Pollinators do not avoid or prefer a locally rare pollen colour morph in Erythronium americanum (Liliaceae)

The red-yellow pollen colour polymorphism that occurs in populations of Erythronium americanum provides an excellent opportunity to investigate the conditions leading to maintenance of phenotypic variation. Using arrays of cut E. americanum flowers with red- or yellow-pollen set in a naturally monomorphic red-pollen population, we tested whether pollinators exhibit frequency-dependent behaviours . As was previously observed when pollinator preference was tested in a pollen-colour polymorphic population, pollinators accustomed to the monomorphic red-pollen population in this study exhibited no pollen colour preference among flowers cut from a polymorphic population. The lack of pollinator colour preference against either a polymorphic or red-monomorphic background suggests that pollinators do not impose frequency-dependent selection. It is possible, however, that results would differ against a monomorphic yellow-pollen background.