Alternative flowers affect model and mimic flower discrimination performance of bumblebees

Some animal-pollinated flowers produce no rewards but attract pollinators by imitating rewarding flowers. Termed Batesian floral mimicry, this phenomenon has generally been understood in terms of a common system of the organisms performing one of three roles as model flowers, mimic flowers or signal receivers (a Batesian mimicry trinity). However, organisms other than those of the mimicry trinity may play important roles in the relationships of the trinity members. This study examined the effect of alternative flowers that are dissimilar to either model or mimic flowers on bumblebee discrimination between model and mimic flowers. To this end, we observed bumblebees Bombus ignitus (Smith), foraging in mixed arrays of artificial flowers mirroring either model, mimic or alternative flowers. Bumblebees’ ability to discriminate mimic from model flowers was impacted by the presence of alternative flowers; however, the effect was dependent on the similarity between the model and mimic flowers. This might occur because the presence of alternative flowers imposed an additional cognitive load on the bees’ working memory. Our study suggests that alternative flowers in a community may have beneficial effects on mimic flowers by reducing the discrimination performance of pollinators. A variety of environmental factors that impose complex sensory inputs on pollinators’ working memory might have contributed to the maintenance of Batesian floral mimicry. A free Plain Language Summary can be found within the Supporting Information of this article.