Linking pollination effectiveness and interspecific displacement success in bees.

Pollen deposition, a surrogate for bee efficiency, becomes increasingly important during their interspecific interactions. We conducted field experiments on highly cross-pollinated melon (Cucumis melo) and watermelon (Citrullus lanatus) in order to understand how bee species with different pollination efficiencies displace each other from floral resources. We observed significant displacement of less abundant but more efficient bees by the more abundant but less efficient bees in both crops, which may lead to deficient pollination. We did not find significant relationship of the bee displacement success and body size or abundance. Apis florea (Fabricius) and Nomia sp.2 (Latreille) had significantly more winner events in melon, while the former also had significantly more winner events in watermelon. A. florea was the only bee species that foraged mostly within the 1-m(2) virtual area after their displacement, which may indicate its behavior of geitinogamous pollination. The two bee species, Ceratina sexmaculata (Smith) and Lasioglossum sp. (Curtis), were more sensitive to displacement as their proportion of leaving the 1-m(2) virtual area was higher.