Pacific Northwest native plants and native cultivars, part I: pollinator visitation.

Abstract

Planting native flora is a popular conservation strategy for pollinators. When searching for native plants, consumers may encounter cultivars of native plants, which can have different phenotypic traits than plants found in wild populations ("wild-type native plants"). Previous research evaluating pollinator visitation to wild-type native plants and native cultivars has yielded mixed results, in terms of whether their visitation rates are similar or distinct. We established a garden experiment in Corvallis, Oregon, to examine pollinator visitation and utilization of Pacific Northwest native plant species and cultivars. Over 3 years, we collected and observed bees (Hymenoptera: Apoidea), butterflies (Lepidoptera: Papilionoidea), and syrphid flies (Diptera: Syrphidae) to understand (i) if plant pairs had different visitation rates, (ii) whether any pollinators were associated with differential visitation, and (iii) if specialist taxa preferred wild types over cultivars. Pollinator visitation rates varied by plant and pollinator groupings, but in comparisons between native plant and cultivar pairs, native plants were preferred 37.2% of the time (n = 29 comparisons), cultivars 7.7% of the time (n = 6), and there was no difference in 55.1% of comparisons (n = 43). Our pollinator community data found native plants had greater observed total pollinator richness (except for 1 tie) and bee richness than cultivars, though predicted richness varied. Specialist bees were collected more often from wild types. Cultivars with high visitation rates were minimally developed selections, as opposed to interspecific hybrids. Our results join a growing body of literature in suggesting wild-type native and minimally developed plants should be emphasized for supporting pollinator fauna.