Are different bee species attracted to different floral traits in alfalfa (Medicago sativa)?

More than 75% of flowering plants are animal pollinated. Various floral traits such as flower color and display size are attractive to pollinators and influence their foraging behavior.  Pollinators learn to associate floral traits with floral rewards to maximize foraging efficiency (resources per unit time).  This study aims to identify the floral traits of alfalfa that are most attractive to three distinct species of bees: honey bees (Apis mellifera), bumble bees (Bombus impatiens), and alfalfa leafcutting bees (Megachile rotundata). Attractiveness is defined as the relative number of visits per plant.  We hypothesize that higher number of racemes per plant and greater numbers of open flowers per raceme will be the most attractive traits for honey bees and bumble bees.  We also hypothesize that all bees will be more attracted to blue flowers. Multiple regressions were used to identify, for each bee species, floral traits that best explain variation in attractiveness of plants. Understanding the impact of floral traits on the foraging behavior of bees will help predict their movements, and ultimately gene flow.