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Balbuena MS, Buchmann SL, Papaj DR, Raguso RA. Organ-specific volatiles from Sonoran desert Krameria flowers as potential signals for oil-collecting bees. PHYTOCHEMISTRY 2024; 218:113937. [PMID: 38035972 DOI: 10.1016/j.phytochem.2023.113937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 11/21/2023] [Accepted: 11/23/2023] [Indexed: 12/02/2023]
Abstract
The evolution of flowers that offer oils as rewards and are pollinated by specialized bees represents a distinctive theme in plant-pollinator co-diversification. Some plants that offer acetylated glycerols as floral oils emit diacetin, a volatile by-product of oil metabolism, which is utilized by oil-collecting bees as an index signal for the presence of floral oil. However, floral oils in the genus Krameria (Krameriaceae) contain β-acetoxy-substituted fatty acids instead of acetylated glycerols, making them unlikely to emit diacetin as an oil-bee attractant. We analyzed floral headspace composition from K. bicolor and K. erecta, native to the Sonoran Desert of southwestern North America, in search of alternative candidates for volatile index signals. Using solid-phase microextraction, combined with gas chromatography-mass spectrometry, we identified 26 and 45 floral volatiles, respectively, from whole flowers and dissected flower parts of these two Krameria species. As expected, diacetin was not detected. Instead, β-ionone emerged as a strong candidate for an index signal, as it was uniquely present in dissected oil-producing floral tissues (elaiophores) of K. bicolor, as well as the larval cells and provisions from its oil-bee pollinator, Centris cockerelli. This finding suggests that the floral oil of K. bicolor is perfused with β-ionone in its tissue of origin and retains the distinctive raspberry-like scent of this volatile after being harvested by C. cockerelli bees. In contrast, the elaiophores of K. erecta, which are not thought to be pollinated by C. cockerelli, produced a blend of anise-related oxygenated aromatics not found in the elaiophores of K. bicolor. Our findings suggest that β-ionone has the potential to impact oil-foraging by C. cockerelli bees through several potential mechanisms, including larval imprinting on scented provisions or innate or learned preferences by foraging adults.
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Affiliation(s)
- Maria Sol Balbuena
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, 14853, USA.
| | - Stephen L Buchmann
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA; Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
| | - Daniel R Papaj
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA.
| | - Robert A Raguso
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, 14853, USA.
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Maldonado M, Fornoni J, Boege K, Pérez Ishiwara R, Santos-Gally R, Domínguez CA. The role of within-plant variation in nectar production: an experimental approach. ANNALS OF BOTANY 2023; 132:95-106. [PMID: 37419457 PMCID: PMC10550272 DOI: 10.1093/aob/mcad082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Indexed: 07/09/2023]
Abstract
BACKGROUND AND AIMS Nectar, a plant reward for pollinators, can be energetically expensive. Hence, a higher investment in nectar production can lead to reduced allocation to other vital functions and/or increased geitonogamous pollination. One possible strategy employed by plants to reduce these costs is to offer variable amounts of nectar among flowers within a plant, to manipulate pollinator behaviour. Using artificial flowers, we tested this hypothesis by examining how pollinator visitation responds to inter- and intra-plant variation in nectar production, assessing how these responses impact the energetic cost per visit. METHODS We conducted a 2 × 2 factorial experiment using artificial flowers, with two levels of nectar investment (high and low sugar concentration) and two degrees of intra-plant variation in nectar concentration (coefficient of variation 0 and 20 %). The experimental plants were exposed to visits (number and type) from a captive Bombus impatiens colony, and we recorded the total visitation rate, distinguishing geitonogamous from exogamous visits. Additionally, we calculated two estimators of the energetic cost per visit and examined whether flowers with higher nectar concentrations (richer flowers) attracted more bumblebees. KEY RESULTS Plants in the variable nectar production treatment (coefficient of variation 20 %) had a greater proportion of flowers visited by pollinators, with higher rates of total, geitonogamous and exogamous visitation, compared with plants with invariable nectar production. When assuming no nectar reabsorption, variable plants incurred a lower cost per visit compared with invariable plants. Moreover, highly rewarding flowers on variable plants had higher rates of pollination visits compared with flowers with few rewards. CONCLUSIONS Intra-plant variation in nectar concentration can represent a mechanism for pollinator manipulation, enabling plants to decrease the energetic costs of the interaction while still ensuring consistent pollinator visitation. However, our findings did not provide support for the hypothesis that intra-plant variation in nectar concentration acts as a mechanism to avoid geitonogamy. Additionally, our results confirmed the hypothesis that increased visitation to variable plants is dependent on the presence of flowers with nectar concentration above the mean.
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Affiliation(s)
- Michelle Maldonado
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de MéxicoA.P. 70-275, 04510 Mexico City, Mexico
| | - Juan Fornoni
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de MéxicoA.P. 70-275, 04510 Mexico City, Mexico
| | - Karina Boege
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de MéxicoA.P. 70-275, 04510 Mexico City, Mexico
| | - Rubén Pérez Ishiwara
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de MéxicoA.P. 70-275, 04510 Mexico City, Mexico
| | - Rocío Santos-Gally
- CONAHCYT-Instituto de Ecología, Departamento de Ecología Evolutiva, Universidad Nacional Autónoma de MéxicoA.P. 70-275, 04510 Mexico City, Mexico
| | - César A Domínguez
- Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de MéxicoA.P. 70-275, 04510 Mexico City, Mexico
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Russell AL, Sanders SR, Wilson LA, Papaj DR. The Size of it: Scant Evidence That Flower Size Variation Affects Deception in Intersexual Floral Mimicry. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.724712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutualisms involve cooperation, but also frequently involve conflict. Plant-pollinator mutualisms are no exception. To facilitate animal pollination, flowering plants often offer pollen (their male gametes) as a food reward. Since plants benefit by maximizing pollen export to conspecific flowers, we might expect plants to cheat on pollen rewards. In intersexual floral mimicry, rewarding pollen-bearing male flowers (models) are mimicked by rewardless female flowers (mimics) on the same plant. Pollinators should therefore learn to avoid the unrewarding mimics. Plants might impede such learning by producing phenotypically variable flowers that cause bees to generalize among models and mimics during learning. In this laboratory study, we used partially artificial flowers (artificial petals, live reproductive parts) modeled after Begonia odorata to test whether variation in the size of rewarding male flowers (models) and unrewarding female flowers (mimics) affected how quickly bees learned both to recognize models and to reject mimics. Live unrewarding female flowers have 33% longer petals and have 31% greater surface area than live rewarding male flowers, which bees should easily discriminate. Yet while bees rapidly learned to reduce foraging effort on mimics, learning was not significantly affected by the degree to which flower size varied. Additionally, we found scant evidence that this was a result of bees altering response speed to maintain decision accuracy. Our study failed to provide evidence that flower size variation in intersexual floral mimicry systems exploits pollinator cognition, though we cannot rule out that other floral traits that are variable may be important. Furthermore, we propose that contrary to expectation, phenotypic variability in a Batesian mimicry system may not necessarily have significant effects on whether receivers effectively learn to discriminate models and mimics.
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Russell AL, Kikuchi DW, Giebink NW, Papaj DR. Sensory bias and signal detection trade-offs maintain intersexual floral mimicry. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190469. [PMID: 32420844 DOI: 10.1098/rstb.2019.0469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mimicry is common in interspecies interactions, yet conditions maintaining Batesian mimicry have been primarily tested in predator-prey interactions. In pollination mutualisms, floral mimetic signals thought to dupe animals into pollinating unrewarding flowers are widespread (greater than 32 plant families). Yet whether animals learn to both correctly identify floral models and reject floral mimics and whether these responses are frequency-dependent is not well understood. We tested how learning affected the effectiveness and frequency-dependence of imperfect Batesian mimicry among flowers using the generalist bumblebee, Bombus impatiens, visiting Begonia odorata, a plant species exhibiting intersexual floral mimicry. Unrewarding female flowers are mimics of pollen-rewarding male flowers (models), though mimicry to the human eye is imperfect. Flower-naive bees exhibited a perceptual bias for mimics over models, but rapidly learned to avoid mimics. Surprisingly, altering the frequency of models and mimics only marginally shaped responses by naive bees and by bees experienced with the distribution and frequency of models and mimics. Our results provide evidence both of exploitation by the plant of signal detection trade-offs in bees and of resistance by the bees, via learning, to this exploitation. Critically, we provide experimental evidence that imperfect Batesian mimicry can be adaptive and, in contrast with expectations of signal detection theory, functions largely independently of the model and mimic frequency. This article is part of the theme issue 'Signal detection theory in recognition systems: from evolving models to experimental tests'.
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Affiliation(s)
- Avery L Russell
- Department of Biology, Missouri State University, 910 South John Q Hammons Parkway, Springfield, MO 65897, USA.,Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 87521, USA
| | - David W Kikuchi
- Wissenschaftskolleg zu Berlin, Berlin 14193, Germany.,Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 87521, USA
| | - Noah W Giebink
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 87521, USA
| | - Daniel R Papaj
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 87521, USA
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Vázquez V, Barradas I. A plant–pollinator system: How learning versus cost-benefit can induce periodic oscillations. INT J BIOMATH 2018. [DOI: 10.1142/s1793524518500249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this paper, we propose a model describing the interaction between two species: a plant population that gets pollinated by an insect population. We assume the plant population is divided into two groups: the first group in mutualistic relationship with the insect and the second group attracting the insects while deceiving them and not delivering any reward. In addition, we assume that the insect population reduces the number of visits to the plants after several unsuccessful visits. We are interested in the conditions for the coexistence of both species, especially in the appearance of damped or sustained oscillations. We focus the analysis on the parameters that measure the balance among deceit, the benefit that the insect gets from the plant, and the learning by the pollinators. We are especially interested in analyzing the effect of learning by the insect population due to unsuccessfully visiting the deceiving plants.
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Affiliation(s)
- Virgilio Vázquez
- Instituto de Física y Matemáticas, Universidad Tecnológica de la Mixteca, Huajuapan de León, Oaxaca 69000, México
| | - Ignacio Barradas
- Centro de Investigación en Matemáticas, Apartado Postal 402, Guanajuato, Guanajuato 36000, México
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Knauer AC, Schiestl FP. Bees use honest floral signals as indicators of reward when visiting flowers. Ecol Lett 2014; 18:135-43. [PMID: 25491788 DOI: 10.1111/ele.12386] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 09/20/2014] [Indexed: 11/27/2022]
Abstract
Pollinators visit flowers for rewards and should therefore have a preference for floral signals that indicate reward status, so called 'honest signals'. We investigated honest signalling in Brassica rapa L. and its relevance for the attraction of a generalised pollinator, the bumble bee Bombus terrestris (L.). We found a positive association between reward amount (nectar sugar and pollen) and the floral scent compound phenylacetaldehyde. Bumble bees developed a preference for phenylacetaldehyde over other scent compounds after foraging on B. rapa. When foraging on artificial flowers scented with synthetic volatiles, bumble bees developed a preference for those specific compounds that honestly indicated reward status. These results show that the honesty of floral signals can play a key role in their attractiveness to pollinators. In plants, a genetic constraint, resource limitation in reward and signal production, and sanctions against cheaters may contribute to the evolution and maintenance of honest signalling.
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Affiliation(s)
- A C Knauer
- Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland
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Twyford AD, Ennos RA, White CD, Ali MS, Kidner CA. The evolution of sex ratio differences and inflorescence architectures in Begonia (Begoniaceae). AMERICAN JOURNAL OF BOTANY 2014; 101:308-317. [PMID: 24491344 DOI: 10.3732/ajb.1300090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
PREMISE OF THE STUDY A major benefit conferred by monoecy is the ability to alter floral sex ratio in response to selection. In monoecious species that produce flowers of a given sex at set positions on the inflorescence, floral sex ratio may be related to inflorescence architecture. We studied the loci underlying differences in inflorescence architecture between two monoecious Begonia species and related this to floral sex ratios. METHODS We performed trait comparisons and quantitative trait locus (QTL) mapping in a segregating backcross population between Central American Begonia plebeja and B. conchifolia. We focused on traits related to inflorescence architecture, sex ratios, and other reproductive traits. KEY RESULTS The inflorescence branching pattern of B. conchifolia was more asymmetric than B. plebeja, which in turn affects the floral sex ratio. Colocalizing QTLs of moderate effect influenced both the number of male flowers and the fate decisions of axillary meristems, demonstrating the close link between inflorescence architecture and sex ratio. Additional QTLs were found for stamen number (30% variance explained, VE) and pollen sterility (12.3% VE). CONCLUSIONS One way in which Begonia species develop different floral sex ratios is through modifications of their inflorescence architecture. The potential pleiotropic action of QTL on inflorescence branching and floral sex ratios may have major implications for trait evolution and responses to selection. The presence of a single QTL of large effect on stamen number may allow rapid divergence for this key floral trait. We propose candidate loci for stamen number and inflorescence branching for future characterization.
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Affiliation(s)
- Alex D Twyford
- Department of Biology, Syracuse University, 107 College Place, Room 110 LSC, Syracuse, New York 13244 USA
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