The Timing of Floral Color Change in Lupinus argenteus

Abstract

This paper describes the timing of floral color change with Lupinus argenteus and the behavior of pollinator visitation to manipulated treatments. In theory plants my benefit from color change in two ways. One way is to direct pollinators to rewarding flowers. This may increase the foraging efficiency of the pollinators with the result that before leaving the plant, more flowers are visited. A second benefit plants may get is the prevention of pollen waste on unreceptive stigmas by directing pollinators to receptive flowers (Gori 1989). Floral color changes with un-manipulated (un-pollinated) controls were compared in terms of the rate of color change to hand-pollinated treatments. Three stages of color were used to asses each stage of change. Field comparisons on 30 inflorescences (15 treatments and 15 controls) revealed that treatments moved to stage two twice as fast than controls but stayed longer in stage two than controls. Pollinator visitation behavior was observed by painting the banner spot purple (the last color stage) on young flowers that contained pollen. I also painted white spots as a control. My hypothesis assumed that pollinators would avoid the painted purple spots since the purple stage is a cue to pollinators that less pollen exists (Gori 1989). Herbivory was responsible for the loss of pollinator visitation data. I returned to the field sites to find insects inside the netted plant bags along with damage to the painted petals. 95% of pollinator visits were to natural white spotted flowers.

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