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1. A key floral scent component (β‐trans‐bergamotene) drives pollinator preferences independently of pollen rewards in seep monkeyflower

   https://doi.org/10.1111/1365-2435.13246  

   Haber, Ariela_I ; Sims, James_W ; Mescher, Mark_C ; De_Moraes, Consuelo_M ; Carr, David_E ; Brody, ed., Alison ( December 2018 , Functional Ecology)

   Floral odours play an important role in attracting insect pollinators. Because pollinators visit flowers to obtain pollen and nectar rewards, they should prefer floral odour profiles associated with the highest‐rewarding flowers (honest signals). In previous work, bumblebees exhibited a preference for flowers from outbred over inbredMimulus guttatusplants. Pollen is the only floral reward inM. guttatus, and pollen viability (a reliable indicator of protein content) is reduced in inbred plants. Yet, differences in pollen viability did not explain the observed preferences.

   In this study, we examined the floral volatile profiles of inbred and outbredM. guttatusto identify inbreeding effects and associations between volatile compounds and the number of viable pollen grains per flower, designated “PRQ” (pollen reward quality). We also conducted pairwise choice tests withBombus impatiensto evaluate the ability of bees to discriminate between odours of rewarding and non‐rewarding flowers and to determine whether bumblebee preferences are explained by differences in the floral odours of inbred and outbred plants.

   Inbred plants exhibited reduced emission of β‐trans‐bergamotene, the second‐most abundant compound in the volatile blend of outbred plants. Furthermore, pollen and fertile anthers emitted nonadecane. Six other compounds in the floral blend were positively correlated withPRQ. There was no overlap between compounds affected by inbreeding and compounds associated withPRQ.

   Even when given prior experience foraging onM. guttatus, bumblebees did not distinguish between the floral odours of rewarding and non‐rewarding outbred plants. However, they preferred floral odours from non‐rewarding outbred plants over rewarding inbred plants. Bumblebees without prior experience of flowers preferred volatile blends with higher versus lower amounts of β‐trans‐bergamotene.

   Taken together, these results suggest that the volatile emissions ofM. guttatusprovide reliable indicators of pollen rewards (potential honest signals), but that the preference of bumblebees for outbred plants is not driven by these cues but rather by a sensory bias for β‐trans‐bergamotene. This may represent a subtle form of deceit‐pollination that allows plants to attract pollinators while minimizing investment in costly rewards.

   Aplain language summaryis available for this article.

    

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2. What makes a good pollinator? Abundant and specialised insects with long flight periods transport the most strawberry pollen

   https://doi.org/10.1002/2688-8319.12253  

   Villa‐Galaviz, Edith ; Cirtwill, Alyssa R. ; Gibson, Rachel ; Timberlake, Thomas ; Roslin, Tomas ; Memmott, Jane ( July 2023 , Ecological Solutions and Evidence)

   Despite the importance of insect pollination to produce marketable fruits, insect pollination management is limited by insufficient knowledge about key crop pollinator species. This lack of knowledge is due in part to (1) the extensive labour involved in collecting direct observations of pollen transport, (2) the variability of insect assemblages over space and time and (3) the possibility that pollinators may need access to wild plants as well as crop floral resources.

   We address these problems using strawberry in the United Kingdom as a case study. First, we compare two proxies for estimating pollinator importance: flower visits and pollen transport. Pollen‐transport data might provide a closer approximation of pollination service, but visitation data are less time‐consuming to collect. Second, we identify insectparametersthat are associated with high importance as pollinators, estimated using each of the proxies above. Third, we estimated insects' use of wild plants as well as the strawberry crop.

   Overall, pollinator importances estimated based on easier‐to‐collect visitation data were strongly correlated with importances estimated based on pollen loads. Both frameworks suggest that bees (ApisandBombus) and hoverflies (Eristalis) are likely to be key pollinators of strawberries, although visitation data underestimate the importance of bees.

   Moving beyond species identities, abundant, relatively specialised insects with long active periods are likely to provide more pollination services.

   Most insects visiting strawberry plants also carried pollen from wild plants, suggesting that pollinators need diverse floral resources.

   Identifying essential pollinators or pollinator parameters based on visitation data will reach the same general conclusions as those using pollen transport data, at least in monoculture crop systems. Managers may be able to enhance pollination service by preserving habitats surrounding crop fields to complement pollinators' diets and provide habitats for diverse life stages of wild pollinators.

    

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3. Physical adaptations of butterfly proboscises enable feeding from narrow floral tubes

   https://doi.org/10.1111/1365-2435.13863  

   Lehnert, Matthew S. ; Johnson, Daytona D. ; Wu, Jianing ; Sun, Yu ; Fonseca, Rena J. ; Michels, Jan ; Shell, Jamie S. ; Reiter, Kristen E. ( July 2021 , Functional Ecology)

   Butterflies use a proboscis, a microfluidic probe engineered by natural selection, to feed on nutritive fluids. The structural configuration of proboscises relates to feeding habits; however, the adaptations that enable proboscis entry into narrow floral corollas lack experimental evidence.

   Here, we investigated proboscis adaptations that enable entry into corollas using funnel‐shaped glass capillary tubes and performed feeding trials with six butterfly species of different feeding habits. Proboscises were either guided (natural treatment) or forced (forced treatment) into the capillary tubes that were filled with a 20% sucrose solution. The treatments were video‐recorded to determine the depth the proboscises reached into the tube and how long they remained there. The results were interpreted in terms of proboscis morphology, friction forces and the material properties of the cuticle.

   In the natural treatment, butterflies classified as flower visitors were more efficient at feeding from the tubes, reaching an average 1.83× deeper into the tubes than the other species and never getting their proboscises stuck. The non‐flower‐visiting species, in contrast, had their proboscises remain in the tube 17× longer than the flower‐visiting species, with 90% of them getting their proboscises at least partially stuck. The butterfly species with generalist feeding habits fed more efficiently than the non‐flower visitors, but less than the flower visitors. A similar pattern was observed in the forced treatment.

   Flower‐visiting butterflies had smoother and more tapered proboscises, lower friction forces and a semi‐circular cross‐section that would reduce bendability and was augmented by a more sclerotized cuticle. Proboscises of flower‐visiting butterflies, therefore, have a suite of adaptations that operate synergistically to optimize their feeding habits.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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4. Plant richness and blooming cover affect abundance of flower visitors and network structure in Colombian orchards

   https://doi.org/10.1111/afe.12460  

   Vaca‐Uribe, Jessica L. ; Figueroa, Laura L. ; Santamaría, Maikol ; Poveda, Katja ( July 2021 , Agricultural and Forest Entomology)

   Pollination is essential to fruit production. How plant diversity and blooming events in and around orchards affect the pollinator community and the plant‐flower‐visitor network in neotropical systems remains largely unknown.

   We surveyed the flower visitors in deciduous fruit trees and alternative blooming resources (other crops, hedgerows and weeds) in Colombia across 6 orchards over 12 months. We evaluated whether plant species richness and blooming cover influenced abundance and richness of flower visitors, as well as network‐level connectance and specialization. We also assessed the role of alternative blooming resources for the flower visitors of deciduous fruit trees.

   Overall, we found 66 taxa of flower visitors, 35 of which visited deciduous fruit trees. There was a greater abundance of flower visitors when there was higher richness of weedy species and greater blooming cover of deciduous fruit trees. Networks were less connected when there was lower crop and weedy species richness. Finally, flower visitor abundance and specialization increased when there were multiple hedgerow species in bloom with a high blooming cover.

   We highlight the importance of maintaining alternative blooming resources in and around the orchards to support deciduous fruit tree pollinators and diversity in the plant flower‐visitor network.

    

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5. Flower production decreases with warmer and more humid atmospheric conditions in a western Amazonian forest

   https://doi.org/10.1111/nph.19388  

   Vleminckx, Jason ; Hogan, J. Aaron ; Metz, Margaret R. ; Comita, Liza S. ; Queenborough, Simon A. ; Wright, S. Joseph ; Valencia, Renato ; Zambrano, Milton ; Garwood, Nancy C. ( November 2023 , New Phytologist)

   Climate models predict that everwet western Amazonian forests will face warmer and wetter atmospheric conditions, and increased cloud cover. It remains unclear how these changes will impact plant reproductive performance, such as flowering, which plays a central role in sustaining food webs and forest regeneration. Warmer and wetter nights may cause reduced flower production, via increased dark respiration rates or alteration in the reliability of flowering cue‐based processes. Additionally, more persistent cloud cover should reduce the amounts of solar irradiance, which could limit flower production.

   We tested whether interannual variation in flower production has changed in response to fluctuations in irradiance, rainfall, temperature, and relative humidity over 18 yrs in an everwet forest in Ecuador.

   Analyses of 184 plant species showed that flower production declined as nighttime temperature and relative humidity increased, suggesting that warmer nights and greater atmospheric water saturation negatively impacted reproduction. Species varied in their flowering responses to climatic variables but this variation was not explained by life form or phylogeny.

   Our results shed light on how plant communities will respond to climatic changes in this everwet region, in which the impacts of these changes have been poorly studied compared with more seasonal Neotropical areas.

    

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