) of floral traits received much less attention. We hypothesise that selection may favour lower intraspecific floral trait variation in communities composed of multiple co-flowering congeners. We investigated the floral colour variation of three focal Pedicularis species that share pollinators in 19 communities composed of either single or multiple Pedicularis species. Colour was quantified using image-based colour analysis as perceived by pollinators. We found that most of the intrapopulation floral colour variation was below the colour discrimination threshold of bumblebees, implying strongly constrained by the visual selection by pollinators. Contrary to the hypothesis, there is no significant difference in intraspecific floral colour variation between different community contexts. It may be due to the relatively large interspecific floral colour differences of most co-flowering species. The influence of community context on intraspecific variation may be reflected in floral traits other than colours.