Orchard pollination in Capitol Reef National Park, Utah, USA. Honey bees or native bees?

Abstract

Capitol Reef National Park in central Utah, USA surrounds 22 managed fruit orchards started over a century ago by Mormon pioneers. Honey bees are imported for pollination, although the area in which the Park is embedded has over 700 species of native bees, many of which are potential orchard pollinators. We stud- ied the visitation of native bees to apple, pear, apricot, and sweet cherry over 2 years. Thirty species of bees visited the Xowers but, except for pear Xowers, most were uncommon compared to honey bees. Evidence that honey bees prevented native bees from foraging on orchard crop Xowers was equivocal: generally, honey bee and native bee visitation rates to the Xowers were not negatively correlated, nor were native bee visitation rates positively correlated with distance of orchards from honey bee hives. Conversely, competition was tentatively suggested by much larger numbers of honey bees than natives on the Xowers of apples, apricots and cherry; and by the large increase of native bees on pears, where honey bee numbers were low. At least one-third of the native bee species visiting the Xowers are potential pollinators, including cavity-nesting species such as Osmia lignaria propinqua, currently managed for small orchard pollination in the US, plus several fossorial spe- cies, including one rosaceous Xower specialist (Andrena milwaukiensis). We suggest