Supplemental Pollination Research Articles

Investigating the impact of supplementary pollination methods on seed production and yield in Lucerne (Medicago sativa L.)

Investigating the impact of supplementary pollination methods on seed production and yield in Lucerne (Medicago sativa L.)

Effects of Supplementary Pollination on Macadamia Nut Set, Retention and Yield in Murang’a County, Kenya

Macadamia is a promising prime dessert nut with the potential of alleviating poverty and enhancing food security in Kenya. Nut set and subsequent development of nuts to maturity is dependent on pollination which is mediated by animals, and honey bees are the dominant macadamia flower visitors. However, macadamia is pollen deficit as not all flowers set develop to mature nuts, thus supplemental pollination results to better nut yields. There is limited information in Kenya among the smallholder macadamia growers on the importance of supplementing pollination to enhance nut yields. This study was conducted at Kandara Macadamia Research Centre and in a smallholder macadamia farm located 15 km from the research centre, which was purposively selected from July 2021 to May 2023. Assessment of the influence of pollinators and supplementing pollination to nut set, retention and final yields was done. Honey bee, (Apis mellifera L.) colonies were also introduced at the Macadamia Research Centre to enhance pollination and mitigate deficits. Racemes were bagged to exclude pollinators, others left open to unlimited pollinator access while others received supplemental hand pollination. The results demonstrate that macadamia is pollen limited and pollination is highly reliant on insect pollinators. There were significant differences (p < 0.001) among the bagged (pollinator exclusion), open and hand pollinated racemes in both farms. The initial nut set and retention was increased significantly (21.54%) in hand pollinated racemes compared to those that were left to open pollination (unlimited pollinator visits) depicting pollination deficit in farm B. Introduction of supplementary honey bee colonies at the Kandara Macadamia Research Centre, resulted to higher nut set, retention, nut-in-shell and kernels. Macadamia growers are encouraged to introduce honey bee colonies in their farms to improve yields and also address pollination deficits.

Vibration inducing and airflow guiding coupled tomato pollination method research based on gas–solid two-phase flow model

Supplementary pollination helps to improve yield and quality for tomato planting in greenhouse. Current tomato supplementary pollination methods with vibrator or blower can only realize the vibration induced pollen release without particles guiding. The vibration pollen release inducing and airflow pollen movement guiding coupled tomato pollination method and numeric simulation model were imposed in this paper. Firstly, the numeric simulation model based on gas–solid two-phase flow model of tomato pollination under vibration inducing and airflow guiding was established which considering the shape and surface characteristics of tomato pollen particles. Then, the response surface test of three factors and three levels was conducted using the numerical model by taking airflow angle, airflow start time and airflow velocity as factors, the effective pollination amount as pollination effect evaluation indicators. The test result showed that the maximum effective pollinated pollen particles could be acquired with airflow angle of 12.67°, airflow start time of 519.45 ms and airflow velocity of 0.72 m·s−1. Finally, the movement characteristics of tomato pollen particles in the simulation model were compared with the actual high-speed photography observation. The pollen particles movement trajectories in the simulation model were similar to them in actual observation. And the average movement velocities of the pollen particles moving downward and upward were only 7.59 % and 8.33 % differences between the results in simulation model and in actual observation. The average coverage rate of pollen particles on the stigma was 9.59 % with the vibration inducing and airflow guiding coupled pollination method, which was 85.85 % and 100.63 % relatively higher than vibration pollination and airflow pollination. The results show that vibration inducing and airflow guiding coupled pollination method with the optimized airflow parameters can improve the pollination effect, and the numerical simulation model established in this paper were reliable. The research results in this paper lays a foundation for the design and optimization of tomato pollination method and provides a theoretical basis for the application of gas–solid two-phase flow model in the design of supplementary pollination equipment.

Tomato flower pollination features recognition based on binocular gray value-deformation coupled template matching

It is necessary to recognize the tomato pollination features for the designing demand of intelligent and precise tomato supplementary pollination equipment. Mentioned pollination features include flower opening state and the three-dimensional position and pose of flower anther. Tomato flower pollination features recognition method is designed in this paper based on the deep learning full opened flower recognition model and binocular template matching three-dimensional information recognition method. First of all, a binocular stereo vision system is built to acquire the tomato flower images in greenhouse with natural lighting. Which can help vision system avoid the impact of inconsistent light intensity on image recognition. The acquired images were equalized with three groups parameters to labeled images. And the improved MC-AlexNet deep learning model is established to recognize the full opened tomato flowers in the left image of image pair acquired with binocular vision system. Then, the template is created with the full opened flower recognition result of deep learning model in left image based on gray value and deformation template matching method. And the template matching is established to recognize the corresponding full opened flowers in the right image of image pair. Finally, with the template matching result, the anther segmentation is conducted to calculate three-dimensional position and pose of anther. The experimental results show that the accuracy of full opened tomato flowers recognition model is 96.23%. The average position recognition deviation of anther is 5.94 mm. And the average anther pose recognition deviation in three plane is 6.24° for the images that anthers can be observed. And the average time consuming is about 143.18 ms per image pair. It can be concluded that the method of binocular template matching established in this paper can fulfill the demand of supplementary pollination equipment design, and the research result lays a foundation for designing and improvement of tomato supplementary pollination equipment in greenhouse.

Pollinator probing preference and switching mode-mediated self-interference within a monoecious plant significantly reduced reproductive fitness.

Monoecy is usually interpreted as an important evolutionary route of the plant sexual system from hermaphroditism to dioecy. This floral mechanism can effectively reduce self-interference during the reproductive process, and the services provided by pollinators may play an essential role in monoecious species; however, relevant research is still lacking. Thus, we aimed to determine whether monoecious plants could effectively avoid self-interference and promote the evolution of monoecy under the service of pollinators. Here, we successfully performed manipulation experiments to test self-compatibility, pollinator behavior, and self-interference between male and female functions in Akebia trifoliata, a typical monoecious species. We demonstrated that experimental self-pollination did not yield any fruit, and supplemental pollination significantly increased fruit set and fruit weight compared to natural pollination, suggesting that this species is completely self-incompatible and experiences strong pollen limitation. Simultaneous self- and cross-pollination and self-pollination prior to cross-pollination significantly reduced reproductive fitness, but self-pollination after cross-pollination did not, indicating self-interference in this plant. Moreover, both male flower probing preference and switching modes within inflorescences by pollinators successfully reinforced self-interference and were also responsible for decreasing reproductive fitness in A. trifoliata. In summary, pollinator-mediated self-interference significantly reduced selfing, providing potential dynamics for the maintenance and evolution of monoecy.

Dependency of Crops on Pollinators and Pollination Deficits: An Approach to Measurement Considering the Influence of Various Reproductive Traits

Pollinators provide crucial ecosystem services, i.e., pollination, which determines crops’ reproductive fitness and yield. As pollinators decline, flowering crops might face pollination-deficit stress depending on their dependence on pollinators and pollinator availability. Here, we assessed the dependency of some crops (belonging to diverse plant families) on biotic pollinators based on their maximum reproductive potential in a supplementary pollination treatment and minimum reproductive success in a pollinator exclusion treatment. Additionally, we determined the pollen transfer limitation of the crops in open field conditions. We also determined the influence of the different reproductive traits with the index of dependency of crops on pollinators (IDP) and the coefficient of pollination deficit (D). Based on the values of IDP, members of Cucurbitaceae are obligatorily dependent on pollinators for their fruit set. Members of Brassicaceae and Rutaceae are highly reliant on pollinators. A few crops, like Lablab purpureus and Nigella sativa, are less dependent on pollinators. In open field conditions, most crops have a low pollination deficit, some without pollen transfer limitations, and only a few crops (Citrus × limon and Citrus maxima) show a higher pollination deficit. The IDP is negatively influenced by the pollen–ovule ratio, which also negatively affects the pollination deficit of the crops. This study will be useful in understanding and mitigating the effects of pollinator losses, as well as in choosing crops (those under pollination deficit stress and largely dependent on pollinators for fruit set) for supplemental pollination services to increase agricultural production.

Effect of Osmia bicornis supplemental pollination on seed yield of forest seed orchards

Our study investigated the possibility of using the red mason bee Osmia bicornis as a pollinator of forest seed orchards of frequently grown European trees: insect - pollinated Tilia cordata and Prunus avium. Moreover, we checked whether the presence of O. bicornis has an impact on the pollination results of Quercus petraea, which is wind - pollinated. Data were collected from 8 forest seed orchards in western Poland between 2018 and 2020. We assessed whether the presence of O. bicornis populations affects the number and mass of seeds and seed quality. Supplementing forest orchards with O. bicornis affected seed yield. The generalized linear mixed models indicated that the number of seeds and the proportion of viable seeds, but not seed mass, were higher in the Tilia cordata trees, when additionally pollinated with O. bicornis added as a pollinator.

An Unmanned Aerial Vehicle Based Artificial Pollination in Frost-Affected Walnut (Juglans regia) Orchard

The winter and spring frosts are an important problem in some walnut cultivation areas. The frost damage of male and female flowers results in low fruit set and yield. The temperature dropped -17.2 °C in January 2021 in the Yenişehir, Bursa, an important walnut production area in North-Western Turkey. The present study was carried out to determine the natural frost damage on male flowers of some walnut cultivars and the effectiveness of an unmanned aerial vehicle (UAV) pollination, which has been developed and used in artificial pollination studies recently, on fruit set and fruit characteristics. In the experiment, two pollen concentrations (T1: 5% pollen two times; T2: 5% pollen in the first, 20% pollen in the second time) and the open pollination (control) were tested. Observations showed that frost damage on male flowers varied from 57.31% (Ronde de Montignac) to 99.33% (Franquette). The initial fruit set was significantly higher in the T1 (87.74%) followed by T2 (83.89%). The final fruit set in T2 (75.16%) was higher than the T1 (74.11%), but the difference was insignificant. The box and whisker plot shows that UAV pollination treatments (T1, T2) increased the fruit set, but it was not uniform on the tree compared to open pollination. The highest nut weight, thickness, and length were obtained from control, followed by T1. The results showed that the fruit set was higher in pollination with UAV, and using less pollen (T1) was sufficient. The research results provide support for UAV treatment on supplementary pollination for walnut.

Consumer pressure and supplemental pollination mediate shrub facilitation of a native annual desert plant.

Shrubs are important factors in the assembly of desert plant and animal communities. By providing shelter and resources to other plants and animals, shrubs can change plant-animal interactions including those with consumers and pollinators. Here, we test the hypothesis that shrubs facilitate the reproduction of other desert plants by influencing pollination and compensation for consumer pressure. We used the known benefactor Larrea tridentata as our focal shrub species and the flowering annual Malacothrix glabrata as a potential protege in the Mojave Desert. We tested the effects of facilitation (shrub microsite), consumer pressure (both artificial folivory and florivory), and pollination (ambient or supplemented) on flower and seed production of the annual M. glabrata. We found that floral production and seed mass were similar between microsites but that pollen was limited under shrubs in the absence of any other manipulation. Plants under shrubs produced more flowers and seeds than in the open when folivory and florivory treatments were applied. Malacothrix glabrata experienced a cost to association with L. tridentata in terms of pollen limitation but plants were better able to compensate for consumer pressure under shrubs through increased flower and seed production when damaged. Therefore, association with shrubs involves a reproductive trade-off between costs to pollination and benefits to compensation for consumer pressure.

Effect of Supplemental Pollination, Boron Spray and Cultivar on Fruit Quality and Quantity of Olive (Olea europaea L.)

This study was conducted during the 2020-2021 growing season at orchard of Horticulture Department, College of Agricultural Engineering Sciences, University of Sulaimani, Bakrajo, Iraqi Kurdistan Region, in order to investigate the effects of artificial pollination, boron application, and cultivar on some fruit quality and quantity of olive. Six selective pollinizers (Arbequina, Ashrasi, Hojiblanca, Picual, K18, Kaissy) in addition to self and air-pollination, two boron levels (0 and 200 mg.L-1) as well as two main cultivars (Sourani and Khadrawi) were used. Results showed that cultivars are relatively self-incompatible while cultivar, pollinizer, and boron recorded significant differences with regard to some studied parameters. Sourani Cultivar gave the highest percentage of final fruit set (1.96 %), self-incompatibility index (0.59), fruit weight (2.64 g), fruit volume (2.51cm3), oil content percentage (38.81%), soluble sugar content (185.74 μg/g DW), while the lowest fruit dropping (13.56%), and the lowest acidity value (0.46%). Besides, the highest values of boron content (10.587%) were obtained Sourani cultivar. Boron sprayed with 200 mg.L-1 achieved the highest values of all studied parameters. Moreover, Arbequina, Ashrasi, and Picual pollinizers gave the best results. The dual interactions of the factors revealed that Sourani and 200 mg.L-1 boron, the two cultivars (Sourani and Khadrawi) with Arbequina, Ashrasi, Picual and Hojiblanca pollinizers, and 200 mg.L-1 boron with Arbequina, Ashrasi, Picual and Hojiblanca pollinizers gave the best results. Additionally, triple interactions of the factors indicated that the combination of the two cultivars, 200 mg.L-1 boron and Arbequina, Ashrasi, Picual and Hojiblanca pollinizers, demonstrated the best significant results.

Pollen-Pistil Interaction in Response to Pollination Variants in Subtropical Japanese Plum (Prunus salicina Lindl.) Varieties.

The Japanese plum (Prunus salicina Lindl.) is a fruit tree globally cultivated in temperate regions of the world. Its floral biology and yield are affected by several factors, with issues related to self- and cross- (in) compatibility among varieties being emblematic of the whole Rosaceae family. The aim of this work was to elucidate the fruit set, dynamics of pollen tube growth in pistil, and yield and other fruiting attributes, in 'Satluj Purple' and 'Kala Amritsari', probably the most popular subtropical Japanese plum varieties in northern regions of India. Specifically, we examined the response of six different pollination variants, namely to self-pollination, open-pollination with the two cultivars located in adjacent rows, open-pollination with the two cultivars located in distant rows, manual cross-pollination, supplementary pollination, and floral bouquet. During the two years of the investigation, both plum cultivars showed good in vitro pollen germination (on average, above 50%) at different sucrose concentrations, with the highest values for the 'Satluj Purple' and for the 15% concentration. In vivo, the analysis of the pollen growth in the various sections of the style indicated the best performance when pistils of 'Satluj Purple' were pollinated by pollen grains of cv. 'Kala Amritsari'. Cross-pollination also registered faster growth of pollen tube in pistil with the lowest number of incompatible pollen tubes compared to open- and self-pollination. From the productive point of view, cross-pollination showed the most pronounced results among the different pollination variants, with the highest initial fruit set (36.6%) and yield (28.0 kg/tree), and the shorter fruit development in 'Satluj Purple' (fruit set and yield in self-pollinated 'Satluj Purple' trees were 3.3% and 2.0 kg/tree, respectively). Conversely, the use of 'Satluj Purple' pollen for 'Kala Amritsari' showed poor results. Finally, in our study, 'Kala Amritsari' showed self-compatibility. We conclude that the main cause of poor fruit set in 'Satluj Purple' is self-incompatibility. The relevant genotypic-specific effects revealed by the analysis of the various pollination treatments also highlighted the importance of interplanting to increase fruit set and yield for subtropical Japanese plum varieties.

Pollen limitation of native plant reproduction in an urban landscape.

Evidence suggests that bees may benefit from moderate levels of human development. However, the effects of human development on pollination and reproduction of bee-pollinated plants are less-well understood. Studies have measured natural variation in pollination and plant reproduction as a function of urbanization, but few have experimentally measured the magnitude of pollen limitation in urban vs. non-urban sites. Doing so is important to unambiguously link changes in pollination to plant reproduction. Previous work in the Southeastern United States found that urban sites supported twice the abundance of bees compared to non-urban sites. We tested the hypothesis that greater bee abundance in some of the same urban sites translates into reduced pollen limitation compared to non-urban sites. We manipulated pollination to three native, wild-growing, bee-pollinated plants: Gelsemium sempervirens, Oenothera fruticosa, and Campsis radicans. Using supplemental pollinations, we tested for pollen limitation of three components of female reproduction in paired urban and non-urban sites. We also measured pollen receipt as a proxy for pollinator visitation. We found that all three plant species were pollen-limited for some measures of female reproduction. However, opposite to our original hypothesis, two of the three species were more pollen-limited in urban relative to non-urban sites. We found that open-pollinated flowers in urban sites received less conspecific and more heterospecific pollen on average than those in non-urban sites. These results suggest that even when urban sites have more abundant pollinators, this may not alleviate pollen limitation of native plant reproduction in urban landscapes.

Declining abundance of pollinating insects drives falls in loquat (Eriobotrya japonica) fruit yields in the Pothwar region of Pakistan

Insects perform numerous vital ecosystem services, so widespread reports of insect declines are of considerable concern. However, there are huge knowledge gaps with regard to the extent and scale of insect declines, with most studies being from Europe and North America and very few long-term data sets on insect population change in Asia, Africa or South America. The current study describes trends in abundance of insect pollinators visiting loquat (Eriobotrya japonica) over 13 years (2006–2018) in ten widely-spaced orchards in the Pothwar region of Pakistan. Results reveal a significant and concerning decline of 89.9% in overall abundance of flower-visitors across the study period. All pollinator species declined; for example numbers of Apis dorsata fell by 97%, A. mellifera by 96%, A. cerana by 93%, and Bombus haemorrhoidalis by 84%. Declines were non-linear, being most rapid in 2006–2009. In parallel, the average yield per loquat tree fell by 61%; sugar and organic acid content also declined. Total flower-visiting insect abundance was a strong predictor of crop yield and quality over time and across sites, while pollinator species richness was less powerful. Trees that were given supplemental pollination by caging them with small honeybee colonies during flowering showed no decrease in yield or fruit quality. These results indicate that declines in populations of wild pollinators are negatively impacting loquat production and the livelihood of the small farmers of the area. Further research to identify the cause of these insect declines is urgently needed, alongside development of conservation strategies for pollinators in this region.

Effects of Different Pollination Methods on Oilseed Rape (Brassica napus) Plant Growth Traits and Rapeseed Yields.

Pollination success is essential for hybrid oilseed rape (OSR, Brassica napus) seed production, and the pollination method has some influences on the OSR plant growth traits. In order to explore the roles of different pollination methods, four pollination methods of “unmanned agricultural aerial system” (UAAS), “natural wind + UAAS” (NW+UAAS), “honeybee” (HB), and “no pollinators” (NP) were set in a hybrid OSR field to investigate their effects on OSR plant traits and rapeseed yields in this study. The control check (CK) area with natural wind (NW) pollination was set as a reference for comparison. The experiments were conducted continuously for 20 days during the OSR plant early to full-bloom stage. The results based on the evaluated OSR plants showed that the growth traits and the rapeseed yields exhibited some differences under different pollination methods. The average plant height under NP pollination was maximum, which was 231.52 cm, while the average plant heights under the other pollination methods exhibited nearly no difference. Except for the HB pollination, the average first-branch heights of the evaluated plants all exceeded 100 cm under the other pollination methods. The average once branch quantity of all the evaluated plants under different pollination methods was 5–7. The average number of effective siliques per plant varied greatly. The average quantity of effective siliques in each OSR plant was about 160 under UAAS, NW+UAAS, and NW pollination, about 100 under HB pollination, and only 2.12 under NP pollination. The thousand-rapeseed weight was 7.32 g under HB pollination, which was the highest of all of the pollination areas. In terms of rapeseed yield, the average rapeseed yields per plant were all more than 10 g, except for the one under NP pollination; the yield per hectare was highest under NW+UAAS pollination, reaching 4741.28 kg, and the yield under NP pollination was lowest, which was only 360.39 kg. The research results provide technical support for supplementary pollination in hybrid OSR seed production.

The effect of pollination on the growth and reproduction of oilseed rape (Brassica napus)

Phenotypic plasticity is an organism's ability to alter its development and life history in response to environmental conditions. In plants, biotic and abiotic factors drive the distribution of resources between growth and reproductive traits. One such biotic factor is pollination. Studies show that wind and insect pollination enhance oilseed rape (Brassica napus) yield. However, the impact of pollination on resource allocation towards growth and reproduction is less understood. We conducted a controlled experiment to assess the effect of pollination on growth and functional reproductive traits. We compared two simulated supplementary pollen deposition methods (representing wind and insect pollination) alongside a non-supplementary control. Pollinated plants allocated resources towards growth and reproduction similarly, irrespective of deposition method. Plants receiving no supplementary pollination produced fewer seeds, allocating resources to growth, more prolific and persistent flowering, and heavier seeds. Pollinated plants had a reduced flowering period and were shorter, indicating resources were allocated to seed production rather than growth or the production of additional flowers. This allocation of resources from growth and flowering metrics can increase yield directly through increased seed production and indirectly through shorter plants and a reduced flowering period with seeds that mature earlier (agronomically beneficial traits).Wind and insect pollination can enhance and stabilise oilseed rape yield under various environmental conditions by acting in complementary ways. Since pollination limits yield in oilseed rape, it must be considered an input that can be actively managed. Successful management of pollination services requires growers to detect pollination deficits. Inadequately pollinated oilseed rape plants exhibit apparent morphological changes (e.g. taller plants that flower for longer), acting as an early warning to growers. Equipping growers with this knowledge provides them with a means of detecting deficits and thus enables them to take positive action to restore pollination services by introducing honeybees or enhancing wild pollinators.

Simulation and experiment of tomato pollen particles release and motion characteristics based on optical flow target tracking method

Due to the reduction of the amount of natural pollinators, it is necessary to study the method and mechanism of greenhouse tomato mechanical vibration supplementary pollination. The release process and motion characteristics of pollen particles are very important for precision tomato supplementary pollination. In this paper, the pollen particles release and motion simulation model based on discrete element and hydrodynamics coupling method is established. The pollen particles position and trajectories detection algorithm based on optical flow target tracking method is designed. Compared with the detection results of high speed photography system, the relative error of pollen distribution range angle and pollen motion velocity of the simulation model is 7.94% and 8.87%, which shows the rationality and reliability of the established simulation model. Through the comprehensive analysis of the high speed photography observation results and simulation results, it can be concluded that the trend of pollen particles trajectories are vertical downward with random direction change, and greater vibration amplitude cause greater distribution range angle of pollen particles. There is no obvious trend of velocity change during the release process of each single pollen particle, and the relationship between vibration amplitude and average velocity of pollen particles is not obvious. The research results and the established model of this paper provide a mechanism basis for tomato mechanical vibration supplementary pollination and lay a foundation for the optimization of mechanical pollination method.

Detection of Rice Spikelet Flowering for Hybrid Rice Seed Production Using Hyperspectral Technique and Machine Learning

Effective detection of rice spikelet flowering is crucial to the determination of optimal pollination timing for hybrid rice seed production. Currently, the detection of rice spikelet flowering status relies on manual observation of farmers, which has low efficiency and large errors. This study attempts to acquire rice spikelet flowering information using a hyperspectral technique and machine learning in order to meet the needs of hybrid rice seed pollination rapidly and automatically. Hyperspectral data of rice male parents with flowering and non-flowering in two experimental sites were collected with an ASD FieldSpec® HandHeld™2 spectrometer. Three traditional classifiers, Random Forest (RF), Support Vector Machine (SVM) and Back Propagation (BP) neural network, and Convolutional Neural Network (CNN), were used to build classification models for rice spikelets flowering detection. Three data processing methods, PCA feature extraction, GA feature selection, and the PCA and GA combination algorithm, were used for data dimensionality reduction. By comparing the precision and recall rate of different algorithms and data processing methods, the algorithms applicable to identify rice spikelet flowering were investigated. Results show that by evaluating different feature reduction methods and classifiers, the optimal model for rice spikelets flowering detection is the BP model with PCA feature extraction. The accuracy of the model reaches up to 96–100%. Hyperspectral technology and machine learning algorithm are capable of effective detection of rice spikelet flowering. This study provides technical reference for accurate judgment of rice flowering and helps to determine the optimal operation time for supplementary pollination of hybrid rice.

A generalized bird pollination system in Schotia brachypetala (Fabaceae).

Bird pollination systems are diverse, ranging from narrow-tubed flowers pollinated by specialist nectarivores such as hummingbirds and sunbirds, to relatively open flowers pollinated by opportunistic (i.e. generalist) nectarivores. The role of opportunistic avian nectarivores as pollinators has historically been under-appreciated. A key aspect to understanding the importance of opportunistic birds as pollinators is to investigate how efficiently they transfer pollen among flowers. Here, we document the pollination and breeding systems of Schotia brachypetala, a southern African tree known as the 'weeping boer-bean' on account of its prolific production of dilute hexose-dominated nectar. The cup-shaped flowers of this tree attract a large number of bird species, including both opportunistic and specialist nectarivores. We identified floral visitors using observations and camera traps and quantified the floral traits responsible for animal attraction. We documented the breeding system, used selective pollinator exclusion to test the contribution of birds to fecundity, and performed supplemental pollination to test for pollen limitation. Single-visit pollen deposition trials were undertaken to determine the efficacy of bird pollinators. Controlled hand-pollination experiments showed that S. brachypetala is genetically self-incompatible and therefore dependent on pollinators for seed production. Supplemental hand-pollination experiments showed that natural fecundity is limited by either the amount and/or the quality of pollen on stigmas. Flowers from which birds but not insects were experimentally excluded set fewer seeds than open control flowers. Opportunistic birds deposited more pollen per visit than did specialist sunbirds. We conclude that S. brachypetala has a generalized bird pollination system that mainly involves opportunistic nectarivores.

The use of multisource spatial data for determining the proliferation of stingless bees in Kenya

ABSTRACT Stingless/meliponine bees are eusocial insects whose polylactic nature enables interaction with a wide variety of wild plants and crops that enhance pollination and, hence, support ecosystem services. However, their true potential regarding pollination services and honey production is yet to be fully recognized. Worldwide, there are over 800 species of meliponine bees, with over 20 species documented on the African continent. Out of these, only 12 species have been well documented in Kenya. Moreover, interest on meliponine bees has increased amid climate change, agricultural intensification, and other anthropogenic effects. Generally, stingless bees are under-researched, with no previous documented evidence of their ecological niche (EN) distribution in most African countries. Hence, this study sought to establish the influence of bioclimatic, topographic, and vegetation phenology on their spatial distribution and change patterns. Stingless response variables from 490 sample points were collected and used in conjunction with 11 non-conflating features to build stingless ecological niche models. Six machine learning-based EN models were used to predict the distribution of seven stingless bees’ species combined. The results from the EN models showed that annual precipitation was the most influential variable to stingless bee distribution (contributing 43.09% logit), while potential evapotranspiration and temperature seasonality contributed 21.18% of the information needed to predict the spatial distribution of stingless bees. Vegetation phenology (21.36%) and topography (14.36%) had moderate effect on stingless bees’ distribution. On the other hand, high seasonality in precipitation and temperature indicated high stingless niche variability in the future (i.e. 2055). The performance of six EN algorithms used to predict distribution of stingless bees was found to be “excellent” for random forest (true skills statistics (TSS) = 0.91) and ranger (TSS = 0.90) and “good” for generalized additive models (TSS = 0.87), multivariate adaptive regression spline (TSS = 0.80), and boosted regression trees (TSS = 0.80), while they were “fair” for recursive portioning and regression trees (TSS = 0.79). These EN models could be utilized to inform stingless bee farming and insects pollinated crops by highlighting regions that provide highly suitable conditions for stingless bees. Additionally, the findings could be harnessed to increase both bee and agricultural productivity and forest conservation efforts through supplementary pollination services.

Supplemental bee pollination effect on the productivity of soybean grown in a low yield potential condition

Brazil is the leading soybean producing country in the world, and soybean is the major crop of Brazilian agriculture, spread over 36 million hectares during the 2020/21 season, producing almost 125 million tons. The honey bee, Apis mellifera Linnaeus, 1758 (Hymenoptera: Apidae), and other bees are known as soybean flowers visitors, being potential pollinators of the crop, normally resulting in higher soybean yields. Over the last ten years, it has been observed an increasing interest of both beekeepers and soybean growers, to place honey bee colonies close to soybean fields, using the crop as a forage source. In the majority of the reports of soybeans growers, an increase of the soybean yield was observed when following this practice, while a small number claimed no yield modification. The purpose of the present work was to study the effect of visits of individuals of A. mellifera to soybean flowers and the consequent pollination on soybean productivity, when there is a constraint to the expression of the potential crop yield. The experiments were set up in Londrina, Brazil, during the 2016/17 and 2019/20 crop seasons, in areas with known sub superficial compaction layers, preventing soybean roots from deepening in the soil, therefore restricting the absorption of water and nutrients by the plants. Treatments consisted of 1) open plots, resembling a typical grower field with free access of bees; 2) a caged plot with an A. mellifera beehive inside, and 3) a caged plot with no bees or any other potential pollinating insect inside. Results indicated no yield differences due to the pollination of soybean flowers by the bees, compared to the treatment with the absence of bee visit. Among the yield components, only pods with 1 or 2 seeds were lower on caged plots with bees on the 1st experiment. No differences were detected for all others observed parameters on 1st and for all components on 2nd experiments. Observations of the honey bee behavior demonstrated that only 27.9% of the bee visits to soybean flowers resulted in nectar hoarding, with a time lapse of 4.52 seconds for a visit to a single flower. When a flower was only tested (72.1%), without nectar collection, the average time of a honey bee visit was 1.38 seconds. New studies should be performed to verify if other biotic or abiotic stresses that depress soybean yield also prevent the expression of the benefit of bees’ pollination to soybean yield.