Insect Pollinators Research Articles

Relationships between flower-visiting insects and forest cover in cocoa-growing landscapes in Ghana

Abstract Context Increased cocoa cultivation (Theobroma cacao) has led to the conversion of over 6 million hectares of rainforest to cocoa farmlands in West Africa. Globally, pollinator decline has been driven by land use changes. Though land use change through cocoa expansion may affect insect pollinators and, by extension, pollination services, this has rarely been assessed. Objectives Our study examined the relationships between the proportion of natural forest in the landscape (reduced primarily due to cocoa expansion) and flower-visiting insect abundance, and bee abundance, richness, diversity and community composition. The effect of pan trap type (aerial or ground) was also tested. Methods Eighteen sites were selected along a gradient of an increasing proportion of natural forests in the surrounding landscape (from 9 to 100%). Ground and aerial pan traps were deployed in each site to sample flower-visiting insects. Two sampling sessions were conducted; during the rainy season in 2021 and during the dry season in 2022. Results The abundances of Coleoptera, Hymenoptera and Hemiptera increased with increasing proportion of natural forests in the landscape, while Diptera decreased. Natural forest and trap type did not significantly influence bee abundance, species richness, and Shannon diversity. However, bee community composition differed along the forest gradient, indicating that forests and cocoa farms harbour different bee communities. Ground pan traps captured more insects (61% of 19,927 flower-visiting insects) than aerial pan traps, which was driven by the Diptera as the abundances of the other orders were not significantly related to trap type. Conclusions Preserving natural forest in cocoa-growing landscapes is important to sustain the coexistence of diverse flower-visiting insect communities owing to their differential responses to the proportions of natural forests.

Insect Pollinators and Plant Interactions; Identification of Selected Melliferous Plants Using Pollen Morphological Features

Insect Pollinators and Plant Interactions; Identification of Selected Melliferous Plants Using Pollen Morphological Features

Unraveling the acute sublethal effects of acetamiprid on honey bee neurological redox equilibrium.

Understanding the off-target effects of neonicotinoid insecticides, including acetamiprid, which is the most commonly applied agricultural chemical, is crucial as it may be an important factor of negative impact on pollinator insects causing a number of problems such as colony collapse disorder (CCD) of honey bees. While CCD is known as a multifactorial disease, the role of pesticides in this context is not negligible. Therefore, it is essential to gain a deeper comprehension of the mechanisms through which they function. The aim of this research was to study the effects of sublethal acetamiprid doses on honey bees, specifically focusing on the redox homeostasis of the brain. According to our findings, it can be confirmed that acetamiprid detrimentally impacts the redox balance of the brain increasing hydrogen peroxide and malondialdehyde levels, suggesting consequential lipid peroxidation and membrane damage as consequences. Moreover, acetamiprid had negative effects on the glutathione system and total antioxidant capacity, as well as key enzymes involved in the maintenance of redox homeostasis. In summary, it can be concluded that acetamiprid adversely affected the redox balance of the central nervous system of honey bees in our study. Our findings could potentially contribute to a better understanding of pesticide-related consequences and to improvement of bee health.

Optimizing sunflower yield: Understanding pollinator contribution to inform agri-environmental strategies

ContextThe agricultural intensification due to global increased food demand has harmed pollinator communities worldwide. However, some of the economically most important oilseed crops, such as the sunflower, depend on pollinators to produce seeds. While self-fertile varieties have undergone genetic selection to guarantee productivity, the pollinator-dependence levels and the economic contribution of pollinators have not been fully estimated. ObjectiveHere, we aimed to explore floral and pollinator constraints limiting the agricultural yield of sunflower varieties most frequently used in the Iberian Peninsula. MethodsPollination experiments were undertaken to analyse the pollinator-dependence level of 12 varieties under controlled conditions and also under natural conditions in 23 fields of two Spanish agricultural regions. The selfing ability and economic contribution of pollinators were estimated by comparing bagged and open-pollination treatments. ResultsOur results showed that the degree of pollinator-dependence is highly dependent on sunflower variety, with impacts on production and productivity outcomes, e.g. individual plant yield values varied between 0.188 and 0.692. Several varieties could self-fertilize and produce seeds regardless of pollinators. However, outcrossing significantly increased seed set in most varieties with increments up to 0.341. Overall, a trade-off between the number and weight of seeds was observed. Under natural field conditions, pollinators significantly increased overall sunflower production, although differences were observed among regions (increment of 275 kg/ha in Burgos and 382 kg/ha in Cuenca), with an associated economic outcome. ConclusionsThe self-fertilization ability and the level of pollinator-dependence vary according to the intrinsic reproductive traits of the variety analysed. Although some varieties are able to produce seeds despite the absence of pollinators, the sunflower clearly benefits from insect pollination. The landscape context and the availability of pollinator communities influenced the final crop yield and the economic outcome. SignificanceCombining landscape-restoring interventions with the cultivation of self-compatible varieties during at least the first years of implementation may be a solid additional agri-environmental strategy to maintain production levels and economic outcomes, which may particularly mitigate effects of pollinator and biodiversity losses mainly in highly simplified agroecosystems.

Flying by night: Comparing nocturnal pollinator networks over time in the Colorado Rocky Mountains

Abstract Where climate is seasonal, such as in high‐altitude ecosystems, the occurrence and activity patterns of insect pollinators may vary with the varying occurrence of floral resources. This high turnover of species occurrence and interactions may lead to changes in the structure and properties of plant–pollinator networks. Here, we systematically compared the properties of moth pollen‐transport networks in Colorado, USA, over the course of a season, and tested for a link between moth species specialisation and morphology. We predicted that network properties would change through the season as the abundance and diversity of available floral resources increased. We also predicted that there would be a link between moth specialisation and morphology, as moth proboscis length can restrict their ability to utilise different floral resources. We sampled moths for pollen over 9 weeks in June through August 2021. We then constructed pollen‐transport networks, and used mixed models to test for differences in network indices between different parts of the 2021 season; we also tested for a relationship between moth proboscis length, the duration of moth species' presence across the season and the number of flower species pollinated. As expected, we found high rates of species turnover and high rates of plant–pollinator interactions over the summer. However, linkage density and robustness were the only overall network metrics that changed. We also found that longer proboscis lengths and more persistent species occurrence over the season were predictive of higher generalisation among moth species. We suggest that even with high rates of species turnover, nocturnal moth pollen‐transport networks may maintain their overall structure over a season, with variations in the availability of floral resources driving limited variation in some network metrics. Our study highlights the necessity of continuing to research moth pollen‐transport networks over different temporal scales, to better understand how ecological factors can lead to changes in network structure over time.

Vanilla planifolia: Artificial and Insect Pollination, Floral Guides and Volatiles.

The natural pollinator of the major species of commercially-grown vanilla, Vanilla planifolia, is unknown, and the crop requires hand pollination to achieve significant levels of fruit set; however, the traditional technique (using a toothpick) is costly, as it requires skilled personnel. To overcome this problem, two native Australian bees, Tetragonula carbonaria and Austroplebeia australis, and the blowfly, Lucilia cuprina, were trialled as pollinators. Three alternatives to the toothpick method were also trialled. The appearance of vanilla flowers under ultraviolet radiation was examined to determine the presence of cryptic pollination guides, and the chemical composition of nectar from extrafloral nectaries and aroma volatiles from the flowers were characterised. None of the three insects effected pollination due to their small size and behaviour; other insect pollinators need to be identified. The alternative mechanical methods of pollination trialled resulted in fruit set; however, the percentages of fruit set were lower than the traditional toothpick method, and the fruit were of inferior quality. The nectar produced predominantly consisted of sucrose and melezitose. Melezitose is a strong attractant of various ant species, which may explain the concentration of ants around the nectaries and the apparent lack of nectar production in part of this study. The aroma volatiles included monoterpenoids, terpenes, sesquiterpenoids, aromatics, nitrogen-containing compounds and fatty acids, the most abundant being a-pinene and eucalyptol. Illumination of the flowers with UV-A radiation revealed fluorescence from the stamens, the column and the callus, which is located on the labellum. These observations may aid the identification and use of potential pollinators.

Biodiversity measures of a grassland plant-pollinator community are resilient to the introduction of honey bees (Apis mellifera).

The prairies of Canada support a diversity of insect pollinators that contribute pollination services to flowering crops and wild plants. Habitat loss and use of managed pollinators has increased conservation concerns for wild pollinators, as mounting evidence suggests that honey bees (Apis mellifera) may reduce their diversity and abundance. Plant-pollinator community analyses often omit non-bee pollinators, which can be valuable contributors to pollination services. Here, we experimentally introduced honey bees to examine how their abundance affects the species richness, diversity, abundance, species composition, interaction richness, and interaction diversity of all wild pollinators, and of four higher taxa separately. We identified all insect pollinators and analyzed how honey bee abundance affected the above biodiversity metrics, controlling for flower abundance and flower species richness. Even with high honey bee densities, there was no change to any of these variables, except that beetle species diversity increased. All other taxa had no significant relationship to honey bee abundance. Considering the widespread use of managed honey bees, the effect they have on wild pollinators should be firmly established. Our results suggest that honey bees have little to no short-term impact on the wild pollinator community or its interactions with plants in this native grassland.

From Stream to Bloom: Exploring the Potential Role of Aquatic Insects for Pollination in Wetland Environments

From Stream to Bloom: Exploring the Potential Role of Aquatic Insects for Pollination in Wetland Environments

Assessing the economic and nutritional value of pollination services in Nepal

Pollination is a key ecosystem service crucial for supporting agricultural production, economic growth, social inclusion, and environmental protection. Understanding the economic value of pollination and its impact on human health and nutrition is essential for effective pollinator conservation and management. This study evaluates the economic and nutritional value of pollination services in Nepal and quantifies historic changes in pollinator reliance. Using public data on agricultural production and commodity prices, in combination with published nutritional composition values, we employ the dependency-ratio method to quantify economic and nutritional value across different regions of the country and through time. We conservatively estimate the annual economic value of pollination services in Nepal at US $477 million, representing 9% of total agricultural revenue. Pollinator-dependent crops, particularly fruits and vegetables are the source of essential nutrients; 40% of plant-based vitamin A and 14% of vitamin C are directly attributable to insect pollination. The cultivated area of these pollinator-dependent crops has increased by 91% in Nepal over 20 years – 3.7 times faster than equivalent increases in non-pollinator-dependent crops. The decline in wild pollinators during the same time period poses a threat, leading to potential pollination deficits and crop losses. Our study underscores the importance of conserving and managing pollinators to ensure sustainable agriculture, food security, and nutrition. Targeted efforts, including policy interventions and conservation strategies, are needed to safeguard pollinator populations and enhance pollination services.

Complementary effects of pollination and biocontrol services enable ecological intensification in macadamia orchards.

In many crops, both pollination and biocontrol determine crop yield, whereby the relative importance of the two ecosystem services can be moderated by the landscape context. However, additive and interactive effects of pollination and biocontrol in different landscape contexts are still poorly understood. We examined both ecosystem services in South African macadamia orchards. Combining observations and experiments, we disentangled their relative additive and interactive effects on crop production with variation in orchard design and landscape context (i.e., cover of natural habitat and altitude). Insect pollination increased the nut set on average by 280% (initial nut set) and 525% (final nut set), while biocontrol provided by bats and birds reduced the insect damage on average by 40%. Pollination services increased in orchards where macadamia tree rows were positioned perpendicular to orchard edges facing natural habitat. Biocontrol services decreased with elevation. Pest damage was reduced by higher cover of natural habitat at landscape scale but increased with elevation. Pollination and biocontrol are both important ecosystem services and complementary in providing high macadamia crop yield. Smart orchard design and the retention of natural habitat can simultaneously enhance both services. Conjoint management of ecosystem services can thus enable the ecological intensification of agricultural production.

Foraging behaviour and pollinator dynamics in lucerne crop of the Bundelkhand region: Implications for crop management in the subtropics

Abstract Pollination stands out as the paramount ecosystem service facilitated by insect pollinators, providing benefits to over three quarters of the world’s major crops. The conservation and effective management of honeybees constitute integral components for ensuring the sustainable productivity of cross-pollinated crops. The present study aimed to document the potential pollinators of lucerne in the Bundelkhand region in India, which is known for its subtropical climatic conditions. Further, the foraging behaviour, including foraging rate and speed, was meticulously documented. A total of 13 insect species from seven families across three insect orders were observed visiting lucerne flowers. Hymenopterans comprised the majority of the floral visitors (73.48%), followed by Lepidoptera (26.51%) during the study period. Among them, Apis dorsata (Hymenoptera: Apidae) emerged as the most predominant floral visitor, exhibiting peak activity at 12:00 h with a density of 7.85 bees/m2/10 min. Surprisingly, among the major floral visitors, A. florea has the highest mean foraging rate (number of flowers visited/minute/forager), i.e., 11.56, 11.59 and 10.79 bees/flowers/minute during the initial flowering stage, peak flowering stage and late flowering stage, respectively. However, the foraging speed (time spent by the forager on each flower) was longest in A. dorsata, i.e., 5.05, 3.78 and 5.41 s/flower during initial, peak and late flowering stages, respectively. The findings emphasize the importance of enhancing honeybee activity to boost lucerne seed yield. Further, the outcomes of the study can be leveraged to optimize honeybee colony management, scheduling field operations such as pesticide application and weeding during periods of minimal honeybee activity.

The all-day pollinator visits of sunflower inflorescences in Helianthus annuus plantations are independent of head orientation: Testing a widespread hypothesis.

Mature inflorescences of sunflowers (Helianthus annuus) orient constantly on average to the geographical east. According to one of the explanations of this phenomenon, the eastward orientation of sunflower inflorescences increases the number of attracted insect pollinators. We tested this hypothesis in three field experiments performed in flowering sunflower plantations. In experiments 1 and 2 we measured the number of insects trapped by the vertical walls of sticky sunflower models facing north, east, south, and west. In experiment 3 we counted the pollinators' landings on real sunflower inflorescences facing naturally east or turned artificially toward north, south, and west. We found that the all-day number of pollinators (predominantly bees) attracted to model and real sunflowers in H. annuus plantations is independent of the azimuth direction of sunflower heads, and after 10 h in the morning, the average number of pollinators counted every 20 min is practically constant in the rest of the day.

Significance of honeybee pollination in increasing seed yield of Trifolium alexandrinum (Fabales: Fabaceae)and its impact on economic sustainability of smallholder farmers.

A major limitation to producing high seed yields in berseem clover (Trifolium alexandrinum L.) is failure to set seed, predominantly due to lack of pollination. Despite the importance of berseem clover as a leading forage legume, the contribution of pollinators to seed set is scarce. In Pakistan, the honeybee population is declining mainly because of the extensive use of neonicotinoid pesticides and habitat fragmentation. This, combined with the region's harsh environment and the use of inferior, locally bred genotypes, has resulted in low seed yields. Insufficient seed availability leads to limited forage supply, resulting in poor livestock nutrition, which subsequently impacts livestock health and productivity, and reduces farmers' income. The present study estimated the seed production of 3 berseem clover genotypes resulting from honeybees [Apis mellifera L. (Hymenoptera: Apidae)] pollination in 2 growing seasons (2012-2014) in the central Punjab region of Pakistan. Experiments had 2 pollination treatments (open pollination and honeybee inclusion) and 3 seed genotypes, viz. farmer own-saved, market, and the improved variety cultivars. For both growing seasons, honeybee pollination resulted in significant increases in seed yields ranging from 35% to 67%, regardless of seed genotype. With the exception of the number of seed heads/m2, all seed yield parameters also increased significantly in response to honeybee inclusion. The combination of improved variety and honeybee inclusion resulted in the production of a maximum number of seeds per head (45.3), 1,000-seed weight (3.7g), and estimated seed yield (375.5kg/ha). In addition, the increase in estimated net income of seed ranged from PKR 82,485 Rs/ha (US$844/ha) to PKR 168,975 Rs/ha (US$1728/ha) with the use of honeybees as an insect pollinator across all the seed genotypes. Honeybee pollination has broader implications for mixed farming systems by playing a key role in preserving biodiversity and promoting sustainable agriculture. It also enhances the quality and quantity of berseem crops by increasing the production of high-quality seeds and forage leading to improved livestock productivity and family food security which strengthens the economic resilience of rural communities.

Critical thermal maxima differ between groups of insect pollinators and their foraging times: Implications for their responses to climate change

Insects perform essential roles within ecosystems and can be vulnerable to climate change because of their small body size and limited capacity to regulate body temperature. Several groups of insects, such as bees and flies, are important pollinators of wild and cultivated plants. However, aspects of their thermal biology remain poorly studied, which limits predictions of their responses to climate change. We assessed the critical thermal maximum (CTMax) of bees and flies visiting flowers in urban and periurban areas in tropical and subtropical regions of the Americas. We also assessed the effect of the foraging time of the day on CTMax. Overall, we found that bees displayed higher CTMax than flies. Flies foraging in the morning and afternoon displayed similar CTMax while bees in the morning displayed a higher CTMax than in the afternoon. The results of this study suggest differences in the vulnerability to climate change between these two major groups of pollinators, with flies being more at risk.

Pollen trapping as Honeybees pollination management and identification of dominant pollinators of Guizotia abyssinica (L.f).

Pollination is one of the most fascinating aspects of insect-plant interactions. Pollen is the male reproductive element of flowering plants, gathered by foraging Honeybees from the male parts of flowering plants called the anther. Guizotia abyssinica (L.f) is an important oilseed crop cultivated in Ethiopia and India, which belongs to the family Asteraceae. Although self-incompatibility is found in Guizotia abyssinica, a higher seed set is experienced in places with an active Honeybees population. Agricultural practices usually focus on inputs such as fertilizer application to improve seed yield of Guizotia abyssinica. However, these practices have little effect on yield if the availability of insect pollination is too low. To fill this gap, an experiment was carried out at Dandi district, West Shao zone, Oromia, Ethiopia to see the effect of Honeybees pollination management as an agronomic input. Pollination management of Honeybees was tested under feeding and non-feeding of colonies management. Pollen was trapped with and without sugar syrup feeding. The results discovered that Honeybees fed sugar syrup collected much more pollen than colonies not fed sugar syrup. The proportion of Guizotia abyssinica pollen collected through sugar syrup feeding of the colony was greater (62.2%), compared to the proportion of Guizotia abyssinica pollen trapped without sugar syrup feeding (37.8%). This indicates that sugar syrup feeding enhances the collection of pollen and probably enhances the pollination efficiency of Honeybees since they visit frequently to fulfill their daily protein requirement of pollen. Therefore, Honeybees pollination services should be included as one of the agronomic inputs with sugar syrup feeding as pollination management that might increase the yield of Guizotia abyssinica since it increases visiting frequency.

Density, Abundance and Diversity of Insect Pollinators at Agro-Ecosystems of Kodagu District, Karnataka, India

Density, Abundance and Diversity of Insect Pollinators at Agro-Ecosystems of Kodagu District, Karnataka, India

Evaluating the role of insect pollinators in the viability of true seeds of shallot in tropical agroecosystems

Pollen transfer in tropical agroecosystems to increase seed production has received limited research, notably on shallot pollination and insect pollinators. This study evaluated how insect pollinators optimize shallot seed production in tropical agroecosystems, i.e. Batu and Malang Districts in Indonesia. This study was conducted from June to October in 2023. We examined pollinator diversity, foraging behavior, and the effectiveness of dominating insect pollinators during umbel flower anthesis, as well as visiting insect foraging and visiting patterns. We assessed pollinator effectiveness by comparing visitation rates under four treatments. A total of 21 insect species belonging to three orders visited the shallot flowers, of which 14 species have the potential to act as pollinators. Apis cerana Fabricius, 1793 (Hymenoptera: Apidae) and Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) emerged as potentially effective pollinators. Air temperature significantly influenced pollinator activity in visiting anthesis umbels. Evaluations of pollinator efficiency showed that A. cerana was more efficient than L. sericata in promoting the production of true shallot seed and has a significant role in ensuring high-quality pollination. This highlights the necessity of comprehending the specialized contributions of pollinators for shallot seed production.

Influence of climate, weather and floral associations on pollinator community composition across an elevational gradient

Insect pollinators, which are ectothermic, are especially sensitive to abiotic conditions, which often drive predictable patterns of pollinator species turnover along environmental gradients. However, pollinator activity is also reliant on suitable biotic conditions, such as the presence of host plants. High‐elevation environments provide a useful setting to examine the relative contribution of abiotic and biotic factors in shaping species interactions as they are often characterised by strong environmental gradients over short geographic distances. Here, we examined pollination interaction networks across an elevational gradient from 930–2000 m a.s.l. in southern Australia, to determine the underlying patterns of pollinator activity and their interactions with flowers. Interaction frequency of Diptera increased at high elevations, while interaction frequency of Hymenoptera and Coleoptera decreased. We provide evidence that this elevational pattern of activity is partly driven by floral associations, with interactions dominated by Hymenoptera‐attracting plant families at lower elevations (Proteaceae, Fabaceae) and a Diptera‐attracting family at high elevation (Asteraceae). Pollinator activity was also influenced by weather conditions, with reduced activity for all three orders at lower temperatures, and Diptera active across the broadest range of temperature, humidity and wind conditions. We suggest that changes across elevation gradients in pollinator community composition are driven by both direct responses to abiotic conditions such as temperature, as well as the elevational distribution patterns of associated flowering plants. Despite these distinct shifts in composition of the pollinator assemblage with elevation, pollination network structure was stable across the elevational gradient, with moderate levels of specialisation and low levels of connectance and nestedness present across the gradient. By considering both abiotic conditions and biotic processes, our results provide insight for predicting the impacts of upslope vegetation shifts on pollinator communities in the face of climate change.

Multi-method approach to assessing the floral-visiting insect assemblage of rare, abophilous plant Baccharis vanessae in Southern California.

Insects are the major pollination vectors for angiosperms, and insects native to a given habitat can play an irreplaceable ecological role in food webs and plant reproduction. With precipitous declines in insect species over the last decades, it is urgent to document insect assemblages in native plant communities to support conservation efforts. Identifying pollinators and their pollination activity is challenging; however, emerging technological methods are providing new monitoring capabilities. In this study, we compare the accuracy of two different methods of monitoring to assess the flower-visiting insect assemblage and likely pollinators of Encinitas baccharis (Baccharis vanessae): focal observations and video recordings from camera traps. B. vanessae is a rare, endemic species found in Coastal Sage Scrub communities in San Diego County. This federally listed species is threatened by habitat loss and fragmentation, which may also be affecting the availability of its insect pollinators. Results indicate that B. vanessae supports and is supported by a variety of flower-visiting insect groups. The diversity of insect visitors at male and female plants were similar across all diversity measurements. The insect vectors identified were as expected given B. vanessae pollination syndrome. This syndrome also aligns with wind as a pollination vector, providing evidence of ambophily. While focal observations underreported insect activity by approximately half, the proportions of common diurnal visitors were similar with both methods. Camera traps were unable to provide sufficient detail to discern visually similar groups, but were able to record nocturnal insect activity, which was dominated by moths (Lepidoptera, 82%). While collection protocol in this study did not record the time an insect spent interacting with a flower, we anecdotally observed moths spent notably longer periods in contact with flowers than most diurnal insects. This study has implications for effective monitoring and conservation of endangered plant species and their affiliated pollinators.

Molecular characterization and identification of insect pollinators of Valeriana jatamansi Jones from Shimla Hills, Western Himalaya, India

Valeriana jatamansi Jones a perennial medicinal herb belongs to the family Caprifoliaceae and highly pollinated by wild insect pollinators. In present investigation a total of 51 species of flower visitors were reported on V. jatamansi at altitude range of 1,927 to 2,850 m, in different localities of Shimla Hills, Western Himalaya. The collected insect pollinator species were taxonomically identified and 29 of them were olecularly characterized and identified using the cytochrome c oxidase subunit 1 (COI) sequence from mitochondrial DNA (mtDNA). BLAST analysis revealed 98 to 100 per cent similarity with the existing GenBank sequences. The average AT content was found to be significantly higher (69.8%) compared to the GC content (30.0%), indicating AT bias in all sequences. Phylogenetic analysis of 29 different species of insect ‘pollinator of V. jatamansi revealed two clades, one shows phylogenetic relationship between 28 species which belongs to four orders Diptera, Hymenoptera, Hemiptera and Lepidoptera and the other shows the one species which belongs to order Coleoptera. This study contributes to increasing the number of published accounts of NCBI and helps to accurately distinguish the pollinator fauna of Valeriana Jatamansi.