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The Melipona gut microbiota differs from other social bees, being characterized by the absence of crucial corbiculate core gut symbionts and a high occurrence of environmental strains. We studied the microbial diversity and composition of three Melipona species and their honey to understand which strains are obtained by horizontal transmission (HT) from the pollination environment, represent symbionts with HT from the hive/food stores or social transmission (ST) between nestmates. Bees harbored higher microbial alpha diversity and a different and more species-specific bacterial composition than honey. The fungal communities of bee and honey samples are also different but less dissimilar. As expected, the eusocial corbiculate core symbionts Snodgrassella and Gilliamella were absent in bees that had a prevalence of Lactobacillaceae - including Lactobacillus (formerly known as Firm-5), Bifidobacteriaceae, Acetobacteraceae, and Streptococcaceae - mainly strains close to Floricoccus, a putative novel symbiont acquired from flowers. They might have co-evolved with these bees via ST, and along with environmental Lactobacillaceae and Pectinatus (Veillonellaceae) strains obtained by HT, and Metschnikowia and Saccharomycetales yeasts acquired by HT from honey or the pollination environment, including plants/flowers, possibly compose the Melipona core microbiota. This work contributes to the understanding of Melipona symbionts and their modes of transmission.

Bacterial symbionts play an important role in insect survival by contributing to key metabolic and defensive functions. While stingless bees are known to harbor diverse microbial communities, their core bacterial symbionts remain poorly characterized. In this study, we analyzed the gut microbiota of sixteen stingless bee species collected from different regions of Mexico using 16S rRNA gene sequencing on the Illumina® MiSeq™ platform. Our results revealed that Proteobacteria, Firmicutes, and Actinobacteria are the most abundant bacterial phyla across species. Among the dominant genera, lactic acid bacteria, such as Lactobacillus spp., Bifidobacterium, and Fructobacillus spp., were the most prevalent. These bacteria are responsible for developing biochemical functions in metabolic processes like lactic fermentation and the biotransformation of complex organic compounds into molecules that are more easily assimilated by bees. This study offers a novel perspective on the diversity and predicted composition of gut microbiota in Mexican stingless bees. By highlighting differences in microbial communities among species with different feeding habits, our results emphasize the importance of preserving microbial biodiversity in these pollinators.

Female bees store scattered pollens grains from their bodies for transport by different modes of grooming and pollen packing. Species with corbiculae, such as honey or bumble bees, compress grains into dense pellets borne on the hind tibiae. Other species sweep grains into local concentrations of hairs (scopae), typically around the legs (in Halictidae and Andrenidae) or the ventral abdomen (Megachilidae), in which grains remain loose. Do these modes of pollen packing affect the functional value of pollen? We transferred grains from the bodies of four groups of bees—the corbiculate bees: Bombus impatiens and Apis mellifera, and the non-corbiculate bees: Megachile rotundata and Halictus spp.—onto previously unvisited stigmas of Brassica rapa. We wiped corbicular or scopal pollen and body pollen from each bee’s body separately and measured the resulting fruit set and the number of seeds in successful fruits. The type of pollen significantly affected the number of fruits for the corbiculate bee species but not the non-corbiculate bees, and the type of pollen significantly affected the number of seeds in successful fruits for A. mellifera but not B. impatiens, M. rotundata, or Halictus spp. These results suggest that loose scopal pollen is fully functional, but corbicular pollen is sometimes impaired. In some situations, non-corbiculate bees may be more valuable pollinators than corbiculate species because their treatment of pollen leaves its capabilities intact.

Stingless bees, a social corbiculate bee member, play a crucial role in providing pollination services. Despite their importance, the structure of their microbiome, particularly the fungal communities, remains poorly understood. This study presents an initial characterization of the fungal community associated with two Thai commercial stingless bee species, Lepidotrigona terminata (Smith) and Tetragonula pagdeni (Schwarz) from Chiang Mai, Thailand. Utilizing ITS amplicon sequencing, we identified distinct fungal microbiomes in these two species. Notably, fungi from the phyla Ascomycota, Basidiomycota, Mucoromycota, Mortierellomycota, and Rozellomycota were present. The most dominant genera, which varied significantly between species, included Candida and Starmerella . Additionally, several key enzymes associated with energy metabolism, structural strength, and host defense reactions, such as adenosine triphosphatase, alcohol dehydrogenase, β -glucosidase, chitinase, and peptidylprolyl isomerase, were predicted. Our findings not only augment the limited knowledge of the fungal microbiome in Thai commercial stingless bees but also provide insights for their sustainable management through understanding their microbiome.

The Eurasian bumble bee Bombus terrestris Linnaeus has been used commercially for pollination of a large number of crop species worldwide. This species has become invasive in several countries where it has escaped into natural environments. This species has become naturalized in many zones of Chile and southern Argentina, and may potentially invade other regions and countries in South America. These naturalized populations of B. terrestris have been associated with rapid population declines of the native bee B. dahlbomii Guérin-Méneville. We report new records of the exotic bee B. terrestris in the Region de Arica y Parinacota in the far north of Chile, which includes portions of the Atacama Desert. We used species distribution models (SDMs) and multivariate analyses to evaluate whether these occurrences represent new escapes from managed colonies or natural dispersal of the species from its southern invaded range. These reports of B. terrestris indicate a northward expansion of this bee. In our analyses, these new areas of occurrences have environmental conditions similar to those observed in the species’ southern invaded range, and our SDMs predict that B. terrestris dispersal through the Atacama is possible, although not likely given the occasional flower blooming in that region of Chile. These new occurrences in northern Chile reflect a potential for future invasion into other regions of South America by B. terrestris . Future surveys in the area should be intensified to evaluate if viable populations of this invasive species may become established.

Gilliamella and Snodgrassella, members of core gut microbiota in corbiculate bees, have high species diversity and adaptability to a wide range of hosts. In this study, we performed species taxonomy and phylogenetic analysis for Gilliamella and Snodgrassella strains that we isolated in our laboratory, in combination with published whole-genome. Functional effects of accessory and unique genes were investigated by KEGG category and pathway annotation in pan-genome analysis. Consequently, in Gilliamella, we inferred the importance of carbohydrate metabolism, amino acid metabolism, membrane transport, energy metabolism, and metabolism of cofactors and vitamins in accessory or unique genes. The pathway mentioned above, plus infectious disease, lipid metabolism, nucleotide metabolism as well as replication and repair exert a pivotal role in accessory or unique genes of Snodgrassella. Further analysis revealed the existence of functional differentiation of accessory and unique genes among Apis-derived genomes and Bombus-derived genomes. We also identified eight and four biosynthetic gene clusters in all Gilliamella and Snodgrassella genomes, respectively. Our study provides a good insight to better understand how host heterogeneity influences the bacterial speciation and affects the versatility of the genome of the gut bacteria.

Bees provide indispensable pollination services to both agricultural crops and wild plant populations, and several species of bees have become important models for the study of learning and memory, plant–insect interactions, and social behavior. Orchid bees (Apidae: Euglossini) are especially important to the fields of pollination ecology, evolution, and species conservation. Here we report the nuclear and mitochondrial genome sequences of the orchid bee Euglossa dilemma Bembé & Eltz. E. dilemma was selected because it is widely distributed, highly abundant, and it was recently naturalized in the southeastern United States. We provide a high-quality assembly of the 3.3 Gb genome, and an official gene set of 15,904 gene annotations. We find high conservation of gene synteny with the honey bee throughout 80 MY of divergence time. This genomic resource represents the first draft genome of the orchid bee genus Euglossa, and the first draft orchid bee mitochondrial genome, thus representing a valuable resource to the research community.

Different views of the pattern of social evolution among the highly eusocial bees have arisen as a result of discordance between past molecular and morphology-based phylogenies. Here we present new data and taxa for four molecular data sets and reassess the morphological characters available to date. We show there is no significant character incongruence between four molecular data sets (two nuclear and two mitochondrial), but highly significant character incongruence leads to topological incongruence between the molecular and morphological data. We investigate the effects of using different outgroup combinations to root the estimated tree. We also consider various ways in which biases in the sequence data could be misleading, using several maximum likelihood models, LogDet corrections, and spectral analyses. Ultimately, we concede there is strong discordance between the molecular and morphological data partitions and appropriately apply the conditional combination approach in this case. We also find two equally well supported placements of the root for the molecular trees, one supported by 16S and 28S sequences, the other supported by cytochrome b and opsin. The strength of the evidence leads us to accept two equally well supported hypotheses based on analyses of the molecular data sets. These are the most rigorously supported hypotheses of corbiculate bee relationships at this time, and frame our argument that highly eusocial behavior within the corbiculate bees evolved twice independently.

When asked where to find bees, people often picture fields of wildflowers. While true for almost all species, there is a group of specialized bees, also known as the vulture bees, that instead can be found slicing chunks of meat from carcasses in tropical rainforests. Diet and gut microbiomes are intricately linked on both short and long timescales. Changes in diet can alter the microbiome, while microbes in turn allow hosts to access novel diets. Bees are wasps that switched to a vegetarian lifestyle, and the vast majority of bees feed on pollen and nectar. Some stingless bee species, however, also collect carrion, and a few have fully reverted to a necrophagous lifestyle, relying on carrion for protein and forgoing flower visitation altogether. These “vulture” bees belong to the corbiculate apid clade, which is known for its ancient association with a small group of core microbiome phylotypes. Here, we investigate the vulture bee microbiome, along with closely related facultatively necrophagous and obligately pollinivorous species, to understand how these diets interact with microbiome structure. Via deep sequencing of the 16S rRNA gene and subsequent community analyses, we find that vulture bees have lost some core microbes, retained others, and entered into novel associations with acidophilic microbes found in the environment and on carrion. The abundance of acidophilic bacteria suggests that an acidic gut is important for vulture bee nutrition and health, as has been found in other carrion-feeding animals. Facultatively necrophagous bees have more variable microbiomes than strictly pollinivorous bees, suggesting that bee diet may interact with microbiomes on both short and long timescales. Further study of vulture bees promises to provide rich insights into the role of the microbiome in extreme diet switches. IMPORTANCE When asked where to find bees, people often picture fields of wildflowers. While true for almost all species, there is a group of specialized bees, also known as the vulture bees, that instead can be found slicing chunks of meat from carcasses in tropical rainforests. In this study, researchers compared the microbiomes of closely related bees that live in the same region but vary in their dietary lifestyles: some exclusively consume pollen and nectar, others exclusively depend on carrion for their protein, and some consume all of the above. Researchers found that vulture bees lost some ancestral “core” microbes, retained others, and entered into novel associations with acidophilic microbes, which have similarly been found in other carrion-feeding animals such as vultures, these bees’ namesake. This research expands our understanding of how diet interacts with microbiomes on both short and long timescales in one of the world’s biodiversity hot spots.

Bacteria residing in the guts of pollinating insects play a key role in nutrient acquisition, digestion, and resistance to pests and diseases. Imbalances in microbial flora in response to environmental change and stress can therefore impact insect health and resilience. This study is aimed at defining the core gut microbiome of the Australian native stingless bee, Tetragonula carbonaria , and exploring the impact of colony transplantation on gut health. The gut microbiomes of nine forager bees from natural (log) and manufactured (box) hives were examined via 16S rRNA gene amplicon sequencing. Some differences were observed at the ASV level between the microbiomes of log and box hive bees. However, a core microbiome, dominated by Lactobacillus spp., unclassified Acetobacteraceae spp., and Bombella spp., was maintained. Further, the inferred functional potential of the microbiomes was consistent across all individuals. This study highlights that although hive transplantation has an impact on the overall diversity of stingless bee gut microbiomes, it is unlikely to have a significant negative impact on the overall health and resilience of the colony.