Pollinator preferences

Visual and Olfactory Preferences of distinct pollinators

We are interested in identifying the plant traits, including floral volatiles, that are most attractive to different pollinators. In alfalfa, we contrasted the visual floral traits that are most attracting to three bee species, honeybees, leaf cutting bees and bumble bees. We examined how preference by bee species influenced frequency of visits and subsequent female reproductive success   (Bauer et al. 2017). In addition, we examined the influence of these three bee species on selection for distinct floral traits  (Bauer and Brunet in preparation).

We are also examining and contrasting the floral volatiles of different alfalfa cultivars and wild populations of alfalfa subspecies and examining the impact of such olfactory differences on pollinator preferences (Link and Brunet in preparation). 

In the Rocky Mountain columbine,  we examined how bumble bees and hawkmoths affected the maintenance of the flower color polymorphism commonly found in populations of the Rocky Mountain columbine  (Brunet 2009).  Hawkmoths preferred blue flowers under both day and dust light conditions and bumble bees quickly learn to associate flower color with pollen reward such that the pollinators did not help explain the maintenance of the flower color polymorphism in the Rocky Mountain columbine populations (Thairu and Brunet 2015, Annals of Botany). Using the Rocky Mountain columbine as a model system, we also examined the role of floral display size, flower size, and reward sizes on bumble bee choices in a dichogamous species where both male- and female-phase flowers are opened simultaneously on inflorescences (Brunet et al. 2015, IJPS).  Bees could quantify the number of pollen-producing flowers on an inflorescence and preferred inflorescences with more pollen-producing flowers rather than inflorescences with more open flowers. Bee preference for floral traits was strongly associated with pollen reward and correlations between floral traits and pollen reward are likely to have a major impact on selection on floral traits by pollinators. 

USDA-ARS and Department of Entomology, University of Wisconsin-Madison