Use Of Floral Resources Research Articles

Seasonal shifts and complementary use of pollen sources by two bees, a lacewing and a ladybeetle species in European agricultural landscapes

Abstract Continuous availability of food resources, such as pollen, is vital for many insects that provide pollination and pest control services to agriculture. However, there is a lack of knowledge about the shared or complementary use of floral resources by such species, which hampers more effective landscape management to simultaneously promote them in agroecosystems. Here, we simultaneously quantified pollen use by a bumblebee (Bombus terrestris) and a mason bee (Osmia bicornis), two bee species recognized as important crop pollinators, as well as a lacewing (Chrysoperla carnea) and a ladybeetle species (Harmonia axyridis), both common predators of crop aphids, throughout the season in 23 agricultural landscapes in Germany and Switzerland. Pollen diets were more diverse and similar among C. carnea and H. axyridis compared to the two bee species, but all four species shared key pollen types early in the season such as Acer, Quercus, Salix and Prunus. All species exhibited a pronounced shift in pollen sources from primarily woody plants (mainly trees) in spring to primarily herbaceous plants in summer. The majority of pollen (overall ≥64%) came from non‐agricultural plants even in crop‐dominated landscapes. Synthesis and applications. Our results highlight the importance of trees as pollen sources for many insect species, particularly early in the season. Our findings support incentives that promote heterogeneous agricultural landscapes including both woody and herbaceous semi‐natural habitats, ensuring phenological complementarity of floral resources for insect species that can provide pollination and pest control services to agriculture. The identified key plant species can help to design and optimize agri‐environment schemes to promote these functionally important insects.

Spatial variability in a plant–pollinator community across a continuous habitat: high heterogeneity in the face of apparent uniformity

Large‐scale spatial variability in plant–pollinator communities (e.g. along geographic gradients, across different landscapes) is relatively well understood. However, we know much less about how these communities vary at small scales within a uniform landscape. Plants are sessile and highly sensitive to microhabitat conditions, whereas pollinators are highly mobile and, for the most part, display generalist feeding habits. Therefore, we expect plants to show greater spatial variability than pollinators. We analysed the spatial heterogeneity of a community of flowering plants and their pollinators in 40 plots across a 40‐km2area within an uninterrupted Mediterranean scrubland. We recorded 3577 pollinator visits to 49 plant species. The pollinator community (170 species) was strongly dominated by honey bees (71.8% of the visits recorded). Flower and pollinator communities showed similar beta‐diversity, indicating that spatial variability was similar in the two groups. We used path analysis to establish the direct and indirect effects of flower community distribution and honey bee visitation rate (a measure of the use of floral resources by this species) on the spatial distribution of the pollinator community. Wild pollinator abundance was positively related to flower abundance. Wild pollinator visitation rate was negatively related to flower abundance, suggesting that floral resources were not limiting. Pollinator and flower richness were positively related. Pollinator species composition was weakly related to flower species composition, reflecting the generalist nature of flower–pollinator interactions and the opportunistic nature of pollinator flower choices. Honey bee visitation rate did not affect the distribution of the wild pollinator community. Overall, we show that, in spite of the apparent physiognomic uniformity, both flowers and pollinators display high levels of heterogeneity, resulting in a mosaic of idiosyncratic local communities. Our results provide a measure of the background of intrinsic heterogeneity within a uniform habitat, with potential consequences on low‐scale ecosystem function and microevolutionary patterns.

Low trophic niche overlap among trap-nesting bee species (Hymenoptera: Anthophila) in a semideciduous forest fragment

Bees are important components of mutualistic interactions with plants, playing a key role as pollinators of both wild and crop plants. In this context, studies on the plants visited by bees are important to determining conservation strategies. We investigated the use of floral resources by the trap-nesting bee species sampled in a semideciduous forest fragment. Trap nests were set in the forest fragment in three different zones: forest edge, 250 m away from the edge and 500 m away from the forest edge. Pollen analysis of the residual pollen content removed from the nests of 12 bee species revealed a total of 63 pollen types from 16 botanical families. The bee community showed specialized populations with no overlap in diet. Within the community, the diet overlap was higher in closely related species, the two Tetrapedia species and the two Centris (Heterocentris) species, than in the other sampled species. Although the studied bee community is composed of widespread bee species, our data showed a low niche overlap among them, suggesting the occurrence of food niche partitioning at our study site. The asymmetry in the period of nesting activities and floral preferences among the bee species are factors that might have contributed to the low niche overlap observed.

Assessing the role of dispersed floral resources for managed bees in providing supporting ecosystem services for crop pollination.

Most pollination ecosystem services studies have focussed on wild pollinators and their dependence on natural floral resources adjacent to crop fields. However, managed pollinators depend on a mixture of floral resources that are spatially separated from the crop field. Here, we consider the supporting role these resources play as an ecosystem services provider to quantify the use and availability of floral resources, and to estimate their relative contribution to support pollination services of managed honeybees. Beekeepers supplying pollination services to the Western Cape deciduous fruit industry were interviewed to obtain information on their use of floral resources. For 120 apiary sites, we also analysed floral resources within a two km radius of each site based on geographic data. The relative availability of floral resources at sites was compared to regional availability. The relative contribution of floral resources-types to sustain managed honeybees was estimated. Beekeepers showed a strong preference for eucalypts and canola. Beekeepers selectively placed more hives at sites with eucalypt and canola and less with natural vegetation. However, at the landscape-scale, eucalypt was the least available resource, whereas natural vegetation was most common. Based on analysis of apiary sites, we estimated that 700,818 ha of natural vegetation, 73,910 ha of canola fields, and 10,485 ha of eucalypt are used to support the managed honeybee industry in the Western Cape. Whereas the Cape managed honeybee system uses a bee native to the region, alien plant species appear disproportionately important among the floral resources being exploited. We suggest that an integrated approach, including evidence from interview and landscape data, and fine-scale biological data is needed to study floral resources supporting managed honeybees.

Experimental shifts in phenology affect fitness, foraging, and parasitism in a native solitary bee

Phenological shifts have been observed in a wide range of taxa, but the fitness consequences of these shifts are largely unknown, and we often lack experimental studies to assess their population-level and evolutionary consequences. Here, we describe an experimental study to determine the fitness consequences of phenological shifts in blue orchard bee (Osmia lignaria) emergence, compare the measured seasonal fitness landscape with observed phenology in the unmanipulated population, and assess seasonal variation in key factors related to reproduction, foraging, and brood parasitism that were expected to affect the shape of the fitness landscape. By tracking individually marked females, we were able to estimate the lifetime fitness impacts of phenological advances and delays. We also measured parasitism risk, floral resource use, and nesting behavior to understand how each varies seasonally, and their combined effects on realized fitness. Survival to nesting decreased non-monotonically throughout the season, with a 20.4% decline in survival rates between the first and second cohorts. The total reproductive output per maternal bee was 14.9% higher in the second cohort compared to the first, and 161% higher in the second cohort compared to the third. Combining seasonal patterns in survival and reproductive output, experimentally advanced females showed 30.6% higher fitness than bees released at the historic peak. In contrast, the nesting phenology of unmanipulated bees showed nearly equal numbers of nesting attempts in the first two cohorts. Both increased resource availability and reduced parasitism risk favored earlier emergence. These results are consistent with a population experiencing directional selection for earlier emergence, adaptive bet-hedging, or developmental constraints. Our study offers insight into the fitness consequences of phenological shifts, the mechanisms affecting the fitness consequences of phenological shifts in a community context, and the potential for adaptive responses to climate change.

Floral usage partitioning and competition between social (Apis mellifera, Bombus terrestris) and solitary bees in New Zealand: Niche partitioning via floral preferences?

AbstractWorldwide, studies of interactions between introduced and native bees have produced contradictory evidence regarding the potential for competition. Different resource requirements and the impact of tongue length on resource use are often overlooked aspects of these studies. Here, we examine floral resource use and niche overlap between introduced social bees and native solitary bees over two flowering seasons on The Remarkables mountain range, South Island, New Zealand. The native bee fauna of New Zealand is composed of short‐tongued solitary bees in the families Colletidae and Halictidae. Long‐tongued social bees were introduced 150 years ago, and Apis mellifera and Bombus species are now widespread. We analysed floral resource utilization by introduced bees (mainly Bombus terrestris) and native bees in relation to resource abundance across elevations in montane to alpine grassland communities. We modelled resource utilization and overlap between bee taxa using a novel index of floral resource availability, developed to more accurately describe floral density. Additionally, we sought to quantify the impact of honey bees by introducing hives, however, low densities in study plots prevented direct conclusions from being drawn. Native and introduced bees did, however, have distinctly different floral preferences over the flowering season with more niche overlap within, rather than between, native and introduced groups. Introduced bees showed a preference for introduced species in the family Fabaceae which native bees could not access. Native bees heavily utilized introduced Asteraceae as well as native floral resources that introduced bees did not prefer. The limited resource overlap between bee taxa indicated that bee communities in New Zealand may have reduced potential for competition, owing to the different resource requirements of solitary versus social bees and their differing abilities to access floral resources. These findings provide some potential explanations for contradictory evidence worldwide regarding the perceived detrimental impacts of introduced social bees.

Using Colony Monitoring Devices to Evaluate the Impacts of Land Use and Nutritional Value of Forage on Honey Bee Health

Colony monitoring devices used to track and assess the health status of honey bees are becoming more widely available and used by both beekeepers and researchers. These devices monitor parameters relevant to colony health at frequent intervals, often approximating real time. The fine-scale record of hive condition can be further related to static or dynamic features of the landscape, such as weather, climate, colony density, land use, pesticide use, vegetation class, and forage quality. In this study, we fit commercial honey bee colonies in two apiaries with pollen traps and digital scales to monitor floral resource use, pollen quality, and honey production. One apiary was situated in low-intensity agriculture; the other in high-intensity agriculture. Pollen traps were open for 72 h every two weeks while scales recorded weight every 15 min throughout the growing season. From collected pollen, we determined forage quantity per day, species identity using DNA sequencing, pesticide residues, amino acid content, and total protein content. From scales, we determined the accumulated hive weight change over the growing season, relating to honey production and final colony weight going into winter. Hive scales may also be used to identify the occurrence of environmental pollen and nectar dearth, and track phenological changes in plant communities. We provide comparisons of device-derived data between two apiaries over the growing season and discuss the potential for employing apiary monitoring devices to infer colony health in the context of divergent agricultural land use conditions.

Community level niche overlap and broad scale biogeographic patterns of bee communities are driven by phylogenetic history

AbstractAimBecause the ecological similarity between species is expected to increase with relatedness and that speciation is a local process, phylogeny may provide a common measure for the influence of ecological and biogeographic processes on community assembly. We tested if similarities in floral visitation patterns within communities and the phylogenetic beta‐diversity among communities were related to the position of bees within the bee phylogeny.LocationGlobal.MethodsWe combined a genus level phylogeny with within‐genera phylogenies for the bee species occurring within 18 globally distributed bee‐flower networks. Networks consisted of a matrix of bee and plant species and information on whether or not a bee species had been observed visiting flowers of a given plant species. For each network, we used Abouheif's Cmean to test if the similarity in floral associations (niche similarity) between bees and the number of plant species visited displayed a significant phylogenetic signal. To test if biogeography influenced the relatedness among species within networks we tested if the phylogenetic beta‐diversity increased with geographical distance and dissimilarity in climatic conditions among networks.ResultsWe found a phylogenetic signal for niche similarity in only 50% of the bee‐flower networks. However, network size influenced the likelihood of observing a phylogenetic signal and for seven of the eight bee‐flower networks with >20 species it was statistically significant. On a global scale, the phylogenetic beta‐diversity increased with geographical distances and with climatic dissimilarity between sites.Main conclusionsBee communities are structured by processes of speciation and migration so that regional species pools are dominated by a subset of the global phylogenetic clades, resulting in increasing phylogenetic beta‐diversity with geographical distance. Moreover, ecological filtering processes operating at both local (floral resource use) and continental (climatic constraints) scale determine the distribution of species among resources and geographical regions. The assembly of bee communities should therefore be understood as a product of both biogeographic and community ecological processes.

Assessment of Habitat Modification and Varied Planting Dates to Enhance Potential Natural Enemies of Anasa tristis (Hemiptera: Coreidae) in Squash.

The squash bug, Anasa tristis (DeGeer) (Hemiptera: Coreidae), is an indigenous pest of squash and other cucurbits. Pesticides can control squash bug populations although many small-scale growers in the Southeast seek alternative methods of management. Cultural control methods, including varying the planting date and farmscaping, are not well understood under southeastern conditions. The goal of farmscaping is to increase natural ecosystem functions to aid in the control of pest populations. In the summers of 2014 and 2015, field plots of squash, separated by a minimum of 150 m were organized in a split-split plot design, with floral resources at the whole-plot level and varied planting date at the subplot level. Data were collected on squash bug abundance and fruit yield (kg), and abundance of potential natural enemies of A. tristis. Plots with added floral resources had fewer squash bug adults than plots without added floral resources in four of eight possible year × site × planting date combinations. Furthermore, the site in 2014 which had a reduction in squash bug adult abundance also had an increase in the abundance of potential enemies, including spiders, ground beetles, and predaceous Hemiptera. There were additional instances when potential natural enemy abundance was greater in resource-enhanced plots, but they were not associated with sites that had a reduction in yield loss or squash bug abundance. The use of floral resources to attract natural enemies and beneficial insects merits further investigation.

Flower use of the butterfly Maniola jurtina in nectar‐rich and nectar‐poor grasslands: a nectar generalist with a strong preference?

Abstract Butterflies are often considered as opportunistic nectar consumers that visit a range of flower species. The degree of specialisation in foraging behaviour and flower choice may, however, vary considerably at the inter‐specific level, from highly specialised to generalist species. In generalist nectar use, there can be intra‐specific variation in the availability and use of floral resources (diversity and abundance) among different populations. Knowing the preferences of nectar‐feeding butterflies can increase the understanding of ecological relationships and resource use and help in developing better strategies for butterfly conservation. By means of behavioural tracking, we identified foraging patterns of Maniola jurtina butterflies in nectar‐rich and nectar‐poor grasslands. For both males and females, we showed significant preference for the brown knapweed Centaurea jacea and thistles (Cirsium sp.) in nectar‐rich, extensively managed grasslands. In the absence of these preferred species, as is typically the case in nectar‐poor intensively managed sites, M. jurtina nectared on Trifolium pratense and Leucanthemum vulgare. Flower visits were on average shorter on T. pratense compared to C. jacea. These observational results were confirmed by a field experiment in which a wild flower nectar array with C. jacea and T. pratense was introduced. In extensively managed grasslands, foraging bouts were generally confined to patches of flowering plants and did not involve long flights between flower visits. In intensively managed meadows, butterflies performed longer flights, and ignored more flowers between two consecutive visits. Despite the variety of flower species visited, M. jurtina showed a significant preference for a few nectar sources in a context‐dependent way.

Patterns of floral resource use by two dominant ant species in a biodiversity hotspot

Ecological dominance in ants is often fuelled by carbohydrate intake. Most studies have focused on the importance of invasive ant mutualistic associations with trophobionts whereas few studies have investigated the importance of floral nectar on invasion success. In this study, utilisation of temporarily available floral nectar by the invasive Argentine ant, Linepithema humile, was compared to that of the dominant native ant, Anoplolepis custodiens, within the Cape Floristic Region (CFR), a biodiversity hotspot. The effect of these two focal ant species on species composition and abundance of ground foraging ants as well as floral arthropod visitors in inflorescences of Proteacea species was assessed. Foraging activity, and trophic ecology inferred from the abundance of natural stable isotopes of Carbon (δ13C) and Nitrogen (δ15N), and the ratio of Carbon to Nitrogen (C:N) were compared between the two ant species during three flowering periods. Linepithema humile significantly reduced the abundance and species diversity of both above-ground and floral arthropod species abundance and composition. Linepithema humile increased its foraging activity with increasing nectar availability, switching its diet to a more herbivorous one. Anoplolepis custodiens did not respond as effectively to increasing floral nectar or negatively impact floral arthropod visitors. This study showed that the availability of floral nectar and ability of L. humile to more effectively utilise this temporarily available resource than native ants, can contribute significantly to the further spread and persistence of L. humile in natural environments in the CFR.

Evaluating the effects of floral resource specialisation and of nitrogen regulation on the vulnerability of social bees in agricultural landscapes

The abundance and the diversity of bumblebees have been declining for the past decades. While some species remain abundant and widespread, others have experienced vast declines. We tested if diet breadth and exclusiveness of floral resource use affected abundance and land-use response of bumblebees and honeybees in heterogeneous agricultural landscapes. Based on an ecological niche modelling approach, we discovered that three of 13 species (12 Bombus spp. and A. mellifera) responded negatively to land use, while no species responded positively. Overall abundance as well as land-use response of different bee species was unrelated to resource use. The generalist forager B. lapidarius, the slightly more specialised forager B. terrestris/lucorum species complex and the specialist forager B. wurflenii declined most with land use. Moreover, we found that honeybees and two bumblebee species contained higher levels of nitrogen than other non-predatory Hymenoptera and performed almost perfect homeostasis despite variable nitrogen contents of floral resources. We conclude that at least common species of social bees have good nitrogen homeostasis capacity. Generally, our data do not support the notion that species with more specialised floral resource use are more likely to suffer from land use.

Influence of the honeybee and trait similarity on the effect of a non‐native plant on pollination and network rewiring

SummaryIntroduced entomophilous non‐native plants usually become well integrated into the diet of generalist pollinators. This integration can affect the entire recipient plant–pollinator network. Effects vary from facilitative to competitive, and understanding the factors that govern such variability is one of the fundamental goals in invasion ecology. Species traits determine the linking patterns between plant and pollinator species. Therefore, trait similarity among plants or among pollinators might modulate how they affect each other.We conducted a flower removal experiment to investigate the effects of the non‐native entomophilous legumeHedysarum coronariumon the pollination patterns of a Mediterranean shrubland plant–pollinator network. Specifically, we explored whether effects were influenced by similarity with the resident plant species in flower morphology (papilionate vs. non‐papilionate), and whether effects on the pollinator community were influenced by similarity in functional group with its main visitor species (bees vs. non‐bees). In addition, we explored whetherHedysarumhad an effect on the identity of interactions. For this purpose, we calculated the interaction rewiring, that is the number of plant–pollinator interactions that were gained or lost after invasion.Hedysarumwas well integrated into the diet of 15 generalist pollinators having the honeybee as its main visitor species. Such integration did not affect visitation rates, normalized degree (i.e. proportion of pollinators they are visited by) nor niche overlap (i.e. proportion of plant species they share pollinators with) of plants, irrespective of their flower morphology. Only the proportion of honeybee visits to resident plants decreased with invasion. On the other hand,Hedysarumreduced visitation rates and niche overlap of pollinators, mainly those of bee species. Finally, we observed that changes in the foraging behaviour of the honeybee were positively associated with the interaction rewiring involving the rest (92 taxa) of pollinators.In conclusion, pollinators show a plastic use of floral resources, responding to the presence of non‐native plants. When the non‐native attracts highly competitive pollinators such as the honeybee, plasticity is especially significant in pollinators that are functionally close to that competitive pollinator. The result is an interaction rewiring, probably due to pollinators avoiding competition with the honeybee. Though this plasticity might not quantitatively affect the pollination of plants, consequences on their reproduction and the functioning of the network can derive from the interaction rewiring.ALay Summaryis available for this article.

INTERAÇÕES PLANTA-POLINIZADOR EM VEGETAÇÃO DE ALTITUDE NA MATA ATLÂNTICA

Tropical high-altitude vegetation is unique due to susceptibility to severe weather conditions in relation to lower for­mations, and by the peculiarity of its flora with many relictual components. Studies on plant-pollinator interactions in high-altitude rocky outcrops and forests of the Atlantic Forest are scarce, but compilation of information allows us to identify some patterns: low frequency of visits, high floral longevity and generalized pollination system. In tropical mountain ecosystems, the degree of generalization of pollination systems in functional (pollinator groups) and ecological (number of species) terms tends to be high, mainly due to the over-representation of certain plant taxa (e.g., Asteraceae in rocky outcrops and Fabaceae, Myrtaceae, Rubiaceae and Sapindaceae in montane forests). Generalized pollination systems and autogamy may be advantageous for tropical high-altitude plants due to the more severe weather conditions (e.g., low temperature), which decrease abundance and limit the activity of pollinators, resulting in lower visitation frequency. Nevertheless, some well represented groups in forests, such as orchids and plants pollinated by hummingbirds and bats, exemplify cases of higher functional specialization, as well as plants with poricidal anthers pollinated by bees in the high-altitude grasslands. However, in rocky outcrops, for some functional groups of pollinators (e.g., hummingbirds, bats, beetles and hawkmoths), the availability of resources does not allow the maintenance of all species throughout the year, favoring possible local or altitudinal migrations. Thus, rocky outcrops and high-altitude forests constitute a unit in the sense of sustaining the pollinator community. Indeed ro­cky outcrops and high-altitude forests share an evolutionary history at the regional scale since they passed through similar events of expansion and retraction in response to climate changes in the Quaternary. This could explain the complementarity between the two types of vegetation in the use of floral resources by pollinators. Besides the associations identified here, the ecology and evolution of plant-pollinator interactions in high-altitude vegetation of the Atlantic Forest remain poorly understood, making urgent the development of an integrative research program, as well as projects on issues related to climate change and biodiversity conservation.

Flowering phenology influences bee community dynamics in old fields dominated by the invasive plant Centaurea stoebe

Wild and managed bees provide critical pollination services to both native and cultivated plants, and the invasion of exotic plants can have positive or negative effects on bee communities. In this study we investigated the influence of the exotic invasive Centaurea stoebe ssp. micranthos (spotted knapweed) on bee species diversity and abundance in old-fields (Michigan, USA). We conducted field observations in knapweed dominated fields and adjacent fields with greater forb diversity to determine whether the bee communities foraging in each field type differed in their composition, diversity, and abundance, and to determine how bees’ use of floral resources changed throughout the growing season. This was coupled with a common garden experiment that contrasted the attractiveness of C. stoebe to 12 native plant species, which occur in similar habitats. Both studies were conducted throughout the 2012–2013 growing seasons to examine the temporal effect of floral resource availability. C. stoebe was the most heavily-visited plant, in terms of total bee visitation and bee species richness in both studies. While C. stoebe-dominated old-fields had high floral resource levels during its peak bloom period, before and after this period these fields contained very few floral resources. In contrast, diverse fields had a number of flowering plant species that provided floral resources before, during, and after C. stoebe bloom. As a result, diverse fields contained significantly greater season-long floral resource availability and significantly greater season-total bee abundance, diversity and species richness. This greater species richness was driven at least in part by the ability of diverse flowering plant communities to support bee species that are active before and after the bloom period of C. stoebe. Our results suggest that efforts to manage C. stoebe should take into account the floral resources the plant is providing, and coincide with the restoration of diverse forb communities in order to enhance bee foraging habitat in old-fields.

Effects of alien invasion by Bombus terrestris L. (Apidae) on the visitation patterns of native bumblebees in coastal plants in northern Japan

When alien pollinator species enter a native community of pollinators in which resource partitioning has been established, the pollination network between plants and pollinators may be modified through the interactions between the pollinators over the use of floral resources. We observed the floral-use patterns of native (Bombus hypocrita and B. deuteronymus) and alien (B. terrestris) bumblebee species in a coastal grassland in northern Japan. We analyzed the factors determining resource partitioning patterns. B. hypocrita tended to visit flowers with shallow or wide open corollas, such as Rosa rugosa, whereas B. deuteronymus visited flowers with complex or deeper corollas, such as Lathyrus japonicus. Given the wider floral preference of B. terrestris, floral use by the alien bumblebees consistently overlapped with that of native bumblebees. The visitation of B. terrestris to R. rugosa flowers was positively correlated with that of B. hypocrita. These bumblebee species frequently used similar floral resources, in part because of the large overlap in the seasonality of their foraging activity. The visitation frequency of B. deuteronymus to L. japonicus flowers was independent of the visitation frequency of other bumblebee species. The major visitation periods of the bumblebees to L. japonicus flowers reciprocally differed between B. deuteronymus and B. terrestris, suggesting phenological resource partitioning between these species. Our study suggests that phenological niche partitioning is more common in specialized flowers (L. japonicus) than in generalized flowers (R. rugosa).

Niche Overlap and Network Specialization of Flower-Visiting Bees in an Agricultural System.

Different resource use strategies manifest as differences in the realized niches of species. Niche segregation may involve several dimensions of the niche, such as diet, space, and time. We measured the level of redundancy and complementarity of a bee-plant interaction network in an agricultural system. Because flower resource diversity is high and resource abundance associated with flowering phenology varies throughout the year, we hypothesized that trophic overlap in the community would be low (i.e., high niche complementarity). In contrast, we expected a combination of physiological constraints and exploitation competition to create high temporal overlap, leading to high redundancy in the time of use of floral resources. Dietary overlap was low (NOih = 0.18): niches of 88% of species pairs had less than 30% overlap. In contrast, temporal overlap was intermediate (NOih = 0.49): niches of 65% of species pairs had 30% to 60% overlap. Network analysis showed that bees separated their dietary niches and had intermediate complementary specialization (H2' = 0.46). In terms of their temporal niches (H2' = 0.12), bees were generalists, with high temporal redundancy. Temperature was not a key factor in the determination of niche overlap, suggesting that environmental factors do not likely have a primary role in determining high redundancy in the temporal use of floral resources. Rather, temporal overlap is likely associated with the timing of nectar production by flowers. Our results suggest that bees partition a wide variety of available floral resources, resulting in low dietary overlap and intermediate temporal overlap.

Pollen types collected by Tetragonisca angustula (Hymenoptera: Apidae) in dry vegetation in Northeastern Brazil

Knowing the floral origin of the pollen collected by native bees in Neotropical ecosystems enables us to understand the dynamics of the interdependent relationships between the insects and the native flora. The objectives of this study were to: (i) investigate the spectrum of plant species from which pollen is collected by Tetragonisca angustula in caatinga (dry vegetation) areas in the semiarid region of Northeastern Brazil; (ii) identify pollen types that could be used as regional geographical markers and (iii) determine the pollen niche breadth and the pattern of use of floral resources by this stingless bee. In total, 23 samples of the pollen stored by T. angustula were collected monthly and subjected to acetolysis. Of the 45 pollen types identified that of Prosopis juliflora (Fabaceae) and Solanum (Solanaceae) were the most frequently represented in the samples and 19 were collected by the bees at both study sites. Species characteristic of caatinga, such as Poincianella pyramidalis (Tulasne) L.P. Queiroz and Senna macranthera (de Candolle ex Colladon) H.S. Irwin & Barneby, were among the pollen identified and they were used as indicators of the geographical origin of the samples. The average values of the pollen niche breadth (H') and equitability (J') indicate that T. angustula is a generalist and homogeneous forager of the floral resources in caatinga.

Ecological meta‐networks integrate spatial and temporal dynamics of plant–bumble bee interactions

Bumble bees can forage on a large number of wild plants and crops. The survival of a colony depends on the availability of suitable food resources within foraging range and throughout their forage season. We studied the spatial and temporal use of floral resources by bumble bees in a set of 30 local plant communities and used these data to model colony survival under different combinations of patch size and bumble bee flight distance. Floral resources vary spatially and temporally at the landscape level, and bumble bees track these resources across the landscape during the season. The simulation model showed that different patterns of resources availability could affect the survival and distribution of bumble bee nests across the landscape. This model can be used to generate hypotheses explaining bumble bee richness and abundance that can be tested in real landscapes. Integrating the spatial and temporal dynamics of the flower resources used by bumble bees provides a new perspective that can be used to inform bumble bee conservation, particularly in the context of their widespread decline in recent decades.

Bees (Hymenoptera: Apoidea) and flowers in natural forest patches of southern Pantanal

This is the first systematic survey of bees in the Pantanal wetland, Brazil. We recorded bee species and their floral resources within grassland and natural forest edge habitats in the Pantanal. Surveys were conducted during two to four-days per month, for a total of 12 months. Overall, we recorded 56 bee species visiting a total of 63 flowering plants. Asteraceae and Fabaceae presented the highest number of visited species, however Hyptis suaveolens (Lamiaceae) was the plant most visited by different bee species (18). The most generalist native bee was Trigona fuscipennis visiting a total of 17 flowering plant species. Apis mellifera, an exotic bee, visited 27 species. We also report the overlap (37.5%) in the use of floral resources between the exotic bee Apis mellifera and native bee species. Our updated bee checklist here presented includes 10 new records for the State of Mato Grosso do Sul. These data will support management strategies targeting the conservation of plant-pollinator interactions in the Pantanal ecosystem.