Wild Bee Diversity Research Articles

Effects of landscape complexity and local management on bee pollinator diversity in apple orchards in Changping District, Beijing, China.

Pollinators provide important ecosystem services for crop production and food security. With the development of agricultural economy and the increasing intensity of land-use, a large number of natural or semi-natural habitats have been converted to croplands. Landscape homogenization and intensive management lead to the decline of wild bee diversity and threaten the sustainable agricultural production. In this study, we investigated the effects of landscape complexity (proportion of semi-natural habitats), local management practices (local flowering plant diversity and soil total nitrogen), and their interactions on diversity of bee pollinators in apple orchard in Changping District, Beijing. A total of 8642 bee individuals were captured, including 5125 honey bees and 3517 wild bees from 5 families, 14 genera, and 49 species. The optimal landscape scale for the response of bee diversity to landscape complexity and local management intensity was 500 m. Within 500 m radius of the site, the abundance of overall bees and wild bees significantly increased with increasing proportion of semi-natural habitats. The landscape complexity interacting with local flowering plant diversity significantly affected the richness of overall bee and wild bee. When the proportion of semi-natural habitats surrounding the apple orchards was low (≤29.9%), we found a positive effect of flowering plant diversity on the richness of overall bee and wild bee, whereas a reversed trend was found when the proportion of semi-natural habitats surrounding the apple orchards was high (>29.9%). In addition, the abundance of honey bees significantly increased with the increase of local flowering plant diversity and soil total nitrogen. The soil total nitrogen interacting with local flowering plant diversity significantly affected the honey bee abundance. At low levels of soil total nitrogen (≤1.9 g·kg-1), there was a positive effect of flowering plant diversity on honey bee abundance; whereas this trend was reversed at high levels of soil total nitrogen (>1.9 g·kg-1). Increasing the proportion of semi-natural habitats in agricultural landscape was beneficial to the increase of wild bee abundance, and flowering plant diversity could promote bee diversity but depending on landscape scale (proportion of semi-natural habitats) and local scale (nitrogen application). Therefore, multi-scale factors should be considered to develop conservation strategies to maintain the diversity of wild bees in agricultural landscape. Maintaining a higher proportion of cultivated land as much as possible is still a long-term requirement for production, while maintaining intermediate landscape complexity, increasing the diversity of flowering plants on the ground, and reducing the application of nitrogen fertilizer would be effective ways to promote the diversity of pollinating bees in apple orchards.

Seasonal dynamics of competition between honey bees and wild bees in a protected Mediterranean scrubland

Due to the widespread use of pesticides and the lack of floral resources in many agricultural landscapes, beekeepers have moved numerous honey bee colonies in protected areas which could shelter an important diversity of wild bees. Here, we investigated the seasonal dynamics of the competition between honey bees and wild bees through a two‐year study of plant–bee networks in a Mediterranean protected area. We recorded the visitation rates of four bee groups: honey bees, small wild bees, large wild bees and bumblebees. Our study reveals that the competition for floral resources induced by honey bees is especially strong during the early spring and then decreases along the season for all groups of wild bees. We observed a competitive exclusion of all groups of wild bees illustrated by an avoidance of well‐flowered plant species in presence of honey bees. As a consequence, we detected a rewiring of large and small bee floral preferences linked to the presence of honey bees. In presence of honey bees, Rosmarinus officinalis and Cistus albidus were significantly less visited by large bees. This study underlines the need to mitigate the establishment of numerous honey bee colonies in protected areas as honey bees could strongly affect the foraging activity of wild bees.

From pastures to forests: Changes in Mediterranean wild bee communities after rural land abandonment

Abstract In farmland landscapes worldwide, there are pervasive trends for either intensification or abandonment. Intensification is a widely recognised driver of wild bee declines, but little is known about the consequences of land abandonment, though it involves major habitat shifts from fallows, pastures and meadows, to shrublands and forests. Focusing on a Mediterranean landscape, we investigated long‐term changes in wild bee communities during secondary vegetation succession after land abandonment. We used a space‐for‐time substitution approach, sampling plants and wild bees on five successional stages, from grasslands, through shrublands, to oak woodlands. We recorded 2721 bees, representing over 150 species. Grasslands had the highest wild bee abundance and high diversity of oligolectic species. Moving through successional stages, there was a rapid decline in bee abundance combined with a progressive accumulation of rare species, resulting in maximum diversity of the overall community, ground nesters, polyleges, and oligoleges in oak woodlands. Bee diversity was positively related to plant taxonomic and phylogenetic diversity. There was high turnover in community composition along the succession, with species occurring in grasslands being largely absent from later successional stages, and vice versa. From 21 indicator species, 17 were associated with grasslands, including the only threatened species. Our results suggest that a mosaic of habitats at different successional stages, particularly grasslands and oak woodlands, are necessary to maximise the diversity and abundance of wild bees at the landscape scale. Sustained management is thus needed under land abandonment to retain early‐successional herbaceous habitats and to ensure woodland regeneration and protection.

Pollinator enhancement in agriculture: comparing sown flower strips, hedges and sown hedge herb layers in apple orchards

In intensive agricultural landscapes semi-natural habitats for pollinators are often limited, although willingness to establish pollinator habitat is increasing among farmers. A common pollinator enhancement measure is to provide flower strips, but existent or improved hedgerows might be more effective. In this study, we compare the effectiveness of three pollinator enhancement measures at edges of conventional apple orchards: (i) perennial flower strips, (ii) existent hedgerows, and (iii) existent hedgerows complemented with a sown herb layer. We used orchard edges without any enhancement as control. The study took place over three consecutive years in Southern Germany. Wild bee abundance and species richness were highest in flower strips followed by improved hedges. Hoverflies were also most abundant in flower strips, but not more species rich than at control sites. Wild bee but not hoverfly community composition differed between control and enhancement sites. The overall pollinator community included only few threatened or specialized species. Flower abundance was the main driver for wild bee diversity, whereas hoverflies were largely unaffected by floral resources. Pollinator enhancement had neither an effect on the abundance or species richness within the orchards nor on apple flower visitation. Perennial flower strips seem most effective to enhance wild bees in intensive agricultural landscapes. Additionally, flower-rich hedgerows should be promoted to complement flower strips by extending the flowering period and to increase connectivity of pollinator habitat in agricultural landscapes.

MetaComNet: A random forest‐based framework for making spatial predictions of plant–pollinator interactions

Abstract Predicting plant–pollinator interaction networks over space and time will improve our understanding of how environmental change is likely to impact the functioning of ecosystems. Here we propose a framework for producing spatially explicit predictions of the occurrence and number of pairwise plant–pollinator interactions and of the species richness, diversity and abundance of pollinators visiting flowers. We call the framework ‘MetaComNet’ because it aims to link metacommunity dynamics to the assembly of ecological networks. To illustrate the MetaComNet functionality, we used a dataset on bee–flower networks sampled at 16 sites in southeast Norway along with random forest models to predict bee–flower interactions. We included variables associated with climatic conditions (elevation) and habitat availability within a 250 m radius of each site. Regional commonness, site‐specific distance to conspecifics, social guild and floral preference were included as bee traits. Each plant species was assigned a score reflecting its site‐specific abundance, and four scores reflecting the bee species that the plant family is known to attract. We used leave‐one‐out cross‐validations to assess the models' ability to predict pairwise plant–bee interactions across the landscape. The relationship between observed occurrence or absence of interactions and the predicted probability of interactions was nearly proportional (GLMlogistic regression slope = 1.09), matching the data well (AUC = 0.88), and explained 30% of the variation. Predicted probability of interactions was also correlated with the number of observed pairwise interactions (r = 0.32). The sum of predicted probabilities of bee–flower interactions were positively correlated with observed species richness (r = 0.50), diversity (r = 0.48) and abundance (r = 0.42) of wild bees interacting with plant species within sites. Our findings show that the MetaComNet framework can be a useful approach for making spatially explicit predictions and mapping plant–pollinator interactions. Such predictions have the potential to identify areas where the pollination potential for wild plants is particularly high, and where conservation action should be directed to preserve this ecosystem function.

Bee aware! Signs of a global decline in wild bee diversity

There is more to bees than honey: wild bees ensure efficient pollination of most flowering plants and food crops. Yet a recent study counting the number of species recorded worldwide every year suggests a bleak picture, finding a steep reduction in recent years. Although changes in how we record bees could overstate these results, such strong decline in bee diversity should trigger some alarms. - submission by Eduardo E. Zattara

High resolution prediction maps of solitary bee diversity can guide conservation measures

Wild bees are key ecosystem components making their decline a cause for concern. An effective measure to increase wild bee diversity is to enhance plant diversity. However, the effect on bee diversity of augmenting plant diversity depends on site-specific environmental conditions. We aimed to make spatial predictions of where: (a) environmental conditions maximize bee diversity, so that such areas can be prioritized for augmenting plant diversity; and (b) populations of threatened wild bee species are most likely to occur. We surveyed bee communities in traditionally managed hay meadows in SE Norway and modelled bee diversity as a function of climate, habitat area, and distance to nesting substrates. We used independent data to validate our predictions and found that plant and predicted bee species richness together explained 76% and 69% of the variation in observed solitary bee species richness in forested and agricultural ecosystems, respectively. In urban areas, the predicted bee species richness alone explained 31% of the variation in observed solitary bee species richness. Using data from online species occurrence records, we found that – compared to species of lower conservation concern – threatened solitary bee species were more typically recorded in areas with a high predicted solitary bee species richness. We show that spatial predictions of bee diversity can identify sites where augmenting plant diversity is likely to be most effective. Maps of predicted bee diversity can guide species surveys and monitoring projects and increase the chances of locating populations of threatened bees.

Dominance of honey bees is negatively associated with wild bee diversity in commercial apple orchards regardless of management practices

Commercial apple production relies on managed honey bees (Apis mellifera) for pollination, and on intensive management for pest control. Previous studies have highlighted the potentially detrimental effects of intensive crop management on wild bee diversity in agroecosystems, potentially jeopardizing the pollination services they provide. However, the extent to which honey bee dominance and crop management interact under field-realistic conditions and drive the structure of wild bee assemblages has not been investigated so far. In this study, we measured species richness, as well as the functional and phylogenetic diversity of wild bee assemblages in 36 paired organic and non-organic apple orchards during their flowering season and along a geographic gradient across western Europe. Our results show a strong significant and negative association between honey bee dominance and all wild bee diversity metrics, regardless of local management. Semi-natural habitats had a significant and positive effect on functional diversity, while urbanization and crop cover around the orchards showed no effect on all measured diversity metrics. A greater number of species exhibited less common, or frequent, combinations of functional traits at sites with high honey bee dominance, especially larger bee species with longer tongues. Collectively, we show that wild bee diversity decreases with increasing honey bee dominance, and that this negative association is not buffered by alternative (i.e., organic) management practices in commercial apple orchards. Although organic farming can bring about biodiversity benefits, our study demonstrates that, in the context of commercial apple production, other measures are needed to enhance and harness biodiversity for sustainable and profitable crop production. In particular, a lowered reliance on honey bees and a redesign of orchards through configurational crop heterogeneity and/or the restoration of in-field semi‐natural elements are required beyond agricultural input substitution.

Managed honeybee hives and the diversity of wild bees in a dryland nature reserve

Honeybee hives may influence pollen and nectar availability in natural ecosystems, which may consequently affect wild pollinators. We studied the effects of managed honeybee hives on wild bee diversity in Villavicencio Nature Reserve (Mendoza, Argentina). We placed pan traps at increasing distances from honeybee hives to estimate wild bee abundance, richness, and composition. Wild bee abundance did not change detectably with distance to honeybee hives, although the abundance of the most common species, Arhysosage bifasciata, increased with increasing distance to the hives. Wild bee richness increased weakly with increasing distance to hives. Although wild bee composition did not change significantly with distance to the apiaries for the full data set, it changed significantly when we excluded A. bifasciata from the analyses. We found no relationship between body size and distance to the apiaries. Overall, our results indicate that managed honeybee hives had mixed effects on the wild bee assemblage in our study area. Given the relatively low hive density used in our study compared to other studies, we recommend an adaptive management strategy with continuous impact assessment.

Identifying key forage plants to support wild bee diversity and a species at risk in the Prairie Pothole Region

Abstract Global wild bee declines have been well documented in recent decades, with a regularly cited driver being habitat loss and the associated reduction of food and nesting resources. In North America's Prairie Pothole Region, habitat loss is largely attributed to agricultural intensification, resulting in the reduction of once common native grasslands surrounding wetlands. Although restoration of these grassland–wetland complexes has been implemented across the region, wild bees are not often the primary target for recovery. Restoration efforts may better support wild bees by including specific flowering plants (i.e. food resources) intended to provision the highest diversity of taxa; however, very little information is available specific to this region, which covers over 700 000 km2 in Canada and the United States. Our objective is to inform habitat restoration intended to support wild bee conservation through the addition of targeted flowering plant species at restored sites. As such, we used a model‐based approach to identify 16 key flowering plants present in remnant grassland–wetland complexes that are highly visited by diverse wild bee species, as well as by Bombus terricola Kirby, which is a species at risk in this region. The key plants represented eight families and supported approximately 82% of all visits from 69 out of the 75 observed bee species. By incorporating the recommended floral resources into restoration practices in the Prairie Pothole Region, practitioners can more efficiently mitigate the habitat loss that is thought to be a major driver of wild bee decline.

Contribution to the knowledge of the bee fauna (Hymenoptera, Apoidea, Anthophila) in Serbia.

The current work represents summarised data on the bee fauna in Serbia from previous publications, collections, and field data in the period from 1890 to 2020. A total of 706 species from all six of the globally widespread bee families is recorded; of the total number of recorded species, 314 have been confirmed by determination, while 392 species are from published data. Fourteen species, collected in the last three years, are the first published records of these taxa from Serbia: Andrenabarbareae (Panzer, 1805), A.clarkella (Kirby, 1802), A.fulvicornis (Schenck, 1853), A.intermedia (Thomson, 1870), A.lapponica (Zetterstedt, 1838), A.pandellei (Pérez, 1895), A.paucisquama (Noskiewicz, 1924), A.simillima (Smith, 1851), Panurginusherzi (Morawitz, 1892), Epeoloidescoecutiens (Fabricius, 1775), Nomadaleucophthalma (Kirby, 1802), Chelostomanasutum (Pérez, 1895), Hoplitisclaviventris (Thomson, 1872), and Dasypodapyrotrichia (Förster, 1855). Almost all the species recorded so far in Serbia belong to the West-Palaearctic biogeographical region, except Megachilesculpturalis (Smith, 1853), which is an alien invasive species native to East Asia. According to the European Red List of bees, 221 species listed in this paper were assessed as Data Deficient; threatened species mostly belong to the families Apidae with 13 species, Colletidae with eight species, and Halictidae with five species. This study contributes to the knowledge of the distribution of bee species in Europe. The present work provides a baseline for future research of wild bee diversity in Serbia and neighbouring regions at the local and regional levels, and a basis for their conservation.

Impacts of beekeeping on wild bee diversity and pollination networks in the Aegean Archipelago

Maintaining the diversity of wild bees is a priority for preserving ecosystem function and promoting stability and productivity of agroecosystems. However, wild bee communities face many threats and beekeeping could be one of them, because honey bees may have a strong potential to outcompete wild pollinators when placed at high densities. Yet, we still know little about how beekeeping intensity affects wild bee diversity and their pollinator interactions. Here, we explore how honey bee density relates to wild bee diversity and the structure of their pollination networks in 41 sites on 13 Cycladic Islands (Greece) with similar landscapes but differing in beekeeping intensity. Our large‐scale study shows that increasing honey bee visitation rate had a negative effect on wild bee species richness and abundance, although the latter effect was relatively weak compared to the effect of other landscape variables. Competition for flowering resources (as indicated by a resource sharing index) increased with the abundance of honey bees, but the effect was more moderate for wild bees in family Apidae than for bees in other families, suggesting a stronger niche segregation in Apidae in response to honey bees. Honey bees also influenced the structure of wild bee pollination networks indirectly, through changes in wild bee richness. Low richness of wild bees in sites with high honey bee abundance resulted in wild bee networks with fewer links and lower linkage density. Our results warn against beekeeping intensification in these islands and similar hotspots of bee diversity, and shed light on how benefits to pollination services of introducing honey bees may be counterbalanced by detriments to wild bees and their ecosystem services.

Five years of citizen science and standardised field surveys in an informal urban green space reveal a threatened Eden for wild bees in Brussels, Belgium

Abstract Urbanisation is often put forward as an important driver of biodiversity loss, including for pollinators such as wild bees. However, recent evidence shows that the mosaics of urban green spaces, and in particular certain categories of informal urban green spaces (IGS), can play an important role to help native wild bees thrive in cities. Here, we describe the results of 5 years of citizen science and standardised field surveys of wild bees conducted at the Friche Josaphat, a 24‐ha urban wasteland in the Brussels‐Capital Region (Belgium). These field surveys were initiated following the planned restructuring and partial destruction of this site by the regional authorities. We recorded a total of 2507 specimens belonging to 127 species of wild bees, i.e. 60.5% of the 210 species recorded regionally, including nine that are threatened with extinction at national or European scales. The Friche Josaphat encompasses a significant share of the functional and phylogenetic diversity of wild bees known from the Brussels‐Capital Region and is one of the most species‐rich localities known to date for wild bees in Belgium. Collectively, our results highlight the strong complementarity of citizen science and academic approaches in biodiversity surveys, and they reaffirm that wastelands are essential components of urban biodiversity. Our study stresses the need to provide biodiverse IGS with a formal status within the mosaic of urban green spaces but also to acknowledge and safeguard their natural capital and the multiple ecosystem services they provide.

Role of floral strips and semi-natural habitats as enhancers of wild bee functional diversity in intensive agricultural landscapes

Installing patches of flowering plants is a commonly used strategy to enhance refuge and food resources for pollinators in intensive agricultural landscapes. Here, we evaluated how floral strips and semi-natural habitats impact the taxonomic and functional diversity of wild bees in intensively farmed sunflower fields. Pan traps were used to assess bee richness and functional diversity at 22 sampling sites (11 sites were positioned in sunflower fields with floral strips, and 11 control sites were adjacent to semi-natural habitats). Five sampling levels were established in each field, positioned at different distances from the flower strip or semi-natural habitat. Wild bee species richness and functional richness were significantly higher inside floral strips and semi-natural habitats compared to sunflower fields. Functional redundancy was significantly higher inside agricultural fields compared to inside floral strips and semi-natural habitats. Sunflower fields with floral strips had lower Rao values compared to sunflower fields adjacent to semi-natural habitats. The community-weighted mean (CWM) of intertegular distance (distance between where wings attach to body) of wild bees was significantly higher in sunflower fields adjacent to semi-natural habitats. In comparison, the CWM of wing length varied across sampling levels in sunflower fields with semi-natural habitats. Our results show it is essential to have semi-natural habitats within intensive agricultural landscapes to ensure the conservation of wild bee diversity, while the installation of floral strips offers a partial substitute to enhance wild bee diversity when semi-natural habitats are scarce or absent.

Wild bees benefit from structural complexity enhancement in a forest restoration experiment

Structural complexity enhancement (SCE) is a forest restoration approach aiming to maintain or increase biodiversity in managed, secondary forests. Whether the diversity of wild bees also benefits from such restoration measures in temperate forests is not well studied. We conducted a restoration experiment in secondary spruce forests on twelve 50 × 50 m plots in the Black Forest National Park in Baden-Württemberg, Germany. SCE was carried out on half of the study plots (six) in 2016 comprised create deadwood through girdling and uprooting of 20 spruce trees per plot and thus initiating small gaps. The other six plots were used as control plots with no SCE. Wild bees were sampled in June 2018 and 2019 using coloured pan traps. We hypothesized that creation of deadwood influences bee abundance and richness, especially of aboveground-nesting bees, and thus would also change bee community composition at the plot scale. Furthermore, we assessed the influence of bilberry (Vaccinium myrtillus L.) cover in the plots and areas of meadows and roads of the intermediate surrounding on wild bees.Estimated species richness was higher on restored plots than on control plots. Deadwood originating from restoration increased the number of aboveground-nesting, solitary and cuckoo bee individuals. In particular standing deadwood had a positive impact on bee individuals. Increased bilberry cover and nearby meadow areas increased abundance and richness of the bee community.We conclude that creation of deadwood in coniferous forest is a promising restoration measure to promote solitary, aboveground-nesting bees. Increased light availability through restoration, which promotes bilberry flowering, is also beneficial for bees.

Functional traits and nesting habitats distinguish the structure of bee communities in clearcut and managed hardwood & pine forests in Southeastern USA

The role of nesting resources has been largely neglected in wild bee community ecology studies. Anthropogenic forest openings such as clearcuts and roads are common features within the managed forest matrix which may have varying impacts on bee nesting habitats and thus, drive their community structure. We sampled wild bees in mature hardwood, managed pine, and regenerating clearcuts across a gradient from the edge of a road into each site-type. Each site was surveyed for nesting habitat indicators including depth of duff layer, volume of downed wood, decay class of downed wood, and number of snags. Regenerating clearcuts had higher alpha diversity of wild bees than other sites, but displayed higher functional overlap in the bee community, favoring soil nesting groups. Forested sites, especially hardwoods provided more nesting niche opportunities leading to higher functional dispersion, evenness and higher beta diversity, and supported more cavity nesting, softwood nesting, solitary, and early season bees. Nesting habitat indicators explained 53% of the variation in nest guild composition. Cavity nesting bees responded positively to the volume of downed wood, and in a bimodal way to woody decay class. Soil nesting bees responded negatively to the depth of duff layer and presence of snags. Overall, results indicate that regenerating clearcuts are foci of species diversity, while hardwood forests are foci of functional diversity. Hardwood forests may be source of functionally diverse groups of bees, and maintaining patches or swaths of hardwood forests with some downed wood accumulation may be critical for maintaining functional diversity of bees in managed forested ecosystems.

Comparison of wild bee communities of three semi-natural meadow habitats at Harghita–Covasna Region, Transylvania, Romania

In the temperate climate wild bees are the most important pollinator organisms. Pollination is essential for the communities of semi-natural habitats since this ecosystem service directly affects plant reproduction. The diversity of wild bees living in such areas is remarkably high, but they are susceptible to various anthropogenic influences.In our study, the composition and structure of wild bee communities were examined in Romania (Transylvania) at three semi-natural areas near Filia, Merești and Vârghiș. The surveyed areas were used as extensive meadows under relatively low but slightly different anthropogenic influence levels. We collected bees in these areas at several places (9 sampling points/area) by individual netting four times during the season. In the studied areas, 129 bee species were found, which makes up about 18% of the approximately 726 wild bee species registered in Romania. In addition to the high number of species, we also observed high diversity values. Our results showed that, even at our sampling site closest to the human settlements, the extensive use of the surveyed areas as meadows allows the development of diverse, species-rich bee communities.

Enhancing flowering plant functional richness improves wild bee diversity in vineyard inter-rows in different floral kingdoms.

Wild bees are threatened by multiple interacting stressors, such as habitat loss, land use change, parasites, and pathogens. However, vineyards with vegetated inter‐rows can offer high floral resources within viticultural landscapes and provide foraging and nesting habitats for wild bees. Here, we assess how vineyard management regimes (organic vs. conventional; inter‐row vegetation management) and landscape composition determine the inter‐row plant and wild bee assemblages, as well as how these variables relate to functional traits in 24 Austrian and 10 South African vineyards. Vineyards had either permanent vegetation cover in untilled inter‐rows or temporary vegetation cover in infrequently tilled inter‐rows. Proportion of seminatural habitats (e.g., fallows, grassland, field margins) and woody structures (e.g., woodlots, single trees, tree rows) were used as proxies for landscape composition and mapped within 500‐m radius around the study vineyards. Organic vineyard management increased functional richness (FRic) of wild bees and flowering plants, with woody structures marginally increasing species richness and FRic of wild bees. Wild bee and floral traits were differently associated across the countries. In Austria, several bee traits (e.g., lecty, pollen collection type, proboscis length) were associated with flower color and symmetry, while in South African vineyards, only bees’ proboscis length was positively correlated with floral traits characteristic of Asteraceae flowers (e.g., ray–disk morphology, yellow colors). Solitary bee species in Austria benefitted from infrequent tillage, while ground nesting species preferred inter‐rows with undisturbed soils. Higher proportions of woody structures in surrounding landscapes resulted in less solitary and corbiculate bees in Austria, but more aboveground nesting species in South Africa. In both countries, associations between FRic of wild bees and flowering plants were positive both in organic and in conventional vineyards. We recommend the use of diverse cover crop seed mixtures to enhance plant flowering diversity in inter‐rows, to increase wild bee richness in viticultural landscapes.

Enhancing flowering plant functional richness improves wild bee diversity in vineyard inter-rows in different floral kingdoms

Enhancing flowering plant functional richness improves wild bee diversity in vineyard inter-rows in different floral kingdoms

Roads, railways, and power lines: Are they crucial for bees in urban woodlands?

The loss and transformation of habitats due to human impact are commonly regarded as major factors decreasing the diversity of pollinators. However, there is also some evidence that industrial infrastructure can play a positive role in shaping the composition of many animal communities. Still, little is known about how artificial linear structures, such as roads, railways, and electric power lines, affect the abundance and diversity of wild bees in urban ecosystems. Thus, we attempted to verify which of the habitats mentioned above is crucial for the occurrence of bee species of various functional groups. We conducted field research in woodlands of the city of Bydgoszcz (northern Poland). Site conditions were evaluated on the basis of phytoindicators (plant indicator species). In the study area, we recorded 32 % of all bee species reported from Poland. In respect of species richness and abundance, the habitats along railway lines were the most attractive to bees. Besides, in respect to bee species richness, these sites were the most similar to roadsides. The habitats located under power lines were the poorest in species. About 20 % of bee species were recorded only along railways and 3 % only along roads, while no bee species was recorded exclusively under power lines. Bee species richness and abundance increased with growing cover of the sites by bee food plants and an increasing proportion of bare soil. Moreover, bee abundance increased with an increasing share of plant indicator species of very dry or dry soils and of alkaline soils. Bee abundance declined with an increasing share of plant indicator species of sandy soils. The presented results indicate that roads, railway lines, and power lines, in structurally simplified and floristically poor pine forests, are important for wild bees in urban ecosystems.