Relationship Between Pollination Behavior of Invasive Honeybees and Native Bumblebees in Montane Meadows

Data on plant-pollinator interactions collected over six summers in montane meadows of the HJ Andrews Experimental Forest provided an opportunity to explore the association between two genera of generalist pollinators: Apis and Bombus. Ten plots in each meadow were “watched” for fifteen minutes five times every summer, and each flower species in a meadow-watch was assigned a class based on the ratio of Apis to Bombus interactions. Flowers were also designated expected classes based on flower traits and prior knowledge about the plant and pollinator species at play. The study found that Apis and Bombus rarely visited a single flower species equally in a given meadow-watch, even when flower traits suggested that the number of interactions should be uniformly divided between the two pollinators. A predictive modeling approach, which took advantage of an ensemble method for tree classification called AdaBoost, found that this partitioning of interactions was best explained by a combination of environmental covariates and flower traits. The proportion of Apis to all social bees in the meadow-watch was the most important predictor variable in the classification task. This finding suggests that there is a significant relationship between pollinator presence and the flower preferences of other pollinator species in a meadow.