Pre-print coming soon!
Abundant honey bees are known to compete with wild bees for floral resources, but less is known about how competition affects ecological processes at other trophic levels (e.g., pollination). Using experimental hive additions and field observations in montane meadows, we show that honey bee introductions indirectly reduce pollination of an ecologically important wildflower, Camassia quamash, by competitively excluding visits from more effective bees. Increased honey bee abundance led to decreased nectar and pollen availability, which may explain why native bee visits declined. We demonstrate that honey bee introductions can erode longstanding mutualisms, with negative consequences for plant reproduction.