Abstract:The evolution of floral traits is often considered to reflect selection for increased pollination efficiency. Known as the pollination-precision hypothesis, increased pollination efficiency is achieved by enhancing pollen deposition on precise areas of the pollinator. Most research to date addressing this hypothesis has examined plant species that are a priori predicted to place pollen precisely, but we still lack comparisons with species predicted to have low pollination efficiency.We studied 39 plant species… Show more
“…In bilateral flowers, the direction of approach affects the proportion of legitimate landings (bee touching anthers and stigma), and the amount of pollen both collected and deposited by pollinators (Ushimaru and Hyodo, 2005;Ushimaru et al, 2009). The heterantherous, enantiostylyous flowers of S. rostratum may require consistent and stereotypical alignment between the bee's body and the flower's sexual organs as is hypothesized to occur in bilateral flowers in general (Fenster et al, 2009;Armbruster and Muchhala, 2020;Stewart et al, 2022). If pendant flowers cause increased variation in the location of contact between anthers and stigma and the pollinator's body, as found in a study of 33 bee-pollinated plants (Stewart et al, 2022), then outcross-pollen transfer efficiency might be lower.…”
Section: Effect Of Floral Orientation In Complex Bilaterally Symmetri...mentioning
confidence: 99%
“…Meanwhile, a horizontal or vertical orientation might make flowers more attractive to pollinators or easier to access (Haverkamp et al, 2019 ; Nakata et al, 2022 ). Crucially, a horizontal orientation in bilaterally symmetrical flowers is understood to promote precise pollinator positioning and improve pollen transfer, relative to pendant flowers (Giurfa et al, 1999 ; Fenster et al, 2009 ; Armbruster and Muchhala, 2020 ; Stewart et al, 2022 ). According to the pollen position hypothesis (Neal et al, 1998 ), bilateral flowers constrain the position of the bee pollinator on the flower and promote consistency in the site of contact between the pollinator body and the flower's sexual organs, impacting both pollen removal and deposition (Neal et al, 1998 ; Giurfa et al, 1999 ; Ushimaru et al, 2009 ; Armbruster et al, 2014 ; Culbert and Forrest, 2016 ; Armbruster and Muchhala, 2020 ).…”
Premise: Floral orientation is central to plant-pollinator interactions and is commonly associated with floral symmetry. Bilaterally symmetrical flowers are often oriented horizontally for optimal pollinator positioning and pollen transfer efficiency, while the orientation of radially symmetrical flowers is variable. Buzz-pollinated species (pollinated by vibration-producing bees) include bilateral, horizontally oriented flowers, and radial, pendant flowers. The effect of floral orientation on pollen transfer has never been tested in buzz-pollinated species. Methods: Here, we examined the effect of floral orientation on bumblebee-mediated pollen deposition in three buzz-pollinated Solanum species with different floral symmetry and natural orientations: S. lycopersicum and S. seaforthianum (radial, pendant), and S. rostratum (bilateral, horizontal). We tested whether orientation affects total stigmatic pollen deposition (both self and outcross pollen) when all flowers have the same orientation (either pendant or horizontal). In a second experiment, we evaluated whether different orientations of donor and recipient flowers affects the receipt of outcross pollen by S. rostratum. Results: For the three Solanum species studied, there was no effect of floral orientation on total pollen deposition (both self and outcross) when flowers shared the same orientation. In contrast, in our experiment with S. rostratum, we found that pendant flowers received fewer outcross-pollen grains when paired with pendant donors. Conclusions: We suggest that floral orientation influences the quality of pollen transferred, with more outcross pollen transferred to horizontally oriented recipients in the bilaterally symmetrical S. rostratum. Whether other bilaterally symmetrical, buzz-pollinated flowers also benefit from increased cross-pollination when presented horizontally remains to be established.
“…In bilateral flowers, the direction of approach affects the proportion of legitimate landings (bee touching anthers and stigma), and the amount of pollen both collected and deposited by pollinators (Ushimaru and Hyodo, 2005;Ushimaru et al, 2009). The heterantherous, enantiostylyous flowers of S. rostratum may require consistent and stereotypical alignment between the bee's body and the flower's sexual organs as is hypothesized to occur in bilateral flowers in general (Fenster et al, 2009;Armbruster and Muchhala, 2020;Stewart et al, 2022). If pendant flowers cause increased variation in the location of contact between anthers and stigma and the pollinator's body, as found in a study of 33 bee-pollinated plants (Stewart et al, 2022), then outcross-pollen transfer efficiency might be lower.…”
Section: Effect Of Floral Orientation In Complex Bilaterally Symmetri...mentioning
confidence: 99%
“…Meanwhile, a horizontal or vertical orientation might make flowers more attractive to pollinators or easier to access (Haverkamp et al, 2019 ; Nakata et al, 2022 ). Crucially, a horizontal orientation in bilaterally symmetrical flowers is understood to promote precise pollinator positioning and improve pollen transfer, relative to pendant flowers (Giurfa et al, 1999 ; Fenster et al, 2009 ; Armbruster and Muchhala, 2020 ; Stewart et al, 2022 ). According to the pollen position hypothesis (Neal et al, 1998 ), bilateral flowers constrain the position of the bee pollinator on the flower and promote consistency in the site of contact between the pollinator body and the flower's sexual organs, impacting both pollen removal and deposition (Neal et al, 1998 ; Giurfa et al, 1999 ; Ushimaru et al, 2009 ; Armbruster et al, 2014 ; Culbert and Forrest, 2016 ; Armbruster and Muchhala, 2020 ).…”
Premise: Floral orientation is central to plant-pollinator interactions and is commonly associated with floral symmetry. Bilaterally symmetrical flowers are often oriented horizontally for optimal pollinator positioning and pollen transfer efficiency, while the orientation of radially symmetrical flowers is variable. Buzz-pollinated species (pollinated by vibration-producing bees) include bilateral, horizontally oriented flowers, and radial, pendant flowers. The effect of floral orientation on pollen transfer has never been tested in buzz-pollinated species. Methods: Here, we examined the effect of floral orientation on bumblebee-mediated pollen deposition in three buzz-pollinated Solanum species with different floral symmetry and natural orientations: S. lycopersicum and S. seaforthianum (radial, pendant), and S. rostratum (bilateral, horizontal). We tested whether orientation affects total stigmatic pollen deposition (both self and outcross pollen) when all flowers have the same orientation (either pendant or horizontal). In a second experiment, we evaluated whether different orientations of donor and recipient flowers affects the receipt of outcross pollen by S. rostratum. Results: For the three Solanum species studied, there was no effect of floral orientation on total pollen deposition (both self and outcross) when flowers shared the same orientation. In contrast, in our experiment with S. rostratum, we found that pendant flowers received fewer outcross-pollen grains when paired with pendant donors. Conclusions: We suggest that floral orientation influences the quality of pollen transferred, with more outcross pollen transferred to horizontally oriented recipients in the bilaterally symmetrical S. rostratum. Whether other bilaterally symmetrical, buzz-pollinated flowers also benefit from increased cross-pollination when presented horizontally remains to be established.
“…This imbalance is beginning to change, as evidenced by a new paper in this issue of New Phytologist by Stewart et al . (2022; pp. 1629–1640).‘This study by Stewart and colleagues shows the importance of thinking about floral evolution from the perspective of the physical mechanics of pollination …’…”
Section: Figmentioning
confidence: 99%
“…Although traits influencing pollination efficiency are widely accepted to be important (see reviews in Armbruster, 2014Armbruster, , 2017Minnaar et al, 2019), they have received less scientific attention than floral adaptations influencing pollinator identity and visitation rates. This imbalance is beginning to change, as evidenced by a new paper in this issue of New Phytologist by Stewart et al (2022;pp. 1629-1640.…”
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“…There are so many excellent and interesting papers in New Phytologist lately that it is quite hard to choose just a few. I am impressed by the detailed insights into the effects of floral morphology on pollination precision revealed by Stewart et al (2022). Another interesting topic addressed in a very original way is the investigation of the significance and basis of intra-floral modularity in Ipomoea, as revealed in an impressive study by Liao et al (2022).…”
Section: What Are Your Favourite New Phytologist Papers Of Recent Yea...mentioning
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