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The western honeybee, Apis mellifera, is used worldwide as a pollinator of crops such as strawberries; however, it is an introduced species in Japan. The mason bee, Osmia orientalis Benoist (Hymenoptera: Megachilidae), is native to Japan, where it nests in empty snail shells and has potential as a crop pollinator. We conducted three experiments to collect information on the nesting habits and potential agricultural use of this species as a pollinator of greenhouse-grown strawberries. Our first experiment investigated the bees’ nesting preferences in the field by placing the empty shells of four snail species, Euhadra amaliae, Satsuma japonica, Sinotaia quadrata histrica, and Helix lucorum, in six different environments. The nesting rate was significantly higher in medium-sized, empty E. amaliae shells. Regarding the surrounding environment, O. orientalis preferred tall and short grasslands to bare ground and forest interiors. Our second experiment investigated per-visit strawberry flower pollination efficiency. The results indicated that the efficiency of O. orientalis was equal to or greater than that of A. mellifera. In our third experiment, as a replacement for empty snail shells, which are scarce natural sources, four types of plastic artificial shells were created and placed inside a greenhouse together with E. amaliae shells. The nesting rates in three types of artificial shells were nearly identical to those in E. amaliae shells, implying that these artificial shells may be effective nesting materials. Although many questions remain before practical application, our results indicate the potential for using O. orientalis as a pollinator of greenhouse-grown strawberries.

Floral traits are hypothesized to evolve primarily in response to selection by pollinators. However, selection can also be mediated by other environmental factors. To understand the relative importance of pollinator-mediated selection and its variation among trait and pollinator types, we analyzed directional selection gradients on floral traits from experiments that manipulated the environment to identify agents of selection. Pollinator-mediated selection was stronger than selection by other biotic factors (e.g., herbivores), but similar in strength to selection by abiotic factors (e.g., soil water), providing partial support for the hypothesis that floral traits evolve primarily in response to pollinators. Pollinator-mediated selection was stronger on pollination efficiency traits than on other trait types, as expected if efficiency traits affect fitness via interactions with pollinators, but other trait types also affect fitness via other environmental factors. In addition to varying among trait types, pollinator-mediated selection varied among pollinator taxa: selection was stronger when bees, long-tongued flies, or birds were the primary visitors than when the primary visitors were Lepidoptera or multiple animal taxa. Finally, reducing pollinator access to flowers had a relatively small effect on selection on floral traits, suggesting that anthropogenic declines in pollinator populations would initially have modest effects on floral evolution.

Evolutionary shifts from bee to vertebrate pollination are common in tropical mountains. Reduction in bee pollination efficiency under adverse montane weather conditions was proposed to drive these shifts. Although pollinator shifts are central to the evolution and diversification of angiosperms, we lack experimental evidence of the ecological processes underlying such shifts. Here, we combine phylogenetic and distributional data for 138 species of the Neotropical plant tribe Merianieae (Melastomataceae) with pollinator observations of 11 and field pollination experiments of six species to test whether the mountain environment may indeed drive such shifts. We demonstrate that shifts from bee to vertebrate pollination coincided with occurrence at high elevations. We show that vertebrates were highly efficient pollinators even under the harsh environmental conditions of tropical mountains, whereas bee pollination efficiency was lowered significantly through reductions in flower visitation rates. Furthermore, we show that pollinator shifts in Merianieae coincided with the final phases of the Andean uplift and were contingent on adaptive floral trait changes to alternative rewards and mechanisms facilitating pollen dispersal. Our results provide evidence that abiotic environmental conditions (i.e. mountain climate) may indeed reduce the efficiency of a plant clade’s ancestral pollinator group and correlate with shifts to more efficient new pollinators.

Pollinator-mediated selection to a large extent shapes angiosperm floral diversity, but clearly not in isolation. To understand how selection by pollinators interacts with other selective factors and depends on environmental context, studies that address multiple selective agents are necessary. Here, I illustrate how antagonistic interactions, community context, and resource availability may influence selection on floral traits. I discuss approaches to quantify the context dependence of pollinator-mediated selection, emphasizing experimental studies that manipulate pollination regime in combination with other putative selective factors. I also discuss how context dependence may differ between floral traits that affect pollinator attraction versus pollination efficiency. Finally, I suggest some areas where important progress can be made. A better understanding of the context dependence of pollinator-mediated selection is essential to predict when, where, and how environmental change will alter selection on floral traits.

The study of adaptation helps explain biodiversity and predict future evolution. Yet the process of adaptation can be difficult to observe due to limited phenotypic variation in contemporary populations. Furthermore, the scarcity of male fitness estimates has made it difficult to both understand adaptation and evaluate sexual conflict hypotheses. We addressed both issues in our study of two anther position traits in wild radish (Raphanus raphanistrum): anther exsertion (long filament – corolla tube lengths) and anther separation (long – short filament lengths). These traits affect pollination efficiency and are particularly interesting due to the unusually high correlations among their component traits. We measured selection through male and female fitness on wild radish plants from populations artificially selected to recreate ancestral variation in each anther trait. We found little evidence for conflicts between male and female function. We found strong evidence for stabilizing selection on anther exsertion and disruptive selection on anther separation, indicating positive and negative correlational selection on the component traits. Intermediate levels of exsertion are likely an adaptation to best contact small bees. The function of anther separation is less clear, but future studies might investigate pollen placement on pollinators and compare species possessing multiple stamen types.

The ultimate causes of evolution of highly specialized pollination systems are little understood. We investigated the relationship between specialization and pollination efficiency, defined as the proportion of pollinated flowers relative to those that experienced pollen removal, using orchids with different pollination strategies as a model system. Rewarding orchids showed the highest pollination efficiency. Sexually deceptive orchids had comparably high pollination efficiency, but food‐deceptive orchids had significantly lower efficiency. Values for pollinator sharing (a measure of the degree of generalization in pollination systems) showed the reverse pattern, in that groups with high pollination efficiency had low values of pollinator sharing. Low pollinator sharing may thus be the basis for efficient pollination. Population genetic data indicated that both food‐ and sexually deceptive species have higher degrees of among‐population gene flow than do rewarding orchids. Thus, the shift from food to sexual deception may be driven by selection for more efficient pollination, without compromising the high levels of gene flow that are characteristic of deceptive species.

Oil palm (Elaeis guineensis L.), native to Africa but widely cultivated in Southeast Asia, is increasingly grown in Uganda, and pollination efficiency is critical for fruit set and oil yield. The study assessed the population and sexual diversity of the primary pollinator, Elaeidobius kamerunicus FAUST, in introduced hybrid plantations in Kalangala and natural stands in Bundibugyo. Pollinator weevils were sampled across both wet and dry seasons in 2022 and 2023, and data were analyzed using ANOVA and correlation tests in Minitab 17. Results revealed significant variation between sites, with higher populations in Kalangala (7,503 ± 8.682) compared to Bundibugyo (5,164 ± 5.829). Furthermore, females (6,636 ± 4.646) outnumbered males (6,032 ± 5.028), with a slightly higher concentration of females in the middle section of male inflorescences. Seasonal differences were evident, as the wet season supported slightly higher weevil populations relative to the dry season. Correlation analysis indicated a weak negative relationship between weevil abundance and weather variables, suggesting that cooler conditions suppress population growth. Overall, Uganda provides favorable conditions for pollinator weevil multiplication, particularly under moist climatic regimes, while extensive cold conditions limit population expansion. These findings highlight the importance of pollinator dynamics in sustaining oil palm productivity in diverse agro-ecological regions.

Honey bee pollination of entomophilous commercial crops is a major input in agricultural management yet unlike irrigation, fertilisation and plant protection have yet to be integrated into precision agriculture practices. This study examines colony strength as a key determinant of efficient pollination. Over three years and across two study sites, we evaluated the relationship between colony strength (frames of bees, FOBs) and colony productivity using continuous hive weight monitoring. Hive weight data were analysed for both absolute gains and relative gains normalised per FOB across colony strengths. In all study periods, stronger colonies showed disproportionately higher weight gains compared to weaker colonies. For each additional FOB, the average increase in normalised weight gain ranged from 0.1 to 0.41 kg per colony, indicating a non-linear relationship between colony strength and productivity. An efficiency factor calculated for groups of strong and weak colonies ranged from 1.2 to 2.6, depending on the season and crop. Moreover, during periods of forage dearth, strong colonies exhibited lower weight losses than the weak colonies per FOB, making them more efficient under resource limited conditions. Our findings demonstrate that colony strength significantly influences foraging efficiency and colony resilience, ultimately supporting the conclusion that fewer stronger colonies will improve pollination outcomes while reducing the economic and environmental costs associated with commercial pollination services.

Pollination services from insects are important for higher yield and better fruit quality in avocado (Persea americana Mill.). Measuring pollinator effectiveness is significant for capturing the relative contributions of different insect taxa to pollination services and for identification of the most important pollinators of this globally important crop. In the present study, we tested pollinator efficiency of avocado in Kenya based on pollen deposition after single visits of flowers by different pollinator species and visitation frequency. We monitored the pollination frequency during the flowering period replicated across six farms. Three trees were selected per farm, each with five flower panicles. Out of the 14 observed insect flower visitor species, pollen deposition efficiency was highest in the Western honey bee (Apis mellifera L.), followed by the hover fly species (Phytomia incisa W.). These two species had both the highest pollen deposition and pollen grain loads on their bodies. Furthermore, A. mellifera was the most frequent avocado flower visitor followed by Diptera except hoverflies. Our results imply that A. mellifera can be managed to achieve adequate pollination services for avocado, particularly in areas lacking efficient wild pollinators. Graphical showing the visitation frequency and pollinator efficiency of avocado flower insect visitor and their conservation.

Many crop plants rely on insect pollination, particularly insect-pollinated crops which are functionally dioecious. These crops require insects to move pollen between separate plants which are functionally male or female. While honey bees are typically considered the most important crop pollinator species, many other insects are known to visit crops but the pollination contribution of the full diversity of these flower visitors is poorly understood. In this study, we examine the role of diverse insect pollinators for two kiwifruit cultivars as model systems for dioecious crops: Actinidia chinensis var. deliciosa ‘Hayward’ (a green-fleshed variety) and A. chinensis var. chinensis ‘Zesy002’ (a gold-fleshed variety). In our round-the-clock insect surveys, we identified that psychodid flies and mosquitoes were the second and third most frequent floral visitors after honey bees ( Apis mellifera L), but further work is required to investigate their pollination efficiency. Measures of single-visit pollen deposition identified that several insects, including the bees Leioproctus spp. and Bombus spp. and the flies Helophilus hochstetteri and Eristalis tenax , deposited a similar amount of pollen on flowers as honey bees ( Apis mellifera ). Due to their long foraging period and high pollen deposition, we recommend the development of strategies to boost populations of Bombus spp., Eristalis tenax and other hover flies, and unmanaged bees for use as synergistic pollinators alongside honey bees.