Wild bees are widely distributed and effective pollinators, yet they face significant threats such as degradation of forests. Forest restoration has been advocated as a strategy to mitigate these threats and stabilize biodiversity. However, there is a lack of understanding of the ecological consequences of forest restoration on bee diversity, particularly regarding interactions with tree diversity and microenvironment. Using data from the world's largest tree diversity experiment (BEF-China), this study examines how tree species richness, canopy cover, understorey vegetation, and microclimatic conditions affect bee diversity in the context of forest restoration. Our analysis of bee diversity data (8341 individuals from 79 species) revealed that these biotic factors had distinct effects on three dimensions of bee diversity. Specifically, canopy cover had a negative effect on bee taxonomic diversity but a positive effect on phylogenetic and functional diversity. However, these patterns were reversed when the cover of understorey vegetation was accounted for. Moreover, tree species richness exerted an indirect influence on bee diversity through understorey microenvironment. Our findings provide nuance into how tree species richness shapes bee communities via vegetation cover and microclimate, which is informative on habitat characteristics in forest restoration and conservation that better enable the safeguarding of pollinators.

Abstract Interactions between plants and pollinators are crucial for maintaining biodiversity and ecosystem stability. Bees, especially wild and solitary bees, play a vital role in this process. However, the mechanisms underlying the relationship between multiple components of plant diversity and cavity-nesting bee diversity remain unclear, particularly in understudied subtropical forests. This study investigated how plant phylogenetic diversity (PD), functional diversity (FD), and specific leaf morphological-chemical traits influenced solitary bee diversity in a large-scale biodiversity experiment in subtropical China. We sampled solitary bees using trap nests across a tree diversity gradient. Results showed that plant leaf area (LA) and leaf dry matter content (LDMC) positively influenced bee species richness, while plant PD and FD had no significant effects. Our findings highlight the importance of specific plant traits over broad diversity metrics in supporting bee diversity and abundance, suggesting that conservation efforts should prioritize functionally diverse plant assemblages rather than maximizing species counts.

Abstract Wild bees face declines, and forests may serve as critical habitats for pollinators. However, how forest composition and the associated floral environment shape pollen provisioning and resource partitioning among cavity-nesting bees remains poorly understood. Here, we leveraged BEF–China, a large-scale subtropical forest biodiversity experiment with experimentally controlled plant (tree and shrub) communities, to investigate how forest composition and spatial context shape pollen provisioning, resource partitioning, and reproductive success of cavity-nesting bees. We used DNA metabarcoding to analyze floral composition of pollen provisioned by five cavity-nesting bee species, with samples collected from BEF–China across three years (2022– 2024). By comparing pollen taxonomic composition from whole-nest pooled samples and individual brood-cell samples with the experimentally planted species pool, we characterized dietary patterns and temporal dynamics of five bee species. Bees primarily relied on floral resources from the surrounding landscape, with planted trees providing essential but temporally restricted pollen supplements during specific phenological stages. Co-occurring bee species exhibited staggered nesting phenology and distinct dietary preferences for different plant families, with fine-scale resource differentiation even during periods of phenological overlap. Our results suggest that managed forests support cavity-nesting bees by providing critical woody floral resources during specific phenological gaps and offering stable nesting environments. To mitigate pollinator declines, forest management should prioritize maintaining diverse, phenologically complementary flowering vegetation within and surrounding forest stands. This ensures temporal continuity of pollen availability throughout the nesting season, which is particularly crucial for restoring pollinator services in simplified forest landscapes.

Halictidae, as a major pollinator family in bees, has significant ecological value. However, the insufficient molecular data for this group has limited our understanding of the evolutionary history of this group. Herein, we newly sequenced and assembled four mitogenomes of Halictidae, including three species of Nomiinae and one species of Rophitinae. We analyzed the characters of the newly obtained mitogenomes, including nucleotide composition, sequence length, and gene rearrangements. The length of the newly sequenced mitogenomes ranged from 16,492 to 21,192 bp, and all newly obtained mitogenomes contained 22 tRNAs, 13 protein-coding genes, two rRNAs, and one control region. Their AT content (%) ranged from 82.55 to 86.44. Relative synonymous codon usage analysis showed that UUU, UUA, and AUU were the preferred codons. The relative synonymous codon usage > 2 of mostly newly sequenced species was as follows: UUA > UCA > CGA. All newly obtained mitogenomes show gene rearrangement; we found five gene rearrangement patterns in total. Notably, ND4-trnP-ND4L-trnT was the first reported gene rearrangement pattern in bees. In addition, we reconstructed the phylogenetic relationships of Halictidae based on 10 species (eight ingroups and two outgroups), using Bayesian Inference and Maximum Likelihood approaches. Phylogenetic analysis showed that Rophitinae was the basal group within Halictidae.

Xylocopinae, a diverse bee subfamily comprising over 1,000 bee species, and also a major model system for studying the pollination and evolution of sociality. The lack of chromosome-level genome assembly resources for the Xylocopinae limits our research of their biology and evolution. Here, we provided the first pseudo-chromosomes genome assembly of the Xylocopa dejeanii combined PacBio CLR long reads, Illumina sequences, and Hi-C data. The final genome is 194.44 Mb located in 16 chromosomes. Our assembly includes 141 scaffolds, with a scaffold N50 length of 13.15 Mb. BUSCO analysis revealed 99.00% completeness. Genome annotation identified 28.27 Mb of repetitive elements, 10,970 protein-coding genes, and 432 ncRNAs. This high-quality X. dejeanii assembly advances our understanding of Xylocopinae genomics and provides new insights into bee evolution.

Megachile sculpturalis Smith, 1853 native to East Asia, is an important solitary bee species that has invaded both Europe and the United States. This study provides the first chromosome-level genome assembly of M. sculpturalis using a combination of Nanopore long reads, Illumina short reads, and Hi-C data. The genome comprises 296.99 Mb distributed across 16 chromosomes. N50, L50 and BUSCO completeness reached 19.128 Mb, 7 scaffolds, and 96.7%, respectively. The genome contains 104 Mb repetitive elements (35.02% of the assembly size) and 11,446 predicted protein-coding genes. This chromosome-level genome will serve as an essential genomic resource for future research on Megachilidae.

Environmental factors can influence ecological networks, but these effects are poorly understood in the realm of the phylogeny of host-parasitoid interactions. Especially, we lack a comprehensive understanding of the ways that biotic factors, including plant species richness, overall community phylogenetic and functional composition of consumers, and abiotic factors such as microclimate, determine host-parasitoid network structure and host-parasitoid community dynamics. To address this, we leveraged a 5-year dataset of trap-nesting bees and wasps and their parasitoids collected in a highly controlled, large-scale subtropical tree biodiversity experiment. We tested for effects of tree species richness, tree phylogenetic, and functional diversity, and species and phylogenetic composition on species and phylogenetic diversity of both host and parasitoid communities and the composition of their interaction networks. We show that multiple components of tree diversity and canopy cover impacted both, species and phylogenetic composition of hosts and parasitoids. Generally, phylogenetic associations between hosts and parasitoids reflected nonrandomly structured interactions between phylogenetic trees of hosts and parasitoids. Further, host-parasitoid network structure was influenced by tree species richness, tree phylogenetic diversity, and canopy cover. Our study indicates that the composition of higher trophic levels and corresponding interaction networks are determined by plant diversity and canopy cover, especially via trophic links in species-rich ecosystems.

The choice of trap in entomological surveys affects the composition of captured insects, though previous comparative studies have been limited in the types of composition measured, and the effects of environmental context. We assessed the sampling bias of several traps commonly used in pollinator monitoring: blue, yellow, and white pan traps, and blue vane traps, towards different taxonomic and functional groups and their efficiency in measuring taxonomic, phylogenetic, and functional diversity. Analyses were performed in monoculture and mixed forests to understand the environmental context of trap efficiency. We found that blue pan traps generally outperformed other types in bee capture and exhibited a preference for Halictidae bees. Blue pan traps yielded the highest species richness and phylogenetic diversity, while blue vane traps captured the highest functional richness. Bias differences were frequently detected in mixed forests compared with monoculture forests. We also found the combination of blue vane and pan traps consistently correlated highest with a complete survey among two-method combinations. Based on our findings, we recommend a combination of blue vane and pan traps to obtain a more comprehensive bee collection in an efficient manner. Additionally, it is crucial to consider habitat type when designing bee trapping protocols to ensure an accurate representation of bee communities.

Megachile is one of the largest bee genera, including nearly 1,500 species, but very few chromosome-level assemblies exist for this group or the family Megachilidae. Here, we report the chromosome-level genome assembly of Megachile lagopoda collected from Xizang, China. Using PacBio CLR long reads and Hi-C data, we assembled a genome of 256.83 Mb with 96.08% of the assembly located on 16 chromosomes. Our assembly contains 266 scaffolds, with a scaffold N50 length of 15.6 Mb, and BUSCO completeness of 99.20%. We masked 27.10% (69.61 Mb) of the assembly as repetitive elements, identified 459 non-coding RNAs, and predicted 11,157 protein-coding genes. This high-quality genome of M. lagopoda represents an important step forward for our knowledge of megachilid genomics and bee evolution overall.

Pollinators provide important pollination services for crops around the world. In China, numerous studies have been conducted on pollinators within agroecosystems, yet a comprehensive review of such research remains to be completed. This study discusses the existing knowledge of pollinator diversity in Chinese agroecosystems, examines the provision of pollination services, and identifies key achievements and limitations. We propose a series of conservation and management actions to promote pollinator health and ecosystem services in these agroecosystems: (1) long-term monitoring of pollinator populations, (2) designing agricultural landscapes that are conducive to pollinators, and (3) implementing microscale habitat modifications to improve conditions for pollinators.

A new species of bumble bee-mimicking brood parasitic bee, Tetralonioidella mimetica Orr & Zhu, sp. nov., is described from China. The systematic placement of this species was initially challenging but was resolved using a combination of phylogenomic and COI barcode analyses, which strongly support the new species as a member of the genus Tetralonioidella Strand. Interestingly, the new species mimics the color pattern of both a bumble bee (Bombus Latreille), and its host Habropoda Smith species, a mimicry format previously unknown for bees. A review of the other Tetralonioidella species revealed three additional bee mimics, including two further likely model-host-brood parasite mimicry complexes. To our knowledge, these represent the first documented three-tiered mimetic systems in bees. Several additional taxonomic actions recently became necessary in these and related taxa: Tetralonioidella meghalayensis Dohling & Dey, 2024 is synonymized syn. nov. with Habropoda radoszkowskii (Dalla Torre, 1896) and Varthemapistra Engel, stat. rev. is again synonymized with Habrophorula Lieftinck. Our results also highlight issues with the generic classification of the tribe Melectini as currently used, as Melecta Latreille was found paraphyletic in relation to the remaining melectine genera. As a first step toward resolving this issue, we return the Melecta subgenus Eupavlovskia Popov, stat. rev. to genus level and discuss the ongoing systematic uncertainties regarding melectine taxonomy.

Andrena camellia, an effective pollinator of the economicallysignificant crop Camellia oleifera, can withstand the toxic pollen of C. oleifera, making A. camellia a crucial for resource conservation and cultivation of C. oleifera. In this study, the whole genome of A. camellia was sequenced on the Oxford Nanopore platform. The assembled genome size was 340.73 Mb including 50 scaffolds (N50=47.435 Mb) and 131 contigs (N50=17.2 Mb). A total of 11, 258 protein-coding genes were annotated, in addition, 1,104 non-coding RNAs were identified. Further analysis that some chromosomes of A. camellia have a high level of synteny with those of Apis mellifera, Osmia bicornis and Andrena minutula. Thus, our reported genome of A. camellia serves as a valuable resource for studying species evolution, behavioral biology, and adaption to toxic pollen of C. oleifera.

The challenges of bee research in Asia are unique and severe, reflecting different cultures, landscapes, and faunas. Strategies and frameworks developed in North America or Europe may not prove applicable. Virtually none of these species have been assessed by the IUCN and there is a paucity of public data on even the basics of bee distribution. If we do not know the species present, their distribution and threats, we cannot protect them, but our knowledge base is vanishingly small in Asia compared to the rest of the world. To better understand and meet these challenges, this perspective conveys the ideas accumulated over hundreds of years of cumulative study of Asian bees by the authors, including academic, governmental, and other researchers from 13 Asian countries and beyond. We outline the special circumstances of Asian bee research and the current state of affairs, highlight the importance of highly social species as flagships for the lesser-known solitary bees, the dire need for further research for food security, and identify target research areas in need of further study. Finally, we outline a framework via which we will catalyze future research in the region, especially via governmental and other partnerships necessary to effectively conserve species.

Backgruound & Aims:Cavity-nesting Hymenoptera are both predators and pollinators and provide key services for ecosystem functioning.Previously,there have been few studies on cavity-nesting Hymenoptera in subtropical forests.Yet this study aims to better understand the diversity and biology of cavity-nesting Hymenopterans in subtropical forest in China. Methods:Trap nests were used to study the biology,life history,diversity and ecology of solitary bees and wasps.We used this method to collect cavity-nesting Hymenoptera in 88 plots.Based on five years of long-term monitoring and sampling on Biodiversity-Ecosystem Functioning Experiment China(BEF-China)platform,we recorded the species diversity of cavity-nesting Hymenoptera and relevant occurrence patterns of solitary bees and wasps. Results:We found 3 orders,25 families and 128 species in the trap nest system.Pollinators accounted for 26.6％of the diversity,mainly including Colletidae and Megachilidae with 12 species in 2 families.Predators represented 73.4％of the diversity,mainly including Eumeninae,Sphecidae,Pompilidae and Crabronidae with 44 species in 4 families.There were 72 species of parasitoids in 19 families,mainly including Sarcophagidae,Bombyliidae,Chrysididae,Trigonalyidae,and Eulophidae. Conclusion:For species composition,we found the diversity of pollinators was significantly less than that of predators.Meanwhile,we noted the protandry was common in cavity-nesting Hymenoptera and more obvious in overwintering individuals.In addition,we also found variable occurrence patterns in different species.The occurrence time of Megachilidae and Crabronidae were more concentrated than that of Eumeninae and Pompilidae.Finally,by constructing the interaction relationship between host and parasitoids,we explained the abundance and richness of parasitoids to be regulated by the bottom-up effect of lower trophic hosts.Ultimately,a greater understanding of these organisms will help to better protect the resources wild cavity-nesting Hymenoptera use for their ecological services.

The full potential for using DNA barcodes for profiling functional trait diversity has yet to be determined in plants and animals; thus, we outline a general framework for quantifying functional trait diversity of insect community DNA and propose and assess the accuracy of three methods for achieving this. We built a novel dataset of traits and DNA barcodes for wild bees in China. An informatics framework was developed for phylogeny-based integration of these data and prediction of traits for any subject barcodes, which was compared with two distance-based methods. For Phylogenetic Assignment, we additionally conducted a species-level analysis of publically available bee trait data. Under the specimen-level dataset, the rate of trait assignment was negatively correlated with distance between the query and the nearest trait-known reference, for all methods. Phylogenetic Assignment was found to perform best under several criteria; particularly, it had the lowest false-positive rate (rarely returning a state prediction where success was unlikely; where the distance from query to the nearest reference was high). For a wider range of compiled traits, conservative life-history traits showed the highest rates of assignment; for example, sociality was predicted with confidence at 53%, parasitism at 44% and nest location at 33%. As outlined herein, automated trait assignment might be applied at scale to either barcodes or metabarcodes. With further compilation and databasing of DNA barcode and trait data, the rate and accuracy of trait assignment is expected to increase to the point of being a widely viable and informative approach.

Insects are key pollinators to ecosystem function, but much work remains to determine the most cost-effective, reliable scheme to monitor them. Pan traps (PT) and flight interception traps (FIT) are two of the most popular insect sampling methods used. However, their relative sampling performance and cost is poorly known for agroecosystems in China. We conducted a study across 18 oilseed rape fields in smallholder farmland in Zhejiang, China using these two traps. Our results showed that a single FIT had a greater sampling efficiency (more individuals and higher species richness) than a single PT, but controlling for cost, four PTs (the cost for four PTs is close to one FIT) showed a greater sampling efficiency than FITs. PTs collected more small-bodied individuals while FITs and PTs did not significantly differ in terms of monitoring pollinator insects with large body size. When exploring whether semi-natural habitat embedded in the agricultural landscape affected these results, results from both trap types shows that semi-natural habitat had a significant positive impact on wild pollinator diversity and rarefied species richness. Future studies that examine the effects of agricultural landscape on the wild pollinator community should combine PTs with netting or other active methods for long-term wild pollinator monitoring strategies.

Globally, insect pollinators that are linked to increased yields in many crops have experienced severe population declines. Crop diversification is often proposed as an effective conservation measure to boost pollinator populations. Here, we investigate the potential benefits of mixed oilseed rape/milk vetch cultivation for wild pollinator communities by comparing it with oilseed rape monocultures. Studying 8 mixed and 10 monocropping fields positioned along a gradient of increasing semi-natural habitat coverage in mountainous agricultural landscapes, we found that agricultural landscapes with mixed cultivation harboured higher wild pollinator diversity than oilseed rape monocropping landscapes. This positive effect was observed irrespective of the proportion of semi-natural habitat. Meanwhile, the pollinator community composition in mixed cultivation landscapes was similar to that of oilseed rape monoculture landscapes, and, contrary to expectations, mixed cultivation did not benefit specific pollinator trait groups like cavity-nesting bees. Overall, we believe the higher pollinator diversity linked to mixed cultivation can increase insect-pollinated crop yields, and mixed oilseed rape-milk vetch cultivation might represent a potential mitigation measure for the negative impacts agricultural intensification has on wild pollinator communities.

Wild bees provide important pollination services, but they face numerous stressors that threaten them and their ecosystem services. Wild bees can be exposed to heavy metal pollution through the consumption of nectar, pollen, and water, which might cause bee decline. While some studies have measured heavy metal concentrations in honeybees, few studies have monitored heavy metal concentrations in wild bees or explored their potential effects on wild bee communities. To investigate the impact of heavy metal pollution on wild bee communities, heavy metal concentrations, including vanadium (V), chromium (Cr), nickel (Ni), cadmium (Cd), Zinc (Zn) and lead (Pb) in multiple wild bee species were measured. Multiple wild bee species, including: Xylocopa tranquabaroroum, Eucera floralia, Apis cerana, and small bee mixtures (representing multiple small wild bee species) were sampled from 18 sites in Quzhou, Zhejiang Province, China. The findings demonstrated that there were significant differences in heavy metal concentrations among different bee species. The concentrations of V, Zn, Cd, and Pb in X. tranquabaroroum, the largest bee species in this study, were lower than that in the other three sample groups. Furthermore, there were significant negative correlations between heavy metal pollution and wild bee diversity and species richness, but not with abundance. Particularly, there was no significant relationship between heavy metal pollution and the abundance of small bees. Given these worrying findings, monitoring multiple heavy metals in wild bees should be conducted for protecting wild bee diversity and securing their pollination services.

Anthidiini, a large bee tribe characterized by light-colored maculations, represents nearly 1,000 pollinator species, but no genomes are yet available for this tribe. Here, we report a chromosome-level genome assembly of Anthidium xuezhongi collected from the Tibetan Plateau. Using PacBio long reads and Hi-C data, we assembled a genome of 189.14 Mb with 99.94% of the assembly located in 16 chromosomes. Our assembly contains 23 scaffolds, with the scaffold N50 length of 12.53 Mb, and BUSCO completeness of 98.70% (n = 1,367). We masked 25.98 Mb (13.74%) of the assembly as repetitive elements, identified 385 noncoding RNAs, and predicted 10,820 protein-coding genes (99.20% BUSCO completeness). Gene family evolution analyses identified 9,251 gene families, of which 31 gene families experienced rapid evolution. Interspecific chromosomal variation among A. xuezhongi, Bombus terrestris, and Apis mellifera showed strong chromosomal syntenic relationships. This high-quality genome assembly is a valuable resource for evolutionary and comparative genomic analyses of bees.

The halictid genus Lasioglossum, as one of the most species-rich bee groups with persistently contentious subgeneric boundaries, is one of the most challenging bee groups from a systematic standpoint. An enduring question is the relationship of Lasioglossum and Homalictus, whether all halictine bees with weakened distal wing venation comprise one or multiple genera. Here, we analyzed the phylogenetic relationships among the subgroups within Lasioglossum s.l. based on thousands of single-copy orthologs and ultraconserved elements, which were extracted from 23 newly sequenced low-coverage whole genomes alongside a published genome (22 ingroups plus 2 outgroups). Both marker sets provided consistent results across maximum likelihood and coalescent-based species tree approaches. The phylogenetic and topology test results show that the Lasioglossum and Hemihalictus series are reciprocally monophyletic and Homalictus and Rostrohalictus are valid subgenera of Lasioglossum. Consequently, we lower Homalictus to subgenus status within Lasioglossum again, and we also raise Rostrohalictus to subgenus status from its prior synonymy with subgenus Hemihalictus. Lasioglossum przewalskyi is also transferred to the subgenus Hemihalictus. Ultimately, we redefine Lasioglossum to include all halictine bees with weakened distal wing venation.