Plant Pollinator Research Articles

A straight-forward seed production technology system for foxtail millet (Setaria italica).

For autogamous crops, a precondition for using heterosis is to produce sufficient pure male-sterile female parents that can be used to produce hybrid seeds. To date, cytoplasmic male sterility (CMS) and environment-sensitive genic male sterility (EGMS) have been used commercially to exploit heterosis for autogamous species. However, neither CMS nor EGMS has been established for foxtail millet (Setaria italica). Here, we report on the establishment and application of a seed production technology (SPT) system for this crop. First, we established a DsRed-based SPT system, but found that it was unsuitable because it required the use of a fluorescent device for seed sorting. Instead, we constructed an SPT system with de novo betalain biosynthesis as the selection marker. This allowed us to distinguish transgenic seeds with the naked eye, thereby facilitating the identification of SPT maintainer line seeds. In this system, a seed sorter was not required to obtain sufficient seeds. The key point of the strategy is that the seed pool of the SPT maintainer line is propagated by artificial identification and harvesting of male-fertile individuals in the field, and the male-sterile line seed pool for hybrid production is produced and propagated by free pollination of male-sterile plants with the SPT maintainer line. In a field experiment, we obtained 423.96 kg male-sterile line seeds per acre, which is sufficient to plant 700.18 acres of farmland for hybrid seed production or male-sterile line reproduction. Our study therefore describes a powerful tool for hybrid seed production in foxtail millet, and demonstrates how the SPT system can be used for a small-grained crop with high reproduction efficiency.

Plant–pollinator metanetworks in fragmented landscapes: a simulation study

BackgroundThe topology of the plant–pollinator network can be explained by the species’ abundance and their random interactions. Plant–pollinator networks can be studied in the context of a landscape, because each patch can accommodate a certain local network. Local populations of pollinators in the landscape can be connected through migration and then constitute a metanetwork that is known as a combination of spatial and ecological networks. In this regard, habitat fragmentation can affect the topology of plant–pollinator metanetworks through changes in the species abundance and limiting their interactions. However, it is not clear what pattern (fragmented or aggregated) of the landscape structure can accommodate networks with a higher degree of specialization.Methodswe created simulated landscapes with different forest proportions scenarios (from 5% to 50% of the total landscape) and degrees of fragmentation. Then, for each landscape, we limited the proportion of pollinators to the forest patch. We assumed that plants and pollinators are randomly distributed around the landscape and interact randomly. We used landscape metrics to measure different aspects of landscape structure and bipartite metrics for calculating the degree of specialization in plant–pollinator networks.ResultsThe statistical relationship between bipartite and landscape metrics showed that the relationship between the topology of plant–pollinator networks and the landscape structure is affected by the forest amount in the landscape and the degree of forest fragmentation. We also found that according to the nestedness and H2 (a measure of specialization) metrics, fragmented landscapes contain more general plant–pollinator networks.ConclusionsOur findings suggest that fragmented landscapes, characterized by scattered forest patches, can promote higher levels of interaction between limited pollinators and diverse flowers, leading to more general plant–pollinator networks.

The Family Megachilidae (Hymenoptera: Apoidea) In Pollination Ecology- a Review

Family Megachilidae belongs to cosmopolitan family groups, making nests in the soil, and mostly prefer pre-existing cavities such as pithy stems, galls, and dead wood for nesting. Mostly they are solitary, long-tongued, and have pollen-collecting structure scopa present on the ventral side of the abdomen rather than hind legs (mostly in other bees). Genus Megachilid is generally known as leaf cutter and mason bees. Family Megachilidae is characterized by different groups of the bees such as solitary, mason, resin, carder, and leafcutter bees, and are the most important pollinators for agricultural, horticultural, medicinal, and aromatic plants. Female leafcutter bees have a special character to form brood cells by using their mandibles to cut leaves. Family Megachilidae is found throughout the world except for Antarctica, lowland tropical rain forests, deserts, and hilly ecosystems, and 238 species are listed from the Indian region. Our review is based on the significant role of the family Megachilidae and their different adaptive structures and behaviour to enhance their contribution to the pollination ecology.

Crop–pollinator interactions in urban and peri‐urban farms in the United Kingdom

Societal Impact StatementUrban food production could contribute towards sustainable food provision and would also deliver benefits to biodiversity and the health of urban residents. Many crops rely on insect pollination, but urban pollinator populations are under‐studied. In this study, crop–pollinator interactions and pollination quality were quantified in urban allotments in the United Kingdom. A diversity of insects was observed visiting the flowers of food crops, with squash, cucumber and fruit trees attracting the most flower visitors. However, strawberry plants pollinated naturally by insects produced lower quality fruit than those receiving supplemental hand‐pollination. Urban crop pollination could therefore be improved through the provision of food and nesting habitats for insects.Summary Growing food in and around cities could be a partial solution to sustainably increasing food production in an urbanised world. Recent studies have shown that small‐scale urban farms can be as productive, if not more so, than large‐scale conventional farms. However, the question of which insects visit fruit and vegetable crops in urban areas and whether there are sufficiently large and diverse populations to provide adequate pollination to food crops has been little explored. Here we quantified plant–pollinator visitation networks in urban allotments in the city of Brighton and Hove, UK, to determine which insect groups visit commonly grown fruit and vegetable crops. We also conducted pollinator deficit experiments to determine whether there are sufficient pollinators in urban allotments to adequately pollinate two commonly grown insect‐pollinated crops, strawberries (Fragaria x ananassa) and runner beans (Phaseolus coccineus). A broad range of insect‐pollinated fruit and vegetable crops were grown in allotments and were visited by a diversity of insects spanning many taxonomic groups. We found little evidence that runner bean crop yields were limited by a lack of pollination; however, open‐pollinated strawberry plants produced more ‘unmarketable’ fruit suggesting there is potential for improving the delivery of pollination to strawberries grown in urban areas. Our results suggest there are potential opportunities for expanding urban food production to the benefit of both people and biodiversity. We recommend that future work should also consider the effectiveness of different insect groups in pollinating the various crops grown in urban areas.

Pollinators limit seed production in an early blooming rare plant: evidence of a mismatch between plant phenology and pollinator emergence

The reproductive ecology of rare plants is seldom studied, yet the persistence of plant populations depends on successful mutualisms with pollinators. As atmospheric temperatures rise, phenology of plants and pollinators may become mismatched. We investigated the reproduction of Trifolium barnebyi (Barneby's clover), a mat‐forming perennial endemic to central Wyoming, USA, that grows in the crevices of sandstone bedrock. Our objectives were to evaluate a method for monitoring changes in cover as well as assess the pollination and seed‐set of T. barnebyi. We established five monitoring transects using a divided frame to estimate percent cover. We conducted seed‐set experiments at three locations to measure self‐pollination and the degree to which pollinating insects limited seed production. We used vane traps and bee bowls to capture pollinators, and examined pollen carried on bees. Percent cover along transects declined over the four year period and was associated with spring precipitation. Trifolium barnebyi did not self‐pollinate and relied on pollinators to produce seeds. The number and mass of viable seeds per flower, and the number of bees captured increased as the season progressed, indicating that more and larger seeds were made when more pollinators were present. Blooming of T. barnebyi ranged between April and June, depending on the microhabitat the plant lived in, and we observed much higher seed production in later‐blooming plants. Pollen from T. barnebyi was primarily carried by Andrena bees, although we found smaller amounts of pollen on seven other bee genera. A mismatch in timing between blooming and pollinating insect emergence could limit seed production in T. barnebyi if plants bloom earlier over time and bee emergence does not follow the same phenology. Rare plants can be pollinated by rare pollinators showing that conserving these pollinators is crucial for rare plants and early blooming species may be higher at risk.

Low Levels of Hive Stress Are Associated with Decreased Honey Activity and Changes to the Gut Microbiome of Resident Honey Bees.

Honey bees (Apis mellifera) face increasing threats to their health, particularly from the degradation of floral resources and chronic pesticide exposure. The properties of honey and the bee gut microbiome are known to both affect and be affected by bee health. Using samples from healthy hives and hives showing signs of stress from a single apiary with access to the same floral resources, we profiled the antimicrobial activity and chemical properties of honey and determined the bacterial and fungal microbiome of the bee gut and the hive environment. We found honey from healthy hives was significantly more active than honey from stressed hives, with increased phenolics and antioxidant content linked to higher antimicrobial activity. The bacterial microbiome was more diverse in stressed hives, suggesting they may have less capacity to exclude potential pathogens. Finally, bees from healthy and stressed hives had significant differences in core and opportunistically pathogenic taxa in gut samples. Our results emphasize the need for understanding and proactively managing bee health. IMPORTANCE Honey bees serve as pollinators for many plants and crops worldwide and produce valuable hive products such as honey and wax. Various sources of stress can disrupt honey bee colonies, affecting their health and productivity. Growing evidence suggests that honey is vitally important to hive functioning and overall health. In this study, we determined the antimicrobial activity and chemical properties of honey from healthy hives and hives showing signs of stress, finding that honey from healthy hives was significantly more antimicrobial, with increased phenolics and antioxidant content. We next profiled the bacterial and fungal microbiome of the bee gut and the hive environment, finding significant differences between healthy and stressed hives. Our results underscore the need for greater understanding in this area, as we found even apparently minor stress can have implications for overall hive fitness as well as the economic potential of hive products.

Pollen as the link between floral phenotype and fitness

AbstractPollen plays a key role in plant reproductive biology. Despite the long history of research on pollen and pollination, recent advances in pollen‐tracking methods and statistical approaches to linking plant phenotype, pollination performance, and reproductive fitness yield a steady flow of exciting new insights. In this introduction to the Special Issue “Pollen as the Link Between Phenotype and Fitness,” we start by describing a general conceptual model linking functional classes of floral phenotypic traits to pollination‐related performance metrics and reproductive fitness. We use this model as a framework for synthesizing the relevant literature, highlighting the studies included in the Special Issue, and identifying gaps in our understanding and opportunities for further development of the field. The papers that follow in this Special Issue provide new insights into the relationships between pollen production, presentation, flower morphology, and pollination performance (e.g., pollen deposition onto stigmas), the role of pollinators in pollen transfer, and the consequences of heterospecific pollen deposition. Several of the studies demonstrate exciting experimental and analytical approaches that should pave the way for continued work addressing the intriguing role of pollen in linking plant phenotypes to reproductive fitness.

Stingless bee pollen product from Mount Merapi Slope, Turi Yogyakarta Indonesia

Stingless beekeeping practice (meliponiculture) in Indonesia is known to have an important role in flowering plant pollination outcomes as the stingless bee species is widely distributed across most regions of the country. As a social insect, lebah klaceng (the local name of stingless bee) consists of many species which produces honey, bee pollen, and propolis. It has been found that higher diversity of the collected pollens indicates a higher success of pollination outcomes for different kinds of flowering plants. Thus, the aim of this study is to identify the diversity of collected stingless bee pollens in the meliponiculture practice at the Mount Merapi Slope, Turi, Yogyakarta, Indonesia by observing the pollen characteristics. Acetolysis method was used in the preparation of the collected pollens for identification. The pollens were then observed under a light microscope. The result showed that the stingless bee pollens collected from Mount Merapi Slope were successfully obtained from various flowering plants belonging to 31 families dominated by Arecaceae (46.60%), followed by Asteraceae (6.90%), and Malvaceae (5.70%). It can be concluded that the stingless bee, Tetragonula laeviceps, is a good pollinator insect which supports the successful pollination of up to 31 families of flowering plants found at the Mount Merapi Slope, Turi, Yogyakarta, Indonesia.

Bird composition as an environmental quality indicator in Wallacea’s urban area

North Sulawesi Province, part of Wallace Bioregion, has a complex ecosystem. Advanced urban development brings various impacts, such as environmental change. Birds’ existence around human provides some advantages, such as assisting the process of plant pollination, controlling insect populations, and indicators of environmental quality. This study aimed to determine the bird species composition in four locations and the environmental quality was analysed using the Bird Community Index (BCI). This study gathered data on bird species in Manado Bay, Gunung Tumpa, Kawanua Arboretum, and the Kaki Dian areas. We conducted field observation through point count method as primary data and the secondary data were obtained from previous publications. Data were analyzed using Bird Community and Sorenson indexes. This study revealed that the birds’ quantities and composition moderately varied in four locations. This study found 37 bird species in Manado Bay, 33 in Tumpa Mountain, 36 in Kawanua Arboretum, and 49 in the Klabat mountain areas. The Bird Community Index (BCI) accumulation ranged from 56.0 – 68.4 and it was categorized as medium environmental quality. Sorensen’s community similarity index displayed a value of 30.3-51.0% which classified as low to medium community similarity.

From a bee's eye: Effects of UV bullseye size on reproductive success in a dioecious vine Herpetospermum pedunculosum (Cucurbitaceae)

Descriptions of floral traits based on the visual capabilities of pollinators would advance our understanding of flower evolution and plant–pollinator relationships. One such trait is the contrasting UV bullseye color pattern, which is invisible to human eyes but can be perceived by bee pollinators. However, it remains largely unknown how UV bullseye size affects male and female reproductive fitness. We examined UV bullseye patterns in the dioecious Herpetospermum pedunculosum, and quantified the effects of UV bullseye size on male and female fitness. Both UV bullseye size and flower size were larger in male flowers than in female flowers. The dominant pollinators of H. pedunculosum were bees, which could perceive the UV bullseye pattern. Bee pollinators exhibited a preference for male flowers with nectar rewards, and visited a greater number of male flowers on plants with a larger UV bullseye. Male reproductive fitness was found to decrease in plants with larger UV bullseyes, likely due to the high rate of intra-plant pollen transfer. Rewardless female flowers were less attractive to bee pollinators, resulting in pollen limitation of seed production. Female flowers with moderate UV bullseye size produced more seeds. Our results suggest that UV bullseye is subject to different selection via male and female fitness of H. pedunculosum with deceptive pollination, and large UV bullseye is generally not favored. This research is the first to examine the relationship between UV bullseye size and plant reproductive success, highlighting that floral evolution should be investigated from the pollinator's eye in future research.

Tropical plant–hummingbird interactions withstand short‐term experimental removal of a common flowering plant

Theory suggests that species loss can trigger a coextinction cascade within a community, leading to declines in ecosystem function. However, experiments testing this prediction for plant–pollinator interactions remain uncommon. In this study, we simulated the local extinction of a hummingbird‐pollinated understory plant, Heliconia tortuosa, from tropical forest fragments using a replicated before‐after‐control‐impact (BACI) design while quantifying hummingbird abundance and space use (383 hummingbird captures and 36 radio‐tagged individuals), flower visitation rates (> 19 000 observation hours), and pollination success (529 flowers). We expected that H. tortuosa removal would either result in 1) coextinction, in which hummingbirds vacate fragments and compromise the reproductive success of the remaining flowering plants, or 2) increased hummingbird reliance on alternative floral resources, leading to sustained fragment use (persistence). In our experiment, hummingbird behavior and plant–hummingbird interactions were remarkably resistant to loss of H. tortuosa, a locally common plant species representing at least 30–40% of the available nectar resources on average. However, we did not discover evidence that hummingbirds increasingly used alternative floral resources to cope with this temporary resource loss. With the important caution that short‐term experiments may not emulate natural extinction processes, our study suggests that plant–pollinator interactions may be able to withstand single‐species plant losses, but the exact mechanisms enabling hummingbird persistence after resource removal require further research.

Spatio‐temporal variation in plant–pollinator interactions: a multilayer network approach

Despite the dynamic nature of communities, most research typically treated interaction networks as static entities, and only a few analysed the spatial and the temporal scales simultaneously. Here, we used spatial and temporal multilayer networks to explore the persistence of species and interactions in space and time, as well as the variation of species role (centrality) according to biotic factors. We further investigated, for the first time, the spatio‐temporal variation in multilayer network structure. Species exhibited substantial turnover across time mainly due to differences in species phenology. In contrast, interaction turnover was more pronounced across habitats, which seems to be a common strategy of pollinators to adjust interactions spatially to different ecological scenarios. Plant species were comparatively more important to the cohesiveness of spatial than temporal networks, whereas the centrality of pollinators correlated between scales. The importance of plant species fluctuated temporally due mainly to changes in flower density, whereas that of pollinators fluctuated in space and time according to their relative abundance. Module composition was highly unstable in time. Species were highly capable of changing partners and module affiliation across both scales. We conclude that plant–pollinator interactions are highly dynamic in space and time, and that there are differences between plants and pollinators in their use of resources across habitats and subseasons with implications for the understanding of functional connectivity and multilayer structure.

Solitary bee behaviour and pollination service delivery is differentially impacted by neonicotinoid and pyrethroid insecticides

Solitary bees are important pollinators of crops and wild plants, and their decline poses a risk to the sustained provision of the services they provide. Although evidence suggests that exposure to insecticides can affect bees, most pesticide research and risk assessment has focussed on social bees and mortality while solitary species are understudied. The ability to forage is critical for solitary bee reproduction, also in how they deliver pollination services, and we know little about how insecticides can impact these behaviours. We exposed solitary red mason bees (Osmia bicornis) to field realistic levels of two widely used insecticides with differing modes of action (lambda-cyhalothrin (pyrethroid) and acetamiprid (neonicotinoid)), in a semi-field setting over multiple rounds of exposure. We then tested impacts on bee behaviour and pollination in apples, an important global insect-pollinated crop. Pollination by insecticide-treated bees reduced apple production by up to 86 % depending on the compound and the number of exposures, but the underlying mechanism behind this remains unclear and should be investigated further. Other measurements of pollination services including number of seeds per apple and stigma pollen deposition showed no relationship with pesticide treatment. Bee foraging behaviour was also affected by treatment where both insecticides appear to induce an excitatory effect which was constant for acetamiprid and eventually ceased for lambda-cyhalothrin after multiple exposures. This suggests that both neonicotinoid and non‑neonicotinoid insecticides can potentially affect behaviour and pollination services of solitary bees depending on how often they are exposed, which is particularly important given the changing usage patterns of these compound classes based on regulations around their use. This highlights the importance of moving insecticide risk assessment towards more field realistic scenarios and including sublethal effects on solitary and social bees, in addition to considering repeated exposures of bees to pesticides as is realistic in the field.

Crop-pollinating Diptera have diverse diets and habitat needs in both larval and adult stages.

Insects are important pollinators of global food crops and wild plants. The adult and larval diet and habitat needs are well known for many bee taxa, but poorly understood for other pollinating taxa. Non-bee pollinators often feed on different substrates in their larval and adult life stages, and this diet and habitat diversity has important implications for their conservation and management. We reviewed the global literature on crop pollinating Diptera (the true flies) to identify both larval and adult fly diet and habitat needs. We then assembled the published larval and adult diets and habitat needs of beneficial fly pollinators found globally into a freely accessible database. Of the 405 fly species known to visit global food crops, we found relevant published evidence regarding larval and adult diet and habitat information for 254 species, which inhabited all eight global biogeographic regions. We found the larvae of these species lived in 35 different natural habitats and belong to 10 different feeding guilds. Additionally, differences between adult Diptera sexes also impacted diet needs; females from 14 species across five families fed on protein sources other than pollen to start the reproductive process of oogenesis (egg development) while males of the same species fed exclusively on pollen and nectar. While all adult species fed at least partially on floral nectar and/or pollen, only five species were recorded feeding on pollen and no fly larvae fed on nectar. Of the 242 species of larvae with established diet information, 33% were predators (n = 79) and 30% were detritivores (n = 73). Detritivores were the most generalist taxa and utilized 17 different habitats and 12 different feeding substrates. Of all fly taxa, only 2% belonged to the same feeding guild in both active life stages. Our results show that many floral management schemes may be insufficient to support pollinating Diptera. Pollinator conservation strategies in agroecosystems should consider other non-floral resources, such as wet organic materials and dung, as habitats for beneficial fly larvae.

Xylocopa caerulea and Xylocopa auripennis harbor a homologous gut microbiome related to that of eusocial bees.

Eusocial bees, such as bumblebees and honey bees, harbor host-specific gut microbiota through their social behaviors. Conversely, the gut microbiota of solitary bees is erratic owing to their lack of eusocial activities. Carpenter bees (genus Xylocopa) are long-lived bees that do not exhibit advanced eusociality like honey bees. However, they often compete for nests to reproduce. Xylocopa caerulea and Xylocopa auripennis are important pollinators of wild plants on Hainan Island. Whether they have host-specific bacteria in their guts similar to eusocial bees remains unknown. We targeted the bacterial 16S rRNA V3-V4 region to investigate the diversity of bacterial symbionts in the fore-midgut and hindgut of two carpenter bees, X. caerulea and X. auripennis. A maximum of 4,429 unique amplicon sequence variants (ASVs) were detected from all samples, belonging to 10 different phyla. X. caerulea and X. auripennis shared similar bacterial community profiles, with Lactobacillaceae, Bifidobacteriaceae, and Orbaceae being dominant in their entire guts. X. caerulea and X. auripennis harbor a highly conserved core set of bacteria, including the genera Candidatus Schmidhempelia and Bombiscardovia. These two bacterial taxa from carpenter bees are closely related to those isolated from bumblebees. The LEfSe analysis showed that Lactobacillaceae, Bifidobacteriaceae, and the genus Bombilactobacillus were significantly enriched in the hindguts of both carpenter bees. Functional prediction suggested that the most enriched pathways were involved in carbohydrate and lipid metabolism. Our results revealed the structure of the gut microbiota in two carpenter bees and confirmed the presence of some core bacterial taxa that were previously only found in the guts of social bees.

Long-term changes in the composition and distribution of the Hungarian bumble bee fauna (Hymenoptera, Apidae, Bombus)

One of the most important pollinator taxa is Bombus (Hymenoptera, Apidae), the genus of bumble bees, since they are important, often specialized, pollinators of many plants. As a result of climate change, warming winters and changes in landscape structure, the distribution and frequency of Bombus species is constantly changing. To develop appropriate protection strategies, it is essential to monitor them and update the occurrence and threat status of the species. The last review of the distribution of Bombus species in Hungary was completed 20 years ago. Here we present updated distribution maps based on published data from the last 20 years together with unpublished data collected in 2018–2021. Based on the new data, we examine changes in the last two decades. In the case of 9 species further studies should be carried out to confirm the presence of stable populations, while 3 species are recommended for protection by law in Hungary. Seven species showed increasing frequency, B. argillaceus and B. haematurus.

Interspecific competition shapes the structural stability of mutualistic networks

Mutualistic networks, such as plant–pollinator networks, have attracted increasing attention in the ecological literature in the last decades, not only because of their fascinating natural history, but also because mutualistic interactions have been shown to play a key role in the maintenance of biodiversity. Although inter-specific competition has long been known to be a crucial driver of species coexistence as well, there is a lack of theory investigating the interplay between the structures of competitive and mutualistic networks when jointly considered. Here, we develop an analytical framework to study the structural stability — the range of conditions under which all species coexist stably, i.e. where the community is both feasible and stable — of ecological communities in which both mutualistic interactions between plants and pollinators and competitive interactions among plants and among pollinators are present. Using the structure of 50 real networks for mutualistic interactions, combined with analytical and numerical analyses, we show that the structure of the competitive network radically alters the necessary conditions for species coexistence in these communities. Our mathematical framework also allows to accurately characterize the structural stability of these systems. Moreover, we introduce a new metric that accurately links the network structures of competitive and mutualistic interactions to species coexistence. Our results highlight the joint role of the structures of different interaction types to understand the stability of ecological communities and facilitate the analysis of similar natural and artificial systems in which mutualism and competition coexist.

Landscape composition and pollinator traits interact to influence pollination success in an individual‐based model

Abstract The arrangement of plant species within a landscape influences pollination via changes in pollinator movement trajectories and plant–pollinator encounter rates. Yet the combined effects of landscape composition and pollinator traits (especially specialisation) on pollination success remain hard to quantify empirically. We used an individual‐based model to explore how landscape and pollinator specialisation (degree) interact to influence pollination. We modelled variation in the landscape by generating gradients of plant species intermixing—from no mixing to complete intermixing. Furthermore, we varied the level of pollinator specialisation by simulating plant–pollinator (six to eight species) networks of different connectance. We then compared the impacts of these drivers on three proxies for pollination: visitation rate, number of consecutive visits to the focal plant species and expected number of plants pollinated. We found that the spatial arrangements of plants and pollinator degree interact to determine pollination success, and that the influence of these drivers on pollination depends on how pollination is estimated. For most pollinators, visitation rate increases in more plant mixed landscapes. Compared to the two more functional measures of pollination, visitation rate overestimates pollination service. This is particularly severe in landscapes with high plant intermixing and for generalist pollinators. Interestingly, visitation rate is less influenced by pollinator traits (pollinator degree and body size) than are the two functional metrics, likely because ‘visitation rate’ ignores the order in which pollinators visit plants. However, the visitation sequence order is crucial for the expected number of plants pollinated, since only prior visits to conspecific individuals can contribute to pollination. We show here that this order strongly depends on the spatial arrangements of plants, on pollinator traits and on the interaction between them. Taken together, our findings suggest that visitation rate, the most commonly used proxy for pollination in network studies, should be complemented with more functional metrics which reflect the frequency with which individual pollinators revisit the same plant species. Our findings also suggest that measures of landscape structure such as plant intermixing and density—in combination with pollinators' level of specialism—can improve estimates of the probability of pollination. Read the free Plain Language Summary for this article on the Journal blog.

In Which Way Do the Flower Properties of the Specialist Orchid Goodyera repens Meet the Requirements of Its Generalist Pollinators?

This article is the next part of a series of studies documenting the influence of flower traits on the reproductive success (RS) of orchids. Knowledge of factors influencing RS helps to understand the mechanisms and processes crucial for shaping plant-pollinator interactions. The aim of the present study was to determine the role of flower structure and nectar composition in shaping the RS of the specialist orchid Goodyea repens, which is pollinated by generalist bumblebees. We found a high level of pollinaria removal (PR) and female reproductive success (fruiting, FRS) as well as a high level of variation between populations, although in certain populations pollination efficiency was low. Floral display traits, mainly inflorescence length, influenced FRS in certain populations. Among the flower traits, only the height of flowers was correlated with FRS in one population, suggesting that the flower structure of this orchid is well adapted to pollination by bumblebees. The nectar of G. repens is diluted and dominated by hexoses. Sugars were less important in shaping RS than amino acids. At the species level, twenty proteogenic and six non-proteogenic AAs were noted, along with their differentiated amounts and participation in particular populations. We found that distinct AAs or their groups mainly shaped PR, especially when correlations were considered at the species level. Our results suggest that both the individual nectar components and the ratios between them have an impact on G. repens RS. Because different nectar components influence the RS parameters in different ways (i.e., negatively or positively), we suggest that different Bombus species play the role of main pollinators in distinct populations.

Complex preference relationships between native and non-native angiosperms and foraging insect visitors in a suburban greenspace under field and laboratory conditions

The introduction and spread of non-native flora threatens native pollinators and plants. Non-native angiosperms can compete with native plants for pollinators, space, and other resources which can leave native bees without adequate nutritional or nesting resources, particularly specialist species. In the current study, we conducted flower preference experiments through field observations and controlled binary choice tests in an artificial arena to determine the impact of field vs. laboratory methods on flower preferences of native bees for native or non-native flowers within their foraging range. We conducted counts of insect pollinators foraging on the flowers of three plant species in a suburban green belt including one native (Arthropodium strictum) and two non-native (Arctotheca calendula and Taraxacum officinale) plant species. We then collected native halictid bees foraging on each of the three plant species and conducted controlled binary tests to determine their preferences for the flowers of native or non-native plant species. In the field counts, halictid bees visited the native plant significantly more than the non-native species. However, in the behavioural assays when comparing A. strictum vs. A. calendula, Lasioglossum (Chilalictus) lanarium (Family: Halictidae), bees significantly preferred the non-native species, regardless of their foraging history. When comparing A. strictum vs. T. officinale, bees only showed a preference for the non-native flower when it had been collected foraging on the flowers of that plant species immediately prior to the experiment; otherwise, they showed no flower preference. Our results highlight the influence that non-native angiosperms have on native pollinators and we discuss the complexities of the results and the possible reasons for different flower preferences under laboratory and field conditions.