Abundant Floral Resources Research Articles

Missing the biodiversity for the bee: Natural land management strategies impact functional invertebrate diversity in commercial cranberry production

Abstract Simplification of agricultural environments is linked to declines in biodiversity. Improving the floral diversity within and around these areas may result in more robust and diverse ecosystems. We investigated how floral resource abundance, diversity, and species composition in a cranberry agricultural system correlated to the abundance and overall invertebrate diversity and to the abundance and diversity of specific invertebrate groups of agricultural importance (e.g. parasitoids, phytophagous taxa, pollinators and predators). This study focused on habitats immediately surrounding cranberry production and included grassy dikes under a managed system (‘dike’), and semi‐natural areas growing on the surrounding support land (‘semi‐natural’). Floral resource availability and diversity tended to be similar between habitats, while invertebrate richness, diversity and composition differed. As the availability of floral resources increased, invertebrate abundance increased but diversity decreased. Overall invertebrate community composition differed with the specific species and availability of floral resources. The habitat type and floral resource composition impacted some agriculturally important groups, as pollinator abundance was higher in the semi‐natural habitat, and parasitoid abundance varied with floral resource composition across both habitats. These results suggest that managing the structural and floral resource diversity associated with agroecosystems can help support local biodiversity. However, these systems may disproportionately benefit more common taxonomic groups. The difference in responses of individual taxonomic groups also highlights the potential tradeoffs of focusing on only a subset of biodiversity aspects.

Stable pollinator communities in different white clover populations suggest potential win-win scenarios for crop yield and biodiversity

Compared to monocultures, intercropping systems offer many agronomic benefits, including higher yield stability. In this study, we assessed whether cropping systems that are beneficial for yield stability are also beneficial for pollinator communities and whether the effect is modulated by the landscape type. Using a replicated block design in one heterogeneous and one homogeneous agricultural landscape, we studied the pollinator communities in eight populations (i.e., genotypes) of white clover (Trifolium repens) grown as a monoculture or as a two-species mixture (together with perennial ryegrass, Lolium perenne) or three-species mixture (together with perennial ryegrass and chicory, Cichorium intybus). We recorded 1486 honey bees and 1254 wild pollinators belonging to 46 species. Bumble bees were the most abundant wild pollinators (49.6 %), followed by hover flies (23.4 %), and non-Bombus wild bees (21.5 %). Lepidoptera accounted for only 5.4 % of the wild pollinators. We found a higher species richness and abundance of wild pollinators in monocultures than in two-species mixtures, but white clover population did not influence pollinators. Moreover, species richness and abundance were also higher in the homogeneous landscape than in the heterogenous one. Most species were foraging on white clover. However, 18 species (39.1 %, n = 18/46) were recorded foraging on chicory and/or weeds, and ten of these wild pollinator species were never recorded on white clover. Our study highlights that diverse pollinator communities require both abundant floral resources and diverse plant communities, that their needs are not in conflict with the goal of achieving yield stability, and that the landscape type can modulate the effect of the cropping system. Moreover, the lack of pollinator preference for different white clover populations suggests that farmers can select mixtures that enhance yield stability without negatively affecting pollinator communities. Overall, these results highlight that intercropping systems comprising several plant species and plant genotypes can guarantee yield stability without compromising the pollinator community, showing that win-win situations for farmers and biodiversity are possible.

Consistent generalization of plant-hummingbird networks despite increasing vegetation cover across a tropical urban landscape

Human activities, particularly urbanization, profoundly impact ecosystems often resulting in biotic homogenization. Whether or not urban landscapes can sustain diverse pollinator and plant communities is an important question to be addressed. Here, we investigated the influence of urbanization on plant-hummingbird interaction networks in a large tropical city, Belo Horizonte, Brazil. We recorded 13198 legitimate interactions between seven hummingbirds and 57 plant species across 12 local networks. Urban landscapes exhibited predominantly generalized networks, maintaining this pattern across varying vegetation cover and floral resource abundance. Although some functionally specialized hummingbirds with long bills were recorded performing more specialized interactions, urban environments did not generally support specialized networks. Nevertheless, network specialization did increase with the proportion of native nectar plants, emphasizing their importance for maintaining some specialized interactions. Furthermore, we observed a positive effect of plant richness, but not of flower abundance, on hummingbird abundance, indicating that it is not only the amount of flowers, but the diversity of floral resources that may be a key factor in maintaining hummingbirds. Therefore, promoting a diverse assemblage of native plants in urban green areas is crucial for sustainable pollinator communities. Our study highlights that while a biodiverse urban landscape will require careful urban vegetation planning considering both floral resource diversity and availability, vegetation cover per se may not be sufficient to mitigate the negative impacts of urbanization. Maintaining a diverse vegetation with different life forms, flowering phenology, and especially of native plants across the urban landscape is needed to create welcoming spaces for pollinators.

Emergence of structure in plant–pollinator networks: low floral resource constrains network specialisation

Specialisation enhances the efficiency of plant–pollinator networks through the exchange of conspecific pollen transfer for floral resources. Floral resources form the currency of plant–pollinator interactions, but the understanding of how floral resources affect the structure of plant–pollinator networks remains modest. Previous theory predicts that optimally foraging animal species will specialise to improve resource acquisition under high resource availability. Although floral resource availability depends on both the plant production and animal consumption of the resources, previous work has assumed that production and availability are equivalent. This potentially may have led to erroneous inferences on the effect of resource availability on specialisation. We develop a mutualistic Lotka–Volterra consumer‐resource model to investigate the influence of floral resource availability on plant–pollinator network structure. The model incorporates animal adaptive foraging behaviour, floral resource dynamics, and density‐dependent dynamics. Specialisation, nestedness and modularity of simulated networks generated from the model under a wide range of parameters were explained using the generalised linear model. We found that the distinction between floral resource dynamics and plant density dynamics was necessary for partial specialisation of plant–pollinator networks. This is because floral resource dynamics constrained animal preference due to its depletion by animal species. Floral resource abundance had a positive effect on network specialisation, but animal density had a negative effect on network specialisation. Floral resource dynamics thus play key roles in the structure of plant–pollinator networks, distinctive from plant species density dynamics.

Land-use affects pollinator-specific resource availability and pollinator foraging behaviour.

Land-use management is a key factor causing pollinator declines in agricultural grasslands. This decline can not only be directly driven by land-use (e.g., habitat loss) but also be indirectly mediated through a reduction in floral resource abundance and diversity, which might in turn affect pollinator health and foraging. We conducted surveys of the abundance of flowering plant species and behavioural observations of two common generalist pollinator species, namely the bumblebee Bombus lapidarius and the syrphid fly Episyrphus balteatus, in managed grasslands of variable land-use intensity (LUI) to investigate whether land-use affects (1) resource availability of the pollinators, (2) their host plant selection and (3) pollinator foraging behaviour. We have found that the floral composition of plant species that were used as resource by the investigated pollinator species depends on land-use intensity and practices such as mowing or grazing. We have also found that bumblebees, but not syrphid flies, visit different plants depending on LUI or management type. Furthermore, LUI indirectly changed pollinator behaviour via a reduction in plot-level flower diversity and abundance. For example, bumblebees show longer flight durations with decreasing flower cover indicating higher energy expenditure when foraging on land-use intensive plots. Syrphid flies were generally less affected by local land use, showing how different pollinator groups can differently react to land-use change. Overall, we show that land-use can change resource composition, abundance and diversity for pollinators, which can in turn affect pollinator foraging behaviour and potentially contribute to pollinator decline in agricultural grasslands.

Influence of generalist stingless bees on the structure of mutualistic flower–pollinator networks in the tropics: Temporal variation

Abstract Stingless bees (Meliponini) are expected to play a central role in structuring mutualistic networks in the Neotropics, as they are generalist and often abundant pollinators. Living in populous social colonies with a perennial life cycle, they require continuous large amounts of resources and often forage on abundant flowerings such as mass‐flowering throughout the year. In this field research, we seek to understand how temporal variations on foraging activity of stingless bees and abundance of mass‐flowering partner plants affect the topology of the plant–pollinator mutualistic networks. The networks were compared between spring and summer, periods of high and low abundances of flowerings and mass‐flowering, respectively. Bees were sampled on flowers, in replicates of floodplain fields in Atlantic Forest of southern Brazil. Interactions with partner plants were considered effective only when bees had pollen on their bodies (potential pollinators). Through analysis of pollen grains attached to their bodies, several topological metrics of networks and functional categories were obtained. The robustness or networks resistance to secondary species loss due to simulated focal species extinction was also measured. The networks maintained similar general structure throughout the year (high nestedness, moderate modularity and connectance, low community‐level specialisation and negative dependency asymmetry). Particularly, nestedness and dependency asymmetry did not change between the two seasons. Community‐level specialisation was higher in summer, contrary to expectations, when there was a collapse in the supply of floral resources and also a reduction in the abundance and foraging pressure of stingless bees. As there was also a greater number of specialist pollinators in summer, the hypothesis of temporal displacement due to foraging pressure from generalists was proposed. At the same time, stingless bees oscillated between network hubs in spring and connectors in summer, reflecting the variation in their abundance between these two seasons. In spring, the greater concentration of foraging by these generalists in the abundant mass‐flowering probably attenuated their diffuse competitive pressure on all other pollinators, even though the foraging overlap was higher in this period. In this period of high abundance of floral resources, specialist pollinators capable of expanding the realised niche are active. Based on recent theoretical conclusions of dynamic model of mutualistic networks structure that incorporated effects of inter‐specific competition and adaptive foraging, we argue that the adaptive foraging of generalist and abundant stingless bees contributes in an important way to the high nestedness and robustness of networks, which ultimately favour the coexistence of species in the long term. Particularly, taking the high intra‐annual turnover of bee and plant species between the two seasons, and the similar floral constancy of both generalist stingless bees and specialist pollinators, we also infer that stingless bees act as generalised pollinators in the networks rewiring throughout the year.

Fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna

AbstractFire‐dependent savanna provides key habitat for butterflies globally, but we know little about how fire regimes, including fire frequency and season, affect them. These impacts are likely to be primarily indirect, through changes in overall habitat structure, the abundance of larval host plants, and/or the provision of nectar resources for adults. We examined the relationships among fire regime, butterfly abundance and diversity, and vegetation structure and floral resources within a long‐term fire experiment near Darwin in the Australian monsoon tropics. We surveyed butterflies and floral resources throughout the 2019–2020 wet season in three replicate plots of each of six experimental treatments that had been operating for 15 years. All plots subject to fire had been burned in the previous dry season. We observed 24 butterfly species and 280 individuals representing all five butterfly families found in Northern Australia. Butterfly abundance was highest under early dry‐season (June) fire regimes (mean = 11.9 individuals per plot survey) compared with a late dry‐season (October) regime (mean = 6.7) and in the long‐term absence of fire (mean = 5.3), and this was correlated with the abundance of floral resources. The distribution of butterflies was also highly associated with floral resources within plots regardless of fire treatment. Butterfly species richness was significantly higher in early dry‐season (mean = 6.8) compared with unburned (mean = 3.3) plots but did not differ between early and late dry‐season (mean = 4.7) plots. Butterfly and floral diversity were similar across all early dry‐season fire treatments regardless of whether they had been burned every 1, 2, 3, or 5 years. Our finding that early dry‐season burning promotes butterfly diversity and abundance by increasing the supply of nectar resources has important implications for biodiversity management more broadly, given that nectar is a critical resource for many animal taxa.

A review and field verification of avian diversity and habitat use in the greater Sundarbans of India, Bangladesh and their hinterland

<p>The world-famous greater Sundarbans, the largest single block of tidal halophytic mangrove forest in the world and endangered ecosystem located in the Bengal delta, is now confined to 10,277 km<sup>2</sup>conservation areas in India (4260 km<sup>2</sup>) and Bangladesh (6017 km<sup>2</sup>) over 250 odd-islands, designated as the Natural World Heritage-cum-Ramsar Sites of ornithological importance. The Sundarbans is fringed by 11,936.26 km<sup>2</sup> reclaimed agricultural fields/human settlements [‘Sundarbans Transition Zone’ (STZ), India and Ecologically Critical Areas (ECAs) plus Sundarbans Impact Zone (SIZ), Bangladesh]. This highly productive ecosystem provides diverse and abundant floral and faunal food resources, having high caloric concentrations, for the aves. A comprehensive study was conducted during 2019–2022 to bridge the knowledge-gaps of the avian diversity and habitat use through structural review of published and grey literature as well as field-based rapid assessment in the potential sites. 598 species, classified under 23 orders, 85 families and 277 genera, including seven extinct and about 40 old records, have been recorded in the study area. The terrestrial, arboreal and aquatic habitats are conveniently utilised by 32% resident and 68% migratory (summer and winter) birds for meeting their biological needs. 32.27% of them are commonly sighted and 67.73% rarely confronted. Considering the present biotic and abiotic threats, the rare birds are of high priority for future conservation actions.</p>

Evaluating remnant vegetation management practices adjacent to apple orchards to support native bee pollinators

SummaryMaintenance of a diverse pollinator community helps ensure resilience in pollination services. Fragments of woody and grassy vegetation in the vicinity of croplands have been shown to encourage the presence of crop‐pollinating bees. However, to date, little attention has been given to the management practices that may enhance the presence of bees in such fragments. We investigated how the maintenance of remnant forest fragments adjacent to apple orchards in South Australia affects floral resources and native bee communities. The fragments had been subject to either (a) fire (assessments three years post‐burn), (b) cattle grazing under trees and (c) low maintenance management (>20 years not grazed or burnt). Plant communities were sampled along transects in plots. Bee communities were sampled using hand netting. We fitted generalised linear mixed models to investigate differences in plant and bee diversity between treatments and to elucidate the effect of plant diversity on bee diversity. We compared plant and bee community composition among treatments using non‐metric multidimensional scaling and conducted network analysis to measure the robustness of plant‐pollinator interactions to the removal of species. Both floral resource abundance and bee diversity were higher in burnt and low‐maintenance fragments than in grazed fragments. Bee species richness was positively associated with plant species richness. The species richness of bees that visit apple flowers was positively associated with flower abundance but not with floral species richness. Plant‐pollinator networks in grazed sites had fewer links per species and a higher proportion of realised links than those under other management practices. However, the resilience of pollinator networks did not differ significantly between management practices. Thus, controlled burns or low‐maintenance management of forest fragments appear to be the most suitable landscape management practices to support apple pollinating bees. Burning requires consideration of additional ecological consequences, such as the conservation of fire‐sensitive species and specialist woodland fauna. Cattle grazing adjacent to orchards results in simplified bee communities and pollination networks and is not recommended if pollination services are required for adjacent land uses. This information can benefit orchardist as well as managers of fragments of native vegetation adjacent to orchard crops.

Native vegetation embedded in landscapes dominated by corn and soybean improves honey bee health and productivity

Abstract Balancing demand for food while supporting biodiversity and ecosystem services in landscapes committed to crop production may require integrating conservation with agriculture. Adding strips of diverse, native, perennial vegetation, through the recently created prairie strips practice of the U.S. Conservation Reserve Program, into annual cropland reduces soil and nutrient loss, and supports more diverse and abundant communities of birds and insects, including native pollinators. It remains unclear if prairie strips can reverse declines in the health and productivity of the exotic honey bee in the U.S. This study determined if prairie strips provide floral resources to honey bees and support colony vigour, in a highly farmed landscape with limited perennial habitat. We hypothesized that honey bee health and productivity would be improved if given access to prairie strips, and this hypothesis was tested in a multi‐year, replicated, longitudinal study on commercial, conventional farms committed to corn and soybean production with and without prairie strips. We predicted that prairie strips would have more diverse flowering plants, and colonies located in these strips would be healthier and more productive than colonies kept at farms without purposefully established native vegetation (i.e. control fields). We found that prairie strips had more diverse flowering plants and abundant floral resources than control fields. Colonies kept at fields with prairie strips collected 50% more pollen during the growing season (June–September), had a 24% larger end‐of‐season worker bee populations, and 20% higher overwinter survival than colonies kept at control fields. Furthermore, colonies kept at prairie strips were 24% heavier when they reached their peak‐weight in August, an indicator of honey production. Honey bees collected pollen from flowering plants found in prairie strips, revealing the potential for interactions with wild pollinators. However, this was limited to 50% of the taxa in prairie strips, suggesting honey bees may not deplete all of the food resources simultaneously used by wild pollinators. Synthesis and applications. Our results suggest that efforts to enhance habitat diversity within croplands with native plants increase honey bee health and productivity while providing multiple additional ecosystem services important to agriculture.

Urbanization and abundance of floral resources affect bee communities in medium‐sized neotropical cities

AbstractBees are important pollinators that have been negatively impacted by anthropogenic environmental changes, such as urbanization. In addition, urban development can reduce and degrade the natural habitat of bees by increasing the proportion of impervious surfaces, decreasing green areas and increasing the number of exotic ornamental plants. However, cities can provide refuge for bees because they provide an environment with a wide variety of nesting and foraging resources. The objective of our study was to evaluate the richness and abundance of bees, their respective functional groups, and community composition along with an urbanization gradient in 21 locations distributed among six medium‐sized Brazilian cities (with populations between 80 000 and 170 000 inhabitants). We also evaluated the effect of richness, number of plants and proportion of native plants. We collected a total of 132 species of bees. Total bee richness decreased with increasing impervious cover and increased with landscape heterogeneity, which also had a positive effect on the richness of above‐ground nesting bees and generalist bees. Regarding abundance data, solitary bees and belowground‐nesting bees were positively influenced by the increase in grass cover. The total number of native and exotic plants collected positively influenced the total abundance of bees, as well as the abundances of eusocial bees, which nest above‐ and belowground, and generalists. The proportion of native plants positively influenced the total richness and abundance of specialist bees. Our results indicate that medium‐sized urban areas may be home to a wide diversity of bee species, but species that nest in the soil and specialist species may be more sensitive to urbanization and the decrease in the supply of floral resources.

The influence of field margin characteristics on syrphid abundance

Field margins have an important ecological role in agroecosystems including hosting beneficial insect such as syrphids. However, little is known of syrphid preferences for different types of field margins. Syrphids were sampled in field margins in an organic agroecosystem to test the hypothesis that syrphid abundance in field margins depends not only on the floral resource abundance but also on field margin component type, field margin complexity, and adjacent land-use type. Floral resource abundance had the greatest influence on the number of syrphids surveyed. Field margin characteristics were deemed to effect syrphid abundance both independently of their effect on floral resources and by altering floral resource abundance. Syrphids were more abundant in field margins adjacent to cropped fields than those adjacent to grazed fields or roads. More syrphids were found in ditch components than in tree or grass strip components. The influence of floral resources on syrphid abundance varied depending on their botanical families, although no significant differences were observed for the effect of botanical family floral resource index on syrphid abundance. These findings demonstrate that field margin characteristics play an important role in facilitating plant–syrphid interactions and offer an insight in agroecosystem management for the promotion of beneficial insects. The influence of field margin characteristics on other beneficial insect groups should also be investigated.

Evaluating the effects of observation period, floral density, and weather conditions on the consistency and accuracy of timed pollinator counts

Insect pollinators are experiencing substantial declines as a result of habitat loss, agricultural intensification, invasive pests, and climate change. To investigate factors causing pollinator declines, evaluate the success of conservation measures, and institute long-term monitoring schemes, it is essential to validate and standardize pollinator sampling techniques. This study investigated how sampling duration, weather conditions, and abundance of floral resources influenced the results of timed pollinator counts by repeatedly sampling the same pollinator assemblage in an Irish meadow. The likelihood of detection of Apis mellifera, Bombus spp, solitary bees, and Syrphidae was strongly associated with the density of floral units or floral cover in the observation plot. Also, even though protocol criteria restricted pollinator counts to the middle of the day and benevolent weather, pollinator counts were strongly influenced by factors such as cloud cover, light levels, wind speed and relative humidity. Increasing the duration of the timed counts from 5-minutes to 30-minutes considerably increased the probability of detection of each pollinator group. Additionally, the perceived diversity of the pollinator assemblage at the meadow was markedly affected by sampling duration and floral abundance. To improve the consistency or comparability of studies using timed pollinator counts, we recommend that criteria are set restricting surveys to narrow ranges of weather conditions and floral density when possible. Additionally, pollinator field investigations or monitoring programs would benefit from a systematic evaluation of how erroneous non-detection of target taxa can be reduced to acceptable levels by modifying sampling duration.

Climate driven disruption of transitional alpine bumble bee communities.

Pollinators at high elevations face multiple threats from climate change including heat stress, failure to phenological match advancing flower resources and competitive pressure from range-expanding species of lower elevations. We conducted long-term multi-site surveys of alpine bumble bees to determine how phenology of range-stable and range-expanding species is responding to climate change. We ask whether bumble bee responses generate mismatches with floral resources, and whether these mismatches in turn promote community disruption and potential species replacement. In alpine environments of the central Rocky Mountains, range-stable and range-expanding bumble bees exhibit phenological mismatches with flowering host plants due to earlier flowering of preferred resources under warmer spring temperatures. However, workers of range-stable species are more canalised in their foraging schedules, exploiting a relatively narrow portion of the flowering season. Specifically, range-stable species show less variance in phenology in response to temporally and spatially changing conditions than range-expanding ones. Because flowering duration drives the seasonal abundance of floral resources at the landscape scale, we hypothesize that canalisation of phenology in alpine bumble bees could reduce their access to earlier or later season flowers. Warmer conditions are decreasing abundances of range-stable alpine bumble bees above the timberline, increasing abundance of range-expanding species, and facilitating a novel and more species-diverse bumble bee community. However, this trend is not explained by greater phenological mismatch of range-stable bees. Results suggest that conversion of historic habitats for cold-adapted alpine bumble bee species into refugia for more heat-tolerant congeners is disrupting bumble bee communities at high elevations, though the precise mechanisms accounting for these changes are not yet known. If warming continues, we predict that the transient increase in diversity due to colonization by historically low-elevation species will likely give way to declines of alpine bumble bees in the central Rocky Mountains.

Effects of neonicotinoid seed treatments on wild bee populations in soybean and corn fields in eastern Ontario

Abstract Neonicotinoid‐coated corn and soybean seeds are a common crop in Canada and the US. A growing body of research is demonstrating that, through various exposure routes, neonicotinoids can impact a suite of nontarget organisms including beneficial insects such as bees. However, to date, only a few studies have examined the effects of neonicotinoids in field settings. We assessed the relationship between agricultural crop soil neonicotinoid levels and wild bee abundance and diversity at 16 agricultural sites representing different soil neonicotinoid levels. We detected clothianidin at 11 sites, thiamethoxam at three sites; imidacloprid was not detected. Hedgerow and crop soils were consistent in terms of where clothianidin was detected; thiamethoxan was not detected in hedgerow soils. Based on model outcomes, fields with higher levels of soil neonicotinoids exhibited significantly lower wild bee abundance and diversity than those with low or no neonicotinoids detected. Crop soil neonicotinoid level, hedgerow floral resource abundance and crop type were consistent predictors of bee abundance across models; only neonicotinoid level and crop type were significant predictors of diversity. Our results are consistent with recent findings in the midwestern US, and underscore the potential risk of soil neonicotinoids to wild bee populations across regions and crop systems.

Threats and benefits of invasive alien plant species on pollinators

Invasive alien plant species are usually disliked due to their high pressure on native communities. However, their ecological effects on pollinators are complex: some species provide abundant floral resources, boosting the number of pollinators, while they often disrupt plant-pollinator interactions by outcompeting native plants. Our direct knowledge is mainly based on single-species studies, while understanding the mechanism of these complex ecological interactions needs multi-species field-based approaches. It is also imperative to clarify the pros and cons of invasive plants and drivers of invasion from the perspective of pollinators. We conducted a standard protocol-driven regional study in Central and Eastern Europe, comparing 6-7 invaded and non-invaded sites of 12 herbaceous invasive plant species. We sampled floral resources, bees, and hoverflies before and during the flowering of the invasive plants. We analysed the effects of plant invasion at the invasive plant species level and in combined analyses, and tested whether the life span (perennial vs. annual) and flowering time (early-, middle-, and late-flowering) of invasive plants affect the abundance, species richness, diversity and species composition of native plants and pollinators. The combined analyses showed lower abundance and species richness of flowering plants and pollinators before, and higher abundance of both during the flowering of invasive plants in invaded sites. However, invasive plants had significant species-specific effects. Perennial invasive plants had a stronger negative impact on floral resources and pollinators already before their flowering compared to annuals. Flowering time of invasive plants affected the pollinator guilds differently. We suggest that in certain critical time periods of the year, invasive plants might provide the dominant foraging resources for pollinators in an invaded ecosystem. But, they also often cause significant losses in native floral resources over the year. Instead of simple eradication, careful preparation and consideration might be needed during removal of invasive plants.

Grassy–herbaceous land moderates regional climate effects on honey bee colonies in the Northcentral US

The lack of seasonally sustained floral resources (i.e. pollen and nectar) is considered a primary global threat to pollinator health. However, the ability to predict the abundance of flowering resources for pollinators based upon climate, weather, and land cover is difficult due to insufficient monitoring over adequate spatial and temporal scales. Here we use spatiotemporally distributed honey bee hive scales that continuously measure hive weights as a standardized method to assess nectar intake. We analyze late summer colony weight gain as the response variable in a random forest regression model to determine the importance of climate, weather, and land cover on honey bee colony productivity. Our random forest model predicted resource acquisition by honey bee colonies with 71% accuracy, highlighting the detrimental effects of warm, wet regions in the Northcentral United States on nectar intake, as well as the detrimental effect of years with high growing degree day accumulation. Our model also predicted that grassy–herbaceous natural land had a positive effect on the summer nectar flow and that large areas of natural grassy–herbaceous land around apiaries can moderate the detrimental effects of warm, wet climates. These patterns characterize multi-scale ecological processes that constrain the quantity and quality of pollinator nutritional resources. That is, broad climate conditions constrain regional floral communities, while land use and weather act to further modify the quantity and quality of pollinator nutritional resources. Observing such broad-scale trends demonstrates the potential for utilizing hive scales to monitor the effects of climate change on landscape-level floral resources for pollinators. The interaction of climate and land use also present an opportunity to manage for climate-resilient landscapes that support pollinators through abundant floral resources under climate change.

Spatially discrete disturbance processes enhance grassland floral resources

Abstract Grasslands provide essential floral resources for both managed and wild pollinators. However, grassland flowers in remaining native landscapes are threatened due to non‐native plant invasions and alterations to historic disturbance regimes such as fire and grazing. The potential for managed disturbance to promote grassland floral resources remains unclear. Fire and grazing historically occurred interactively, but uniform application of each may be a detriment to floral resources and the pollinators depending on them. Though fire can increase resources available to plants and stimulate flowering, it initially destroys floral resources and may delay flower availability. Similarly, grazing removes competitors of flowering plants, but destroys flower heads. To address this knowledge gap, we investigated the impacts of rotational fire and cattle grazing (patch‐burn grazing with one and two seasons of fire per year) versus traditional season‐long grazing with no fire on floral resources in mixed‐grass prairie. In patch‐burn treatments, part of each pasture is burned each year, which focuses grazing activity due to the high‐quality regrowth. We aimed to use fire to remove litter around flowering plants while also sheltering established flower heads from grazing pressure by directing cattle away from regenerating forbs in unburned portions of the landscape. Over two summers, we performed weekly flower surveys in season‐long grazing and patch‐burn grazing pastures. We analysed total seasonal floral resources, maximum floral abundance and seasonal species richness between treatments. Over 2 years, we surveyed 1,238,241 ramets of 160 species, focusing on 36 common species for individual analysis. We found broad positive associations between patch‐burn grazing and total seasonal flower abundance, maximum flower abundance and species richness compared to traditional management. In most cases, patch‐burn grazing with dormant and growing season fires produced higher floral abundance, total seasonal floral resources and species richness than patch‐burning with dormant season fires alone, suggesting benefits of increased levels of pyrodiversity. Synthesis and applications. Under increasing pressure to manage for declining pollinators, rangeland managers must consider strategies to enhance floral resources within the context of livestock production goals. The spatiotemporal interaction of cattle grazing and fire shows promise for promoting floral resource abundance and diversity.

Temporal Variation in Pollinators’ Visitation of Lantana camara in a Tropical Urban Landscape: Does Butterfly Abundance and Richness Drive the Fruit Set?

Abstract Pollinator richness, abundance and visitation frequency may be affected by the abundance of floral resources and abiotic factors, influencing plant reproductive success. We analysed whether the diversity, abundance and frequency of butterfly visitation on Lantana camara vary across the year in a tropical urban landscape and whether this variation in butterfly community influences plant’s reproductive success. A two-period survey, referred to here as rainier and drier seasons, was carried out in 12 spatially independent plants. Five pollination treatments were applied: single visit, hand cross-pollination, hand self-pollination, spontaneous self-pollination and open pollination (control). A total of 15,749 flowers were used for fruit production analysis. Butterfly richness, abundance and the reproductive success of L. camara increased in the drier season. Open pollination was ninefold more reproductively successful during the drier season. Fruit production of hand cross-pollinated plants was threefold higher than open-pollinated plants during the rainier season. No significant difference was found between these treatments in the drier season, attesting the highest abundance of pollination during this period. We provide evidence that changes in the pollinator community affect fruit production. The increase in pollinator diversity allows different visitors to pollinate the plant, increasing fruit set through functional complementarity. This effort establishes baseline data of plant–pollinator interactions for further long-term investigations across different weather seasons. The understanding of L. camara and butterflies’ synergism will support conservation measures of pollinator populations.

Exploring multifunctionality of summer cover crops for organic vegetable farms in the Upper Midwest

AbstractIntensive vegetable crop rotations can have detrimental effects on soil health, draining soil of organic matter reserves and necessitating nitrogen (N) inputs. In addition, many vegetable crop rotations leave little time or space to integrate beneficial arthropod and pollinator habitat into crop rotations; the lack of habitat may cause declines in beneficial arthropods, which can lead to insufficient pollination services and increased pest pressure. Nine treatments, each containing one to seven species of cover crops, were evaluated for flowering, aboveground biomass production and N content, soil${\rm NO}_3^-$-N contribution after biomass incorporation, and beneficial arthropod visitation. A seven-species mix composed of oat (Avena sativaL.), field pea (Pisum sativumsubsp.ArvenseL.) and five clover species (Trifoliumspp.) added the largest amount of biomass (8747 kg ha−1). Likewise, this mix contributed the most organic N (265.6 kg N ha−1), and increased soil${\rm NO}_3^-$-N after biomass incorporation (10.9 mg${\rm NO}_3^-$-N kg−1of soil). Buckwheat (Fagopyrum esculentumMoench) and phacelia (Phacelia tanacetifoliaBendth.) monoculture produced most abundant floral resources. Beneficial arthropods observed included pollinators (native, honey and bumblebees), predators (syrphid flies and green lacewings) and parasitoids. Increased floral diversity was associated with abundance of flies in the Syrphidae family. Phacelia monoculture was most attractive for bees in the Apidae and Halictidae family, both of which may provide pollination services. These results highlight floral visitation patterns as an indicator for beneficial insect community support and conservation, especially in summer months, when greater insect reproduction occurs. Summer-planted cover crops are an underexplored rotation option for organic farming systems in the Upper Midwest, and may provide a wide range of ecosystem services including increases in available soil N and beneficial arthropod populations.