Pollen carried by native and non-native bees in large-scale forest restoration in Hawaii: implications for pollination

Due to habitat loss, disease, and introduction of nonnative species, many native species in Hawai'i have gone extinct or are at risk of extinction. As a result of interspecific interactions such as pollination, the decline, loss, or introduction of species can have cascading effects on island ecosystems. We studied Hylaeus spp., Hawai'i's yellow-faced bees, the only native bees in Hawai'i. This group of potentially important pollinators has been largely overlooked until recently, and its conservation status and ecological role are virtually unknown. We investigated how native ( Hylaeus spp.) and nonnative (Apis mellifera) bees interact with flowering plants in a large-scale pasture-to-forest restoration system. We used pan traps and nets to collect bees in mature forest, remnant corridors, planted Acacia koa tracts, and open pastureland. We removed pollen from each specimen and identified it using pollen samples collected on-site. We found that Hylaeus spp. were more likely to carry less pollen and more likely to exhibit higher pollinator fidelity compared with A. mellifera. By contrast, A. mellifera was more likely to carry mixed pollen and forage on invasive plant species. This is the first investigation in Hawai'i to compare patterns of pollen carriage between native and nonnative bees and the first study to document pollen carried by Hylaeus spp. in the context of forest restoration.