Bee communities in canola are affected by landscape context and farm management

Bees are key pollinators that promote greater yield and seed quality of oilseed crops such as canola. Canola acreage has increased over 1,000% in the past decade in the Pacific Northwest USA, providing a major pulse of sugar-rich nectar and pollen resources that may affect bee health and community structure. However, because canola does not require insect pollination for seed production, few studies have examined the biodiversity of pollinators taking advantage of these resources, or the floral traits of canola that affect pollinators across variable landscapes. Here, we conducted pollinator surveys at canola farms across the inland Northwest region of the USA. We surveyed bee biodiversity and abundance, and assessed how these metrics correlated with landscape context, canola production practices, and floral traits of various canola varieties. We found that bee communities differed between sites and across growing seasons, with sweat bees more abundant later in the season, and mining bees more abundant earlier in the season. We also found that bees were more abundant overall on farms with less floral nectar and with less developed landscape surrounding the sampling area. Bee diversity was greater in spring canola than winter canola, and floral traits were also correlated with differing bee community diversity. This research provides important information for canola growers and land managers and offers a framework for future research in pollinator management in the inland Northwest.

Floral Nectar Chemistry in Orchids: A Short Review and Meta-Analysis

Nectar is one of the most important flower traits, shaping plant–pollinator interactions and reproductive success. Despite Orchidaceae including numerous nectariferous species, nectar chemistry in this family has been infrequently studied. Therefore, the aim of this study is to compile data about nectar attributes in different orchid species. The scarcity of data restricted analyses to sugar concentration and composition. Our results suggest that the most important factor shaping nectar traits in orchids is the pollinator type, although we also found differentiation of nectar traits according to geographical regions. In spurred orchids, the length of the spur impacted nectar traits. We recommend the development of studies on nectar chemistry in orchids, including a wider range of species (both in taxonomic and geographical contexts), as well as extending the analyses to other nectar components (such as amino acids and secondary metabolites). The nectar biome would be also worth investigating, since it could affect the chemical composition of nectar. This will enrich the understanding of the mechanisms of plants–pollinators interactions.

Can floral nectars reduce transmission of Leishmania?

Insect-vectored Leishmania are the second-most debilitating of human parasites worldwide. Elucidation of the environmental factors that affect parasite transmission by vectors is essential to develop sustainable methods of parasite control that do not have off-target effects on beneficial insects or environmental health. Many phytochemicals that inhibit growth of sand fly-vectored Leishmania- which have been exhaustively studied in the search for phytochemical-based drugs- are abundant in nectar, which provide sugar-based meals to infected sand flies. In a quantitative meta-analysis, we compare inhibitory phytochemical concentrations for Leishmania to concentrations present in floral nectar and pollen. We show that nectar concentrations of several flowering plant species exceed those that inhibit growth of Leishmania cell cultures, suggesting an unexplored, landscape ecology-based approach to reduce Leishmania transmission. Strategic planting of antiparasitic phytochemical-rich floral resources or phytochemically enriched baits could reduce Leishmania loads in vectors, providing an environmentally friendly complement to existing means of disease control.

Elevated Temperature May Affect Nectar Microbes, Nectar Sugars, and Bumble Bee Foraging Preference

Floral nectar, an important resource for pollinators, is inhabited by microbes such as yeasts and bacteria, which have been shown to influence pollinator preference. Dynamic and complex plant-pollinator-microbe interactions are likely to be affected by a rapidly changing climate, as each player has their own optimal growth temperatures and phenological responses to environmental triggers, such as temperature. To understand how warming due to climate change is influencing nectar microbial communities, we incubated a natural nectar microbial community at different temperatures and assessed the subsequent nectar chemistry and preference of the common eastern bumble bee, Bombus impatiens. The microbial community in floral nectar is often species-poor, and the cultured Brassica rapa nectar community was dominated by the bacterium Fructobacillus. Temperature increased the abundance of bacteria in the warmer treatment. Bumble bees preferred nectar inoculated with microbes, but only at the lower, ambient temperature. Warming therefore induced an increase in bacterial abundance which altered nectar sugars and led to significant differences in pollinator preference.

The effect of sugar concentration on yeast growth associated with floral nectar and honey

Background: Floral nectar and honey vary in sugar concentration, from low concentration in nectar to high concentration in honey. Variation in sugar concentration is a gradient that determines yeast growth and can lead to its ecological niche specialization. Objective: Evaluate the effect of a sugar concentration gradient on the growth kinetics and cell size of yeasts isolated from the floral nectar and honey of Melipona beecheii. Methods: Four strains identified as Metschnikowia koreensis and Sympodiomycopsis paphiopedili, isolated from floral nectar, and Starmerella apicola and Starmerella apicola 2, isolated from honey of Melipona beecheii were grown in artificial media with a gradient of 2, 10, 20, 40 and 60% glucose. We evaluated culture density (cells / µL), growth parameters, and cell size in each strain. Results and Conclusions: Strains isolated from honey had high growth rates at the highest glucose concentrations, while strains isolated from floral nectar grew best at low concentrations. Cell size decreased as glucose concentration increased in all strains. The data supports the hypothesis that sugar concentration gradient is an ecological filter that modifies the growth and morphology of yeasts associated with flowers and honey and leads to niche specialization in yeasts that colonize plant-bee environments.

Nectar non-protein amino acids (NPAAs) do not change nectar palatability but enhance learning and memory in honey bees

Floral nectar is a pivotal element of the intimate relationship between plants and pollinators. Nectars are composed of a plethora of nutritionally valuable compounds but also hundreds of secondary metabolites (SMs) whose function remains elusive. Here we performed a set of behavioural experiments to study whether five ubiquitous nectar non-protein amino acids (NPAAs: β-alanine, GABA, citrulline, ornithine and taurine) interact with gustation, feeding preference, and learning and memory in Apis mellifera. We showed that foragers were unable to discriminate NPAAs from water when only accessing antennal chemo-tactile information and that freely moving bees did not exhibit innate feeding preferences for NPAAs. Also, NPAAs did not alter food consumption or longevity in caged bees over 10 days. Taken together our data suggest that natural concentrations of NPAAs did not alter nectar palatability to bees. Olfactory conditioning assays showed that honey bees were more likely to learn a scent when it signalled a sucrose reward containing either β-alanine or GABA, and that GABA enhanced specific memory retention. Conversely, when ingested two hours prior to conditioning, GABA, β-alanine, and taurine weakened bees’ acquisition performances but not specific memory retention, which was enhanced in the case of β-alanine and taurine. Neither citrulline nor ornithine affected learning and memory. NPAAs in nectars may represent a cooperative strategy adopted by plants to attract beneficial pollinators.

Discontinued alcohol consumption elicits withdrawal symptoms in honeybees

The honeybee continues to be developed as a model species in many research areas, including studies related to the effects of alcohol. Here, we investigate whether workers display one of the key features of alcoholism, namely withdrawal symptoms. We show that workers fed for a prolonged time on food spiked with ethanol, after discontinuation of access to such food, exhibited a marked increase in the consumption of ethanol and a slight increase in mortality. We additionally show that withdrawal symptoms do not include an increase in appetitiveness of ethanol diluted in water. Our results demonstrate that workers can develop alcohol dependence, which might be especially important in the natural setting of repeated exposure to ethanol in floral nectar and for their potential as a model of alcohol addiction.