Figure 3. Pollinator preferences and evolution of nectarless plants.

(a) First choices of bumblebees (left pair of bars, n=43) and hoverflies (right pair of bars, n=34) when allowed to choose between bumblebee- (BB) and hoverfly-pollinated plants (HF) of generation 11. Bumblebees preferred bumblebee-pollinated plants (binomial test, P=0.001), which shows that those plants have adapted to bumblebee preferences. Hoverflies showed no preferences (P=0.864). (b) Number of nectarless plants in bumblebee- (light grey) hoverfly- (dark grey) and hand-pollinated plants (black) in generations 1–11. The number of nectarless plants was significantly different in generation 9 (generalized linear model with bimodal distribution, χ²₁=13.41, P=0.001) and 11 (χ²₁=6.11, P=0.047). Photos by the authors.