Floral Resources Research Articles

Factors driving bumble bee (Hymenoptera: Apidae: Bombus) and butterfly (Lepidoptera: Rhopalocera) use of sheared shrubland and young forest communities of the western Great Lakes.

In the northern Great Lakes region, the creation and maintenance of early-successional woody communities as wildlife habitat have increasingly become a conservation priority. The extent to which insect pollinators use these systems remains largely anecdotal. In summer (June-August) of 2021, we surveyed 49 early-successional sites in the western Great Lakes region treated with either shrub-shearing or silviculture (young forest) for bumble bees, butterflies, and habitat components (i.e., structural vegetation and floral resources). Hierarchical distance models predicted pollinator densities (λ^) to be, on average, λ^ = 84 bumble bees/ha and λ^ = 102 butterflies/ha. Although sheared shrubland and young forest communities supported comparable densities of bumble bees and butterflies, density was not equal across all sites. At the microhabitat scale, butterfly density and morphospecies richness were negatively associated with tall shrub cover and butterfly morphospecies richness (but not density) was driven by floral richness. Similarly, bumble bee density was positively associated with metrics of floral resources, underscoring the importance of blooming plants within these woody systems. Landscape covariates explained variation in butterfly density/richness but not bumble bee density. Ultimately, our results demonstrate that blooming plant abundance is an important driver of bumble bee and butterfly densities within these managed early-successional communities. Because early-successional woody communities are dynamic and their herbaceous openings are ephemeral, routine management would ensure that a variety of successional conditions exist on the landscape to meet the needs of bumble bees, butterflies, and potentially other insect pollinators.

The role of seasonality in shaping the interactions of honeybees with other taxa.

The Eltonian niche of a species is defined as its set of interactions with other taxa. How this set varies with biotic, abiotic and human influences is a core question of modern ecology. In seasonal environments, the realized Eltonian niche is likely to vary due to periodic changes in the occurrence and abundance of interaction partners and changes in species behavior and preferences. Also, human management decisions may leave strong imprints on species interactions. To compare the impact of seasonality to that of management effects, honeybees provide an excellent model system. Based on DNA traces of interaction partners archived in honey, we can infer honeybee interactions with floral resources and microbes in the surrounding habitats, their hives, and themselves. Here, we resolved seasonal and management-based impacts on honeybee interactions by sampling beehives repeatedly during the honey-storing period of honeybees in Finland. We then use a genome-skimming approach to identify the taxonomic contents of the DNA in the samples. To compare the effects of the season to the effects of location, management, and the colony itself in shaping honeybee interactions, we used joint species distribution modeling. We found that honeybee interactions with other taxa varied greatly among taxonomic and functional groups. Against a backdrop of wide variation in the interactions documented in the DNA content of honey from bees from different hives, regions, and beekeepers, the imprint of the season remained relatively small. Overall, a honey-based approach offers unique insights into seasonal variation in the identity and abundance of interaction partners among honeybees. During the summer, the availability and use of different interaction partners changed substantially, but hive- and taxon-specific patterns were largely idiosyncratic as modified by hive management. Thus, the beekeeper and colony identity are as important determinants of the honeybee's realized Eltonian niche as is seasonality.

Bad company expands in highland areas: Overlapping distribution, floral resources and habitat suggest competition between invasive and native bumblebees

Bad company expands in highland areas: Overlapping distribution, floral resources and habitat suggest competition between invasive and native bumblebees

The buzz around biodiversity decline: Detecting pollinator shifts using a systematic review

Climate and land use change are two of the largest drivers of worldwide biodiversity loss, but detecting drivers of insect decline is more complex. Online data sources can elucidate such responses while identifying systematic data gaps. Using a systematic review, we found 119 studies that document bumble bee and butterfly responses to climate change. While bee literature was limited, there is high confidence that species are emerging earlier (∼17days), mismatching with floral resources (100% of studies), and changing range distributions (-25%). More butterfly literature was available but did not yield consistent responses. Evidence shows earlier emergences (∼5days), decreasing range distributions (-19%), and population shifts amongst generalist (87% increase) versus specialist (65% decrease) groups. We argue that the effect of changing climates on floral emergence, abundance, and distribution may be more significant than the impact of climate change on biodiversity; however, further research is required, particularly within the Southern Hemisphere.

Drivers of cultivated and wild plant pollination in urban agroecosystems

Pollination is a vital ecosystem service in urban agriculture. Yet the environmental drivers of both crop and wild plant pollination in urban agroecosystems are still not well understood. Pollination experiments involve the manipulation of pollen transfer between plants, for instance, to study the effects of pollinators on fruit and seed production (pollination service). In this study, we conducted a pollination exclusion experiment using four experimental plants: two cultivated plant species, strawberry (Fragaria x ananassa) and chili pepper (Capsicum frutescens), and two wild plant species, buttercup (Ranunculus acris) and clover (Trifolium pratense). We placed experimental plants for over 20 days in 13 urban community gardens in Munich, Germany. We compared fruit and seed mass between “open” and “bagged” flowers and tested the effect of biotic factors (floral resources and pollinator diversity) and abiotic factors (urbanization, microclimate) on pollination service (fruit and seed mass) on the experimental plant species. For the two cultivated plants (F. ananassa and C. frutescens), we found that fruit and seed mass were both positively correlated with temperature and pollinator diversity. For the two wild plants (R. acris and T. pretense), we found that floral abundance was negatively related to R. acris seed mass but was positively related to T. pratense seed mass. In summary, we found that biotic and abiotic parameters affected the plant species studied here in different ways, suggesting that there may be synergies and trade-offs in what factors promote the overall pollination of urban plant communities. Our results suggest that gardeners can potentially increase the pollination services on certain garden plants by providing floral resources for pollinating insects.

Floral resources used by bees in urban areas: the case of Geneva, Switzerland

It is now largely recognized that pollinators are threatened in agricultural habitats. Cities are thus seen as potential refuges for pollinators, if suitable green spaces are available, because they present favorable abiotic conditions for many pollinator species. However, data on resources used by bees in urban habitats are scarce. Moreover, promoting indigenous meadows in urban green spaces could help pollinator’s survival. In this study, Apis mellifera was taken as a model to investigate potential difference in plant diversity used in agricultural and urban habitat. Pollen loads were sampled in 15 hives in both habitat types, using pollen traps. Then, the attractiveness of a melliferous meadow on wild bees was tested. To that end, a new seed mix (BF) including 35 indigenous plants producing nectar and/or pollen harvested by bees was developed and its attractiveness was compared to a seed mix widely used in Geneva (PFG). For most of the season, quantity and diversity of the pollen sampled was not significantly different between agricultural and urban habitats. Nevertheless, honey bees used different species in both habitats, probably because different plant communities are present. Sixty-one wild bee species were observed foraging in the new BF seed mix compared to only 47 species in the PFG. Likewise, more plants species were used in the BF seed mix than in the PFG. These results show that urban zones can be interesting for pollinators because they display diverse and abundant plant communities. Additionally, it shows that urban parks are species rich habitats, and that pollinator communities respond immediately to additional resources when available.

Spatio-temporal complementarity of floral resources sustains wild bee pollinators in agricultural landscapes

Targeted conservation and promotion of wild bees in agroecosystems requires understanding of relationships between different groups of bees and available floral resources across land-use types during the season and at the landscape scale. Here, we quantified floral resource amount and diversity across habitat types at different times during the season at the scale of entire landscapes (500 m radius) across 20 different agricultural landscapes. Moreover, we examined whether floral resource metrics obtained from these high-resolution floral resource maps are more suitable to assess and predict abundance and species richness of different bee pollinator groups, including rare species and important crop pollinators, sampled in these agricultural landscapes compared to traditional land-cover metrics. Floral resource availability shifted from flower-rich woody vegetation early in the season to herbaceous vegetation such as grasslands and crops later in the season, which was associated with a ten-fold decline in overall floral resource availability. Forest edges had highest per-area floral contributions in spring, whereas floral diversity of grasslands, in particular if extensively managed, was continuously high. Total wild bee species richness, as well as rare species richness and abundance of important crop pollinators, increased with floral resource availability and/or diversity contributed by forest edges and floral diversity of permanent grasslands. Rare bee richness was also positively related to floral resource amount provided by crops. Total bee richness and important crop pollinator abundance, but not rare bee richness, were positively related to overall floral resource amount, but not floral diversity, in the landscape. Floral resource maps based on floral resource supply by major habitat types early or late in the season predicted wild bee species richness (R2 =0.61) better than traditional descriptors of landscape composition such as proportion of semi-natural habitat. The pronounced temporal shifts in floral resource availability for pollinators from woody towards herbaceous vegetation during the season highlights the importance of taking a landscape-scale perspective on pollinator conservation. Our findings indicate that both rare bees and important crop pollinators benefit from complementary floral resources of forest edges and grasslands in agroecosystems. This reveals a potential synergy between the conservation of endangered species and the landscape scale management to promote pollination services. Our study also highlights that floral resource maps are useful tools in supporting more targeted pollinator conservation and pollination service management at the landscape level.

Flowering Time Variation in Two Sympatric Tree Species Contributes to Avoid Competition for Pollinator Services.

Competition is an important biological filter that can define crucial features of species' natural history, like survival and reproduction success. We evaluated in the Brazilian tropical savanna whether two sympatric and congenereric species, Qualea multiflora Mart. and Q. parviflora Mart. (Vochysiaceae), compete for pollinator services, testing whether there is a better competitor or whether plants present any anti-competitive mechanism. Additionally, we investigated the breeding system, pollinators, and flowering phenology of both species. The results showed that Q. multiflora and Q. parviflora are dependent on pollinators for fruit formation, as they exhibited a self-incompatible and non-agamospermic breeding system. These plants shared the same guild of pollinators, which was formed by bees and hummingbirds, and an overlap in the flower visitation time was observed. Each plant species had different pollinator attraction strategies: Q. multiflora invested in floral resource quality, while Q. parviflora invested in resource quantity. The blooming time showed a temporal flowering partition, with highly sequential flowering and no overlap. Qualea parviflora bloomed intensely from September to October, while Q. multiflora bloomed from November to January, with the flowering peak occurring in December. The two Qualea species have morphologically similar flowers, are sympatric, and share the same pollinator community, with overlapping foraging activity during the day. However, they do not compete for pollinator services as they exhibit an anti-competitive mechanism mediated by temporal flowering partition.

Effect of spontaneous vegetation on beneficial arthropods in Mediterranean vineyards

Habitat destruction and land use intensification are major causes of arthropod decline in agroecosystems. Arthropods are key organisms that are linked to many ecosystem functions and sustainability of agriculture. Using 37 vineyards in Southern France as a model system, we analysed which characteristics of spontaneous inter-row vegetation positively influence beneficial arthropods and pest insect predation. We specifically studied the effects of flower cover, grass cover, the ratio of perennials to annuals, plant species richness and extrafloral nectar on beneficial arthropod communities in vineyards. We used direct observation and net hunting to evaluate arthropod abundance. Sentinel cards with Lucilia sp. larvae were placed on grapevine plants to analyse caterpillar predation. We found that most groups of tested beneficial arthropods were positively influenced by flower cover and plant species richness. In particular, the abundance of predators such as ladybirds (adults and larvae) and crab spiders and the abundance of parasitic wasps were positively correlated to flower cover in vineyard inter-row vegetation. The abundance of ladybirds, hoverflies and crab spiders was also positively related to plant species richness. Our results demonstrated the importance of floral resources and plant diversity for beneficial arthropods and caterpillar predation confirming their key role in biological control of pest insects.

Wild bee response to forest management varies seasonally and is mediated by resource availability

In many temperate, deciduous forests, long-term management suppression has led to mesophication (cool, damp, and shaded conditions), resulting in habitat with homogenous composition and structure. Management approaches that emulate historical disturbance regimes (e.g., prescribed fire and thinning) have the potential to restore habitat heterogeneity, but effects on biodiversity remain poorly understood, especially for insects. Specifically, the ramifications of forest management practices for beneficial insects such as bees are unclear and rarely considered in management outcomes. Furthermore, the majority of bee studies in temperate, deciduous forests and do not consider how seasonality and management may interact to affect bee composition. To address these knowledge gaps, we sampled bees across spring and summer for two years in 28 plots comprised of non-treated control plots and three different treatment types (burn-only, thin-only, and the combination of both (thin-burn)). Our overall objective was to determine how bee communities respond to forest management and identify the primary predictors of community composition and structure. We found that bee communities varied across management types, with more intensely managed plots (thin-burn) consistently having the highest bee diversity and abundance. On average, more intensely managed plots had three times as many bees in comparison to control plots. Comparing spring to summer, we found that different resources predicted bee diversity and abundance. Most notably, floral resources predicted bee diversity in spring, while in summer, management type, as well as floral and nesting resources were most important. Surprisingly, deadwood did not predict bee diversity and abundance despite being a critical nesting resource. Overall, our results suggest that forest management practices that emulate historical disturbance regimes can affect bee communities, with more intense management enhancing abundance and diversity.

Diversity matters: Diet of Apis cerana in southeast India includes one consistently occurring and several seasonally available floral sources

Little is known about the agroecological implications of the Asian honey bee Apis cerana Fabricius in its vast native range including southeast India. To identify the foraging preferences of this generalist species, we collected 388 corbicular pollen samples over three years at Merveille, an eco-restoration site in Puducherry region, southeast India. Pollen was collected twice or thrice weekly from March 2018 to December 2021 in three locations within the site. We used canonical correspondence analysis to evaluate how average daily temperature, humidity and other meteorological changes over the years would influence A. cerana’s diet. We show that (1) A. cerana has a large dietary niche (87 pollen taxa), but essentially feeds on Cocos nucifera (all year long) and on Borassus flabellifer, Turnera, Acacia, Mollugo/Trianthema, Leucaena/Prosopis, Portulaca, Poaceae, Syzygium-t, Dodonaea viscosa and Boerhavia seasonally; these were most frequently and abundantly foraged at all locations. (2) In all locations, bees preferentially feed on arboreal plants (44 taxa). (3) Bees' pollen diet varies in composition according to seasons. It is also least diverse in the hottest and driest months (March-May) with 2–4 taxa against 7–13 taxa in other months. (4) In 2021, which was more humid and slightly cooler than 2018 and 2019, bee diet included more pollen of Cyperaceae, Dodonaea viscosa, Liliaceae and fallow land weeds such as Boerhavia and Mimosa pudica. In conclusion, corbicular pollen loads of Apis cerana provide a long and continuous record of the bee’s diet and its changes through time and space. The diet changed according to subtle changes in humidity and temperature as also drastic changes in rainfall at the study site, likely reflecting changes in the floral resource availability and the bees’ preference. The sustained presence of this bee species within its native ranges can be a bellwether of pollinator friendly habitats.

Osmophores and petal surface traits in Bignonieae species.

This study characterizes the osmophores and corolla traits in 18 species of Bignonieae Dumort., a Bignoniaceae tribe occurring in the Cerrado, a neotropical savanna in Brazil. To detect osmophore distribution, whole, newly opened flowers were immersed in Neutral Red Solution. Samples from the corolla tube and lobes were also fixed and analyzed micromorphologically, anatomically, and histochemically. The osmophores showed six markedly different distribution patterns that were not clearly associated with histological features. In most species, osmophores comprised papillose secretory epidermises and a few layers of subepidermal parenchyma. Starch grains, lipid droplets, and terpenes were detected in osmophores. An ornamented cuticle, cuticular folds, glandular and non-glandular trichomes, raised stomata and epicuticular wax granules are common traits in the species studied and may be useful in determining the taxonomy of the group. We found that 94% of the species visited by bees had papillose epidermises while the single hummingbird-pollinated species presented a flattened epidermis. Variations in osmophore pattern among species visited by bees, including variations within the same plant genus, are novel finding. Additionally, the Bignonieae species visited by bees presented a textured corolla surface, which has been reported as facilitating bee attachment and movement towards the floral resource. Future studies with a greater number of Bignonieae species and more detailed pollinator behavioral assays may help in the interpretation of the variations in corolla traits and functional relationships between flowers and pollinators.

Landscape-scale floral resource discontinuity decreases bumble bee occurrence and alters community composition.

Agricultural practices and intensification during the past two centuries have dramatically altered the abundance and temporal continuity of floral resources that support pollinating insects such as bumble bees. Long-term trends among bumble bees within agricultural regions suggest that intensive agricultural conditions have created inhospitable conditions for some species, while other species have maintained their relative abundances despite landscape-level changes in flower availability. Bumble bee responses to spatiotemporal resource heterogeneity have been explored at the colony and behavioral level, but we have yet to understand whether these conditions drive community structure and ultimately explain the diverging patterns in long-term species trends. To explore the relationship between landscape-level floral resource continuity and the likelihood of bumble bee occurrence, we mapped the relative spatial and temporal availability of floral resources within an intensive agricultural region in the US Upper Midwest and related this resource availability with bumble bee species relative abundance. Across the bee community, we found that relative bumble bee occurrence increases in landscapes containing more abundant and more temporally continuous floral resources. Declining species, such as Bombus terricola, exhibited the strongest, positive responses to resource abundance and continuity whereas common, stable species, such as Bombus impatiens, showed no statistical relationship to either. Together with existing experimental evidence, this work suggests that efforts to increase spatiotemporal flower availability, along with overall flower abundance at landscape scales may have positive effects on bumble bee communities in the US Upper Midwest.

Honeybees’ foraging choices for nectar and pollen revealed by DNA metabarcoding

Honeybees are the most widespread managed pollinators of our food crops, and a crucial part of their well-being is a suitable diet. Yet, we do not know how they choose flowers to collect nectar or pollen from. Here we studied forty-three honeybee colonies in six apiaries over a summer, identifying the floral origins of honey and hive-stored pollen samples by DNA-metabarcoding. We recorded the available flowering plants and analyzed the specialized metabolites in honey. Overall, we find that honeybees use mostly the same plants for both nectar and pollen, yet per colony less than half of the plant genera are used for both nectar and pollen at a time. Across samples, on average fewer plant genera were used for pollen, but the composition was more variable among samples, suggesting higher selectivity for pollen sources. Of the available flowering plants, honeybees used only a fraction for either nectar or pollen foraging. The time of summer guided the plant choices the most, and the location impacted both the plants selected and the specialized metabolite composition in honey. Thus, honeybees are selective for both nectar and pollen, implicating a need of a wide variety of floral resources to choose an optimal diet from.

Flowers of ruderal species are numerous but small, short and low‐rewarding

Weed species are ecological models that recently received considerable attention due to their particular strategies linked to their ruderal‐competitive traits. They are known to have the potential to provide additional floral resources for insects in flower‐poor agroecosystems. However, their floral traits are much more scarcely studied than those of plants found in other habitats, such as grasslands. The aim of this study was to describe the floral phenotype of weeds and to determine to what extent their floral traits match their ecological strategies as described based on leaf traits. We cultivated 19 forb weeds from perennial agroecosystems, previously identified in Mediterranean fields, in a greenhouse for seven months and collected data on 12 floral and five leaf traits. We tested whether these traits covaried and exhibited an ecological strategy at the phenotype scale. We found that in matters of flower production, weed species face a tradeoff: either numerous small, low‐stature flowers with small quantities of pollen and nectar, or few, large, higher‐held flowers with more pollen and nectar. The floral traits were found to reflect Grime's CSR strategies: the weed species producing fewer but costlier flowers belonged to C‐strategy species, whereas those producing more but less costly flowers belonged to species dominated by an R strategy. These findings indicate that the potential of weeds as floral resources for insects is related to their ecological strategies, which are known to be affected by agricultural practices that filter species composition. This implies that, as for the provision of other ecosystem services, weed communities can be managed to select species with floral traits matching the requirements of flower‐visiting insects like pollinators or parasitoid wasps.

Local and landscape context affects bee communities in mixed fruit orchards in Southern Thailand

Abstract Bees play an important role by contributing to the pollination of a diverse range of crops and wild plants. However, bees are threatened by deforestation and habitat degradation caused by urbanization and agricultural intensification, which reduce floral and nesting resources. In this study, the effects of local (orchard size, flowering plant abundance and richness and floral abundance) and landscape factors (surrounding agricultural, forest and urban cover) on bee richness and abundance in mixed fruit orchards were determined from 28 mature orchards interspersed along a gradient of landscape complexity. Bees were observed for 15 min in 2 × 2 m plots. We categorized all bees into one of the three groups: (a) honey bees, (b) solitary bees and (c) stingless bees. Several local and landscape factors were found to influence bee richness and abundance. Honey bee abundance was positively affected by orchard size, whereas honey bee richness was not. Stingless bee richness and abundance were positively correlated with floral abundance. Forest cover within a 3‐km radius positively affected solitary bee richness. Solitary bee abundance was positively affected by forest cover within a 3‐km radius and negatively impacted by urban cover within a 1.5‐km radius. In our study area, small forest patches are found in abundance; thus, the high proportion of forest edge, relative to the forest interior, greatly supports solitary bee abundance and richness in this landscape. Moreover, most solitary bees are soil‐nesting species that may be excluded from environments that are converted from natural to anthropogenically developed areas. Recommendations to protect pollinators included conserving existing forest patches, especially forest margins; restoring forest patches within farmland landscapes; maintaining a diversity of herbs and grasses within mixed fruit orchards; establishing live fences composed of diverse plant species and retaining dead trees within farmland. For urban areas, augmenting floral resources in green spaces is suggested.

Honeybee visitation to shared flowers increases Vairimorpha ceranae prevalence in bumblebees.

Vairimorpha (=Nosema) ceranae is a widespread pollinator parasite that commonly infects honeybees and wild pollinators, including bumblebees. Honeybees are highly competent V. ceranae hosts and previous work in experimental flight cages suggests V. ceranae can be transmitted during visitation to shared flowers. However, the relationship between floral visitation in the natural environment and the prevalence of V. ceranae among multiple bee species has not been explored. Here, we analyzed the number and duration of pollinator visits to particular components of squash flowers-including the petals, stamen, and nectary-at six farms in southeastern Michigan, USA. We also determined the prevalence of V. ceranae in honeybees and bumblebees at each site. Our results showed that more honeybee flower contacts and longer duration of contacts with pollen and nectar were linked with greater V. ceranae prevalence in bumblebees. Honeybee visitation patterns appear to have a disproportionately large impact on V. ceranae prevalence in bumblebees even though honeybees are not the most frequent flower visitors. Floral visitation by squash bees or other pollinators was not linked with V. ceranae prevalence in bumblebees. Further, V. ceranae prevalence in honeybees was unaffected by floral visitation behaviors by any pollinator species. These results suggest that honeybee visitation behaviors on shared floral resources may be an important contributor to increased V. ceranae spillover to bumblebees in the field. Understanding how V. ceranae prevalence is influenced by pollinator behavior in the shared floral landscape is critical for reducing parasite spillover into declining wild bee populations.

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>

SEASONAL TROPHIC NICHE BREADTH AND OVERLAP IN A GUILD OF SIX MOST FREQUENT BEE SPECIES IN BAHAWALPUR, PAKISTAN

Agonistic relationships in plant-pollinator assemblages are poorly understood as compared to mutualistic relationships. We estimated the floral resource competition in terms of seasonal trophic niche breadth and overlap among the guild of six most frequent bee species i.e., Ceratina smaragdula, Lasioglossum sp., Ceylalictus sp., Halictus sp., Apis dorsata and Apis florea in Bahawalpur (Punjab), Pakistan. The species exhibiting the maximum niche breadth had the minimum abundance in spring and summer seasons. The niche breadth of two solitary bees i.e., Lasioglossum sp. and C. smaragdula was higher than the social A. florae but they were much less abundant. Ceratina smaragdula showed the maximum pair-wise niche overlap with A. florea and Halictus sp. in spring and with Ceylalictus sp. in summer. Apis florea and A. dorsata had the maximum pair-wise niche overlap in both the autumn and winter seasons. No significant pair-wise niche overlap and interspecific competition was observed among all the six species in any season. This shows that pollination system in arid Bahawalpur is stable and less prone to competition and species loss.

Butterflies are not a robust bioindicator for assessing pollinator communities, but floral resources offer a promising way forward

Monitoring pollinators is crucial for the evaluation of biodiversity and potential pollination services. Yet, efficiently monitoring multiple taxa over large areas can be costly. An alternative approach is using simple species bioindicators that represent the entire pollinator community. One of the requirements of a good bioindicator is that it can be easily identified to lower taxonomic levels and be sensitive to changes in habitat. This is the case for butterflies, a taxon for which many countries have a country-wide long-term monitoring scheme. We tested whether butterfly diversity can be used to predict diversity of bees and hoverflies both spatially and temporally. We surveyed 42 transects of the Dutch Butterfly Monitoring Scheme in 2020, to record species richness and abundance of butterflies, bees and hoverflies. We also recorded flower area and richness in the pollinator transects. To test whether pollinators with similar functional traits are more closely correlated than the entire pollinator community, we categorized bee and butterfly species according to their diet breadth (polyphagous vs. non-polyphagous), nitrogen-affinity (nitrophobous vs. nitrophilous larval resources) and body size. We used the same methods to test for temporal correlations over seven years for one site in Spain. Butterfly richness was not spatially correlated with bee richness (Pearson's r = 0.13), nor were the two taxa temporally correlated (Pearson's r = 0.02). Interestingly, hoverfly richness was spatially correlated with butterfly richness (Pearson's r = 0.43) and with bee richness (Pearson's r = 0.36) in the Netherlands and, hence, hoverflies might be slightly more suitable as a bioindicator of pollinator diversity in this area. Abundance of all three taxa showed no significant inter-correlation, except for correlations between diet specialist bees and butterflies (Pearson's r = 0.39). Importantly, all three taxa were strongly correlated with flower richness, but they varied in their preferences for host plant families. This is in line with 75% of the plant-pollinator studies finding significant positive relations. For monitoring schemes to be effective in informing better pollinator conservation, they should expand to include bees and hoverflies as well as simple indicators of habitat quality such as floral resources.