Cavity-nesting Bees Research Articles

Decreased bee emergence along an elevation gradient: Implications for climate change revealed by a transplant experiment.

Bees experience differences in thermal tolerance based on their geographical range; however, there are virtually no studies that examine how overwintering temperatures may influence immature survival rates. Here, we conducted a transplant experiment along an elevation gradient to test for climate-change effects on immature overwinter survival using movement along elevational gradient for a community of 26 cavity-nesting bee species in the family Megachilidae along the San Francisco Peaks, Arizona elevational gradient. In each of three years, we placed nest blocks at three elevations, to be colonized by native Megachilidae. Colonized blocks were then (1) moved to lower (warmer) elevations; (2) moved to higher (cooler) elevations; or (3) left in their natal habitat (no change in temperature). Because Megachilidae occupy high elevations with colder temperatures more than any other family of bees, we predicted that emergence would decrease in nest blocks moved to lower elevations, but that we would find no differences in emergence when nest blocks were moved to higher elevations. We found three major results: (1) Bee species moved to lower (warmer) habitats exhibited a 30% decrease in emergence compared with species moved within their natal habitat. (2) Habitat generalists were more likely than habitat specialists to emerge when moved up or down in elevation regardless of their natal life zones. (3) At our highest elevation treatment, emergence increased when blocks were moved to higher elevations, indicating that at least some Megachilidae species can survive at colder temperatures. Our results suggest that direct effects of warming temperatures will have negative impacts on the overall survival of Megachilidae. Additionally, above the tree line, low availability of wood-nesting resources is a probable limiting factor on bees moving up in elevation.

Petals and leaves: quantifying the use of nest building materials by the world's most valuable solitary bee.

The alfalfa leafcutter bee (Megachile rotundata, hereafter simply "leafcutter bee") is a solitary, cavity-nesting bee native to Eurasia, managed as an agricultural pollinator of alfalfa and several other crops in North America since the 1940s (Pitts-Singer and Cane 2011). The most intensively managed and economically valuable solitary bee worldwide, it serves as a model organism for studying solitary bee biology (Pitts-Singer and Cane 2011). Understanding this species' nesting behavior is critical to its propagation for commercial pollination services. As its common name suggests, female leafcutter bees construct their nests in above-ground holes using carefully clipped pieces of leaves (Pitts-Singer and Cane 2011).

Landscape heterogeneity and forest cover shape cavity-nesting hymenopteran communities in a multi-scale perspective

Increasing biodiversity loss due to human activities may compromise ecosystem functions and services, with serious consequences for human well-being. Pollination and biological control are among the ecosystem services most affected by landscape changes, where cavity-nesting hymenopteran species are important agents of such services. We analyzed how cavity-nesting bee and wasp communities are affected by landscape structure at different scales since a multi-scale perspective is more efficient in detecting landscape effects on species, communities, and ecological processes. The study was carried out in the Cantareira-Mantiqueira Corridor (CCM) located within the Atlantic Forest, São Paulo, Brazil. We used trap-nests distributed in 29 sampling points following a nested design of ten regional landscapes with three nested local landscapes. We recorded 25 bee species, 21 wasp species, and 25 species of brood cell parasites. The bee and wasp communities were explained by landscape heterogeneity and forest cover: at the local level, landscape heterogeneity had a positive effect on almost all response variables, while forest cover was also important at the regional level, mainly for bee diversity and wasp abundance. Our results highlight the need to conduct studies at multiple scales to understand how landscape heterogeneity and forest cover affect the diversity of pollinating and predatory insects.

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.

Effects of urban greenspace configuration and native vegetation on bee and wasp reproduction.

Pollinator welfare is a recognized research and policy target, and urban greenspaces have been identified as important habitats. Yet, landscape-scale habitat fragmentation and greenspace management practices may limit a city's conservation potential. We examined how landscape configuration, composition, and local patch quality influenced insect nesting success across inner-city Cleveland, Ohio (U.S.A.), a postindustrial legacy city containing a high abundance of vacant land (over 1600 ha). Here, 40 vacant lots were assigned 1 of 5 habitat treatments (T1, vacant lot; T2, grass lawn; T3, flowering lawn; T4, grass prairie; and T5, flowering prairie), and we evaluated how seeded vegetation, greenspace size, and landscape connectivity influenced cavity-nesting bee and wasp reproduction. Native bee and wasp larvae were more abundant in landscapes that contained a large patch (i.e., >6 ha) of contiguous greenspace, in habitats with low plant biomass, and in vacant lots seeded with a native wildflower seed mix or with fine-fescue grass, suggesting that fitness was influenced by urban landscape features and habitat management. Our results can guide urban planning by demonstrating that actions that maintain large contiguous greenspace in the landscape and establish native plants would support the conservation of bees and wasps. Moreover, our study highlights that the world's estimated 350 legacy cities are promising urban conservation targets due to their high abundance of vacant greenspace that could accommodate taxa's habitat needs in urban areas.

Multi-trophic communities re-establish with canopy cover and microclimate in a subtropical forest biodiversity experiment

Plant diversity affects multi-trophic communities, but in young regrowth forests, where forest insects are in the process of re-establishment, other biotic and also abiotic factors might be more important. We studied cavity-nesting bees, wasps and their natural enemies along an experimental tree diversity gradient in subtropical South-East China. We compared insect communities of experimental young forests with communities of established natural forests nearby the experiment and tested for direct and indirect effects of tree diversity, tree basal area (a proxy of tree biomass), canopy cover and microclimate on bee and wasp community composition, abundance and species richness. Finally, we tested if the trophic levels of bees, herbivore-hunting wasps, spider-hunting wasps and their natural enemies respond similarly. Forest bee and wasp community composition re-established towards communities of the natural forest with increasing tree biomass and canopy cover. These factors directly and indirectly, via microclimatic conditions, increased the abundance of bees, wasps and their natural enemies. While bee and wasp species richness increased with abundance and both were not related to tree diversity, abundance increased directly with canopy cover, mediated by tree biomass. Abundance of natural enemies increased with host (bee and wasp) abundance irrespective of their trophic position. In conclusion, although maximizing tree diversity is an important goal of reforestation and forest conservation, rapid closure of canopies is also important for re-establishing communities of forest bees, wasps and their natural enemies.

Re-establishment of cavity-nesting bee and wasp communities along a reforestation gradient in southern Amazonia.

Global initiatives to reforest degraded areas have intensified in recent years, in an attempt to reverse the environmental impacts of habitat loss on species and ecosystem provided by them. However, the effectiveness of such reforestation initiatives in re-establishing biodiversity is still poorly understood. Here, we test how reforestation type and intensity applied to deforested areas affect the reestablishment of communities of cavity-nesting bees and wasps. We deployed experimental trap-nests along a reforestation gradient of increasing structural similarity to primary forest, after 18years of reforestation. We found that reestablishment, in terms of abundance and richness of both bees and wasps, was greatest at an intermediate point along the reforestation gradient. However, these communities were highly dissimilar to primary forest, and recovery of intact insect community composition was only achieved when reforestation was more similar in structure to natural forests. This effect was more pronounced for bees than for wasps. Our findings suggest that along the reforestation gradient, services provided by wasps will be more easily recovered than those provided by bees. Our results have important implications for the challenges of restoring and maintaining species biodiversity as well as their associated ecosystem services.

Red and black mason wasp, Pachodynerus erynnis (Lepeletier)

Pachodynerus erynnis (Lepeletier) is a predatory wasp that specializes in preying upon caterpillars, the larvae of moths and butterflies (Lepidoptera). This insect does not yet have an officially accepted common name and has been referred to as the red and black mason wasp, red-marked Pachodynerus, and a mason wasp. As with other closely related wasps, Pachodynerus erynnis does not form a communal hive, but builds solitary nests in holes or crevices of trees or man-made structures, as well as abandoned nests created by other cavity-nesting bees and wasps. The red and black mason wasp frequently visits flowering plants and can be found entering nesting cavities nearby. This insect is considered highly beneficial because it feeds on several key caterpillar pests, including armyworms (Spodoptera spp.), cutworms (Agrotis spp.), and loopers (Noctuoidea), and has been associated with increased pest control in managed landscapes. Although fairly common, this wasp often goes unnoticed due to its solitary nature and quick flight.
 Also published on the Featured Creatures website at http://entnemdept.ufl.edu/creatures/MISC/WASPS/Pachodynerus_erynnis.html

Reproductive patterns of solitary cavity-nesting bees responsive to both local and landscape factors

Understanding how local and landscape-level factors influence species abundances and distributions is crucial for conservation and restoration efforts. Effects of urbanization are often negative at a landscape level, but some taxa such as solitary cavity-nesting bees perform better in urban areas, due to increases in food, nesting, and habitat resources at the local level. In this study, we ask how local and landscape factors across an urbanization gradient influence three demographic aspects of reproduction for solitary-nesting bees: fecundity, brood survivorship, and total adults to emerge in the spring. In 2018–2019, we surveyed solitary cavity-nesting bees active in 18 grassland restoration sites across the city of Louisville, Kentucky, USA using constructed nest boxes. We found that bee larvae had increased survivorship in urban areas as compared to surrounding rural areas, possibly due to decreased nest parasitism. Additionally, we found bee fecundity to increase with the proportion of native flowers in the surrounding floral community. These results indicate that urbanization can benefit some groups of solitary bees when paired with local grassland restoration efforts. This highlights the importance of native plants and natural areas in the urban matrix to support pollinator communities.

Effect of height and colour of bee bricks on nesting occupancy of bees and wasps in SW England

Bee bricks are a novel solitary-bee nesting habitat made from reclaimed concrete, designed to be built into walls to provide nest sites in urban areas. We tested if cavity-nesting bees and wasps used bee bricks, and if they showed any preference for nesting in bricks of different colours or at different heights. We carried out surveys of solitary bees in 15 private urban gardens and eight rural public gardens, where the bee bricks were then placed for two years (2016-2017). Bee bricks were placed on structures that were either 1 m in height with 4 bricks (red, yellow, white and wooden control) or with three platforms where white bricks were placed at 0 m, 0.6 m or 1.0 m above the ground. The number of occupied nest holes was counted at the end of each summer. Nesting holes that were capped with mud were more common than those capped with chewed or cut leaves. The average % of holes capped with either mud or chewed leaf was greatest in red bricks and lowest in wooden controls. Only one brick out of 39 placed at ground level had capped holes, although the difference in the % of holes capped between heights was not statistically significant. Cavity-nesting bees and wasps use solitary-bee bricks for nests, but population level impacts are still untested.

Non-rotational set-aside fields improve reproductive success of cavity-nesting bees and wasps at the landscape scale, but have no effect on other wild bees and hoverflies in mid-summer

Wild bees, hoverflies and wasps are valuable ecosystem service providers in agricultural systems through pollination and biological control, and their species richness, abundance and reproductive success well indicate ecosystem health. However, they are often limited by foraging and nesting resources that are major drivers behind their steep decline. Although agri-environmental measurements improve resources for these groups, their wider landscape-scale impacts are basically unknown. Here, we questioned whether 2–3 years old, sown set-aside fields could have a potential in enhancing pollinator and predatory wasp communities at the landscape scale in a Central European agroecosystem. We measured reproductive success and parasitism of cavity-nesting bees and wasps by trapnests throughout the vegetation period, and sampled bee and hoverfly communities by colored pan traps in mid-summer, comparing landscapes with and without set-aside fields. We measured the effects of increasing distance from set-aside fields, the effects of share of different habitats and flower resources, and the effects of increasing set-aside field percentage area at landscape scale. The landscape scale effects of set-aside fields varied among taxa and/or at different time scales. Reproductive success of cavity-nesting bees and wasps was positively related to the presence of set-aside fields in the landscape and together with the number of cavity-nesting bee and wasp genera increased with the proportion of set-aside fields. Species richness or abundance of bees or hoverflies showed no difference between landscape plots with or without set-aside fields in the mid-summer period according to the pan trap samples, and flower abundance and distance from the set-aside fields had only a limited effect. Set-aside fields had no effect on either the most abundant wild bee species or on composition of species of intermediate abundance. Our results suggest that reproductive success of cavity-nesting bees and wasps can be enhanced by additional flower resources and nesting habitats through set-aside fields at the landscape scale. Other wild bees and hoverflies can be less sensitive to the presence of set-aside fields according to our results that might need different conservation approaches. But this might also suggest that such landscape-scale benefits of set-aside field management might be measureable only with samplings covering the whole vegetation period. We argue that well-defined measures specific to spatial scale and target groups are mandatory and should be adapted to the different histories and local contexts of agricultural landscapes in Europe to strengthen ecosystem service provider insects and have the highest benefit for agricultural production.

Urban fragment of the Atlantic Rainforest as a refuge for cavity-nesting bees and wasps (Hymenoptera: Aculeata)

ABSTRACT Due to the fragmentation of many natural habitats, urban areas have become important refuges for various species, including bees and wasps. The present study aimed to determine the species composition, richness, and abundance of solitary bees and wasps that nest in pre-existing cavities in an urban fragment of the Atlantic Rainforest in the city of Salvador, Brazil. Data on the occupancy of the trap-nests and offspring mortality are also reported. The study was conducted at the Parque Zoobotânico Getulio Vargas (PZBGV) and the campus of Universidade Federal da Bahia (UFBA), the areas of which form the urban fragment. Traps were inspected once a month for 2 years. The composition and diversity of bee species were similar between the areas, but richness and abundance of wasp species were higher at UFBA. Centris analis (Fabricius) was the most abundant bee species in both areas, and Podium denticulatum (Smith) and Trypoxylon sp.2 were the most abundant wasp species at UFBA and PZBGV, respectively. Most nesting of these species occurred in the warm season. Centris analis and Trypoxylon sp.2 preferred traps made of cardboard, whereas P. denticulatum was the most generalist species, occupying all types of trap-nests. The main factor of mortality among immature specimens was ‘unknown cause’ for both bees and wasps. Only three species of natural enemies emerged from nests of C. analis. The increase in the richness of bee and wasp species in comparison with the results showed in previous studies made in the same areas indicates that the fragment offers valuable nesting places for species of cavity-nesting bees and wasps and can ensure the maintenance of these insects.

Cavity Length Affects the Occupation of Trap-Nests by Centris analis and Tetrapedia diversipes (Hymenoptera: Apidae)

The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed as pollinators have not been getting proper attention. We investigated whether the occupancy of trap-nests by Centris analis Fabricius and Tetrapedia diversipes Klug, and other nesting aspects, are affected by different trap-nest length. The used trap-nests were cardboard tubes 5, 10, 15 and 20 cm in length, and Ø 8 mm. Occupation rates of 10-cm trap-nests by C. analis was higher than that of the 5-cm ones (χ2=11.17, gl=1, p<0.001). On the other hand, there was not difference between the occupation rates of 10 and 15-cm long trap-nests (χ2=0.51, gl=1, p=0.48), and between the ones measuring 15 and 20 cm long (χ2=1.36, gl=1, p=0.24). T. diversipes occupied a smaller number of 5-cm trap-nests than the 10-cm ones (χ2=1.52, gl=1, p=0.22), as well as that the 15-cm ones were more occupied than the 10-cm trap-nests (χ2=4.23, gl=1, p=0.04); moreover, there was not difference between the occupation of 15 and 20-cm trap-nests (χ2=0.28, gl=1, p=0.59). Both species showed higher rates of dead immatures in nests set in the shortest trap-nests, whereas these mortality rates were lower in the longest ones. By taking into consideration that there was not significant difference in many of the assessed parameters in comparison to values recorded for 15 and 20-cm long trap-nests, it seems likely to recommend the adoption of 10-cm long trap-nests for C. analis reproduction in agricultural sites that depend on the pollination service provided by this bees species.

Green patches among a grey patchwork: the importance of preserving natural habitats to harbour cavity-nesting bees and wasps (Hymenoptera) and their natural enemies in urban areas

Urbanisation is fast-growing worldwide characterised by the conversion of natural vegetation ecosystems into densely paved areas with a high concentration of human constructions and few remnants of natural habitats. This phenomenon may threaten wildlife, especially high trophic level organisms such as predators and parasitoids, which are known to be more sensitive to habitat fragmentation. We investigated the influence of urbanisation on the community of trap-nesting bees and wasps as well as on their parasites in an urban area. Trap-nests were installed in 11 areas within the perimeter of the city of Ribeirao Preto, Brazil. Fourteen land cover categories were distinguished and their percentages calculated for each area from satellite images. The community sampled consisted of 20 wasp and 12 bee species, as well as 25 natural enemy species that attacked 9.75% of the nests. The highest diversity of bees and wasps was observed in areas with higher percentages of natural vegetation, i.e., forests, wastelands, and neighbourhoods with extensive green areas. Rates of parasitism, measured by the abundance and richness of parasites, was positively correlated with the proportion of green areas in the landscape. Even though predatory wasps constitute a higher trophic level than bees they were not more negatively impacted by urbanisation. Our results demonstrate that natural habitats and extensive green areas can host diverse communities of cavity-nesting bees, wasps, and their parasites within a city. The conservation of green areas in urbanised landscapes should be considered as essential to maintain the populations of these important insects.

Plant-solitary bee networks have stable cores but variable peripheries under differing agricultural management: Bioindicator nodes unveiled

• Plant-solitary bee networks have a stable core but a variable periphery. • Osmia caerulescens is a good bioindicator of management types. • Osmia bicornis is a good bioindicator of ecosystem recovery. • Aboveground cavity-nesting bees pollinate many wild herb plants in olive orchards. • Plant species identified at the core are of conservation priority for bees. The identification of important nodes structuring pollination networks represents a key contribution to biodiversity conservation and pollination functioning. Understanding how species and their importance covary with management is essential if we aim to predict anthropic effects on the environment. In this study we used 96 bee trap nests to sample plant (pollen)-solitary bee interaction networks in 18 pairs of olive groves employing differing management techniques (intensive vs. organic). We applied a novel dual analytical approach consisting of identifying important nodes from two different perspectives: nodes that strongly determine the topological structure of the network and nodes that sustain rare or infrequent interactions. We employed this analytical approach to identify important nodes for the conservation of these networks and to study how different agricultural management practices modify the importance of the nodes. Specifically, Osmia caerulescens appeared in the core of the network of organic farms and acts as a good bioindicator of agricultural management types. As well, O. bicornis participated in important singular interactions but only on organic farms and so can be considered as a good bioindicator of ecosystem recovery. Our results highlight the species that should be prioritized for conservation or restoration and reveal a core-periphery structure in networks, in which, despite most structuring species remaining constant across management types, certain important singular interactions differ. We demonstrate that the switch from intensive to organic farming on olive farms can restore the structure of these plant-solitary bee networks, mainly through the recovery of certain species and rare or infrequent interactions.

Spatial variability of hosts, parasitoids and their interactions across a homogeneous landscape.

Species assemblages and their interactions vary through space, generating diversity patterns at different spatial scales. Here, we study the local‐scale spatial variation of a cavity‐nesting bee and wasp community (hosts), their nest associates (parasitoids), and the resulting antagonistic network over a continuous and homogeneous habitat. To obtain bee/wasp nests, we placed trap‐nests at 25 sites over a 32 km2 area. We obtained 1,541 nests (4,954 cells) belonging to 40 host species and containing 27 parasitoid species. The most abundant host species tended to have higher parasitism rate. Community composition dissimilarity was relatively high for both hosts and parasitoids, and the main component of this variability was species turnover, with a very minor contribution of ordered species loss (nestedness). That is, local species richness tended to be similar across the study area and community composition tended to differ between sites. Interestingly, the spatial matching between host and parasitoid composition was low. Host β‐diversity was weakly (positively) but significantly related to geographic distance. On the other hand, parasitoid and host‐parasitoid interaction β‐diversities were not significantly related to geographic distance. Interaction β‐diversity was even higher than host and parasitoid β‐diversity, and mostly due to species turnover. Interaction rewiring between plots and between local webs and the regional metaweb was very low. In sum, species composition was rather idiosyncratic to each site causing a relevant mismatch between hosts and parasitoid composition. However, pairs of host and parasitoid species tended to interact similarly wherever they co‐occurred. Our results additionally show that interaction β‐diversity is better explained by parasitoid than by host β‐diversity. We discuss the importance of identifying the sources of variation to understand the drivers of the observed heterogeneity.

European Wool Carder Bee, Wool Carder Bee Anthidium manicatum (Insecta: Hymenoptera: Megachilidae)

The European wool carder bee Anthidium manicatum (Linnaeus) is a solitary, cavity-nesting bee species in the family Megachilidae (tribe Anthidiini), a family whose members include the mason and leaf cutter bees. Wool carder bees are so named because the female bee scrapes and collects the soft downy hairs (trichomes) of fuzzy plants to use in building a nest for her young. Some consider male wool carder bees very charismatic and enjoy watching them chase after other bees that invade their territory, while others would call them bullies based on male bees’ aggressive tendencies toward other bees when defending floral resources.
 This species has been called the most widely distributed unmanaged bee in the world (Strange et al. 2011) because of its expansive native and non-native range.
 This document describes its synonymy, distribution, description, life cycle and biology, hosts, economic importance, and includes selected references.Available on EDIS at https://edis.ifas.ufl.edu/in1274
 Also available on the Featured Creatures website at http://entnemdept.ufl.edu/creatures/MISC/BEES/Anthidium_manicatum.html

Microclimate Temperatures Impact Nesting Preference in Megachile rotundata (Hymenoptera: Megachilidae).

The temperature of the nest influences fitness in cavity-nesting bees. Females may choose nest cavities that mitigate their offspring’s exposure to stressful temperatures. This study aims to understand how cavity temperature impacts the nesting preference of the solitary bee Megachile rotundata (Fabricius) under field conditions. We designed and 3D printed nest boxes that measured the temperatures of 432 cavities. Nest boxes were four-sided with cavity entrances facing northeast, northwest, southeast, and southwest. Nest boxes were placed along an alfalfa field in Fargo, ND and were observed daily for completed nests. Our study found that cavity temperature varied by direction the cavity faced and by the position of the cavity within the nest box. The southwest sides recorded the highest maximum temperatures while the northeast sides recorded the lowest maximum temperatures. Nesting females filled cavities on the north-facing sides faster than cavities on the south-facing sides. The bees preferred to nest in cavities with lower average temperatures during foraging hours, and cavities that faced to the north. The direction the cavity faced was associated with the number of offspring per nest. The southwest-facing cavities had fewer offspring than nests on the northeast side. Our study indicates that the nesting box acts as a microclimate, with temperature varying by position and direction of the cavity. Variation in cavity temperature affected where females chose to nest, but not their reproductive investment.

Promoting Data Collection in Pollinator Citizen Science Projects

Pollinators provide ecosystem services that are threatened by the loss of wild and managed bees. Citizen scientists can monitor bees to yield useful data that may guide conservation of threatened bee populations. However, the factors that promote data collection in pollinator citizen science projects are largely unknown, inhibiting development of citizen science that promotes pollinator conservation. We used data from two citizen science projects to assess factors that mediated data collection by volunteers who monitored bees in Washington State, USA, from 2015 to 2017. One project monitored bee-plant interactions with photography; the other gave volunteers nest boxes to monitor cavity-nesting bees. Both projects involved educational trainings, although the project methods differed. Volunteers were given post-training questionnaires to assess their motivations for participation and to evaluate if the volunteer’s level of educational attainment influenced data collection. Citizen scientists who monitored cavity-nesting bees were more likely than those who monitored plant-bee interactions to submit data. Data collection was independent of educational attainment, and participants in both projects were more likely to volunteer for their own educational reasons rather than to collect data. Our findings suggest that pollinator citizen science projects which use nest boxes to monitor cavity-nesting bees will receive more data submissions, indicating that these projects may be particularly useful for monitoring pollinators. More broadly, our results suggest that researchers must carefully evaluate project methods, and volunteer motivations, prior to offering trainings to increase rates of data collection.

Habitat area and connectivity support cavity-nesting bees in vineyards more than organic management

The expansion and intensification of agriculture are the main causes of current insect declines. Pollinators like cavity-nesting bees can be limited by reduced nesting and feeding opportunities in farmland. As insects constitute the bulk of terrestrial biodiversity and fulfill important ecological functions, there is an urgent need to identify ways to combine agricultural land use and insect conservation. Perennial crops like grapevine can provide permanent habitats for numerous beneficial organisms including various pollinators. With their dominating character in viticultural areas and >7 million ha covered by vines globally, their potential to contribute to nature conservation should be more widely considered. We compared effects of organic management, inter-row vegetation characteristics and landscape parameters on the abundance and species richness of cavity-nesting bees in Central German vineyards. In a paired study design, we assessed cavity-nesting bees in 15 pairs of organically and conventionally managed vineyards along a gradient of landscape complexity. We found that organic management, even though it enhanced flower availability in the vineyards, was only partially beneficial for cavity-nesting bee abundance. Abundance and species richness were enhanced by either semi-natural habitat area or proximity of woody elements like hedges or forest remnants, most likely due to the nesting demands of this particular group of pollinators. We conclude that vineyards can help to sustain cavity-nesting bee abundance, given that landscapes are managed accordingly. We recommend maintaining or establishing woody elements between vineyards, which is likely to also benefit additional groups of organisms such as breeding birds in viticultural landscapes.