Floral antagonists counteract pollinator-mediated selection on attractiveness traits in the hummingbird-pollinated Collaea cipoensis (Fabaceae)

Pollinator-mediated selection towards larger and abundant flowers is common in naturally pollen-limited populations. However, floral antagonists may counteract this effect, maintaining smaller- and few-flowered individuals within populations. We quantified pollinator and antagonist visit rates and determined a multiplicative female fitness component from attacked and non-attacked flowers of the Brazilian hummingbird-pollinated shrub Collaea cipoensis to determine the selective effects of pollinators and floral antagonists on flower size and number. We predicted that floral antagonists reduce the female fitness component and thus exert negative selective pressures on flower size and number, counteracting the positive effects of pollinators. Pollinators, mainly hummingbirds, comprised 4% of total floral visitation, whereas antagonist ants and bees accounted for 90% of visitation. Nectar-robbers involved about 99% of floral antagonist visit rates, whereas florivores comprised the remaining...