Honey Bee Diversity Research Articles

Genomic diversity and population structure of Carniolan honey bee in its native habitat

BackgroundResearch into the genetic diversity of honey bee (Apis melliferaL.) populations has become increasingly significant in recent decades, primarily due to population declines attributed to human activities and climate change. As a species of great importance, breeding programs that leverage understanding of genomic diversity could offer solutions to mitigate these challenges. The objective of this study was to examine the genomic diversity and population structure of Carniolan honey bees (Apis mellifera carnica) using the Illumina SNP chip on a large honey bee sample collected from Central and South-Eastern European countries. The study also aims to offer recommendations for future breeding programs.ResultsOur analysis involved Discriminant Analysis of Principal Components (DAPC), heterozygosity, admixture analysis, fixation indices (FST), Neighbour-Joining tree, gene flow and Isolation-by-distance analysis. DAPC indicated distinct separation between the Carniolan and Italian honey bee (Apis mellifera ligustica) populations, whereas the admixture analysis revealed varying levels of gene flow and genetic admixture within the Carniolan honey bee populations, demonstrating closer relationships between specific geographic regions (confirmed by Isolation-by-distance analysis). Furthermore, the research of heterozygosity, genomic inbreeding, pairwise FST values, and Neighbour-Joining tree provided insights into the patterns of genetic differentiation and similarity among the populations of Carniolan honey bee within its natural habitat. We have observed genetic homogeneity of the Carniolan honey bee population when considered in a broader genetic/geographical context. However, the Carniolan honey bee has sufficient genetic diversity in its geographical home range that needs to be carefully monitored and maintained.ConclusionsThis study provides important insights into the genetic composition, differentiation, and relationships among Carniolan honey bee populations in Central and South-Eastern European countries. The findings are crucial for conservation efforts, breeding programs, and sustainable beekeeping practices. They emphasise the importance of considering genetic factors and population structure in the breeding and management of honey bees. By understanding these genetic relationships, we can develop strategies to preserve genetic diversity, improve breeding outcomes, and ensure the resilience of honey bee populations in the face of environmental changes and challenges. This knowledge can also inform policy makers and stakeholders on best practices to maintain healthy bee populations, which are vital for ecosystem services and agricultural productivity.

Honey bees and mason bees as biological indicators of landscape pesticide loads: Different results but similar conclusions

Agricultural environments, including crop and non-crop areas, often provide important pollen and nectar resources for managed and wild bees. However, these resources may be contaminated with pesticides detrimental to bees and other non-target organisms, including humans. Differences in life-history traits among bee species influence food resource exploitation and pesticide exposure. This study assesses the potential of honey bees (Apis mellifera) and mason bees (Osmia), two bee species with highly contrasting functional traits, as biological indicators of pesticide exposure in 34 Italian agricultural farms. Pollen loads of both species were used to identify pollen species collected and to analyse multi-residue levels of pesticides. Pesticide risk indexes were calculated for honey bees, mason bees and humans. In mason bees, pesticide risk was not influenced by plant diversity. In agreement with their pollen preferences and short foraging ranges, mason bees collected a high proportion of pollen from flowers of the target crop. Conversely, pesticide risk decreased with increasing pollen diversity in honey bees. In agreement with their generalist foraging habits and long foraging ranges honey bees collected a greater diversity of pollen species and a lower proportion of target crop pollen. Although honey bees and mason bees showed similar toxic loads and pesticide composition, at a field scale pesticide risk of one species is not a good indicator of the risk to the other species. Our study confirms that bees in agricultural environments are pervasively exposed to multi-residue pesticide loads. Exposure is conditioned by specific bee traits but is also highly context-dependent.

Intestinal microbial diversity in domestic honey bees and evaluation of their probiotic properties

As populations of managed honey bees in various regions increase in comparison to wild colonies, there is a need to ensure that threats to bee health and survival in all environments are countered. One of the more direct methods of approaching bee health is through dietary means and as such, we investigated the intestinal microbial diversity in the gut of honey bees in order to identify strains with probiotic potential. Honey bees were fed with several feeds including Feedbee, Megabee, sugar syrup 60% (w/v), Yangbongnonghyup (YBNH), and Test A, to monitor the culture-dependent and culture-independent microbial diversity. In the culture-dependent study, most isolates belonged to Apilactobacillus (24.1%), Fructobacillus (21.8%), and Bacillus (15.4%) at the genus level. Culture-independent results showed that Bacillota and Pseudomonadota were the most abundant groups (99%) among the gut bacteria, while other bacteria showed a lower percentage than 0.1%. Next, the hydrolytic enzymes (α-amylase, protease, and cellulase) and antibacterial and antioxidant activities of the isolated strains were evaluated to examine their applicability as potential probiotics for honey bees. The selected strains showing three hydrolytic enzyme activities were used to determine their antibacterial activity against Paenibacillus larvae. Bacillus subtilis MBLB2796 showed the highest α-amylase (1.24 ± 0.06 U/mL) and cellulase (0.24 ± 0.01 U/mL) activities while B. tequilensis MBLB2834 exhibited the highest protease activity (0.15 ± 0.03 mU/mL) and the highest antioxidant activity (71.0 ± 3.8%). This study suggests that honey bee gut-originated isolates are prime candidates for use as probiotics in honey bees.

Gut microbiota composition of Apis mellifera L. populations from Tunisia

Honey bee populations are major contributors to ecosystem stability, providing vital services such as pollination of crops and food security. Currently, honey bees are undergoing severe global decline which is likely due to the disruption of the gut microbiota underlying honey bee health status. The composition and diversity of honey bees’ gut microbiota are affected by several factors. In Tunisia, studies on honey bees’ gut microbiota remain largely unexplored. This study aimed to characterize the gut community composition of honey bee populations from Tunisia and to assess their diversity by sequencing the 16S rRNA gene amplicons. Our results revealed the presence of a core gut microbiota bound to the 4 phylotypes Snodgrassella, Gilliamella, Lactobacillus and Bifidobacterium which have different relative abundances across analyzed samples and uncovered the occurrence of pathogens in the sampled honey bee populations. Shannon and Simpson’s diversity indices showed consistent variation patterns in each analyzed sample that could be due to the local environment. This study is a first characterization of the honey bees’ gut microbiota from Tunisia and underscores the need to study the impact of environmental factors on microbiome diversity.

Evaluating the phylogenetic relationship of a dwarf honey bee through cytochrome oxidase subunit 1 (COX1) gene sequence databases

Dwarf honey bees, Apis florea, and Apis andreniformis are known as the potential wild pollinator in Asia. Apis florea was introduced to Indonesia, West Asia, and Africa. Based on the cytochrome oxidase subunit 1 (COX1) gene, introduced A. florea in Iran is suggested to come from India. Although the databases of the dwarf honey bee COX1 gene are available in GenBank, however, the phylogeny analysis was focused on the restricted area. Thus, this study aims to evaluate the phylogenetic relationship and genetic diversity of dwarf honey bees based on the COX1 gene sequence from GenBank databases. The COX1 gene sequence databases are collected from NCBI. The genetic diversity and phylogenetic relationship are analyzed using MEGAX. Alignment of 530 bp COX1 gene of dwarf honey bee showed that there are 60 nucleotide variations between A. florea and A. andreniformis. Our analysis indicated that the genetic diversity between A. andreniformis is low (0-0.19%). On the other hand, there are 28 nucleotide variations between A. florea and eight nucleotide sites that are suggested as a marker to differentiate A. florea1 India+Egypt+Iran and A. florea2 Thailand+China with 1.7-3.4% genetic distance. The high genetic distance of A. florea is supported by the separation sub-clade of A. florea1 and A. florea2 in the phylogenetic tree.

Morphometrical analyses revealed high diversity of the eastern honey bee (Apis cerana) in mountains and islands in China

The eastern honey bee (Apis cerana) is of great importance for ecosystems and agriculture in Asia, whose diversity has yet to be explored. Previous studies have found a high diversity of A. cerana in mountainous areas or islands. To better understand the morphological diversity of A. cerana, we focused on the eastern Qinghai-Tibet Plateau (QTP), a region with high mountains, Weizhou Island, Yongxing Island and Hainan Island, much of which lacks systematic investigation of honey bee diversity. Five sampling sites in the plain were also selected as references. A total of 140 colonies of A. cerana were collected from 9 localities in QTP, 3 localities in islands, and 5 localities in plain. We used standard morphometry and geometric morphometrics to assess the level of diversity, in which principal component analysis and discriminant analysis were conducted. The results revealed the A. cerana populations from QTP and islands were differentiated from the plain populations. Moreover, two populations from QTP and one from Yongxing Island showed significant divergence. Our study provided insights into the A. cerana diversity and provides information for the effective conservation of A. cerana genetic resources in China.

The sulfoximine insecticide sulfoxaflor exposure reduces the survival status and disrupts the intestinal metabolism of the honeybee Apis mellifera.

Honeybees (Apis mellifera) are indispensable pollinators in agricultural production, biodiversity conservation, and nutrients provision. The abundance and diversity of honeybees have been rapidly diminishing, possibly related to the extensive use of insecticides in ecosystems. Sulfoxaflor is a novel sulfoximine insecticide that, like neonicotinoids, acts as a competitive modulator of nicotinic acetylcholine receptors (nAChR) in insects. However, few studies have addressed the negative effects of sulfoxaflor on honeybees at environmentally relevant concentrations. In the present study, adult workers were fed a 50% (w/v) of sugar solution containing different concentrations (0, 0.05, 0.5 and 2.0mg/L) of sulfoxaflor for two weeks consecutively. The survival rates, food intake, and body weight of the honeybees significantly decreased after continuous exposure at higher doses (0.5 and 2.0mg/L) of sulfoxaflor when compared with the control. The change in the metabolites in the honeybee gut was determined using high-throughput non-targeted metabolomics on day 14 after sulfoxaflor treatment. The results revealed that 24 and 105 metabolites changed after exposure to 0.5 and 2.0mg/L sulfoxaflor, respectively, compared with that of the control groups. A total of 12 changed compounds including pregenolone and glutathione were detected as potential biomarkers, which were eventually found to be enriched in pathways of the steroid hormone biosynthesis (p=0.0001) and glutathione metabolism (p=0.021). These findings provide a new perspective on the physiological influence of sulfoxaflor stress in honeybees.

Urban ecosystem drives genetic diversity in feral honey bee

Urbanization can change biodiversity in both directions, positive and negative, and despite the rising global trend of urban beekeeping, little is known about the impact of urbanization on the genetic diversity of honey bees. We investigate how urbanization affects the genetic variability of feral and managed honey bee colonies that are spread throughout the entire city, even in highly urban areas, through genetic analysis of 82 worker bees. We found convincing evidence of high genetic differentiation between these two groups. Additionally, by comparing city samples with 241 samples from 46 apiaries in rural parts of the country, variations in mitochondrial tRNAleu-cox2 intergenic region and microsatellite loci indicated that feral colonies have distinct patterns of genetic diversity. These results, with evidence that feral honey bees find niches within highly modified and human-dominated urban landscapes, lead us to conclude that urbanization is a driver of the genetic diversity of feral honey bees in the city.

Molecular genetic diversity and population structure of Iranian honey bee (Apis mellifera meda) populations: implications for breeding and conservation

Molecular genetic diversity and population structure of Iranian honey bee (Apis mellifera meda) populations: implications for breeding and conservation

Further Evidence of Population Admixture in the Serbian Honey Bee Population.

Simple SummaryThe western honey bee is one of the most ecologically and economically important pollinator species. Due to human interference, it faces serious challenges, not only in number decline and habitat loss, but also in natural subspecies diversity and distribution. The conservation of genetic diversity and perseverance of locally adapted populations and subspecies becomes a crucial task in the face of rapid environmental changes. In order to further assess present genetic variability in Serbian honey bee populations, we analyzed 14 microsatellite loci and then compared nine of them with previously published data. Our results suggest that Serbia now harbors a distinct, relatively homogenous honey bee population, although some local differences are still preserved.Socioeconomic interests and beekeeper preferences have often taken precedence over the conservation of locally native honey bee subspecies, leading to the predominance of admixture populations in human-dominated areas. To assess the genetic diversity of contemporary managed Serbian honey bee colonies, we used 14 microsatellite loci and analyzed 237 worker bees from 46 apiaries in eight localities of northern and southern Serbia. Furthermore, we compared data for nine microsatellite loci with 338 individuals from Italy, Hungary, Poland, and Spain. The standard parameters of genetic diversity in Serbian honey bee populations were in line with other analyses, although somewhat smaller. STRUCTURE analysis showed the existence of two equally distributed genetic clusters and Analysis of molecular variances could not confirm the presence of a geographically discrete population but showed local differences. Discriminant analysis of principal components showed overlapping of worker bees from different parts of Serbia. Clear genetic differentiation can be observed when comparing all populations between geographical regions and their corresponding subspecies. The absence of the A. m. macedonica subspecies from its historical distribution range in southern Serbia as well as the lack of distinctive geographical groups suggest that selective breeding, queen import, and migratory beekeeping practices strongly influence the genetic structure and diversity of honey bees, leading to the genetic uniformization and creation of the admixture population.

Population Structure and Diversity in European Honey Bees (Apismellifera L.)-An Empirical Comparison of Pool and Individual Whole-Genome Sequencing.

Background: Whole-genome sequencing has become routine for population genetic studies. Sequencing of individuals provides maximal data but is rather expensive and fewer samples can be studied. In contrast, sequencing a pool of samples (pool-seq) can provide sufficient data, while presenting less of an economic challenge. Few studies have compared the two approaches to infer population genetic structure and diversity in real datasets. Here, we apply individual sequencing (ind-seq) and pool-seq to the study of Western honey bees (Apis mellifera). Methods: We collected honey bee workers that belonged to 14 populations, including 13 subspecies, totaling 1347 colonies, who were individually (139 individuals) and pool-sequenced (14 pools). We compared allele frequencies, genetic diversity estimates, and population structure as inferred by the two approaches. Results: Pool-seq and ind-seq revealed near identical population structure and genetic diversities, albeit at different costs. While pool-seq provides genome-wide polymorphism data at considerably lower costs, ind-seq can provide additional information, including the identification of population substructures, hybridization, or individual outliers. Conclusions: If costs are not the limiting factor, we recommend using ind-seq, as population genetic structure can be inferred similarly well, with the advantage gained from individual genetic information. Not least, it also significantly reduces the effort required for the collection of numerous samples and their further processing in the laboratory.

Honey Bee Diversity in Urban and Peri-urban Agriculture and Urban Forest- Outlook Study from Bengaluru-Silicon Valley of India: A Review

The “Silicon Valley” of India, Bengaluru is one of the fastest growing cities, with many middle-class residents growing fruits and vegetables in their private spaces. This kind of Localized food systems (LFS) has been considered not only for obtaining mental pleasure and health consciousness, but also food for home consumption. This outlook study examined the honey bee diversity and possibilities of integrating different honey bees in urban agriculture and forests across the Bengaluru city. The urban forestry study across the Bengaluru city revealed presence of 374 species with the highest species diversity in parks (291) followed by residential areas and layouts (164) showing species richness. Polyalthia sp. and Pongamia glabra were found to be the most dominated tree species around the Bangaluru city. Majority of the plant species were offering good foraging sources for honey bees, including Apis indica, Apis dorsata, Apis florea and Trigona iridipennis. The urban agriculture and urban forest system in the Bengaluru was ideal for bee-keeping, especially stingless bees, which could be easily reared with limited space and care. Thus, the urban agro-ecosystem and the possible pollination services through integrating honey bees could be very much useful in making the cities more sustainable and resilient.

Insect’s (Honey Bee) Diversity: A Rapidly Growing Threat Accelerated by Environmental Pollutants

Insect’s (Honey Bee) Diversity: A Rapidly Growing Threat Accelerated by Environmental Pollutants

CSI Pollen: Diversity of Honey Bee Collected Pollen Studied by Citizen Scientists.

Simple SummaryHoney bee colonies collect pollen from plants as a source of nutrients. Diverse diets comprising pollen from many different plant species are beneficial for honey bee colony health, because they contain a greater diversity of nutrients than monofloral diets of one plant species only. Here, we present the results of the COLOSS “CSI Pollen” study on the diversity of pollen collected by honey bee colonies. In this study, beekeepers acted as citizen scientists sampling and analyzing pollen collected by their own colonies. As a simple measure of diversity, beekeepers determined the number of different colors found in pollen samples that were collected in a coordinated and standardized way. The support of 750 beekeepers allowed the collection of information about almost 18,000 pollen samples from many European countries. We found that the pollen samples consistently comprised approximately six different colors in total, of which four colors were abundant. ‘Urban’ habitats or ‘artificial surfaces’ were associated with higher pollen color diversity. This investigation highlights seasonal- and land-use-related differences in the pollen supply for honey bees, which affects beekeeping and pollinator health. Determining pollen colors is a simple, useful technique for beekeepers to estimate pollen diversity.A diverse supply of pollen is an important factor for honey bee health, but information about the pollen diversity available to colonies at the landscape scale is largely missing. In this COLOSS study, beekeeper citizen scientists sampled and analyzed the diversity of pollen collected by honey bee colonies. As a simple measure of diversity, beekeepers determined the number of colors found in pollen samples that were collected in a coordinated and standardized way. Altogether, 750 beekeepers from 28 different regions from 24 countries participated in the two-year study and collected and analyzed almost 18,000 pollen samples. Pollen samples contained approximately six different colors in total throughout the sampling period, of which four colors were abundant. We ran generalized linear mixed models to test for possible effects of diverse factors such as collection, i.e., whether a minimum amount of pollen was collected or not, and habitat type on the number of colors found in pollen samples. To identify habitat effects on pollen diversity, beekeepers’ descriptions of the surrounding landscape and CORINE land cover classes were investigated in two different models, which both showed that both the total number and the rare number of colors in pollen samples were positively affected by ‘urban’ habitats or ‘artificial surfaces’, respectively. This citizen science study underlines the importance of the habitat for pollen diversity for bees and suggests higher diversity in urban areas.

Correction to: Insights into Ethiopian honey bee diversity based on wing geomorphometric and mitochondrial DNA analyses

Correction to: Insights into Ethiopian honey bee diversity based on wing geomorphometric and mitochondrial DNA analyses

Honey Bee Diversity Is Swayed by Migratory Beekeeping and Trade Despite Conservation Practices: Genetic Evidence for the Impact of Anthropogenic Factors on Population Structure

The intense admixture of honey bee (Apis melliferaL.) populations at a global scale is mostly attributed to the widespread migratory beekeeping practices and replacement of queens and colonies with non-native races or hybrids of different subspecies. These practices are also common in Anatolia and Thrace, but their influence on the genetic make-up of the five native subspecies of honey bees has not been explored. Here, we present an analysis of 30 microsatellite markers from honey bees from six different regions in Anatolia and Thrace (N= 250 samples), with the aim of comparing the impact of: (1) migratory beekeeping, (2) queen and colony trade, and (3) conservation efforts on the genetic structure of native populations. Populations exposed to migratory beekeeping showed less allegiance than stationary ones. We found genetic evidence for migratory colonies, acting as a hybrid zone mobile in space and time, becoming vectors of otherwise local gene combinations. The effect of honey bee trade leaves very high introgression levels in native honey bees. Despite their narrow geographic range, introgression occurs mainly with the highly commercial Caucasian bees. We also measured the direction and magnitude of gene flow associated with bee trade. A comparison between regions that are open and those closed to migratory beekeeping allowed the evaluation of conservation sites as centers with limited gene flow and demonstrated the importance of establishing such isolated regions. Despite evidence of gene flow, our findings confirm high levels of geographically structured genetic diversity in four subspecies of honey bees in Turkey and emphasize the need to develop policies to maintain this diversity. Our overall results are of interest to the wider scientific community studying anthropogenic effects on the population diversity of honey bees and other insects. Our findings on the effects of migratory beekeeping, replacement of queens and colonies have implications for the conservation of honey bees, other pollinators, and invertebrates, in general, and are informative for policy-makers and other stakeholders in Europe and beyond.

Correction to: Wide genetic diversity in Old World honey bees threaten by introgression

Correction to: Wide genetic diversity in Old World honey bees threaten by introgression

Disentangling Ethiopian Honey Bee (Apis mellifera) Populations Based on Standard Morphometric and Genetic Analyses.

Simple SummaryWe conducted this population study of Ethiopian honey bees, using morphometric and genetic methods, to decipher their controversial classification. These honey bees are highly diverse and showed differentiation based on size and genetic information according to prevailing agro-ecological conditions, demonstrating morphological and molecular signatures of local adaptation. The results of both morphometric and genetic analyses suggest that Ethiopian honey bees differ from populations in the neighboring geographic regions and are characterized by extensive gene flow within the country, enhanced by honey bee colony trade. Consequently, future research that includes studying traits of vitality, behavior and colony performance of honey bees in remaining pocket areas of highland agro-ecological zones could contribute to the development of appropriate conservation management.The diversity and local differentiation of honey bees are subjects of broad general interest. In particular, the classification of Ethiopian honey bees has been a subject of debate for decades. Here, we conducted an integrated analysis based on classical morphometrics and a putative nuclear marker (denoted r7-frag) for elevational adaptation to classify and characterize these honey bees. Therefore, 660 worker bees were collected out of 66 colonies from highland, midland and lowland agro-ecological zones (AEZs) and were analyzed in reference to populations from neighboring countries. Multivariate morphometric analyses show that our Ethiopian samples are separate from Apis mellifera scutellata, A. m. jemenitica, A. m. litorea and A. m. monticola, but are closely related to A. m. simensis reference. Linear discriminant analysis showed differentiation according to AEZs in the form of highland, midland and lowland ecotypes. Moreover, size was positively correlated with elevation. Similarly, our Ethiopian samples were differentiated from A. m. monticola and A. m. scutellata based on r7-frag. There was a low tendency towards genetic differentiation between the Ethiopian samples, likely impacted by increased gene flow. However, the differentiation slightly increased with increasing elevational differences, demonstrated by the highland bees that showed higher differentiation from the lowland bees (FST = 0.024) compared to the midland bees (FST = 0.015). An allelic length polymorphism was detected (denoted as d) within r7-frag, showing a patterned distribution strongly associated with AEZ (X2 = 11.84, p < 0.01) and found predominantly in highland and midland bees of some pocket areas. In conclusion, the Ethiopian honey bees represented in this study are characterized by high gene flow that suppresses differentiation.

Gut microbiota associated with two species of domesticated honey bees from Thailand

Honey bees are universally known to play a critical role in mediating pollination. Recently, attention has been drawn to the influence of gut microbiota on bee health. Studies on the honey bee (Apis mellifera) gut community have become widely appreciated due to conserved phylotypes of gut microbiota. Here, we focused on profiling the gut microbiota of two honey bee species native to Thailand, Apis florea (dwarf honey bee; LB) and Apis dorsata (giant honey bee; GB). Despite inhabiting the same landscape, different Apis species might have different gut microbial profiles. Analysis of gut bacterial diversity and community composition of LB and GB honey bees using deep 16S rRNA gene sequencing revealed major differences in bacterial diversity (OTUs) and abundance of core members in the gut of the two species. Lower species evenness was observed in LB than in GB (P < 0.01). Our results also show that gut microbial communities within LB were dominated by Lactobacillus (P < 0.001), while Gilliamella (P < 0.01) and Snodgrassella (P < 0.05) were predominantly associated with GB. Overall, our study has provided a preliminary overview of the gut microbiota of two honey bee species in Thailand. Further study should therefore focus on the association of host ecology and behavior with the bee gut microbiome.

Morphological diversity of Carniolan honey bee (Apis mellifera carnica) in Croatia and Slovenia

The Carniolan honey bee (Apis mellifera carnica) is an indigenous subspecies of the Western honey bee in Central Europe. Croatia represents a large part of its native range. Hybridization and introgression is a realistic possibility due to unmonitored imports by beekeepers. In this study, we focused on honey bee colonies managed by beekeepers from all over Croatia and Slovenia. The identification of the subspecies was based on wing geometric morphometrics. The similarity of all investigated colonies to A. m. carnica was substantial, which indicates that the native subspecies continues to be present in the study area. However, some of the colonies differed markedly from the currently available reference of this subspecies. The low similarity with reference samples can be related both to hybridization with non-native subspecies and to natural geographical variation within A. m. carnica. The data and results obtained from this morphometric analysis will provide a deeper insight into the phenotypic characterization of the studied honey bee populations and directions for future conservation strategies.