The competition box: a graphical aid to forecasting pollinator performance.
Three major determinants of bees' nectar foraging patterns are the maximum depth at which nectar is accessible (dependent on bee tongue length); the minimum profitable energy content per flower (dependent on foraging costs and hence on bee body mass); and the minimum threshold temperature for flight. These form the axes of a three-dimensional template, the competition box. Thresholds of depths, cost and temperature can be identified for each species of bee, delimiting domains within the box compatible with foraging by each bee species. Changes through a day in temperature and in the depth and sugar content of nectar define the nectar trajectory through the box for a flower species in relation to microclimate and bee activity. By superimposing a bee-species-specific template on a representative nectar trajectory for a given flower species in a given situation, it is possible to make reasoned guesses about the expected interactions of foraging bee species with a novel flower species and with each other in a novel situation. Use of the competition box is illustrated in relation to dawn-to-dusk studies involving measurements of nectar concentration and volume, microclimate, flower form, and the tongue lengths and foraging activity of bees of different species (Bombus spp., Apis mellifera).