Floral Resources Research Articles

Different semi-natural habitat types provide complementary nesting resources for wild bees

Semi-natural habitats provide refuge for pollinating insects such as wild bees. Different types of semi-natural habitat can provide complementary floral resources throughout the year, but it is uncertain to what extent different semi-natural habitat types provide nesting habitat for wild bees. In this study, nesting resources for wild bees and nest-searching bees were surveyed visually in three different types of semi-natural habitat (i.e., hollow roads, tree rows, and forest edges). The composition of nesting resources for wild bees varied across the three types of semi-natural habitat. We also identified clear indicators of nesting resources within the different habitat types. We conclude that different types of semi-natural habitat provide varying and complementary nesting resources for wild bees. This study further highlights the importance of semi-natural habitat for pollinator conservation and emphasizes the need for further research to increase our understanding how different wild bee species use different habitat types for nesting.

Nutrient enrichment and rainfall affect plant phenology and floral resource availability for pollinators

Wild pollinators are critical to maintaining ecosystem services and facilitating crop production, but habitat degradation and resource loss are leading to worldwide pollinator declines. Nutrient enrichment and changes in rainfall due to global warming are drivers of global environmental change, and likely to impact pollinator foraging behavior and reproductive success through changes to the growth and phenology of flowering plants. Here, we provide a short review of pollinator conservation in the context of nutritional ecology and plant-pollinator interactions. Then, we present novel research into the effects of nutrient and rainfall variation on plant phenology. In this study, we experimentally manipulated the amount of water and supplemental nutrients available to wild sunflower (Helianthus annuus) and goldenrod (Solidago spp.) throughout their growing season. We evaluated how changes in growth and bloom time could impact resource availability for bumble bee (Bombus impatiens) queens preparing to overwinter. We found that fertilizer and rainfall alter plant bloom time by 2–18 days, though flowering response was species-specific. Fertilizer did not significantly affect plant growth or number of flowers produced when plants were grown under drought conditions. When water was not limiting, fertilized sunflowers bloomed in floral pulses. These findings carry important implications for growers and land managers, providing insight into potential drivers of wild pollinator decline and possible conservation strategies.

Responses of hover fly diversity and abundance to urbanisation and local attributes of urban greenspaces

Urban greenspaces are vital refugia for insect biodiversity, but seasonal fluctuation responses of insect taxa to urbanisation and local attributes of urban greenspaces are not well known. Regions with mild temperate climates and winter-flowering plants have active winter pollinators that are often neglected. A thorough knowledge of the seasonally fluctuating ecological needs of insects is essential for adequate insect-friendly greenspace management. Hover flies are cosmopolitan inhabitants of urban greenspaces where they provide multiple critical ecosystem services such as pollination and pest control. Our study uses a multi-scale approach to determine the seasonal effects of urbanisation on hover fly richness, abundance, and assemblages in urban greenspaces. We selected 30 sites along an urbanisation gradient (as measured by human population density) in Sydney, Australia, and sampled each site over a year across seasons. We found that hover fly species richness was higher in winter and spring than in summer, while abundance was highest in winter and lowest in summer. Our results also show that a combination urbanisation and local attributes of urban greenspaces (flower richness, flower abundance, human population density, and proportion of native flowers) combined to affect hover fly species richness and abundance in seasonally dependant ways. Hover flies are especially abundant and diverse during winter- a time of the year when other native floral visitors are less active. Thus, hover flies may be important pollinators of the large community of winter-flowering plants in Australia. Urban greenspaces can be made more hospitable to hover flies by implementing simple management initiatives, such as complementing native floral resources with non-native flowers in periods of scarcity.

Fungicide Scent Pollution Disrupts Floral Search-and-Selection in the Bumblebee Bombus impatiens

Bumblebees are valuable generalist pollinators. However, micro- and macro-stressors on bumblebees negatively impact both foraging efficiency and pollination efficacy. Given that colonies have a resource threshold for successful reproduction, factors that decrease foraging efficiency could negatively impact conservation efforts. Recently, agrochemical odor pollution has been shown to hinder floral odor learning and recognition in Bombus impatiens via an associative odor learning assay (FMPER). These results may have implications for the field foraging behavior of bumblebees. Building on this prior work, our study aimed to determine if negative effects of fungicides on associative odor learning and recognition scale up to negative impacts on actively foraging bumblebees. These experiments investigated whether the presence of a background fungicide odor (Reliant® Systemic Fungicide) impacts the location of a learned floral resource (lily of the valley-scented blue flowers) in a wind tunnel. Experiments were run with and without early access to visual cues to determine if fungicide odor pollution is more impactful on bees that are engaged in olfactory versus visual navigation. Fungicide odor pollution reduced landing frequency in both paradigms.

Native and introduced pollinators vary in their seasonal floral resource visitation and selection between native and exotic plant species

Abstract Anthropogenic pressures on native ecosystems have resulted in numerous functional and compositional changes, creating novel ecosystems with new interactions between native and exotic species. How native species utilize these resources is crucial for their management in altered landscapes and the promotion of their essential ecosystem services. We compared seasonal floral selection between European honey bees and their most phylogenetically similar native component in our study region, bumble bees, in North American grasslands with high densities of exotic plant species. Additionally, we determined whether floral species richness, total flowering density, native floral density or exotic floral density best explained the abundance of both groups. Selection analyses revealed that honey bees and native bumble bees differed in selection between native and non‐native floral resource availability, with any significant selection of honey bees being for exotic plants while native bumble bees selected for native plants. Native forb presence and floral richness best explained the variation in bumble bee abundance, while honey bee abundance was associated with flowering densities in the early and mid‐seasons and floral richness in both the early and late seasons. Despite their generalist diets, we emphasize the importance of native floral availability for bumble bee foraging in novel grassland landscapes and the importance of exotic plants to support honey bee production. Synthesis and applications. Our results indicate that pollinator forage management should differ for non‐native and native species, despite morphological and life‐history similarities. However, greater floral diversity provides a common management focus that can benefit honey bees and bumble bees in particular seasonal periods. Our results suggest that management actions promoting resource diversity can benefit functionally different species. In grasslands, implementing disturbance processes that can favour floral expression (e.g. fire; grazing) can support bumble bees of conservation concern and agriculturally important bees simultaneously.

Pollination of urban meadows – Plant reproductive success and urban-related factors influencing frequency of pollinators visits

Pollination is a key ecological service for human food security and the reproduction of the majority of flowering plants. This plant-animal interaction is crucial in both wild and urban habitats, however, increasing urbanization and change in land use alter these interactions. The concerns regarding pollination have led to numerous efforts aimed at improving the quality of wildlife in cities, however, understanding the importance of these activities warrants further research. In Warsaw, the Polish capital, we analyzed the influence of urban-related factors such as floral resource richness, the proportion of green areas in the proximity of foraging sites, air pollution or temperature on plant-pollinator interaction in 14 meadows. We also analyzed the reproductive success and the heterospecific pollen transfer in the case of plants growing in the meadows. Our study revealed that the frequency of visits to flowers was related to city-related factors, but the reaction varied among different groups of pollinators. For example, bumblebees were negatively influenced by higher air pollution, while the rest of the flower visitors were not, Syrphidae flies were more frequent flower visitors when the proportion of green area was higher in the buffer of 150 m, while we did not observe this tendency in other groups of flower visitors. Plants growing in Warsaw meadows were frequently visited and effectively pollinated - urban pollinator assemblages seem to provide sufficient pollination services to plants growing in the city. Species-rich communities were not a threat to pollination; we found mostly conspecific pollen grains on the stigmas of the studied plant species. The results of our study show that species-rich communities make a valuable contribution to pollinator conservation. The conservation activities, however, should be adjusted to the target group of pollinators, since different groups of flower visitors respond differently to urban-related factors studied.

Collection of floral resources by bees in Solanum lycocarpum A.St.-Hil. (Solanaceae): interference of abiotic factors and need for buzzing behavior

The foraging activity of floral visitors is influenced by habitat conditions and abiotic factors. The aim of this research was to define the faunal composition of the visitor community in Solanum lycocarpum A.St.-Hil. (Solanaceae) and to evaluate the influence of abiotic factors on the flight activity of the predominant visitors. The capture of bees was conducted for 15 minutes from the beginning of each hour between 6:00 am and 6:00 pm in a cluster with 15 S. lycocarpum individuals during 10 days. Centridini was the predominant tribe of bees, with 83.5% of the total foraging recorded. About 66.5% of foraging was concentrated in the time interval between 8:00 am and 12:59 pm, characterized as a optimal foraging period. At 6:00 am and from 5:00 pm onwards, bees were discouraged from foraging. Only Epicharis flava Friese and Centris scopipes Friese were classified as predominant species. Centris scopipes was the only predominant species whose abiotic conditions interfered in the foraging activities. Since bee foraging records were developed in the summer, environmental conditions did not limit the foraging of most bees during the entire foraging period of the day.

Foraging distances, habitat preferences and seasonal colony performance of honeybees in Central European forest landscapes

Abstract Unmanaged forest is considered as native habitat of the Western honeybee Apis mellifera and is assumed to provide important pollen and nectar sources. However, resource supply might be spatially and temporally restricted in managed forests and landscape‐scale studies in European forest regions are currently lacking. Capitalizing on a unique communication behaviour, the waggle dance, we investigated honeybee foraging in a deciduous forest region in southern Germany. We analysed 2022 waggle dances performed by bees of 12 colonies placed in the centre of landscapes with varying degree of forest cover (50%–99% at a 2‐km radius) from March to August 2019, thereby identifying foraging distances and habitat preferences over almost an entire foraging season. By connecting dance information with colony weight recordings, we assessed the role of landscape composition and the contribution of different habitat types to colony weight gain. Foraging distances generally increased with the amount of forest in the surrounding landscape pointing to inferior food resources in the forest. Yet, this effect strongly depended on the season and was more pronounced for pollen than for nectar foraging. Even though colonies in forest‐dominated landscapes had to fly further, colony weight was not significantly affected by forest cover. Compared to expectations based on the proportions of different habitats, colonies foraged more frequently in grassland and cropland than in deciduous and coniferous forests, with late summer being an especially difficult period for pollen foraging in forests. During a phase of colony weight gain in early summer, the use of forests for nectar/honeydew foraging was close to the expectation, highlighting forests as an important complementary source of carbohydrates during short periods of the year. Policy implication. The ecological and economic value of managed forest as habitat for honeybees could be significantly increased by the continuous provision of floral resources, especially for pollen foraging. Therefore, we recommend diversifying forest stands with insect‐pollinated trees, permitting secondary successions in forest gaps, and at larger scales, creating forest landscapes with high habitat diversity. This will not only help native, wild‐living honeybees and beekeepers' colonies residing in forest areas but will also foster social bees in general.

Bumblebee flower constancy and pollen diversity over time.

Bees often focus their foraging effort on a few or even a single flower species, even if other equally rewarding flower species are present. Although this phenomenon-called flower constancy-has been widely documented during single foraging trips, it is largely unknown if the behavior persists over longer time periods, especially under field conditions with large temporal variations of resources. We studied the pollen diet of individuals from nine different Bombus terrestris colonies for up to 6 weeks, to investigate flower constancy and pollen diversity of individuals and colonies, and how these change over time. We expected high degrees of flower constancy and foraging consistency over time, based on foraging theory and previous studies. Instead, we found that only 23% of the pollen foraging trips were flower constant. The fraction of constant pollen samples did not change over the study period, although repeatedly sampled individuals that were flower constant once often showed different preferences at other sampling occasions. The similarity of pollen composition in samples collected by the same individuals at different occasions dropped with time. This suggests that the flower preferences change in response to shifting floral resources. The average diversity of pollen from single foraging trips was around 2.5 pollen types, while the colony-level pollen diversity was about three times higher. How rapidly preferences change in response to shifting resources, and if this differs between and within bee species depending on factors such as size, should be the focus of future research.

The expansion of agriculture has shaped the recent evolutionary history of a specialized squash pollinator

The expansion of agriculture is responsible for the mass conversion of biologically diverse natural environments into managed agroecosystems dominated by a handful of genetically homogeneous crop species. Agricultural ecosystems typically have very different abiotic and ecological conditions from those they replaced and create potential niches for those species that are able to exploit the abundant resources offered by crop plants. While there are well-studied examples of crop pests that have adapted into novel agricultural niches, the impact of agricultural intensification on the evolution of crop mutualists such as pollinators is poorly understood. We combined genealogical inference from genomic data with archaeological records to demonstrate that the Holocene demographic history of a wild specialist pollinator of Cucurbita (pumpkins, squashes, and gourds) has been profoundly impacted by the history of agricultural expansion in North America. Populations of the squash bee Eucera pruinosa experienced rapid growth in areas where agriculture intensified within the past 1,000 y, suggesting that the cultivation of Cucurbita in North America has increased the amount of floral resources available to these bees. In addition, we found that roughly 20% of this bee species' genome shows signatures of recent selective sweeps. These signatures are overwhelmingly concentrated in populations from eastern North America where squash bees were historically able to colonize novel environments due to human cultivation of Cucurbita pepo and now exclusively inhabit agricultural niches. These results suggest that the widespread cultivation of crops can prompt adaptation in wild pollinators through the distinct ecological conditions imposed by agricultural environments.

Floral resources in Swedish grasslands remain relatively stable under an experimental drought and are enhanced by soil amendments if regularly mown

Abstract One of the main reasons why insect pollinators are declining is a lack of floral resources. In agricultural landscapes, remaining seminatural grasslands play a key role for providing such resources. However, droughts pose an increasing threat to the abundance and continuity of flowers. Soil amendments are a novel management tool for Swedish grasslands aiming to increase carbon sequestration and soil water holding capacity. In this study, we examined how drought is affecting floral resources (i.e. floral units, nectar quantity and nectar continuity) in grasslands with different mowing regimes, and if soil amendments could mitigate potential negative drought effects. In summer 2019, we set up an experiment combining rain‐out shelters (‘drought’), soil amendments (‘compost’) and different mowing regimes (‘mown’ vs. ‘abandoned’) in four extensively managed Swedish grasslands (48 plots, size 2 m2). Between May and August 2021, we counted the floral units nine times in each plot. We derived values for the nectar sugar production per floral unit from an existing database. We observed a decrease in floral units under drought in the mown, but not in the abandoned plots. Nectar quantity and continuity over the season were not significantly affected by drought across both mowing regimes—in the abandoned plots the nectar provision even extended slightly in duration (towards late summer). The compost treatment had positive effects on the floral units, nectar quantity and continuity (extending it towards early summer) in the mown, but not in the abandoned plots. The plant species in our study reacted differently to the treatments. Most of the nectar was provided by only few species (mainly Lathyrus pratensis, Vicia cracca and Anthriscus sylvestris). The results are species specific, thus other plant communities might respond differently. However, our experiment shows that nectar provision (based on database values) in grasslands with a native plant community and natural soil conditions remains relatively stable under drought. We also found that soil amendments increase floral resources in managed grasslands.

A dataset of nectar sugar production for flowering plants found in urban green spaces

Abstract Nectar and pollen are floral resources that provide food for insect pollinators, so quantifying their supplies can help us to understand and mitigate pollinator declines. However, most existing datasets of floral resource measurements focus on native plants found in rural landscapes, so cannot be used effectively for estimating supplies in urban green spaces, where non‐native ornamental plants often predominate. We sampled floral nectar sugar in 225 plant taxa found in UK residential gardens and other urban green spaces, focussing on the most common species. The vast majority (94%) of our sampled taxa are non‐native, filling an important research gap and ensuring these data are also relevant outside of the United Kingdom. Our dataset includes values of daily nectar sugar production for all 225 taxa and nectar sugar concentration for around half (102) of those sampled. Nectar extraction was conducted according to published methods, ensuring our values can be combined with other datasets. We anticipate that the two main uses of these data are (1) to estimate the nectar production of habitats and landscapes and (2) to identify high‐nectar plants of conservation importance. To increase the utility of our data, we provide guidance for scaling nectar values up from single flowers to floral units, as is commonly done in field studies.

Floral resource maps: a tool to explain flower-visiting insect abundance at multiple spatial scales

Floral resource maps: a tool to explain flower-visiting insect abundance at multiple spatial scales

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.

Managed and unmanaged floral margins for the conservation of bee communities in intensive agricultural areas

Floral resources on crop field margins are a well-accepted measure to increase bee abundance in agricultural landscapes. However, studies have mainly focused on managed margins, while studies on the effect of unmanaged floral margins for the conservation of bees are still scarce. This work aims to test and compare the effects of three types of floral margins (managed herbaceous, managed shrubby, and unmanaged herbaceous) on the abundance and diversity of bees in order to propose a management strategy for the conservation of pollinating insects. Bee abundance was recorded by visual samplings in plots of 2 × 2 square meters over two years in the three margin types in four localities in southern Spain. The diversity of plant species and the flowers they supported were measured to explain the associated bee communities. Differences in the relative abundances of bee families and the number and abundance of bee genera were observed between margin types. Andrenidae was generally more abundant in the herbaceous margins regardless of whether these were managed or not. With the exception of the Halictidae, the majority of bees families (wild Apidae, Apis mellifera, Colletidae and Megachilidae) were more abundant in the managed than unmanaged margins. Moreover, the number of bee genera was higher in managed than in unmanaged margins. In addition, here we show that managed margins supported at least 30% more rare bee genera than unmanaged margins, highlighting the importance of floral margins management for the enhancement and conservation of bee communities, restoring habitat and food resources for pollinators across the Mediterranean agricultural landscape.

Floral enhancement of arable field margins increases moth abundance and diversity

Moth populations have declined across large parts of north-western Europe since the mid-20th century due, in part, to agricultural intensification. Agri-environment schemes (AES) are widely implemented across Europe to protect biodiversity in agricultural landscapes. Grass field margins enriched with wildflowers typically out-perform grass-only margins in terms of increasing insect abundance and diversity. However, the effect of wildflower enrichment on moths remains largely unstudied. Here, the relative importance of larval hostplants and nectar resources for adult moths within AES field margins are investigated. Two treatments and a control were compared: (i) a plain grass mix, the control, (ii) a grass mix enriched with only moth-pollinated flowers, and (iii) a grass mix enriched with 13 wildflower species. Abundance, species richness and Shannon diversity were up to 1.4, 1.8 and 3.5 times higher, respectively, in the wildflower treatment compared to plain grass. The difference in diversity between treatments became greater in the second year. There was no difference in total abundance, richness or diversity between the plain grass treatment and grass enriched with moth-pollinated flowers. The increase in abundance and diversity in the wildflower treatment was due primarily to the provision of larval hostplants, with nectar provision playing a smaller role. The relative abundance of species whose larval hostplants included sown wildflowers increased in the second year, suggesting colonisation of the new habitat.Implications for insect conservation.We show that, at the farm scale, moth diversity can be greatly enhanced and abundance moderately enhanced by sowing diverse wildflower margins, providing these insects with both larval hostplants and floral resources, compared to grass-only margins.

Trait‐based effects of plant invasion on floral resources, hoverflies and bees

AbstractPlant invasions can lead to homogeneous communities with decreased functional diversity. However, invasive plants, with various morphological and phenological traits, may drive pollinator communities in a less predictable, more complex way. They can promote pollinators compatible with their floral traits, while leaving others without foraging resources. Our observational study on 10 invasive herbaceous species applied a trait‐based approach to investigate plant invasion‐driven changes in floral resources, hoverfly and bee communities. We sampled invaded and non‐invaded (control) sites before and during the flowering of the invasive plants. We analysed the differences in floral traits between invasive and native plants, functional diversity and trait distributions of flower and pollinator communities between the invaded and control sites. Five invasive plant species differed from natives in floral traits. Plant invasion caused species‐specific changes in functional diversity and trait distributions of communities. For instance, invaded sites had a decreased functional diversity of hoverflies before flowering of invasive species, and larger hoverflies during flowering of invasive species compared with control sites. Smaller bees were associated with invasive plants with shallow flowers, while larger and long‐tongued bees were associated with two invasive species with restricted floral access. Similar to previous studies, pollinator traits showed mixed or neutral responses to plant invasion. This is probably due to the high integration capability of invasive plants into plant‐pollinator systems, or limitations in sampling, trait resolution, and unrevealed environmental factors. We provide recommendations for future studies to better understand the trait‐based community composition of flowering plants and pollinators.

The pollen virome: A review of pollen-associated viruses and consequences for plants and their interactions with pollinators.

The movement of pollen grains from anthers to stigmas, often by insect pollinator vectors, is essential for plant reproduction. However, pollen is also a unique vehicle for viral spread. Pollen-associated plant viruses reside on the outside or inside of pollen grains, infect susceptible individuals through vertical or horizontal infection pathways, and can decrease plant fitness. These viruses are transferred with pollen between plants by pollinator vectors as they forage for floral resources; thus, pollen-associated viral spread is mediated by floral and pollen grain phenotypes and pollinator traits, much like pollination. Most of what is currently known about pollen-associated viruses was discovered through infection and transmission experiments in controlled settings, usually involving one virus and one plant species of agricultural or horticultural interest. In this review, we first provide an updated, comprehensive list of the recognized pollen-associated viruses. Then, we summarize virus, plant, pollinator vector, and landscape traits that can affect pollen-associated virus transmission,infection, and distribution. Next, we highlight the consequences of plant-pollinator-virus interactions that emerge in complex communities of co-flowering plants and pollinator vectors, such as pollen-associated virus spread between plant species and viral jumps from plant to pollinator hosts. We conclude by emphasizing the need for collaborative research that bridges pollen biology, virology, and pollination biology.

Blooming Forbs Utilized by Breeding-Season Danaus plexippus in the USA North-Central Region

Danaus plexippus (monarch butterfly) populations in North America east of the Rocky Mountains are in decline due to loss of habitat containing Asclepias spp. (milkweed) and blooming forbs. To support D. plexippus recovery, habitat restoration efforts use seed mixes designed to maintain a diversity of species that bloom over the breeding and migration periods. The extent to which these species are uniquely attractive to foraging D. plexippus is unclear. We conducted observational studies at areas in Iowa USA with varying densities and diversities of Asclepias spp. and floral resources to help inform conservation management practices. Forty-two blooming forb species were present across four sites (2-4-ha) in Boone and Story counties from June through September in 2020. Many of the species present are commonly found in pollinator seed mixes. The number of blooming forbs species per site varied from 12 to 24 across the four months; the minimum and maximum density of species-specific inflorescences ranged from 8.45 to 36.3 inflorescence/m2. We observed D. plexippus nectaring on 27 of the 42 species across the sites. Based on total feeding events observed and the species-specific density of inflorescences, Asclepias syriaca, Asclepias verticillata, Helianthus grosseserratus, and Cirsium vulgare were favored for nectaring at each site where they were present. Additional species were favored in some, but not all, sites including Symphyotrichum pilosum, Eupatorium altissimum, Trifolium pratense, Echinacea pallida, and Verbena urticifolia. Findings suggest variation in preference may be due, in part, to site-specific and surrounding landscape features. Future studies on D. plexippus foraging behavior could address the interacting roles of habitat and landscape features, as well as species-specific flower size and shape, scent, nutrition, and nectar abundance. While forb utilization is likely influenced by site- and plant-specific features, preferred species we observed are typically included in recommended native seed mix designed to ensure blooms from June through September to support migratory and non-migratory, breeding D. plexippus.

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.