Pollen Collection Research Articles

Scanning electron imaging of mellitophilous and allergenic pollen grain of arid and northern irrigated agroecological zones of Pakistan.

Palynomorphic studies of 65 common mellitophilous and 16 allergenic flora of Arid and Northern irrigated agroecological zones of Pakistan are carried out in this study by using field emission scanning electron microscope (FESEM). Mellitophilous pollen were extracted from honey samples of selected sites. For collection of local allergenic pollen, previously identified allergy-causing plants were selected. Pollen morphological examination was carried out under FESEM. Diverse range of pollen shapes ranging from monad to polyad and sculpturing ranging from psilate to echinate, scabrate to reticulate, bireticulate, or echinolophate were observed. Brassicaceae, Myrtaceae, Asteraceae, Rosaceae, and Poaceae were observed to be dominant allergenic and mellitophilous families of the selected sites.

Honey bee (Apis mellifera) preference towards micronutrients and their impact on bee colonies.

Honey bees are important pollinators and take micronutrients from different natural floral resources and turbid water to adequately meet their nutritional requirements. But the role of micronutrients for honey bee health is not well understood. Here, the present study was conducted to determine honey bees' micronutrients preference in summer and winter seasons. Also, the impact of micronutrients on foraging behaviour and brood increase was studied in different honey bee colonies. The results elucidated that honey bees exhibited a strong preference for a salt solution compared to deionized water during the summer and winter seasons. However, there was a notable switch in salt preference between seasons. Overall, honey bees showed significantly more foraging activity, more pollen collection, and increased brood area after sodium consumption compared to other minerals in the summer season. Further, pollen collection and brood area were significantly higher after the use of potassium in the winter season. Thus, the food preference of honey bees is strongly linked with the seasons and the availability of the floral resources. Our data suggested that honey bees may seek specific nutrients during variation of the seasonal conditions.

The use of different stingless bee species to pollinate cherry tomatoes under protected cultivation

Under standard greenhouse conditions, the tomato fruits of spontaneous self-pollination are expected to be of lower quality than those of bee pollination, as well as that simultaneously use different bee species which can complement pollination services. To test these hypotheses, we evaluated the complementarity of pollination services from the use of three native stingless bee species that have distinct foraging behaviors, Melipona bicolor Lepeletier 1836, Nannotrigona testaceicornis (Lepeletier 1836) and Partamona helleri (Friese 1900) during flowering of cherry tomatoes in greenhouses. Fruit quality parameters resulted from pollination experiments were measured and the acclimatization of the analyzed bee species was evaluated. Visits of M. bicolor and N. testaceicornis to the tomato flowers contributed significantly to the increase in the average weight, seed number, and thickness of the pericarp (only for N. testaceicornis) of the fruits, compared to the spontaneous self-pollination treatment. Partamona helleri, however, did not show any pollen collection behavior in the experimental conditions. Although N. testaceicornis do not perform the buzzing behavior, fruits from its pollination were equivalent to those fruits from pollination by M. bicolor. The simultaneous use of bee species with different flower-visiting behaviors can optimize tomato pollination in greenhouses, contributing significantly to the quality of the fruits and the increase of productivity and consequently the commercial value.

Phenology of the specialist bee Colletes hederae and its dependence on Hedera helix L. in comparison to a generalist, Apis mellifera

Colletes hederae, the ivy bee, (Hymenoptera: Colletidae) has undergone large range expansions in Europe in recent years, including colonising Britain in 2001 with its original distribution limited to Western mainland Europe and the Channel Islands. It is thought to specialise on Hedera helix L. (Apiales: Ariliaceae), common ivy. However, some research has questioned this dependence. This study quantifies the foraging ecology of C. hederae to determine its relationship with ivy in Sussex. We quantified the phenology of ivy bloom, C. hederae activity and flower visitation, and pollen collection of females through pollen analysis. We also gathered equivalent data on Apis mellifera both as a comparison and to assess alternative pollen sources. The phenology of female C. hederae activity was highly correlated with and phonologically contained within the ivy bloom period. Pollen analysis from C. hederae identified ivy pollen was 98.5% of samples, significantly more than for A. mellifera (90%). Two other plant species were identified and more common in C. hederae samples when ivy bloom was not at its peak. Surveys of ivy flowers surrounding the aggregations found that C. hederae were the most common insect (26%) foraging on ivy. Although C. hederae can forage on other species, ivy was found to be an important floral resource. The results also suggest the potential for competition with A. mellifera, the only other bee present in more than small numbers on H. helix flowers, as although A. mellifera is a generalist, in autumn it mainly forages on ivy.

Evaluating the Impact of Post-Emergence Weed Control in Honeybee Colonies Located in Different Agricultural Surroundings.

Simple SummaryThe honeybee Apis mellifera is one of the main pollinators in agricultural ecosystems and therefore they are exposed to pesticides and the reduction of floral diversity. Cytochrome P450 monooxygenases are enzymes involved in xenobiotic detoxification used by organisms, including insects. In this study, we evaluated honeybee foraging activity and the expression profiles of several cytochromes, before and after the administration of a mixture of three of the most used herbicides in the region during the summer season. Additionally, we investigated whether colonies located in three distinct agricultural environments with different crop/wild flora proportions are affected similarly or differently by herbicide administration. We found that the expression of several cytochrome P450 genes decreased significantly in larvae after post-emergence weed control and they showed significant differences between apiaries in the case of honeybee workers. Besides, we found significant positive correlations between pollen collection and some pesticide detoxification genes. Our results support that diversity and quality of resource availability as well as the presence of herbicides affect colonies’ nutritional state and bee health. Moreover, their detoxification response shows that larvae are more harmed than adults in these agricultural ecosystems.The honeybee Apis mellifera is exposed to agricultural intensification, which leads to an improved reliance upon pesticide use and the reduction of floral diversity. In the present study, we assess the changes in the colony activity and the expression profile of genes involved in xenobiotic detoxification in larvae and adult honeybees from three apiaries located in agricultural environments that differ in their proportion of the crop/wild flora. We evaluated these variables before and after the administration of a mixture of three herbicides during the summer season. The expression of several cytochrome P450 monooxygenases decreased significantly in larvae after post-emergence weed control and showed significant differences between apiaries in the case of honeybee workers. Principal component analysis (PCA) revealed that colonies located in the plot near to a wetland area exhibited a different relative gene expression profile after herbicide application compared with the other plots. Moreover, we found significant positive correlations between pollen collection and the pesticide detoxification genes that discriminated between plots in the PCA. Our results suggest that nutrition may modify herbicide impact on honeybees and that larvae are more harmed than adults in agroecosystems, a factor that will alter the colonies’ population growth at the end of the blooming period.

Botanical origin approach for a better understanding of chemical and nutritional composition of beebread as an important value-added food supplement

Beebread (BB) is a fermented bee product made from plant pollen, honey and bee saliva. The nutritive and biological compounds of BB vary greatly depending on the diversity of flora and the season of pollen collection by bees. In order to evaluate this valuable bee product potential, thirteen BB samples were analyzed on the nutritive proprieties and biologically active compounds, correlated with their botanical origin. The obtained results shows that BB comes with a high content of proteins with values ranging between 18.96 and 23.11 g/100 g, lipids ranging between 4.89 and 14.74 g/100 g, and free sugars, fructose being present in the highest amount (17.27 g/100 g). Analyzed samples contain all the essential amino acids, methionine being the most abundant, 86.93–12.38 mg/100 g, mono- and polyunsaturated fatty acids, ω-6/ω-3 ratio varying between 0.02 – 1.07. BB samples have also high amount of natural antioxidants, from the class of polyphenols and flavonol glycoside derivative. These findings suggest that BB could be used as a source of potential value-added nutrients and bioactive compounds and contributes to the chemical knowledge of this natural product.

Bioecological and Behavioral Interaction between Pollinating Bees and the Pioneer Shrub Ludwigia nervosa in Degraded Area Suggests an Exotic Bee as Its Major Pollinator.

Simple SummaryLudwigia nervosa plants are commonly found in humid environments in the process of regeneration; however, little is known about reproductive contribution to attracting bees in fragmented environments. Therefore, we aimed to identify the bees visiting the flowers, and whether during pollen and/or nectar collection they performed pollination. The absence of pollen limitation shows that there was sufficient and efficient deposition of pollen in L. nervosa flowers during the visit, guaranteeing the formation of larger fruits and seeds with high germinative potential.The flowers of plants of the genus Ludwigia are an important source of food for several species of bees. In the current study, we conducted an experiment with the aim to describe the reproductive biology and phenology of L. nervosa; to identify the species of visiting bees; analyze the foraging behavior of bees; and to investigate whether the reproductive success of the species is related to the foraging activity of bees. We found that the flowers received visits from several native bee species (n = 7), in addition of the exotic honey bees which came to be the dominant species. During visits the majority of the bees foraged in both resources, pollen and nectar. The significantly higher production of fruits in open pollinated pollination experiment compared to artificial cross pollination, suggests honey bees as effective pollinator of this plant species in the study site. Pollen deposition occurs efficiently, given the absence of pollen limitation. Despite massive visitation of honey bees, Ludwigia nervosa is attractive to native bees, and therefore it may help to sustain population of both native and exotic pollinators in fragmented humid areas.

Visual Machine Learning and Artificial Intelligence Application in Aeroallergen Identification During Spring, Summer, and Fall Pollen Season

Continued validation of automated pollen identification (API) is needed. We performed a side-by-side device comparison of pollen counts identified using a Burkard sampler (BS) and an Automate Pollen Sampler (APS) by Pollen SenseTM. The designated gold standard device for comparison, the BS, was co-located with the APS in Waterloo, Iowa. Pollen collection, processing, and identification were performed following NAB requirements. The APS was provided by Pollen SenseTM. The APS collects particulate matter volumetrically from ambient air, automatically images the particulates, and uses a convolutional neural network to identify the individual pollen species. For this first iteration, 57 days were compared in the fall 2019 and spring-summer 2020. The top 10 pollen reported to the NAB in the upper Midwest were chosen for reporting. Accuracy is determined as the number of days a species was identified as present or absent in the APS that matches the Burkard, divided by the number of counting days x 100. Accuracy: ragweed 96, mulberry 50, juniper 8, oak 46, nettle 0, grass 65, ash 58, elm 8, pine 65, birch 23. Current accuracy of APS needs continued improvement. Varying correctness in pollen species identification rely on several factors including whether the APS was trained for that pollen species, morphology complexity, and amount of debris in the background. Identification and enumeration using visual machine learning methods in artificial intelligence is a process that improves automatically through experience. It requires multiple iterations of repetitive learning to achieve desired accuracy.

Collection and Identification of Pollen from Honey Bee Colonies

Collection and Identification of Pollen from Honey Bee Colonies

Collection and Identification of Pollen from Honey Bee Colonies.

Researchers often collect and analyze corbicular pollen from honey bees to identify the plant sources on which they forage for pollen or to estimate pesticide exposure of bees via pollen. Described herein is an effective pollen-trapping method for collecting corbicular pollen from honey bees returning to their hives. This collection method results in large quantities of corbicular pollen that can be used for research purposes. Honey bees collect pollen from many plant species, but typically visit one species during each collection trip. Therefore, each corbicular pollen pellet predominantly represents one plant species, and each pollen pellet can be described by color. This allows the sorting of samples of corbicular pollen by color to segregate plant sources. Researchers can further classify corbicular pollen by analyzing the morphology of acetolyzed pollen grains for taxonomic identification. These methods are commonly used in studies related to pollinators such as pollination efficiency, pollinator foraging dynamics, diet quality, and diversity. Detailed methodologies are presented for collecting corbicular pollen using pollen traps, sorting pollen by color, and acetolyzing pollen grains. Also presented are results pertaining to the frequency of pellet colors and taxa of corbicular pollen collected from honey bees in five different cropping systems.

Reproductive biology of Kalanchoe laetivirens (Crassulaceae) in the edaphoclimatic conditions of Santa Catarina, Brazil

Crassulaceae of the Kalanchoe laetivirens species have ornamental potential, but are poorly studied, especially their reproductive biology and trophic resources made available to visitors. The aim of this study, therefore, was to characterize the reproductive system of K. laetivirens through analyses of floral morphology, trophic resources and floral visitors. Floral structures, pollen / egg ratio, in vitro pollen germination, pollen grain structure in scanning microscopy and the availability of trophic resources by the evaluation of potential and instant nectar were described. The survey of floral visitors was carried out, and the pollen and nectar collection frequencies were recorded. The results show that the species has tubular flowers, complete with tetramer calyx and corolla, eight epipetalous stamens and four pistils with pluriovulated ovaries. Based on pollen / ovule ratio, this species is optionally autogamous. Morphologically, the pollen grain is small, tricolporate and has radial symmetrywith in vitro germination facilitated in the presence of sucrose (20%). Visitors mostly collected pollen with the highest frequency of visits at 9:30 am. The production of instant nectar had little variation between the evaluated times. The results are relevant to the understanding of the reproductive biology of Kalanchoe laetivirens and its relationship with floral visitors.

Productive flight activity of bees in the active period in the conditions of Vinnytsia region

The study aimed to identify the relationship between pollen collection, nectar, and seasonal dynamics of the brood of the bee colonies of the Ukrainian bee breed to study their active activity when changing the period of the active season. We compared the collection of nectar and pollen from honey plants of the garden, white acacia, and sunflower. The number of bees bringing pollen and nectar to the hive was recorded. The active work of bees to collect pollen is associated with the work of the uterus to lay eggs and the number of broods in the hives. Bee colonies increase their flight activity by collecting pollen in early spring and summer. By the beginning of the main honey harvest, pollination work is minimized, especially during the flowering of white acacia, and they switch to collecting nectar. Analysis of the results allows us to conclude that bees' daily dynamics that produce pollen increase in the spring to May and June.

Initial and post-cryogenic assessment of viability of russian plum cultivars pollen (Prunus rossica Erem.) in the conditions of the North-West of Russia

The viability of pollen of 5 collectible varieties of Russian plum of the Pushkinskiye and Pavlovskiye VIR Laboratories SPB before and after cryopreservation was studied. It was found that a significant factor for the level of pollen viability is “variety” (p=0.07), the factors “cryopreservation” (p=0.457), “year” (p=0.221), as well as the interaction of the factors “variety× cryopreservation” (p=0.172), were not significant at the p<0.05 level of significance. For long-term storage of Russian plum pollen in liquid nitrogen, the year of pollen collection is not a significant factor. For most genotypes, no negative impact of cryoсonservation on pollen viability was revealed. The varieties ‘Aureus’, 'Podarok Sankt-Peterburgu’ and ‘Exotica’ after cryopreservation for 1 year showed a tendency to increase the pollen viability indicators.

Comparison of defence buzzes in hoverflies and buzz‐pollinating bees

AbstractBees and many flies, particularly hoverflies (Syrphidae), have evolved a diverse range of mechanisms to gather pollen from a wide variety of flowering plants. Bees and hoverflies use protein‐rich pollen as a food resource to mature reproductive organs and eggs and, in bees, to feed their larvae. A particularly striking pollen‐collecting behaviour involves the production of thoracic vibrations to dislodge pollen from flowers. Vibratile pollen collection is widespread in bees (>11 600 species) but extremely rare in flies (~1 species of hoverfly). Why the use of floral vibrations to collect pollen is so rare among flies is currently unknown. A hypothesis proposed to explain why flies do not engage in vibratile or buzz pollination is that they are unable to reach the vibration amplitude required to expel pollen from anthers. Here we document, for the first time, the mechanical properties of non‐flight thoracic vibrations produced by hoverflies and compare them to the vibrations produced by buzz‐pollinating bees under similar contexts (defence buzzes). We analysed ~4000 vibrations produced by nearly 300 individuals representing 20 species of hoverflies and 22 bee taxa, recorded using a miniature piezoelectric accelerometer. We characterised both frequency and acceleration amplitude components of non‐flight thoracic vibrations and their relationship to insect size. Our results show that, after accounting for size, buzz‐pollinating bees and hoverflies produce vibrations with similar acceleration. We show experimentally that the acceleration amplitude produced by some hoverflies is sufficient to elicit pollen release from buzz‐pollinated flowers (Solanum dulcamara and S. rostratum). Our study does not support the hypothesis that the dearth of buzz‐pollinating flies is caused by their inability to produce vibrations of sufficient amplitude. We discuss alternative hypotheses to explain why most flies do not engage in buzz pollination and suggest that the lack of buzz‐pollinating flies might be best explained through their life history.

Bee-pollen retailed in Tuscany (Italy): Labelling, palynological, microbiological, and mycotoxicological profile

Bee pollen is the result of flower pollen collecting and processing by honey bees. Due to its nutritional profile, it is considered a functional food. The present work aimed at evaluating labelling, pH, Aw, microbiological and mycotoxicological profile of 29 bee pollen samples (dried and fresh) purchased at retail in Tuscany (Italy). Only one pollen lacked more than two mandatory indications. Aw ranged from 0.19 to 0.77, while pH from 4.50 to 6.10. Fresh samples presented higher bacterial loads than dried samples. Total bacterial counts, Enterobacteriaceae, yeasts and molds and lactic acid bacteria ranges were 2.2–6.0, <2–4.1, <1–4 and <2–6.0 log CFU/g, respectively. Escherichia coli, Staphylococcus aureus, Bacillus cereus and sulphite-reducing clostridia loads were lower than the detection limit; Salmonella spp. and Listeria monocytogenes were always absent. As for mycotoxins, total aflatoxins were detected in all samples (5.2–34.4 μg/kg). Higher deoxynivalenol concentrations were detected (maximum: 179.7 μg/kg). Since the occurrence of spoilage microorganisms seems to be frequent, leading to possible alterations of the organoleptic profile, the microbiological quality of fresh bee pollen should be monitored. The risk related to the presence of pathogenic microorganisms seems to be very low, while attention must be paid to the presence of toxic metabolites.

The assessment of field resistance to scab and winter resistance of columnar apple trees in the Samara Region

The research was conducted from 2006 to 2019 in the garden of Research Institute of Horticulture and Medicinal Plants Zhigulevskie Sady in the village of Malaya Tsarevshchina of Krasnoyarsk District of the Samara Region on 14 (0,432 ha), 43 (0,1 ha), 44 (0,05 ha) and 47 (6,8 ha) areas. On the 14th area, to accelerate flowering, fruiting, pollen collection and hybridization, in the springs of 2007, 2009 and 2012, parent varieties-donors of immunity were grafted to scab of domestic and foreign selection in the crown of young fruit-bearing trees of the Northern synapsis. Hybrid seeds obtained by crossing these varieties with local varieties were sown on the seedling plot (in a new plantation) and tested for scab resistance at an early age (from 2 years old). Scab-resistant hybrids were culled, and resistant hybrids were replanted in the breeding garden on the 47th area and tested for winter resistance separately after low-temperature stress in the freezer and in the field. The authors have identified columnar elites resistant to scab, which are superior in winter resistance to the local zoned coastal variety Kutuzovets, zoned variety Northern synapsis and common Antonovka. Apple trees with a columnar crown type of local selection in Research Institute of Horticulture and Medicinal Plants Zhigulevskie Sady with a high field resistance to scab, immunity, winter resistance and other varietal advantages will contribute to the improvement of orchards (amateur, farm, industrial) and import substitution of fruit products in the Samara Region of Russia.

Colony field test reveals dramatically higher toxicity of a widely-used mito-toxic fungicide on honey bees (Apis mellifera).

Honey bees (Apis mellifera) and other pollinator populations are declining worldwide, and the reasons remain controversial. Based on laboratory testing, fungicides have traditionally been considered bee-safe. However, there have been no experimental tests of the effects of fungicides on colony health under field conditions, and limited correlational data suggests there may be negative impacts on bees at levels experienced in the field. We tested the effects of one of the most commonly used fungicides on colony health by feeding honey bee colonies pollen containing Pristine® (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin) at four levels that bracketed concentrations we measured for pollen collected by bees in almond orchards. We also developed a method for calculating per-bee and per-larva dose. Pristine® consumption significantly and dose-dependently reduced worker lifespan and colony population size, with negative health effects observed even at the lowest doses. The lowest concentration we tested caused a 15% reduction in the worker population at an estimated dosage that was three orders of magnitude below the estimated LD15 values for previous acute laboratory studies. The enhanced toxicity under field conditions is at least partially due to activation of colonial nutritional responses missed by lab tests. Pristine® causes colonies to respond to perceived protein malnutrition by increasing colony pollen collection. Additionally, Pristine induces much earlier transitioning to foraging in individual workers, which could be the cause of shortened lifespans. These findings demonstrate that Pristine® can negatively impact honey bee individual and colony health at concentrations relevant to what they experience from pollination behavior under current agricultural conditions.

Nocturnal Bees Feed on Diurnal Leftovers and Pay the Price of Day – Night Lifestyle Transition

1. Bees exemplify flights under bright sunlight. A few species across bee families have evolved nocturnality, displaying remarkable adaptations to overcome limitations of their daylight-suited apposition eyes. Phase inversion to nocturnality in a minority of bees that co-exist with diurnal bees provide a unique opportunity to study ecological benefits that mediate total temporal niche shifts. While floral traits and sensory modalities associated with the evolution of classical nocturnal pollination syndromes, e.g. by bats and moths, are well-studied, nocturnality in bees represent a poorly understood, recently invaded, extreme niche. 2. To test the competitive release hypothesis, we examine how nocturnality shapes foraging by comparing pollen loads, nest pollen and flower visitation of sympatric nocturnal and diurnal carpenter bees. We predicted that nocturnal bees primarily use night-blooming flowers, show little/no resource overlap with diurnal species and competitive release favours night-time pollen collection for provisioning. 3. Contrarily, we found substantial resource overlap between nocturnal and diurnal bees. Flower opening times, floral longevity and plant abundance did not define nocturnal flower use. Smaller pollen loads on nocturnal foragers suggests subsistence on resource leftovers largely from diurnal flowers. Greater pollen types/diversity on nocturnal foragers indicates lower floral constancy compared to diurnal congenerics. Reduced activity during new moon compared to full moon suggests constraints to nocturnal foraging. 4. Invasion and sustenance within the nocturnal niche is characterised by: i)opportunistic foraging on residual resources as indicated by smaller pollen loads, extensive utilisation of day-blooming flowers and substantial overlap with diurnal bees, ii)generalisation at two levels – between and within foraging trips as indicated by lower floral constancy, iii)reduced foraging on darker nights, indicating visual constraints despite sensitive optics. This together with smaller populations and univoltine breeding in nocturnal compared to multivoltine diurnal counterparts, suggest that nocturnality imposes substantial fitness costs. 5. In conclusion, the evolution of nocturnality in bees is accompanied by resource generalisation instead of specialisation. Reduced floral constancy suggests differences in foraging strategies of nocturnal and diurnal bees which merits further investigation. The relative roles of competition, floral rewards and predators should be examined to fully understand the evolution and maintenance of nocturnality in bees.

Using ITS2 metabarcoding and microscopy to analyse shifts in pollen diets of honey bees and bumble bees along a mass‐flowering crop gradient

Worldwide pollinator declines lead to pollination deficits in crops and wild plants, and managed bees are frequently used to meet the increasing demand for pollination. However, their foraging can be affected by flower availability and colony size. We investigated how mass-flowering oilseed rape (OSR) can influence the pollen resource use of small and large honey bee (Apis mellifera L.) and bumble bee (Bombus terrestris L.) colonies. Colonies were placed adjacent to strawberry fields along a gradient of OSR availability in the landscapes. We used ITS2 metabarcoding to identify the pollen richness based on ITS2 amplicon sequencing and microscopy for quantification of target pollen. Bumble bees collected pollen from more different plant genera than honey bees. In both species, strawberry pollen collection decreased with high OSR availability but was facilitated by increasing strawberry flower cover. Colony size had no effect. The relationship between next-generation sequencing-generated ITS2 amplicon reads and microscopic pollen counts was positive but pollen type-specific. Bumble bees and, to a lesser degree, honey bees collected pollen from a wide variety of plants. Therefore, in order to support pollinators and associated pollination services, future conservation schemes should sustain and promote pollen plant richness in agricultural landscapes. Both bee species responded to the availability of flower resources in the landscape. Although honey bees collected slightly more strawberry pollen than bumble bees, both can be considered as crop pollinators. Metabarcoding could provide similar quantitative information to microscopy, taking into account the pollen types, but there remains high potential to improve the methodological weaknesses.

Pollen specialists are more endangered than non-specialised bees even though they collect pollen on flowers of non-endangered plants

Non-parasitic bees differ in the degree of their taxonomic specialisation for pollen collection to feed their brood. Surveys of published data on pollen specialisation by bees of central Europe showed that about two-thirds of species are pollen generalists (polylectic) while the remainder only collect pollen of one family, genus or species (monolectic and oligolectic). Proportions of monolectic and oligolectic species among bee families and genera in central Europe varies widely, from the entirely pollen-specialised but small family Melittidae, to the mostly polylectic Halictidae and Apidae. The Asteraceae plant family attracts the most monolectic and oligolectic species, followed by Fabaceae, Brassicaceae and Campanulaceae. Several plant families in central Europe host only a single bee species. Of the species included in the Red List of bees of Czechia, oligoleges are proportionally more strongly represented than polyleges. Most of these red-listed oligoleges are associated with specific and regionally endangered habitats, i.e. steppes or wetlands. Most of the bees are more limited by the presence of their habitat or nesting site than by the host plant, although this fact is not simple to evaluate due to the incomplete data on the floral relations and distribution of bee species.