Evidence of Competition between Honey Bees and Hylaeus anthracinus (Hymenoptera: Colletidae), an Endangered Hawaiian Yellow-Faced Bee

Abstract

European honey bees (Apis mellifera) were first introduced to the Hawaiian Islands in the late 1800s, and are now ubiquitous across the state in both managed and feral colonies. Though they play an important role in pollination services for native plants and agricultural crops, the competitive impacts they may have on native bees are not well understood. We assessed bee interactions on the preferred floral resources of Hylaeus anthracinus at the Ka Iwi State Scenic Shoreline on O‘ahu, including Heliotropium foertherianum, Scaevola taccada, and Myoporum sandwicense. Bee visitation frequency and duration were documented and analyzed in one-hour increments from 08:00–13:00 totaling 90 hours of video recordings of the focal plants. Honey bee visitation frequency to H. foertherianum peaked at 11:00, and corresponded with a significant reduction in H. anthracinus visitation that resulted in a bimodal activity distribution for H. anthracinus. Feeding duration of H. anthracinus was significantly reduced when visiting H. foertherianum flowers following a honey bee, but unchanged when visiting after conspecifics. Honey bee feeding duration was unaltered by the species of the previous visitor, indicating that deterrence of H. anthracinus to flowers may not be the result of nectar exploitation. S. taccada and M. sandwicense received low overall bee visitation, prohibiting further analyses. We conclude that the presence of honey bees on a preferred foraging resource results in a temporal niche partitioning of H. anthracinus indicative of interference competition, possibly the result of interspecific chemical cues. Future honey bee management considerations are discussed.