Scent and Color, Floral Polymorphisms and Pollination Biology in Polemonium viscosum Nutt.

The breeding system and pollination ecology of Polemonium viscosum Nutt. (Polemoniaceae) were investigated on Pennsylvania Mountain in the Colorado Rocky Mountains. Polemonium viscosum is an obligate entomophilous outcrosser. Flowers are slightly protandrous, have spatially separated stigmas and anthers during anthesis and show little self-compatibility. Within populations, corolla color varies from light blue to purple and flowers may be broadly grouped within this spectrum as light blue, blue purple or purple. Differences in the ultraviolet are very small and probably not effective. Two floral scent morphs, sweet and skunky, occur. Differences in pollination biology can be related to these floral polymorphisms. The distributions of the morphs were examined along an altitudinal gradient. The light blue corolla type is significantly more frequent in the partially shaded krummholz locations whereas blue purple flowers are more common in the alpine. These differences may be related to the relative visibility of the two morphs against their respective backdrops. Potentially effective pollinators of Polemonium viscosum include Bombus kirbyellus (B. balteatus) (Hymenoptera: Apidae), H yles lineata (Lepidoptera: Sphingidae), Muscidae (Diptera) and Syrphidae (Diptera). Preliminary results suggest that bumblebees preferentially visit sweet-smelling flowers, whereas H. lineata does not.