Predators in Higher Trophic Levels Affect Selection on Floral Traits by Altering Plant-Pollinator Interactions
Interactions between plants and pollinators generate selection on floral traits. These interactions, and the resulting selection, may be affected by predators in higher trophic levels that consume and alter the behavior of pollinators. The effect of predators on selection on floral traits should depend on the predator’s hunting-mode. I examined the effects of active-pursuit predators (dragonflies) and sit-and-wait predators (ambush bugs) on selection on floral traits of the bumblebee-pollinated wildflower Lobelia siphilitica. Contrary to my predictions, I found that while selection did differ between dragonfly treatments, it was not caused by decreased plant-pollinator interaction strength. Consistent with my predictions, I found that ambush bugs prefer plants with larger daily displays, and significantly decrease the strength of selection on daily display size. My results suggest that predators in higher trophic levels may be an underappreciated cause of selection on plant traits.