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Verges Along Forest Roads Promote Wild Bees
Abstract
Forests in Germany are occupied with roads, paths, and trails with a density of 5.03 km/km². Their construction and maintenance create a network of verges promoting flowering plants. Whether these verges are visited by bees, which factors are determining their abundance, diversity, and composition, and which flowering resources are used is unknown. We selected 13 verges in the Black Forest (Germany), sweep-netted wild bees along transects, calculated the flowering area of all herbs, and measured the area (hectares) of grassland within 1 km around the transects. To evaluate the resource use of a common bumblebee species, we analyzed the pollen load of common carder bees (Bombus pascuorum) using microscopes. The abundance and diversity of wild bees was positively related to flowering area. With an increasing area of grassland, the abundance of ubiquitous species increased. Wild bee community composition was driven by flowering area. Common carder bees collected pollen from several flower resources but mainly used few species, such as the common hemp nettle (Galeopsis tetrahit L.). As the flowering area influenced wild bee abundance, diversity, and composition, we suggest creating road verges that favor the occurrence of native flowering plants to support wild bees in forest ecosystems.
Study Implications: Forest road verges generally have higher light availability than the forest interior and therefore have higher availability of flowering plants. Although the importance of verges for wild bee conservation in agricultural landscapes is known, forest road verges are understudied. Our study demonstrates that forest road verges are important habitats for many ubiquitous bees and that the flowering area on these verges is the key determinant for the abundance and diversity of wild bees. Therefore, creating road verges that favor the occurrence of native flowering plants is key to support bees on these verges.
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Wild bee populations are declining due to human activities, such as land use, which strongly affect the composition and diversity of available plants and food sources. The chemical composition of food (i.e. nutrition), in turn, determines health, resilience and fitness of bees. However, for pollinators, the term health is recent and subject to debate as is the interaction between nutrition and wild bee health. We define bee health as a multidimensional concept in a novel integrative framework linking bee biological traits (physiology, stoichiometry and disease) and environmental factors (floral diversity, nutritional landscapes). Linking information on tolerated nutritional niches and health in different bee species will allow us to better predict their distribution and responses to environmental change and thus support wild pollinator conservation.
Declines of many bumble bee species have raised concerns because of their importance as pollinators and potential harbingers of declines among other insect taxa. At present, bumble bee conservation is predominantly focused on midsummer flower restoration in open habitats. However, a growing body of evidence suggests that forests may play an important role in bumble bee life history. Compared with open habitats, forests and woody edges provide food resources during phenologically distinct periods, are often preferred nesting and overwintering habitats, and can offer favorable abiotic conditions in a changing climate. Future research efforts are needed in order to anticipate how ongoing changes in forests, such as overbrowsing by deer, plant invasions, and shifting canopy demographics, affect the suitability of these habitats for bumble bees. Forested habitats are increasingly appreciated in the life cycles of many bumble bees, and they deserve greater attention from those who wish to understand bumble bee populations and aid in their conservation.
1. Overall, more than 30% of bee species depend on non-floral resources, such as resin. However, the importance of resin in bee ecology, particularly for solitary bees, has received very little attention thus far.
2. A plethora of loose natural history observations, inferences, and author opinions hint towards a striking range of uses of resin for nesting by bees. In this review, we focus on resin use in solitary bees and identify extant knowledge, knowledge gaps, and future research directions with regard to the functional use of resin in bee nesting biology.
3. Resin use in solitary bee nests can be broadly grouped by functional roles for nest structure, chemical camouflage, defence, moisture regulation, and anti-microbial properties. We point out that resin usage appears to be constrained by environmental and physiological factors. Bee species-specific tolerances for resin toxicity and resin availability in the environment seem to determine resin choices and subsequently functional usage in nests. We finally highlight that resin may play a major role in determining the ambient nest microbiota, due to its strong antimicrobial properties. We conclude that a better mechanistic understanding of resin use in bee nesting biology can aid in assessing species range shifts in light of global change.
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.
ContextTo safeguard insect pollinators and their pollination services, we need to understand how landscape structure regulates the distribution of resources that sustain pollinator populations. However, evidence of how pollinator communities benefit from the variety of resources distributed across different habitat types is scarce.Objectives
To explore complementary resource provision, we conducted a field study to examine the resources available to pollinators in fruit orchards and woody semi-natural habitat.Methods
We studied 13 landscapes containing both habitat types in Flanders, Belgium. In every habitat element, we surveyed nesting resources, floral resources and wild pollinators (i.e. wild bees and hover flies) during three consecutive time periods in the season (once before- and twice after mass-flowering of the fruit orchards).ResultsWe concluded that the composition of nesting resources for wild bees was clearly different between both habitat types. Woody semi-natural habitat also provided more diverse- and a higher cover of floral resources compared to fruit orchards. In addition, the composition of these floral resources became more and more distinct between the two habitat types as the season progressed. Based on the plant − pollinator network we identified key plant species for inclusion in management schemes to support pollinators.Conclusions
Our study highlights that fruit orchards and woody semi-natural habitat provide a set of different, complementary resources during the flight season, for pollinating insects. Due to the higher diversity and abundance of resources in woody semi-natural habitat, conservation of woody semi-natural habitat is essential for the support of pollinators in agricultural landscapes.
Wild bumblebees are key pollinators of crops and wild plants that rely on the continuous availability of floral resources. A better understanding of the spatio-temporal availability and use of floral food resources may help to promote bumblebees and their pollination services in agricultural landscapes. We placed colonies of Bombus terrestris L. in 24 agricultural landscapes with various degrees of floral resource availability and assessed different parameters of colony growth and fitness. We estimated pollen availability during different periods of colony development based on detailed information of the bumblebee pollen diet and the spatial distribution of the visited plant species. Total pollen availability did not significantly explain colony growth or fitness. However, when using habitat maps, the weight gain of colonies, the number of queen cells, and colony survival decreased with increasing distance from the forest. The better explanation of bumblebee performance by forest proximity than by (plant-inferred) pollen availability indicates that other functions of forests than pollen provision were important. The conservation of forests next to agricultural land might help to sustain high populations of these important wild pollinators and enhance their crop pollination services. Combining different mapping approaches might help to further disentangle complex relationships between B. terrestris and their environment in agricultural landscapes.
Road verges provide habitats that have considerable potential as a tool for pollinator conservation, especially given the significant area of land that they collectively cover. Growing societal interest in managing road verges for pollinators suggests an immediate need for evidence-based management guidance.
We used a formal, global literature review to assess evidence for the benefits of road verges for pollinators (as habitats and corridors), the potential negative impacts of roads on pollinators (vehicle-pollinator collisions, pollution, barriers to movement) and how to enhance road verges for pollinators through management.
We identified, reviewed and synthesised 140 relevant studies. Overall, the literature review demonstrated that: (i) road verges are often hotspots of flowers and pollinators (well established), (ii) traffic and road pollution can cause mortality and other negative impacts on pollinators (well established), but available evidence suggests that the benefits of road verges to pollinators far outweigh the costs (established but incomplete), and (iii) road verges can be enhanced for pollinators through strategic management (well established). Future research should address the lack of holistic and large-scale understanding of the net effects of road verges on pollinators.
We provide management recommendations for enhancing both individual road verges for pollinators (e.g. optimised mowing regimes) and entire road networks (e.g. prioritising enhancement of verges with the greatest capacity to benefit pollinators), and highlight three of the most strongly supported recommendations: (i) creating high quality habitats on new and existing road verges, (ii) reducing mowing frequency to 0–2 cuts/year and (iii) reducing impacts of street lighting.
Bees require suitably close foraging and nesting sites to minimize travel time and energy expenditure for brood provisioning. Knowing foraging distances in persistent (‘healthy’) populations is therefore crucial for assessing harmful levels of habitat fragmentation. For small bees, such distances are poorly known because of the difficulty of individual tagging and problems with mark-recapture approaches. Using apiarist’s number tags and colour codes, we marked 2689 males and females of four oligolectic and two polylectic species of Osmiini bees (Megachilidae, genera Chelostoma , Heriades , Hoplitis , Osmia ) with body lengths of 6 to 15 mm. The work was carried out in 21 ha-large urban garden that harbours at least 106 species of wild bees. Based on 450 re-sightings, mean female flight distances ranged from 73 to 121 m and male distances from 59 to 100 m. These foraging distances suggest that as a rule of thumb, flower strips and nesting sites for supporting small solitary bees should be no further than 150 m apart.
Plant-pollinator interactions are partially driven by the expression of plant traits that signal and attract bees to the nutritional resources within flowers. Although multiple physical and chemical floral traits are known to influence the visitation patterns of bees, how distinct bee groups vary in their responses to floral traits has yet to be elucidated. In this study, we used a common garden experiment to test for morphological floral traits associated with pollen quantity at the plant species level, and examined how the visitation patterns of taxonomically and functionally distinct bee groups are related to flower trait characteristics of 39 wildflower species. We also determined how floral traits influence the structure of wild bee communities visiting plants and whether this varies among geographic localities. Our results suggest that floral area is the primary morphological floral trait related to bee visitation of several distinct bee groups, but that wild bee families and functionally distinct bee groups have unique responses to floral trait expression. The composition of the wild bee communities visiting different plants was most strongly associated with variability in floral area, flower height, and the quantity of pollen retained in flowers. Our results inform wildflower habitat management for bees by demonstrating that the visitation patterns of distinct bee taxa can be predicted by floral traits, and highlight that variability in these traits should be considered when selecting plants to support pollinators.
Pollinator nutritional ecology provides insights into plant–pollinator interactions, coevolution, and the restoration of declining pollinator populations. Bees obtain their protein and lipid nutrient intake from pollen, which is essential for larval growth and development as well as adult health and reproduction. Our previous research revealed that pollen protein to lipid ratios (P:L) shape bumble bee foraging preferences among pollen host-plant species, and these preferred ratios link to bumble bee colony health and fitness. Yet, we are still in the early stages of integrating data on P:L ratios across plant and bee species. Here, using a standard laboratory protocol, we present over 80 plant species’ protein and lipid concentrations and P:L values, and we evaluate the P:L ratios of pollen collected by three bee species. We discuss the general phylogenetic, phenotypic, behavioral, and ecological trends observed in these P:L ratios that may drive plant–pollinator interactions; we also present future research questions to further strengthen the field of pollination nutritional ecology. This dataset provides a foundation for researchers studying the nutritional drivers of plant–pollinator interactions as well as for stakeholders developing planting schemes to best support pollinators.
Continuous availability of food resources, such as pollen, is vital for many insects that provide pollination and pest control services to agriculture. However, there is a lack of knowledge about the shared or complementary use of floral resources by such species, which hampers more effective landscape management to simultaneously promote them in agroecosystems. Here, we simultaneously quantified pollen use by a bumblebee (Bombus terrestris) and a mason bee (Osmia bicornis), two bee species recognized as important crop pollinators, as well as a lacewing (Chrysoperla carnea) and a ladybeetle species (Harmonia axyridis), both common predators of crop aphids, throughout the season in 23 agricultural landscapes in Germany and Switzerland. Pollen diets were more diverse and similar among C. carnea and H. axyridis compared to the two bee species, but all four species shared key pollen types early in the season such as Acer, Quercus, Salix and Prunus. All species exhibited a pronounced shift in pollen sources from primarily woody plants (mainly trees) in spring to primarily herbaceous plants in summer. The majority of pollen (overall ≥64%) came from non‐agricultural plants even in crop‐dominated landscapes. Synthesis and applications. Our results highlight the importance of trees as pollen sources for many insect species, particularly early in the season. Our findings support incentives that promote heterogeneous agricultural landscapes including both woody and herbaceous semi‐natural habitats, ensuring phenological complementarity of floral resources for insect species that can provide pollination and pest control services to agriculture. The identified key plant species can help to design and optimize agri‐environment schemes to promote these functionally important insects.
Supporting pollinators in agricultural landscapes is important for reversing their global decline. Road verges and hedges are used by pollinators for feeding and reproduction, but few studies consider entire pollinator communities, and it remains unclear how they are distributed across adjacent verges, hedges and fields, or how they are affected by traffic and verge cutting. We surveyed flowers and pollinators, using transect counts and pan traps, to explore the role of road verges and their associated hedges in supporting pollinators in an agricultural landscape in southwest England, and the impacts of traffic and verge cutting. At 19 sites, we surveyed the road verge (verge edge and verge centre), the verge hedge (both sides), a field hedge and the field interior. Road verges and hedges had a much greater flower abundance, flower species richness and pollinator abundance than field interiors. Verge hedges had far less woody cover than field hedges, but greater flower species richness. There were fewer pollinators along verge edges (next to roads) than along verge centres (2–11 m from roads) and fewer pollinators in road verges next to busier roads. Road verges were generally cut once (in summer), and cuttings were never removed. There were substantially fewer flowers and pollinators in road verges that had been cut, even though surveys often took place many weeks after cutting. Synthesis and applications. Road verges and their associated hedges can provide hotspots of resources for pollinators in agricultural landscapes, but their capacity to do so is reduced by heavy traffic and summer verge cutting. We recommend that beneficial management for pollinators should prioritize wider road verges (at least 2 m wide), roads with less traffic, and areas away from the immediate vicinity of the road. Where possible, verge cutting should not be carried out during peak flowering times.
1.Individual pollinators that specialize on one plant species within a foraging bout transfer more conspecific and less heterospecific pollen, positively affecting plant reproduction. However, we know much less about pollinator specialization at the scale of a foraging bout compared to specialization by pollinator species. 2.In this study, we measured the diversity of pollen carried by individual bees foraging in forest plant communities in the mid‐Atlantic United States. 3.We found that individuals frequently carried low‐diversity pollen loads, suggesting that specialization at the scale of the foraging bout is common. Individuals of solitary bee species carried higher diversity pollen loads than did individuals of social bee species; the latter have been better studied with respect to foraging bout specialization, but account for a small minority of the world's bee species. Bee body size was positively correlated with pollen load diversity and individuals of polylectic (but not oligolectic) species carried increasingly diverse pollen loads as the season progressed, likely reflecting an increase in the diversity of flowers in bloom. Furthermore, the seasonal increase in pollen load diversity was stronger for bees visiting trees and shrubs than for bees visiting herbaceous plants. 4.Overall, our results showed that both plant and pollinator species’ traits as well as community‐level patterns of flowering phenology are likely to be important determinants of individual‐level interactions in plant‐pollinator communities. This article is protected by copyright. All rights reserved.
Pollinators feed on the pollen, nectar, and other plant exudates that are associated with flowers. As a result of this feeding activity, pollen becomes attached to them. Analysis of this pollen can reveal what they eat, their dispersal patterns in and around cropping systems, and their role in pollination. However, finding pollen on and or in a pollinator depends on the technique used to recover pollen. Two very easy techniques are described in detail that have been used to recover pollen from a variety of pollinators including beneficial and harmful insects, spiders, bats, and other pollinators. These techniques can be used to recover pollen from internal tissues (gut, alimentary canal, crop, etc.), external tissues (proboscis, legs, eyes, etc.), or both. By using the proper technique, better pollen recovery can be made and thus better data can be obtained about the pollinators, the foods they eat, the plants they pollinate, their migration routes and source zones.
Large areas of Western Europe are covered with intensively managed agricultural land. In these landscapes, wild pollinators depend on fragments of semi-natural habitat for foraging or reproduction. Small forest patches are often the most abundant type of semi-natural habitat in these agricultural landscapes. We investigated the role these patches play in conserving the pollinator community in intensively managed agricultural landscapes.
Our survey of the pollinator community in 16 forest fragments showed that the pollinator community in the edges of small forest fragments is strongly influenced by forest and forest edge characteristics. Old forest fragments with a well-developed herb layer had more diverse bee communities than recent forests or old forests without a herb layer, but overall lower activity-abundances, while sun exposure of the forest edges had a strong positive effect on pollinater activity-abundance in general. The hoverfly community had higher activity-abundances in forest edges with a higher flower-index, while saproxylic hoverflies were caught in higher numbers in sites with a higher forest cover in the surrounding landscape.
We also detected a strong seasonal effect. The effects of herb layer cover on bee species richness and activity-abundance were much stronger in spring than in summer, while bee species richness was also strongly positively correlated with forest age in spring. A strong positive correlation between pollinator species richness and sun exposure was found in summer, after canopy closure.
While the sampled forest edges harbour a rich and diverse pollinator community, cavity-nesting bees were very scarce. This is probably caused by the low amount of dead wood in the studied forest fragments.
We conclude that small forest fragments can play an important role in conserving the pollinator community, especially bees and saproxylic hoverflies. The importance of these forest fragments is strongest in spring, when the herb layer provides foraging resources.
1.The successional dynamics of forests – from canopy openings to regeneration, maturation and decay – influence the amount and heterogeneity of resources available for forest‐dwelling organisms. Conservation has largely focused only on selected stages of forest succession (e.g. late‐seral stages). However, to develop comprehensive conservation strategies and to understand the impact of forest management on biodiversity, a quantitative understanding of how different trophic groups vary over the course of succession is needed. 2.We classified mixed mountain forests in Central Europe into nine successional stages using airborne LiDAR. We analysed α‐ and β‐diversity of six trophic groups encompassing approximately 3,000 species from three kingdoms. We quantified the effect of successional stage on the number of species with and without controlling for species abundances and tested whether the data fit the more‐individuals hypothesis or the habitat heterogeneity hypothesis. Furthermore, we analysed the similarity of assemblages along successional development. 3.The abundance of producers, first‐order consumers and saprotrophic species showed a U‐shaped response to forest succession. The number of species of producer and consumer groups generally followed this U‐shaped pattern. In contrast to our expectation, the number of saprotrophic species did not change along succession. When we controlled for the effect of abundance, the number of producer and saproxylic beetle species increased linearly with forest succession, whereas the U‐shaped response of the number of consumer species persisted. The analysis of assemblages indicated a large contribution of succession‐mediated β‐diversity to regional γ‐diversity. 4. Synthesis and applications. Depending on the species group, our data supported both the more‐individuals hypothesis and the habitat heterogeneity hypothesis. Our results highlight the strong influence of forest succession on biodiversity and underline the importance of controlling for successional dynamics when assessing biodiversity change in response to external drivers such as climate change. The successional stages with highest diversity (early and late successional stages) are currently strongly underrepresented in the forests of Central Europe. We thus recommend that conservation strategies aim at a more balanced representation of all successional stages. This article is protected by copyright. All rights reserved.
Wild bee community assemblages were surveyed in a high-elevation mixed conifer forest in central Colorado at multiple points during the growing season (April-August) and across a range of forest stand densities using blue vane traps. Understory forb communities were also characterized and related to bee species abundance and diversity. Overall γ-diversity was characterized by 19 genera of bees captured representing five families (Andrenidae, Apidae, Colletidae, Halictidae, and Megachilidae) and 39 unique species. Seasonal variation in abundance and community composition was considerable with early-season (April) communities dominated by Osmia spp. and midsummer (June-July) communities dominated by Bombus spp. Bee abundance and α-diversity were on average 88 and 74% higher in midsummer than in early-and late season. Forest basal area was negatively correlated with bee α-diversity and abundance, as well as understory plant species richness. Trapping locations with a stand basal area of ≤7.5 m 2 /ha exhibited approximately 54% higher bee abundances and 44% higher α-diversity than locations with ≥20.0 m 2 /ha of basal area. Bee α-diversity and abundance positively correlated with understory species richness suggesting that forested sites with low basal area, likely corresponding to overstory canopy gaps and increased site occupancy by forbaceous species, may drive local abundance and diversity of wild bee assemblages. This study provides basal area threshold values in a mixed conifer forest type that may be useful for resource management practitioners concerned with creating or conserving pollinator habitats.
We investigated the effects of repeated prescribed fire, mechanical thinning, and combinations of fire and mechanical thinning on pollinators and flower visitors within the herbaceous understory and midstory of a temperate forest in North Carolina. Using colored pan traps, we sampled flower visitors during the plant growing season between 2014 and 2016. We captured 5,520 flower visitors that were dominated by halictid bees and vespid wasps. Twenty genera of bees representing at least 30 species were captured within our experimental plots. Within the forest understory, we found higher abundances and diversities of bees and other flower visitors within plots that had been treated with prescribed fire or a combination of mechanical thinning and prescribed fire compared to control plots. Within our midstory samples, we found that forest management practices did not affect the abundance of any common flower visitor species/family. However, Augochlora pura and Vespula spp. were more abundant in the midstory compared to the forest understory. Overall, our study demonstrates that repeated applications of prescribed fire maintained elevated abundances and diversity of bees and other flower-visiting insects compared to untreated plots, likely due to increased herbaceous plant diversity and enhanced quality of nesting habitat within the understory. Our results also indicate that many flower visitors utilize the midstory of a temperate forest potentially for foraging habitat.
Count data can be analyzed using generalized linear mixed models when observations are correlated in ways that require random effects. However, count data are often zero-inflated, containing more zeros than would be expected from the typical error distributions. We present a new package, glmmTMB, and compare it to other R packages that fit zero-inflated mixed models. The glmmTMB package fits many types of GLMMs and extensions, including models with continuously distributed responses, but here we focus on count responses. glmmTMB is faster than glmmADMB, MCMCglmm, and brms, and more flexible than INLA and mgcv for zero-inflated modeling. One unique feature of glmmTMB (among packages that fit zero-inflated mixed models) is its ability to estimate the Conway-Maxwell-Poisson distribution parameterized by the mean. Overall, its most appealing features for new users may be the combination of speed, flexibility, and its interface's similarity to lme4.
Conservation of wild bees: translating research into practice.The present study intends to translate the results of the extensive scientific literature on bee conservation into a catalogue of practical measures to enhance a diverse and individual rich bee fauna and to conserve endangered species.
This volume of Fauna Helvetica provides identification keys and distribution maps of the Swiss bee species of the genera Halictus and Lasioglossum.
This volume of Fauna Helvetica provides identification keys and distribution maps of the Swiss bee species of the genera Colletes, Dufourea, Hylaeus, Nomia, Nomioides, Rhophitoides, Rophites, Sphecodes and Systropha.
This volume of Fauna Helvetica provides identification keys and distribution maps of the Swiss bee species of the genera Andrena, Melitturga, Panurginus and Panurgus.
Bees and butterflies generally favor open forest habitats regardless of forest type, geographic region, or methods used to create these habitats. Dense shrub layers of native or nonnative species beneath forest canopies negatively impact herbaceous plant cover and diversity, and pollinators. The presence of nonnative flowers as a source of nectar, pollen, or larval food can have positive or negative effects on pollinators depending on the situation, but in cases where the nonnatives exclude native plants, the results are almost always negative. Roads and roadside corridors offer an opportunity to increase open, pollinator-friendly habitat even in dense forests by thinning the adjacent forest, mowing at appropriate times, and converting to native herbaceous plant communities where nonnative species have been planted or have invaded. Efforts to improve forest conditions for pollinators should consider the needs of specialist species and vulnerable species with small scattered populations. Conservation of bees and butterflies, as well as other pollinating species, in forested areas is important for most forest plant species, and forests may serve as reservoirs of pollinators for recolonization of surrounding habitats.
Context
Anthropogenic landscape simplification and natural habitat loss can negatively affect wild bees. Alternatively, anthropogenic land-use change may diversify landscapes, creating complementary habitats that maintain overall resource continuity and diversity.
Objectives
We examined the effects of landscape composition, including land-cover diversity and percent semi-natural habitat, on wild bee abundance and species richness within apples, a pollinator-dependent crop. We also explored whether different habitats within diverse landscapes can provide complementary floral resources for bees across space and time.
Methods
We sampled bees during apple bloom over 2 years within 35 orchards varying in surrounding landscape diversity and percent woodland (the dominant semi-natural habitat) at 1 km radii. To assess habitat complementarity in resource diversity and temporal continuity, we sampled flowers and bees within four unique habitats, including orchards, woodlands, semi-natural grasslands, and annual croplands, over three periods from April–June.
Results
Surrounding landscape diversity positively affected both wild bee abundance and richness within orchards during bloom. Habitats in diverse landscapes had different flower communities with varying phenologies; flowers were most abundant within orchards and woodlands in mid-spring, but then declined over time, while flowers within grasslands marginally increased throughout spring. Furthermore, bee communities were significantly different between the closed-canopy habitats, orchards and woodlands, and the open habitats, grasslands and annual croplands.
Conclusions
Our results suggest that diverse landscapes, such as ones with both open (grassland) and closed (woodland) semi-natural habitats, support spring wild bees by providing flowers throughout the entire foraging period and diverse niches to meet different species’ requirements.
Introduction
Habitat loss is the leading cause of extinctions on the planet. However, negative effects of habitat loss and fragmentation on biodiversity can be reduced if resources in urban or semi-natural areas in the surrounding matrix can be used by wildlife.
Methods
We investigated the influence of floral and nesting resources in urban- and forest-associated oak-savannah fragments, surrounding urban and forest matrix, and urban areas spatially independent from oak-savannah habitat on pollinator community composition in a fragmented oak-savannah ecosystem.
Results
Both independent urban and urban matrix sites supported high abundance and richness of plants and pollinators relative to other fragment categories, especially towards the end of the season when plants and pollinators in oak-savannah fragments were scarce. A species of particular conservation concern in our region, Bombus occidentalis, was supported by late-flowering resources in our urban sites. Forest-associated oak-savannah fragments were missing late-season species while urban-associated fragments supported high abundance and richness of mid- to late-season pollinators, likely due to supplemental use of floral resources in the urban matrix. Female cavity-nesting and ground-nesting bees were not restricted by the availability of natural nesting resources we expected them to require (e.g. small cavities, bare soil).
Conclusion
These results provide important information on native pollinators in a highly fragmented habitat, and suggest that we should consider matrix quality in conservation planning.
In this study, the daily and seasonal influences of abiotic factors and the amount of floral resources on the foraging frequency of bees were determined. The experiments were performed, during 12 consecutive months, in the main floral sources used by bees in a secondary forest fragment. The foraging frequency of each bee species on flowers of each plant was recorded for 20-min periods, every hour. To verify whether the foraging activity is influenced by abiotic factors, Pearson’s correlation analysis and linear regression tests were performed for the dominant bee species. Temperature and luminosity were the two main abiotic factors regulating foraging activities of bees. A positive correlation was found between the foraging frequency of most bees and these two variables. Conversely, the foraging activity was influenced neither by the relative humidity nor by the wind speed. The activity of each species depends on a combination of factors that include not only abiotic variables, but also the amount of floral resources available during the day, body size, and behavior of each visitor. After a certain period of the day, the scarcity of floral resources produced by most plants can stimulate the bees to forage in the flowers early in subsequent days, which may occur before the period in which the abiotic conditions are really favorable.
1. Wild bees importantly pollinate both crop and wild plants. Yet, in intensive agricultural
landscapes, wild bees are rare due to resource limitations of nectar
and pollen. Flower strips and hedges are often used as resource enhancements
for wild bees to overcome this shortage, but provide floral resources only during
specific time periods. To sustain diverse and stable bee communities, bee-attractive
flowers need to be available during the entire growing season. This may
be achieved by combining flower strips and hedges to complement each other
and provide continuous floral resources.
2. Over three subsequent years, we compared the phenology of flower and wild
bee communities in perennial flower strips, hedges and improved hedges (complemented
with a sown herb layer) in conventional apple orchards in Southern
Germany, a pollination-dependent
crop system.
3. Hedges provided floral resources in the early season while the flower strips took
over later in the season.
4. Bees visited the hedges mostly from March to June, whereas they visited the
flower strips from June to August in the first year, and in the second year already
from April onwards. Flower strips were visited with an overall higher abundance
and species richness than both the hedges and the improved hedges.
5. Synthesis and application. For enhancing wild bees in intensive apple orchards,
hedges and perennial flower strips are complementary in providing flower resources.
Yet, flower strips bloom more constantly and during periods of flower
scarcity, and thus attract a higher diversity of bees than hedges. Perennial flower
strips of different age classes should be preferred over annual strips, at best in
a network with some well-maintained
hedges, as perennial flower strips of different
age attract different bee communities and thus potentially a higher bee
diversity on the landscape level.
Flower strips are a frequently adopted measure to conserve insects, especially pollinators, and are subsidized as Agri-Environmental Scheme in many regions. They provide a high quantity of flowers, but their flower species composition and phenological development is mostly uniform. This may result in only a fraction of pollinator species being enhanced. Flower-rich semi-natural habitat patches along slopes, fences or ditches, may provide resources for additional species, but they are not politically promoted. In this study, we compare pollinator communities in sown perennial flower strips with existing flower-rich herbaceous semi-natural habitat patches, both located at the edge of conventional apple orchards in Southern Germany. The flower strips attracted a higher pollinator abundance and species richness than the existing habitat patches. However, the bee species composition differed between the two habitat types. The existing habitat patches attracted bee species with different pollen specialization than the sown flower strips. Pollinator abundance and species richness varied between the different existing habitat patches indicating a high heterogeneity of these existing habitats, whereas the flower strips showed consistently high pollinator abundance and richness. We conclude that existing herbaceous habitat patches are attractive for pollinators and should be promoted by policy actions. Flower-rich semi-natural habitat patches develop without sowing next to typical agricultural landscape elements like slopes, fences and ditches with moderate mowing or herbicide application. They generally do not compete with agricultural land use and thus have a high potential to promote pollinator conservation.
Forest-associated species, which depend on forest habitat for their survival, are among the world's most vulnerable species due to widespread forest loss. However, in many parts of the world, forests are re-growing. Thus, if forest-associated species can persist in young forests their conservation outlook is less bleak. We examined the effects of forest loss and regrowth on bee pollinators in eastern North America using three datasets totaling 36,605 individual specimens. First, we conducted a regional-scale study to identify forest-associated and habitat generalist bee species. Second, we examined how the abundance and richness of each group change with forest area and age, by collecting bees from forests chosen to vary orthogonally in these variables. Lastly, we examined whether the results of our field studies were consistent with long-term, regional trends in the richness of both groups, using a dataset of museum specimens collected between 1872 and 2011, which was a period of reforestation in our study region. We found that the abundance and richness of forest-associated bees increase with forest area, while being relatively insensitive to forest age. By contrast, habitat generalist bees are unaffected by forest area, but decrease in abundance with forest age. Consistent with these results, we found a 16% increase in the richness of forest-associated bees over a 140-year time series as reforestation occurred in eastern North America, but no significant trend for habitat generalists. Overall, our results show that the loss of forest area from a landscape harms forest-associated bees, and that young forests have high conservation value for both forest-associated and habitat generalist bees.
Native pollinator populations across the United States are increasingly threatened by a multitude of ecological stressors. Although the drivers behind pollinator population declines are varied, habitat loss/degradation remains one of the most important threats. Forested landscapes, where the impacts of habitat loss/degradation are minimized, are known to support robust pollinator populations in eastern North America. Within heavily forested landscapes, timber management is already implemented as a means for improving forest health and enhancing wildlife habitat, however, little is known regarding the characteristics within regenerating timber harvests that affect forest pollinator populations. In 2018 and 2019, we monitored insect pollinators in 143 regenerating (≤9 growing seasons post-harvest) timber harvest sites across Pennsylvania. During 1129 survey events, we observed over 9100 bees and butterflies, 220 blooming plant taxa, and collected over 2200 pollinator specimens. Bee and butterfly abundance were positively associated with season-wide floral abundance and negatively associated with dense vegetation that inhibits the growth of understory floral resources. Particularly in late summer, few pollinators were observed in stands >6 years post-harvest, with models predicting five times more bees in 1-year-old harvests than in 9-year-old harvests. Pollinator species diversity was positively associated with floral diversity and percent forb cover, and negatively associated with percent tall (>1 m) sapling cover. These results suggest that regenerating timber harvests promote abundant and diverse pollinator communities in the Appalachian Mountains, though pollinator abundance declined quickly as woody stems regenerated. Ultimately, our findings contribute to a growing body of literature suggesting that dynamic forest management producing a mix of age classes would benefit forest pollinator populations in the Central Appalachian Mountains.
Populations of bumble bees and other pollinators have declined over the past several decades due to numerous threats, including habitat loss and degradation. However, we can rarely investigate the role of resource loss due to a lack of detailed long‐term records of forage plants and habitats. We use 22‐year repeated surveys of more than 262 sites located in grassland, forest, and wetland habitats across Illinois, USA to explore how the abundance and richness of bumble bee food plants have changed over the period of decline of the endangered rusty patched bumble bee (Bombus affinis). We document a decline in abundance of bumble bee forage plants in forest understories, which our phenology analysis suggests provide the primary nectar and pollen sources for foundress queens in spring, a critical life stage in bumble bee demography. By contrast, the per‐unit area abundance of food plants in primarily midsummer‐flowering grassland and wetland habitats has not declined. However, the total area of grasslands has declined across the region resulting in a net loss of grassland resources. Synthesis and applications. Our results suggest a decline in spring‐flowering forest understory plants is a previously unappreciated bumble bee stressor, compounding factors like agricultural intensification, novel pathogen exposure, and grassland habitat loss. These findings emphasize the need for greater consideration of habitat complementarity in bumble bee conservation. We conclude that continued loss of early‐season floral resources may add additional stress to critical life stages of bumble bees and limit restoration efforts if not explicitly considered in pollinator conservation.
Concerns about long-term pollinator declines have made assessing bee communities a priority in nonagricultural ecosystems, including managed forests. We assessed wild bee communities in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands one to 15 years after clearcut harvest in western Oregon, USA, testing the hypothesis that bee diversity would be high initially and then decline with time-dependent reductions in floral resources. We captured 2,009 individual bees that represented 67 distinct species/morphospecies in 20 genera and five families. Asymptotic estimators of bee diversity representing Shannon and Simpson diversity were greater in communities during the second half of the early seral period, indicating older early seral stands were less diverse and contained more common and dominant bee species. In addition, observed species richness and bee abundance peaked at approximately three years postharvest and declined thereafter by 20% and 30% per year, respectively. Because floral resources declined in concert with reductions in bee diversity as stands aged, food appears to be a key driver of forest bee communities. Our results indicate that postharvest Douglas-fir stands supported a diversity of bees, including important crop pollinators, but their value to bees was restricted to a relatively short window at the beginning of the early seral period.
Global biodiversity declines are attributed to many factors, including landscape fragmentation and vegetation homogenization. These patterns may be exacerbated by the intensification of management in agroecosystems, as management to meet the increasing demand for food, fuel, and fiber often comes at the cost of biodiversity and subsequent ecosystem functions and services. Conserving biodiversity will be necessary to create sustainable agroecosystems capable of optimizing both production and services such as pollination. We conducted a meta-analysis with 109 studies to examine the relationship between plant species richness and pollinator species richness to determine whether higher plant species richness supports higher pollinator species richness, especially in areas prone to biodiversity losses. We found most groups of insect pollinators, including bees, butterflies, flies, moths, and wasps, responded positively to increasing plant species richness, irrespective of location or land use, suggesting the capacity to increase pollinator richness through management strategies that increase plant species richness. However, we found pollinators in manipulated studies did not consistently respond to increasing plant species richness despite the overall positive relationships in observational and experimental studies, highlighting the importance of plant selection when making management decisions aiming to improve pollinator richness. Additional studies in regions such as Africa and South America will help fill in latitudinal gradients and provide greater coverage necessary to refine patterns. Increasing plant species richness through management changes or restorations will likely increase pollinator richness and be beneficial in agroecosystems to support biodiversity.
1. Understanding the roles of habitat fragmentation and resource availability in shaping animal movement are integral for promoting species persistence and conservation. For insects such as bumble bees, their movement patterns affect the survival and reproductive potential of their colonies, as well as the pollen flow of plant species. However, the understanding of their mobility or the impact of putative barriers in natural environments is limited due to the technical difficulties of studying wild populations.
2. Genetic mark–recapture was used to estimate the foraging distance, resource use, and site connectivity of two bumble bee species in a montane meadow complex composed of open meadows within a matrix of forest.
3. There was no evidence that forests or changes in landcover function as barriers to the fine‐scale movement for either species. Substantially greater colony‐specific foraging distances were found for Bombus vosnesenskii (maximum: 1867 m) compared to Bombus bifarius (maximum: 362 m). Despite this difference in absolute range, both species were detected across putative forest barriers at frequencies expected by uninhibited movement. Siblings separated by greater distances were more likely to be foraging on different floral species, potentially suggesting a resource‐based motivation for movement.
4. These results suggest that bumble bee foraging patterns are influenced by species‐specific differences in movement capacity, with little influence of matrix composition between resource patches. They also support the perspective that habitat conservation for bumble bees should prioritise providing abundant and diverse patches of resources within species‐specific movement radii with less emphasis on matrix composition.
Bumble bees ( Bombus) are unusually important pollinators, with approximately 260 wild species native to all biogeographic regions except Africa, Australia, and New Zealand. As they are vitally important in natural ecosystems and to agricultural food production globally, the increase in reports of declining distribution and abundance over the past decade has led to an explosion of interest in bumble bee population decline. We summarize data on the threat status of wild bumble bee species across biogeographic regions, underscoring regions lacking assessment data. Focusing on data-rich studies, we also synthesize recent research on potential causes of population declines. There is evidence that habitat loss, changing climate, pathogen transmission, invasion of nonnative species, and pesticides, operating individually and in combination, negatively impact bumble bee health, and that effects may depend on species and locality. We distinguish between correlational and causal results, underscoring the importance of expanding experimental research beyond the study of two commercially available species to identify causal factors affecting the diversity of wild species.
Expected final online publication date for the Annual Review of Entomology, Volume 65 is January 7, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Increasing the proportion of unmanaged forests in multi-functional forest landscapes is a primary goal of international and national conservation strategies aiming at restoring natural properties in structurally simplified forests. However, the development of structural features and associated habitat suitability for forest species is largely unknown and even controversially discussed, as the development of newly established reserves is uni-directional and passes through dense maturation stages. This may negatively affect open forest species in the first phase after reserve designation. We evaluated the effects of management cessation on key habitat characteristics of four mountain forest bird species indicative of different structural components: Capercaillie (Tetrao urogallus), Hazel grouse (Bonasa bonasia), Three-toed woodpecker (Picoides tridactylus) and Pygmy owl (Glaucidium pas-serinum) across four mountain regions in Central Europe. Habitat suitability was modelled based on 300 forest sites selected independently of their management status, and predicted to an independent dataset of 42 strictly protected forest reserves in the same regions. We then compared forest reserves to managed forests with species presence or absence with regard to habitat suitability and key habitat structures and related both to the time since reserve designation. For all model species, except Pygmy owl, habitat suitability in forest reserves was significantly higher than in managed forests with species' absence, but not different from managed forests with species presence. For the species associated with open forest structures (Capercaillie, Hazel grouse, Pygmy owl) habitat suitability was significantly related to the "reserve age": reserves in the first three decades after management cessation showed a significant decrease in suitability, which increased afterwards up to the maximally recorded time of 100 years. No such correlation was found for the Three-toed woodpecker associated with deadwood and barkbeetle infestations following temporally unpredictable disturbance events. Structural characteristics varied greatly in abundance and distribution, with open structures being related to the time since reserve designation. We therefore recommend focusing on mature, near-natural and structurally diverse forests when designating new strict forest reserves.
Managed conifer forests in temperate regions are critical for supplying wood products, but little is known about
their potential for pollinator conservation. We hosted a workshop for Pacific Northwest managers and biologists to
identify perceived information gaps regarding pollinators in managed conifer forests; we also undertook a literature
review on this topic to assess gaps in the primary literature. The most important gaps identified by workshop
participants were a need for baseline data on pollinators in managed conifer forests, and for determining how
forest management influences pollinators. Our literature review found a dearth of pollinator studies in managed
conifer forests, which were limited to few regions and a subset of taxa. Given these findings, we developed a
research agenda that targets identified knowledge gaps, including the need for documenting fundamental aspects
of pollinator ecology in managed conifer forests and testing how pollinators and their habitats are influenced by
management activities.
Pollinator communities exhibit variable responses to changing landscape composition. A general expectation is that a decreasing cover of semi-natural habitats negatively affects pollinator reproduction, population size and pollination services, but few studies have investigated the simultaneous effects of landscape complexity on different aspects of pollinator communities and functioning. In 20 agricultural landscape plots the size of an average Dutch farm, we studied how changing landscape complexity affected wild bee abundance, species richness and reproduction. To measure pollination, we placed potted strawberry plants as phytometers in landscapes. Landscape complexity was characterized as the area of semi-natural habitats. In addition, we estimated floral resource abundance in each landscape plot. We expected that i) bee species richness, reproduction and pollination would be positively related to area of semi-natural habitats and flower abundance, and that ii) species richness and reproduction would be positively related to pollination. An increase in semi-natural habitats in landscapes increased both the abundance of cavity-nesting bees colonizing trap nests, and the growth rates of experimental Bombus terrestris L. colonies, but not the species richness of wild bees measured by pan traps. There was only a tendency for higher pollination levels of strawberry plants with higher cover of semi-natural habitats. There was no relationship between species richness and bee reproduction in a landscape and the pollination services. Estimated flower abundance in landscape had a positive effect on bumblebee colony growth only and not on the other variables. Our results suggest that, by improving habitat quality on their farms through establishing more semi-natural habitats or enhancing the flower availability in semi-natural habitats, farmers can promote reproduction of a number of functionally important bee species and the pollination services they provide. Bee species richness, however, seems to be more difficult to enhance and requires more than just creating more of the same type of habitats or flowers.
Intensification of agriculture has been one of the major drivers for biodiversity loss in recent decades. Pollinators, which serve an important role in pollinating crops as well as wild plants, have shown a decline in species richness. Flower strips can be used to support pollinators in agro-ecosystems, however the question remains as to how their design can be optimized in order to best benefit pollinators. Increasing plant species diversity has been shown to be beneficial for pollinators, and it is often suggested that functional traits are driving this relationship. Therefore, increasing plant functional diversity could be a tool to support pollinator abundance and diversity. As experimental evidence on this relationship is scarce, we developed a field study with experimental sown flower strips with four functional diversity levels, based on multiple flower traits and with equal plant species richness. We monitored vegetation development, as well as the flower-visiting pollinator community and their interaction networks with flowers. We were able to create a functional diversity gradient while controlling for plant species richness and evenness. However, in contrast to our expectations, pollinator species richness and evenness were not influenced by functional diversity, and increasing functional diversity even resulted in lower flower visitation rates. Network stability metrics showed no effect or negative relationships with functional diversity. We conclude that increasing functional diversity was not the key for supporting pollinators in wildflower strips. Our results also suggest that, for a constant amount of flower resources, increasing plant functional diversity and thus decreasing redundancy of potential pollinator feeding niches, decreases the amount of flower resources present per feeding niche. As pollinator species tended to have less overlap in their feeding niches in flower strips with increased functional diversity, this may lead to a reduction of flower resources available for pollinator species with a more specialized feeding niche.
Dieses Lehrbuch gibt einen Überblick über das komplexe, in zahlreiche Fachdisziplinen aufgesplitterte Gebiet der Ökologie. Im Fokus steht dabei die Ökologie der Baumarten und der Wälder in Mitteleuropa, einem vegetationsgeografisch eigenständigen Naturraum, der sich von der Ostsee bis zu den Südalpen und von Ostfrankreich bis nach Polen und in die Slowakei erstreckt. Die Ausführungen zu den Strukturen und Prozessen in den natürlichen Waldformationen werden ergänzt durch Forschungsergebnisse zu den ökologischen Auswirkungen der Forstwirtschaft. In eigenen Kapiteln werden auch die globalen Problemfelder Biodiversität, Klimawandel und Waldschäden behandelt.
Biologie, Geografie, Landschaftsplanung, Landschaftsökologie, Agrar- und Forstwissenschaften sind Studiengänge, in denen ökologische Themen seit jeher einen wichtigen Teil der Lehrinhalte einnehmen. Hinzu kamen neue Studiengänge für Ressourcenmanagement, Ökosystemmanagement, Natur- und Umweltwissenschaften. Diesen Fachrichtungen bietet das Lehrbuch eine Einführung in die ökologischen Zusammenhänge. Hierbei folgt es einem hierarchischen Aufbau von den Bäumen über die Baumpopulation und das Waldökosystem bis zur Landschaft. Die umfassende Berücksichtigung aktueller und spezieller Literatur macht das Lehrbuch auch zu einem Handbuch und Nachschlagewerk für Masterstudenten, Doktoranden und Dozenten.
Anthropogenic disturbance of habitat is considered a contributing factor of pollinator declines, but some disturbances such as silviculture, may have positive implications for pollinator communities. Silviculture is a key source of disturbance in the eastern USA and thus, developing a better understanding of its ramifications for these keystone species is important for effective ecosystem conservation. We sampled bees in 30 forest openings created by group selection harvest as well as 30 sites in adjacent mature forest to examine the extent to which small forest openings support bees, to identify environmental variables influencing bee abundance and diversity, and to gauge their potential to augment bee populations in adjacent unmanaged forest. Bees were significantly more abundant and diverse in forest openings than in mature forest, but species composition did not differ. There was no relationship between opening size and abundance or diversity of bees in openings or adjacent mature forest. Both abundance and diversity were generally positively related to the amount of early-successional habitat on the landscape. Within openings, overall abundance and diversity decreased with vegetation height and increased with a metric representing floral richness and abundance. Notably, social, soft-wood-nesting, and small bees exhibited the opposite pattern in adjacent forest, increasing with vegetation height in openings and decreasing with greater floral richness and abundance within openings. Our results suggest that the creation of small forest openings helps to promote bees both in openings and adjacent mature forest, but this pattern is not consistent for all guilds.
Bees are herbivorous insects, consuming nectar and pollen throughout their life cycles. This paper is a brief review of the chemistry of these two floral resources and the implications for bee nutrition. Nectar is primarily an energy source, but in addition to sugars contains various minor constituents that may, directly or indirectly, have nutritional significance. Pollen provides bees with the protein, lipids, vitamins and minerals that are essential for larval rearing. Chemical analyses of pollen have tended to focus on the protein component of bee-collected pollens as an index of nutritional quality. However, the substantial nectar content of such samples (~ 50% dry mass) should not be ignored, especially in view of current interest in measuring the nutritional quality of floral resources for bees.
Recent studies have shown that the diversity of flowering plants can enhance pollinator richness and visitation frequency and thereby increase the resilience of pollination. It is assumed that flower traits explain these effects, but it is still unclear which flower traits are responsible, and knowing that, if pollinator richness and visitation frequency are more driven by mass-ratio effects (mean trait values) or by trait diversity. Here, we analyse a three-year data set of pollinator observations collected in a European grassland plant diversity experiment (The Jena experiment). The data entail comprehensive flower trait measurements, including reward traits (nectar and pollen amount), morphological traits (height, symmetry, area, colour spectra), and chemical traits (nectar-amino acid and nectar-sugar concentration). We test if pollinator species richness and visitation frequency of flower communities depend on overall functional diversity combining all flower traits within a community, single trait diversities (within trait variation) and community-weighted means of the single traits, using Bayesian inference. Overall functional diversity did not affect pollinator species richness, but reduced visitation frequency. When looking at individual flower traits separately, we found that single trait diversity of flower reflectance and flower morphology were important predictors of pollinator visitation frequency. Moreover, independent of total flower abundance, community-weighted means of flower height, area, reflectance, nectar-sugar concentration and nectar-amino acid concentration strongly affected both pollinator species richness and visitation frequency. Our results, challenge the idea that functional diversity always positively affects ecosystem functions. Nonetheless, we demonstrate that both single trait diversity and mass-ratio effects of flower traits play an important role for diverse and frequent flower visits, which underlines the functionality of flower traits for pollination services. This article is protected by copyright. All rights reserved.
Understanding patterns of species diversity at different spatial scales is important for adapting management and conservation efforts. We have therefore studied wild bee and wasp (Hymenoptera: Aculeata) diversity structure in forest landscapes and evaluated the importance of conservation management at the local and landscape levels. Surveys were conducted at 32 clearcuts in eight landscapes in a managed boreal forest region. We assessed the influence of local habitat and landscape composition on species richness patterns and the effect of prescribed burning and landscape affinity on species composition for all bees and wasps as well as ecological and functional groups. The relative contribution of alpha and beta diversity on the regional level was assessed by diversity partitioning and the beta diversity between landscapes further partitioned into components of species turnover and nestedness. Bee and wasp species richness increased with high flower richness and clearcut size, and species composition differed between burned and unburned sites. Thus, flower-rich early-successional sites in boreal forest landscapes are important habitats for wild bees and wasps. To support this fauna, openness should be maintained for extended periods by delaying or avoiding tree plantation at flower-rich spots on clear-cuts. Beta diversity between landscapes accounted for the greatest proportion of the total regional gamma diversity, and over 70% of this diversity was due to species turnover. This implies that in order to maintain regional diversity, conservation efforts should be spatially dispersed, i.e. applied to every landscape of a few hundred square kilometers and adapted to the local species assemblages.