Native Solitary Bees Provide Economically Significant Pollination Services to Confection Sunflowers (Helianthus annuus L.) (Asterales: Asteraceae) Grown Across the Northern Great Plains

Abstract

The benefits of insect pollination to crop yields depend on genetic and environmental factors including plant selffertility, pollinator visitation rates, and pollinator efficacy. While many crops benefit from insect pollination, such variation in pollinator benefits across both plant cultivars and growing regions is not well documented. In this study, across three states in the northern Great Plains, United States, from 2016 to 2017, we evaluated the pollinatormediated yield increases for 10 varieties of confection sunflowers, Helianthus annuus L. (Asterales: Asteraceae), a plant that is naturally pollinator-dependent but was bred for self-fertility. We additionally measured pollinator visitation rates and compared per-visit seed set across pollinator taxa in order to determine the most efficacious sunflower pollinators. Across all locations and hybrids, insect pollination increased sunflower yields by 45%, which is a regional economic value of over $40 million and a national value of over $56 million. There was, however, some variation in the extent of pollinator benefits across locations and plant genotypes, and such variation was significantly related to pollinator visitation rates, further highlighting the value of pollinators for confection sunflowers. Female Andrena helianthi Robertson (Hymenoptera: Andrenidae) and Melissodes spp. (Hymenoptera: Apidae) were the most common and effective pollinators, while other bees including managed honey bees (Hymenoptera: Halictidae), Apis mellifera L. (Hymenoptera: Apidae), small-bodied sweat bees (Hymenoptera: Halictidae), bumble bees Bombus spp. (Hymenoptera: Apidae), and male bees were either infrequent or less effective on a per-visit basis. Our results illustrate that wild bees, in particular the sunflower specialists A. helianthi and Melissodes spp., provide significant economic benefits to confection sunflower production.

Contribution of the Cerrado as Habitat for Sunflower Pollinating Bees

“…In this study the 49% increase in the weight of the chapters open to pollinators compared to that of the closed ones, highlights the dependence of the sunflower by the pollinators. Mallinger et al (2018) documented a similar result revealing a 45% increase in the seed produced from the chapters open to the bee visitors. Both results may encourage greater endeavor in wild bee conservation, especially of those species recognized for enhancing crop quality and the commercial value (Klatt et al, 2013).…”

Honey bee and native solitary bee foraging behavior in a crop with dimorphic parental lines

“…Previous studies conducted in commercial fields in North America, where sunflowers are native, have found a great diversity of native wild bees foraging on this crop, among which Melissodes spp. were the most common visitors whereas honey bees were infrequent [9]. Also, they showed high per-visit pollination efficiency on a male-sterile hybrid and their visitation length was considerably longer than the one of the bee populations present in our study.…”

“…Wild bees of the genus Melissodes are important sunflower pollinators in the whole American continent. Their presence has been reported both in commercial sunflower fields [9, 12, 13] as well as in seed-production systems [10, 14–16]. These solitary bees collect both pollen and nectar during single foraging bouts and they have been more frequently found foraging on MF than MS sunflowers.…”

“…In the case of sunflower, Helianthus annuus L., a crop grown worldwide for the production of oil or for direct consumption of seeds, its reliance on animal pollination varies depending on the degree of self-compatibility of such oilseed or confection cultivars [7–9]. However, insect pollination is issential for hybrid seed production systems, among which, introduced and native bees are the primary pollinating agents transferring pollen from male fertile (MF) to male sterile (MS) lines.…”

“…Although Mallinger and coworkers [9] reported the benefits of native wild bees pollinators, including Melissodes spp., for confection sunflower yields across the Great Plains, such cultivars do not involve dimorphism between parental lines. The benefits of diverse wild bees assemblages may differ with both variable attractiveness of the hybrids, in particular in crops for seed production, as well as with changing pollinator communities.…”