Induced mutations affecting pollinator choice in Mimulus lewisii (Phrymaceae)

Abstract

The flowering plants are one of the most phenotypically varied and wide-ranging groups of organisms on earth, and yet, we have limited understanding of the contribution of animal pollinators to the diversification of floral form. To explore the interaction between variation in floral form and pollinator behavior, we observed the foraging behavior of bumblebees (Bombus impatiens) when presented with both wild-type Mimulus lewisii plants and each of three chemically induced single-locus mutants with altered floral phenotypes, including loss of the three lower petals, loss of nectar guides, and a change in petal color patterning. We found that each of the mutants attracted successful pollinator visits at just 29–80% of the rate relative to wild-type flowers, suggesting that effective recruitment of bumblebee pollinators requires the landing platform provided by the lower petals, and visual cues provided by the nectar guides and petal color pattern. Since single-locus recessive mutations are capable of ablating the lower petals, nectar guides, and color pattern, such changes in floral form provide insight into the driving forces behind plant adaptation.