Differential floral rewards and pollination by deceit in unisexual flowers.

Male and female unisexual flowers often offer different levels of rewards for pollinators and in some species pollination is apparently based on deception. A review of the literature indicates that male flowers commonly offer more reward than female, although when the reward is nectar, female flowers sometimes offer more than male. Factors determining which sex offers more reward include the limitations on reproductive success, risks of flower damage, and phylogenetic and structural constraints. Male and female flowers of some species resemble each other in ways that suggest mimicry. Female flowers appear to mimic male flowers more often than vice versa. We suggest that true intersexual floral mimicry can lead to different ecological/evolutionary consequences than deceit-pollination without specific resemblance: In mimicry systems, sexual dimorphism and intrasexual floral polymorphism are less likely and the dependence on naive pollinators is less strong. Proposed mimicry systems should be analyzed both to ascertain the response of the pollinators to the convergent traits and to determine the effects of the convergence on reproductive success.