Apidologie最新文献

Parasitic mites of the genus Varroa pose a serious threat to global apiculture. Host switches from native to introduced Apis species have occurred in multiple Varroa species, in some cases with devastating results. Additional host shifts and hybridisation among mite species and mite lineages on different hosts represent significant risks for apiculture and natural ecosystems. Quantifying this risk is thus an essential step toward management. The risk of hybridization among mite lineages on different hosts is likely to be at its highest in eastern Asia, where multiple host and mite lineages occur sympatrically. The available evidence, however, is somewhat contradictory, suggesting gene flow is occurring in some localities, but limited or absent in others. In this study, we elucidate the relationships between Varroa mites collected from A. mellifera and A. cerana in Vietnam, a region of high overlap of mite species and hosts, using a combination of genome-wide SNPs and mitochondrial sequence data. Our results indicate an absence of any new host shifts and a lack of gene flow across host species and between mite species, despite considerable overlap in mite and host species ranges. This confirms the findings of several earlier studies in this area but contrasts with evidence of hybridization in other regions, suggesting regional differences in the potential for gene flow between host/mite combinations. Nonetheless, we suggest this area remains one of high risk, because of (i) considerable overlap of mite lineages which elsewhere have been shown capable of interbreeding, (ii) evidence we find of human-mediated long-range dispersal events, which increase the chance of interaction among different mite lineages, and (iii) the persistent threat of secondary factors such as disease transmission, which may be facilitated by both of the factors above.

The yellow-legged hornet is an invasive species that has been established in Galicia, northwestern Spain, since 2012. This hornet shows an increased level of invasiveness, which allows it to grow and spread rapidly throughout the territory. Furthermore, the climatic characteristics of the region have contributed to their establishment, with beekeeping being the most affected sector. The study aimed to monitor the predatory behavior of Vespa velutina and its correlation with environmental conditions, as well as the honey bee survival risk of the predation. Temperatures ranging from 17 to 26 °C were the most suitable for observing the higher number of hornets. The hornets were observed in front of the colonies for 16 h a day for 11 months. The presence of five or more hornets posed a risk to the survival of the honey bee colonies. Beekeepers should manage their colonies with artificial feeding and use control methods for survival against V. velutina.

The greater wax moth, Galleria mellonella L., is a noxious pest in beekeeping, causing huge economic loss by weakening the colonies and reducing honey production. Present wax moth management techniques are ineffective, potentially leading to the loss of bee colonies. Utilization of Bacillus thuringiensis is emerging as a sustainable practice for managing G. mellonella. Hence, in the present study, five B. thuringiensis isolates were isolated from soil samples and a G. mellonella cadaver, and all the isolates were characterized for morphological and molecular characteristics. The in vitro bioassay studies showed strain NBAIR BtVGa2 isolated from G. mellonella cadaver is very effective against wax moth second instar larvae with a lower LC₅₀ value of 5.40 μg/mL as compared to other B. thuringiensis strains. Biosafety studies showed NBAIR BtVGa2 is 97% safer for larvae and adults of honeybees since the strain does not consist of any hymenopteran-specific insecticidal genes. The plasmid sequencing of NBAIR BtVGa2 generated 891,714 paired-end reads with 34.13% GC content and a 0.89-Mbp genome size, along with 903 protein-coding genes with a single tRNA. The plasmid profiling of NBAIR BtVGa2 identified many insecticidal genes, viz., cry1Ac5, cry2Aa9, Zwa5A, Zwa5B, Zwa6, mpp46Ab1, and vpb4Ca1, in which mpp46Ab1 and vpb4Ca1 were novel genes with only 33.61 and 66.42% sequence similarity, respectively. The presence of these genes was validated by PCR amplification, and the structure of these insecticidal genes has also been predicted. Overall, the study identified a highly efficient strain of B. thuringiensis for the biological management of G. mellonella. The study also deciphered molecular mechanisms behind the efficiency of the NBAIR BtVGa2 strain. The study opened the path for the biological method of management of G. mellonella considering the safety of honeybees.

Graphical Abstract

Depicting molecular mechanism behind biocontrol potential of Bacillus thuringiensis strain NBAIR BtVGa2

Honey bees rely on haplodiploidy for sex determination. Here, diploid eggs develop into females (i.e., queens and workers) and haploid eggs develop into males (i.e., drones). This system is regulated by complementary sex-determiner (csd)—a single, multi-allelic locus with very high diversity. Honey bees heterozygous at the csd locus will develop into females, while hemizygosity results in normal male development. Homozygosity at csd results in abnormal diploid males. Diploid males are usually destroyed by the workers early in development which can negatively impact the colony population, growth, and productivity. As such, maintaining genetic diversity at csd is critical for the health and productivity of honey bee populations. This is reflected in the increasing number of studies examining csd diversity in local and global populations. However, many csd alleles appear in multiple studies and have been assigned several different names, complicating cross-study comparisons. In 2020, we developed a standardized nomenclature for the hypervariable region (HVR) of honey bee csd alleles to facilitate a better understanding of csd diversity within and between populations. Here, we present an updated database including all csd sequences deposited into GenBank since our last publication. In only the last 4 years, 370 new csd sequences were deposited, including 154 novel HVR sequences.

In honeybees, fertilized eggs with homozygous complementary sex determiner (csd) alleles develop into sterile diploid males, which are eliminated by workers during the larval stage. A decrease in csd allele diversity leads to increased inbreeding and a higher occurrence of diploid males, significantly decreasing the population growth rate and effective population size. Therefore, understanding and maintaining csd gene diversity is crucial. This study aims to analyze the genetic diversity and population structure of Apis cerana csd genes in China. We sequenced the exon 6–8 region of the csd gene in 250 workers across 13 geographical populations, identifying 234 nucleotide haplotypes and 141 unique amino acid sequences, 89 of which were newly discovered. The csd gene in these populations shows high genetic diversity comparable to that of Apis mellifera; however, the distribution of alleles did not show clusters based on geographic regions. Analyses of genetic differentiation showed variable genetic distance among populations. Our results demonstrate a high diversity of csd genes of A. cerana populations across China, suggesting a low risk of inbreeding in the populations.

The thermal preferences of honey bee drones change with their age as a result of sexual maturation. However, the factors influencing them are still unknown. For this reason, the aim of this study was to assess the effect of the rearing temperature during the post-capped development of drones on their body mass at eclosion and thermal preferences. Combs with capped brood of drones from three colonies were kept in incubators in changing temperatures from higher to lower (35–33 °C) or from lower to higher (33–35 °C). After emergence, drones were individually weighed. Subsequently, their thermal preferences were tested at the ages of 1, 5, 10, 15, 20, and 25 days. Body mass at eclosion and thermal preferences of drones significantly depended on the rearing temperature and maternal colony. Drones reared in temperatures changing from higher to lower (35–33 °C) were considerably heavier after emergence compared with those reared in temperatures changing from lower to higher (33–35 °C). The thermal preferences of drones also changed with their age. The greatest differences in thermal preferences of drones from both groups (35–33 °C and 33–35 °C) were on the 5th and 15th days of life. These findings indicate that rearing conditions (temperature and colony) influence the body mass at eclosion and thermal preferences of drones.

Bee populations are declining due to agricultural expansion, habitat loss, and diseases such as nosemosis caused by microsporidian Vairimorpha spp. We evaluate how agricultural intensification affects the abundance of wild (Augochloropsis spp.) and managed (Apis mellifera) bees and how landscape modification impacts bee health quality by altering their susceptibility to be infected by Vairimorpha spp. Bees were collected using pan traps in nine fields with varying management intensities from Argentina, while landscape management intensity was assessed using satellite imagery for each field. We found the abundance of one wild bee species increases as the proportion of landscapes with low intensity management increases. Vairimorpha spores were only found in managed bees. We also found that prevalence of Vairimorpha increases as the proportion of intensive management increases. Our results suggest that agricultural intensification negatively impacts the abundance of wild bee populations and makes managed bees more susceptible to Vairimorpha spp. infection.

Stingless bee hives are commonly managed in the global tropics and subtropics. However, current monitoring methods for these hives are invasive and subjective, relying on manual assessments conducted by beekeepers. This approach may harm bees and, if performed by non-specialists, can lead to the death of key reproducing individuals: the mother queens. These queens are vital for maintaining hive health, as their absence can lead to colony death. Our study is aimed at exploring the potential of three hive indicators: temperature, humidity, and sound, as predictive factors for discerning the presence or absence of a mother queen in Tetragonisca fiebrigi hives. To do this, we collected data on these variables from six hives, including three queenless hives and three queenright hives, monitored over four consecutive days. Temperature and humidity were recorded every 15 min during this period, and 15-min audio recordings were made each day. We then employed five machine learning algorithms (extreme learning machine, K-nearest neighbors, multilayer perceptron, random forest, and support vector machine) to classify the data. Our findings revealed that all tested algorithms consistently achieved accuracy rates exceeding 90%, whether using acoustic or microclimatic variables. However, the highest accuracy was achieved with the microclimatic dataset. This approach holds great potential for reducing the damages caused by manual inspections while also enabling faster and more precise identification of the health of beehives. By implementing remote monitoring systems based on these indicators, beekeepers can benefit from improved efficiency and accuracy in assessing hive conditions.

Bumblebees (Apidae: Bombus) are abundant pollinators in Mediterranean habitats; however, interaction networks with plants have not yet been investigated in large areas of Italy, including its islands. Here, we analyzed plant-bumblebee networks through seasonal transects in a suburban park and a nature reserve of Eastern Sicily. After molecular and morphological identification of bumblebees, we built bipartite networks extracting complementarity, niche overlap, modularity and nestedness. In total, we sampled 10 of the 15 species of Bombus known from Sicily. Richness was close to that predicted by accumulation curves, and no differences in community diversity were found between the two sites. At both sites, the networks were not nested, highly specialized and modular, with high complementarity and low niche overlap, again with no differences between sites. In both sites, species-level specialization varied considerably and was independent from sample size. The network topologies suggest a possible role of local interspecific competition and/or of interspecific morphological variation among generalist bumblebees. Comparison of previously published data revealed that networks in Mediterranean areas are more specialized than those with a continental climate. This suggests the possibility of increased competition and/or phenotypic variation under harsh Mediterranean conditions. The vulnerability of the Mediterranean basin to droughts caused by climate change calls for detailed studies on pollinator-plant networks for conservation plans.