Flower color is a mechanism angiosperm plants use to attract pollinators that facilitate reproduction. Asclepias syriaca (common milkweed) is a flowering plant that varies in color (white to dark pink) and requires insect pollination. In this study, we quantified the effect of flower pigmentation and nectar concentration/volume on A. syriaca pollination. We measured flower pigment concentration, nectar concentration and volume, along with pollen deposition and removal, pollinator type, frequency, and duration of visit. As the flowering season progressed, pollinator visitation was negatively correlated with pigmentation. Also, pollen deposition and removal per flower increased with number of visitations, and nectar volume decreased as flower pigmentation increased. Results suggest a pollinator preference for the lighter-colored flowers because they produce more nectar. The mechanism for this relationship between flower color and nectar concentration is unknown, but it drives a change in flower color preference by insect pollinators that ultimately affects plant reproduction. This project was made possible by funding from F&M's Hackman Summer Scholars Program.
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