Apidologie最新文献

Urbanization, agriculture, and climate change have known negative impacts on global bee populations, but malnutrition as a result of disrupted or altered floral resources also hinders bee survivorship. Hence, understanding the nutritional content of pollen—the main source of protein, minerals, and lipids required by bees—is paramount to capture the requirements of a balanced diet to support bee health. Here, we characterize the non-esterified fatty acid (NEFA) and amino acid (AA) content of 22 pollen species from 11 families commonly found in eastern North America, to assess their nutritional profile and importance to bee diet. We found that total NEFA content was highly variable across pollen families and genera, but essential fatty acids omega-6 and omega-3 were the most abundant across the majority of pollen species. Total AA content was also diverse across pollen families and genera, and the presence of ten essential amino acids was detected in all pollen species (except for methionine in Rhus glabra). P:L ratios ranged broadly from 2.9 in Trifolium sp. to 74.4 in Prunus sp., but omega-6:3 ratios were generally below one for the majority (73%) of studied pollen species. Phylogenetic comparisons detected a significant negative correlation between essential AA against total NEFA and total omega content, suggesting potential trade-offs with lipid and essential AA in pollen nutrition. Our findings suggest that multiple pollen species have the potential to be considered a valuable source of protein and lipid, and that a diversity of flora is essential to meet diverse bee diet and nutritional needs.

Pollinators navigate a complex and dynamic nutritional landscape while foraging for floral resources. Bees are a group of flower-visiting insects that rely on pollen as their sole protein source, and thus, bees have strong incentives to seek pollen with high protein content. Indeed, research has shown that bees may prefer to visit flowers with high-protein pollen, but the mechanisms by which bees are able to detect plants with this high-protein pollen are unknown. One hypothesis is that plants with high-protein pollen advertise this resource quality through volatile emissions. We established 17 native perennial plant species from three plant families (Fabaceae, Asteraceae, and Lamiaceae) in a large field experiment to explore the relationship between nutritional quality, inflorescence volatile emissions, and pollinator visitation. We sampled twenty garden plots composed of these native plant species for 2 years. Our results showed that floral morphology significantly affected pollinator visitation; floral morphology that restricted the accessibility of floral resources reduced the overall foraging female bee visitation rate. In contrast, the visitation rate of foraging female bumble bees was higher on plants with floral morphology that restricted access. Moreover, we showed that (1) plants with less accessible inflorescences had significantly higher pollen protein content and (2) lower volatile emissions, while (3) there was a significant interaction between accessibility and pollen protein for foraging female honey bee visitation; honey bees preferred accessible flowers with lower pollen protein. We found no evidence in support of the hypothesis that floral volatiles advertise pollen protein content. Overall, floral accessibility related significantly to both floral volatile emissions and pollen protein content, determining both the identity of floral visitors and affecting the frequency with which they visited.

Bee venom (BV) extraction has become a standardized practice, characterized by being safe, simple, and causing no harm to bees. Though it demonstrated significant antimicrobial activity, its potential activity against honey bee pathogens have yet to be investigated. Therefore, we investigated for the first time in a controlled laboratory setting the effectiveness of BV administration in sugar syrup against Vairimorpha (Nosema) ceranae, a globally widespread fungal disease of honey bees. To do this, we first determined the BV lethal concentration (LC₅₀), after which newly emerged bees were inoculated with V. ceranae spores (10⁵) or/and chronically fed sugar syrup containing BV at LC₁₀ (0.24 mg/mL) or LC₂₀ (0.34 mg/mL) ad libitum for 12 days. The effects on bee longevity (time to death) were studied. The intensity of V. ceranae and total hemocyte count (THC) were also studied 6 and 12 days after infection. The expression of four antimicrobial peptides (AMPs) encoding genes (defensin1, apismin, hymenopteacin, and PGRPS2) was also measured after 6 days in midgut tissues. We discovered that BV increased bee survival and significantly reduced Vairimorpha intensity. This effect was associated with an increase in THC as well as the expression of the AMP-encoding genes studied. BV’s effects appeared to be concentration- and time-dependent, with a more profound decrease in Vairimorpha intensity at day 12, especially in bees fed BV at LC₂₀. These findings highlight BV’s potent immunomodulatory role against fungal pathogens in honey bees, and its potential role against other bacterial and viral pathogens should be investigated.

Thiamethoxam (TMX) is one of the most widely used neonicotinoid insecticides. However, it is unclear how TMX alters the flower-visiting behavior and seed production of Apis cerana in sunflowers. We conducted cage experiments to study the impact of chronic exposure (10 days) to TMX at sublethal concentrations of 2.4 μg/kg and 10 μg/kg on the number of flower visits per minute, seed setting percentage, 100-seed weight, and seed yield in sunflowers. Bees treated with TMX demonstrated a significantly lower number of flower visits per minute compared with the control group. Although we did not observe a significant difference in yield parameters between TMX treatments and the control group, a positive correlation was observed between yield and the bees’ flower visitation rate. Our study highlights the concern that exposure to field-level concentrations of TMX could pose a threat to the pollination services provided by A. cerana for other crops and wildflowers.

We observed this behaviour, previously studied only in North America and as a rare occurrence, on each of the three visits, one per year, we made to the same site, in Italy. Honey bees Apis mellifera L. preferred collecting pollen from red-tailed bumble bees Bombus lapidarius L. than directly from flowers of the woolly thistle Cirsium eriophorum (L.). In another site, which equally had this thistle species as the only plant in bloom, but fewer bumble bees, honey and bumble bees foraged concomitantly on the same flowers avoiding interspecific contacts. In both sites, the honey bees showed easier foraging in the presence of male, than of less tolerant worker, bumble bees. In a third site, the honey bees preferred foraging independently on the smaller flowers of the Tyrol thistle Centaurea nigrescens Willd., while the bumble bees preferred the woolly thistle. Therefore, when plants offer few foraging choices, honey bees may visit less preferred large composite flowers where a crowd of bumble bees hampers their usual foraging mode, but little-reactive males offer pollen collection from their furry bodies, to which honey bees specialize.

Human sewage can introduce pollutants into food webs and threaten ecosystem integrity. Among the many sewage-associated pollutants, pharmaceuticals and personal care products (PPCPs) are consistent indicators of sewage in ecosystems and can also cause potent ecological consequences, even at minute concentrations (e.g., ng/L). Despite increased study over the past three decades, PPCPs in terrestrial ecosystems have been less studied than those in aquatic ecosystems. To evaluate PPCP prevalence and drivers in a terrestrial ecosystem, we analyzed managed and native bees collected from agroecosystems in Washington State (USA) for PPCPs. Caffeine, paraxanthine, cotinine, and acetaminophen were detected in all three evaluated taxa (Bombus vosnesenskii, Agapostemon texanus, and Apis mellifera), with B. vosnesenskii and A. texanus having a higher probability of PPCP detection relative to A. mellifera. The probability of PPCP presence in all three taxa increased in landscapes with more human development and greater plant abundance, with significant but negative interactions among these factors. These results suggest that human activity, availability of resources, and species-specific pollinator traits affect the introduction and mobilization of PPCPs in terrestrial ecosystems. Consequently, monitoring PPCPs and their ecological responses in terrestrial ecosystems creates opportunities to synthesize effects of sewage pollution across terrestrial and aquatic ecosystem types and organisms.

The ecological interactions of biota with natural ecosystems are still poorly understood. In Subtropical Dry forests, several stingless bees utilize cavities within trees for nesting. Due to their lack of morphological traits for creating these cavities, bees rely on other mechanisms to access and utilize hollow spaces. In the Argentinian Dry Chaco region, we set two main objectives: (1) Determine the richness of cavity-nesting bees and describe the characteristics of trees selected as substrates, and (2) identify the mechanisms employed by stingless bees in selecting trees with hollows. Observational records were used to identify bee-nesting sites, while standard vegetation inventory was conducted to assess preference. Structural equation models were employed to establish the selection mechanisms of tree species for nesting. We found 139 nests belonging to three species: Plebeia catamarcensis (n = 118), Plebeia molesta (n = 14), and Lestrimelitta (L.) chacoana (n = 2). Stingless bees, particularly smaller species like P. catamarcensis, specifically select Neltuma trees for nest installation. This preference is attributed to the presence of galleries and hollows within the heartwood, created by the larvae of Criodion angustatum beetle. Although the larval action may harm the mechanical structure of the trees and hasten their demise, it simultaneously creates suitable hollow spaces for the establishment of bee colonies. Further investigations into these species interactions within the forest are necessary to enhance management practices in this threatened ecosystem, recognizing the important ecological role of Neltuma genus as crucial for ensuring the availability of nesting substrates for these native stingless bees.

Bumblebees have become model organisms for cognitive ecology and social learning. Quantifying the foraging behavior of free-flying bees, however, remains a methodological challenge. We describe and provide the code for a method of studying bee free flying foraging behavior using the open source neural-network based markerless tracking software DeepLabCut. From videos of bees foraging in an arena we trained a neural network to accurately track the position of each bee. We then used this approach to study foraging behavior and show that the ratio between flying time and flower visiting time decreases over repeated foraging bouts, indicating increasing efficiency of bee foraging behavior with experience. Visit durations, a laborious metric to measure by hand, were significantly shorter on flowers that had previously been visited. This experiment illustrates the usefulness of DeepLabCut for objective quantification of behavior, and in this case study shows that previous experience increases bee foraging efficiency.

Native bees are vital pollinators in the Neotropical Region and can serve as bioindicators for maintaining floral diversity in natural environments. However, the use of pesticides, specifically neonicotinoids, in agroecosystems has led to a decline in these pollinating organisms. This study aimed to evaluate the topical (contaminated mist) and residual (contaminated food) acute effect of the insecticide imidacloprid (IMI) on a stingless bee species (native to Brazil) with wide geographical distribution (Tetragonisca angustula) and two species restricted to certain regions (Tetragonisca fiebrigi and Tetragonisca weyrauchi) to determine LC_10–48 h and LC_50–48 h. The bees were exposed to various concentrations of IMI, in both topical and residual effect tests, and the results showed that low concentrations of the insecticide adversely affected the survival of all three species, with T. angustula being the most sensitive. The study also compared the sensitivity of the three species to the standard insecticide Dimethoate, and the results confirmed that T. angustula was the most sensitive. The findings of this study provide crucial ecotoxicological information, particularly concerning the residual effects of neonicotinoids on stingless bees. This evidence reinforces the urgent need to expand research on the effects of neonicotinoids on these important pollinators, so commonly found in nature and meliponaries. In addition, this research contributes significantly to filling the existing knowledge gap about the effects of pesticides on bee species native to Brazil, bringing to light the potential risks that these chemicals pose to the survival of these pollinators and emphasizing the urgent need for efforts of conservation in favor of these precious pollinating agents.