scholarly journals Phenotypic Selection on Flower Color and Floral Display Size by Three Bee Species

2021 ◽  
Vol 11 ◽  
Author(s):  
Johanne Brunet ◽  
Andrew J. Flick ◽  
Austin A. Bauer
Keyword(s):  
Plant Species ◽  
Display Size ◽  
Flower Color ◽  
Phenotypic Selection ◽  
Floral Traits ◽  
Floral Display ◽  
Floral Trait ◽  
Correlational Selection ◽  
Floral Display Size ◽  
Plant Level

Plants exhibit a wide array of floral forms and pollinators can act as agent of selection on floral traits. Two trends have emerged from recent reviews of pollinator-mediated selection in plants. First, pollinator-mediated selection on plant-level attractants such as floral display size is stronger than on flower-level attractant such as flower color. Second, when comparing plant species, distinct pollinators can exert different selection patterns on floral traits. In addition, many plant species are visited by a diverse array of pollinators but very few studies have examined selection by distinct pollinators. In the current study, we examined phenotypic selection on flower color and floral display size by three distinct bee species, the European honey bee, Apis mellifera, the common eastern bumble bee, Bombus impatiens, and the alfalfa leafcutting bee, Megachile rotundata, foraging on Medicago sativa. To estimate phenotypic selection by each bee species and for all bees combined simultaneously and on the same group of plants, we introduce a new method that combines pollinator visitation data to seed set and floral trait measurements data typical of phenotypic selection study. When comparing floral traits, all bee species selected on the number of racemes per stem and the number of stems per plant, two components of floral display size. However, only leafcutting bees selected on hue or flower color and only bumble bees selected on chroma or darkness of flowers. Selection on chroma occurred via correlational selection between chroma and number of open flowers per raceme and we examine how correlational selection may facilitate the evolution of flower color in plant populations. When comparing bee species, the three bee species exerted similar selection pattern on some floral traits but different patterns on other floral traits and differences in selection patterns were observed between flower-level and plant-level attractants. The trends detected were consistent with previous studies and we advocate the approach introduced here for future studies examining the impact of distinct pollinators on floral trait evolution.

scholarly journals Variation in context dependent foraging behavior across pollinators

2017 ◽  
Author(s):  
Heather M. Briggs ◽  
Stuart Graham ◽  
Callin M. Switzer ◽  
Robin Hopkins
Keyword(s):  
Foraging Behavior ◽  
Plant Traits ◽  
Flower Color ◽  
Color Preference ◽  
Field Conditions ◽  
Floral Traits ◽  
Floral Display ◽  
Floral Trait ◽  
Color Preferences ◽  
Natural Field

Pollinator foraging behavior has direct consequences for plant reproduction and has been implicated in driving floral trait evolution. Exploring the degree to which pollinators exhibit flexibility in foraging behavior will add to a mechanistic understanding of how pollinators can impact selection on plant traits. Although plants have evolved suites of floral traits to attract pollinators, flower color is a particularly important aspect of the floral display. Some pollinators show strong innate color preference, but many pollinators display flexibility in preference due to learning associations between rewards and color, or due to variable perception of color in different environments or plant communities. This study examines the flexibility in flower color preference of two groups of native butterfly pollinators under natural field conditions. Our study reveals that pipevine swallowtails and skippers, the predominate pollinators of the two native Texas Phlox species, display distinct patterns of color preferences across different contexts. Pipevine swallowtails exhibit highly flexible color preferences and likely utilize other floral traits to make foraging decisions. In contrast, skippers have consistent color preferences and likely use flower color as a primary cue for foraging. As a result of this variation in color preference flexibility, the two pollinator groups impose concordant selection on flower color in some contexts but discordant selection in other contexts. This variability could have profound implications for how flower traits respond to pollinator-mediated selection. Our findings suggest that studying dynamics of behavior in natural field conditions is important for understanding plant-pollinator interactions.

scholarly journals Selection for two different mating systems in Aquilegia canadensis

2021 ◽  
Author(s):  
Chloë Dean-Moore
Keyword(s):  
Display Size ◽  
Mating Systems ◽  
Floral Traits ◽  
Floral Display ◽  
Reproductive Assurance ◽  
Flower Number ◽  
Positive Direction ◽  
Correlational Selection ◽  
Self Pollination ◽  
Floral Displays

Because plants are sessile, they depend on biotic and/or abiotic vectors to transfer pollen from the male pollen-producing anthers to the female pollen-receiving stigmas. As a result, plant mating systems evolve through selection on the floral traits that influence how much pollen is transferred from anthers to stigmas within flowers (self-pollination) vs. between flowers on different individuals (outcrossing). Thus, mating systems are influenced by the traits that dictate the relative abundance of self-versus outcrossed pollen on stigmas. Spatial separation between anthers and stigmas within flowers (herkogamy) is expected to regulate self-pollination yet there are few estimates of how natural selectin acts on this trait.  Aquilegia canadensis (columbine, Ranunculaceae) is a short-lived herbaceous plant of rocky outcrops throughout eastern North America that makes seed through both self-fertilization which is influenced by herkogamy, and outcrossing, which is likely influenced by the plant’s floral display size (flower number and size). Selfing provides reproductive assurance in natural populations of columbine, whereas outcrossing appears to produce much fitter offspring, and there is a trade-off between thes two components of the mating system. We, therefore, predicted correlational selection between herkogamy and display size: selection would favour reduced herkogamy among individuals with small floral displays (to enhance reproductive assurance) and increased herkogamy among individuals with large floral displays (to reduce selfing when outcrossing is likely). We tested this prediction by using multivariate linear regression to estimate phenotypic selection through seeds/fruit and seeds/plant on floral traits and plant size for 1015 plants from nine populations of A. canadensis at the Queen’s University Biological Station. Although we detected positive direction selection on display size mostly through flower number, we did not detect selection on herkogamy or correlational selection between herkogamy and display size. As expected, large size is universally favoured yet selection of floral morphology is weak.    

scholarly journals Phenotypic selection on floral traits in an urban landscape

2018 ◽  
Vol 285 (1884) ◽  
pp. 20181239 ◽  
Author(s):  
Rebecca E. Irwin ◽  
Paige S. Warren ◽  
Lynn S. Adler
Keyword(s):  
Display Size ◽  
Native Species ◽  
Urban Landscape ◽  
Phenotypic Selection ◽  
Urban Environments ◽  
Urban Landscapes ◽  
Floral Display ◽  
Floral Display Size ◽  
Selection For ◽  
Urban Sites

Native species are increasingly living in urban landscapes associated with abiotic and biotic changes that may influence patterns of phenotypic selection. However, measures of selection in urban and non-urban environments, and exploration of the mechanisms associated with such changes, are uncommon. Plant–animal interactions have played a central role in the evolution of flowering plants and are sensitive to changes in the urban landscape, and thus provide opportunities to explore how urban environments modify selection. We evaluated patterns of phenotypic selection on the floral and resistance traits of Gelsemium sempervirens in urban and non-urban sites. The urban landscape had increased florivory and decreased pollen receipt, but showed only modest differences in patterns of selection. Directional selection for one trait, larger floral display size, was stronger in urban compared to non-urban sites. Neither quadratic nor correlational selection significantly differed between urban and non-urban sites. Pollination was associated with selection for larger floral display size in urban compared to non-urban sites, due to the differences in the translation of pollination into seeds rather than pollinator selectivity. Thus, our data suggest that urban landscapes may not result in sweeping differences in phenotypic selection but rather modest differences for some traits, potentially mediated by species interactions.

scholarly journals The influence of floral display size on selfing rates in Mimulus ringens

Heredity ◽  
2003 ◽  
Vol 92 (3) ◽  
pp. 242-248 ◽  
Author(s):  
J D Karron ◽  
R J Mitchell ◽  
K G Holmquist ◽  
J M Bell ◽  
B Funk
Keyword(s):  
Display Size ◽  
Floral Display ◽  
Floral Display Size ◽  
Mimulus Ringens

scholarly journals Adaptive plasticity of floral display size in animal-pollinated plants

2005 ◽  
Vol 272 (1581) ◽  
pp. 2651-2657 ◽  
Author(s):  
Lawrence D Harder ◽  
Steven D Johnson
Keyword(s):  
Display Size ◽  
Adaptive Plasticity ◽  
Floral Display ◽  
Mating Costs ◽  
Pollen Removal ◽  
Floral Display Size ◽  
Subsequent Exposure ◽  
Pollen Vectors ◽  
Benefit Cost ◽  
Pollination Environment

Plants need not participate passively in their own mating, despite their immobility and reliance on pollen vectors. Instead, plants may respond to their recent pollination experience by adjusting the number of flowers that they display simultaneously. Such responsiveness could arise from the dependence of floral display size on the longevity of individual flowers, which varies with pollination rate in many plant species. By hand-pollinating some inflorescences, but not others, we demonstrate plasticity in display size of the orchid Satyrium longicauda . Pollination induced flower wilting, but did not affect the opening of new flowers, so that within a few days pollinated inflorescences displayed fewer flowers than unpollinated inflorescences. During subsequent exposure to intensive natural pollination, pollen removal and receipt increased proportionally with increasing display size, whereas pollen-removal failure and self-pollination accelerated. Such benefit–cost relations allow plants that adjust display size in response to the prevailing pollination rate to increase their attractiveness when pollinators are rare (large displays), or to limit mating costs when pollinators are abundant (small displays). Seen from this perspective, pollination-induced flower wilting serves the entire plant by allowing it to display the number of flowers that is appropriate for the current pollination environment.

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