Ancestral Pedicularis species with flowers displaying simple galeas are hypothesized to give rise to species with flowers in which the galea is extended into a long beak. This same trend in floral evolution is also evident among the eight taxonomic varieties of Pedicularis bracteosa. Within this one species six varieties display a simple galea and two varieties display a beaked galea. Documented bumblebee pollinator behavior shows that simple galeas serve a double function: queens early in the season pollinate in the nototribic position, and queens and workers late in the season pollinate flowers of the same plant in the sternotribic position. Simple galeas may be a transitional stage in which pollinators shift to an exclusive sternotribic syndrome promoting the evolution of the beaked floral form in P. bracteosa. Bumblebee behavior on one population of the beaked variety, P.b. var. siifolia, supports this hypothesis. Over 95% of the pollinations were sternotribic. In another population of P.b. var. siifolia, however, over 50% of the pollinations were nototribic. Because a beaked galea is oriented parallel to a nototribic pollinator's body resulting in poor stigma contact, seed set should be lower in the population displaying both modes of pollination. A mixed model nested analysis of variance showed that seed set was marginally higher (p = 0.0875) in the population with exclusive sternotribic pollination. The pollinator's behavior and its ability to effectively transfer pollen resulting in seed set thus supports double function pollination as a transitional stage to an exclusive sternotribic syndrome and suggests how the beaked floral form may have evolved in other Pedicularis species.

Key words: evolution, floral form, Pedicularis bracteosa, pollination, Scrophulariaceae