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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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Lanzino M, Palermo AM, Pellegrino G. The effect of inflorescence display size and flower position on pollination success in two deceptive and one rewarding orchid. PLANT BIOLOGY (STUTTGART, GERMANY) 2023; 25:396-402. [PMID: 36719068 DOI: 10.1111/plb.13505] [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: 09/28/2022] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
Inflorescence display size and flower position on the inflorescence play important roles in plant reproduction, in the formation of fruits and are primarily linked to pollinator behaviour. We used three orchids to determine how visitation rates and choice of pollinator depend on number and position of the flowers along the inflorescence. We measured reproductive success in (1) natural conditions, (2) hand-pollination experiments and (3) an experimental design, by modifying composition of inflorescences in populations of two deceptive orchids, Orchis anthropophora and O. italica, and one rewarding orchid, Anacamptis coriophora subsp. fragrans. There were no differences in natural fruit production in relation to flower position on the inflorescence (i.e. upper versus lower part), suggesting no preference of pollinators for different parts of the inflorescence. Hand-pollination experiments highlighted low pollen limitation in A. coriophora subsp. fragrans but high limitation in O. italica and O. anthropophora. Reproductive success of deceptive orchids in experimental plots decreased significantly when flowers on the upper half of the inflorescence were removed leading to reduced floral display, while reproductive success of the nectariferous species did not differ significantly. Our data highlight that in the examined orchids there is no clear relationship between fruit formation and flower position along inflorescences. Thus we can affirm that, for orchids, the entire inflorescence plays a dominant role in insect attraction but the part of the flower spike does not influence the choice of the insect. This implies that all flowers have the same possibility of receiving visits from pollinators, and therefore each flower has the same opportunity to set fruit.
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Affiliation(s)
- M Lanzino
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Cosenza, Italy
| | - A M Palermo
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Cosenza, Italy
| | - G Pellegrino
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Cosenza, Italy
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Brzosko E, Bajguz A, Burzyńska J, Chmur M. Nectar Chemistry or Flower Morphology-What Is More Important for the Reproductive Success of Generalist Orchid Epipactis palustris in Natural and Anthropogenic Populations? Int J Mol Sci 2021; 22:12164. [PMID: 34830045 PMCID: PMC8618778 DOI: 10.3390/ijms222212164] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 11/06/2021] [Accepted: 11/08/2021] [Indexed: 11/17/2022] Open
Abstract
The aim of this study was to determine the level of reproductive success (RS) in natural and anthropogenic populations of generalist orchid Epipactis palustris and its dependence on flower structure and nectar composition, i.e., amino acids and sugars. We found that both pollinaria removal and female reproductive success were high and similar in all populations, despite differences in flower traits and nectar chemistry. Flower structures were weakly correlated with parameters of RS. Nectar traits were more important in shaping RS; although, we noted differentiated selection on nectar components in distinct populations. Individuals in natural populations produced nectar with a larger amount of sugars and amino acids. The sucrose to (fructose and glucose) ratio in natural populations was close to 1, while in anthropogenic ones, a clear domination of fructose and glucose was noted. Our results indicate that the flower traits and nectar composition of E. palustris reflect its generalist character and meet the requirements of a wide range of pollinators, differing according to body sizes, mouth apparatus, and dietary needs. Simultaneously, differentiation of nectar chemistry suggests a variation of pollinator assemblages in particular populations or domination of their some groups. To our knowledge, a comparison of nectar chemistry between natural and anthropogenic populations of orchids is reported for the first time in this paper.
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Affiliation(s)
- Emilia Brzosko
- Faculty of Biology, University of Bialystok, Ciolkowskiego 1J, 15-245 Bialystok, Poland; (J.B.); (M.C.)
| | - Andrzej Bajguz
- Faculty of Biology, University of Bialystok, Ciolkowskiego 1J, 15-245 Bialystok, Poland; (J.B.); (M.C.)
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Brzosko E, Mirski P. Floral Nectar Chemistry in Orchids: A Short Review and Meta-Analysis. PLANTS (BASEL, SWITZERLAND) 2021; 10:2315. [PMID: 34834677 PMCID: PMC8620889 DOI: 10.3390/plants10112315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/21/2021] [Accepted: 10/23/2021] [Indexed: 05/12/2023]
Abstract
Nectar is one of the most important flower traits, shaping plant-pollinator interactions and reproductive success. Despite Orchidaceae including numerous nectariferous species, nectar chemistry in this family has been infrequently studied. Therefore, the aim of this study is to compile data about nectar attributes in different orchid species. The scarcity of data restricted analyses to sugar concentration and composition. Our results suggest that the most important factor shaping nectar traits in orchids is the pollinator type, although we also found differentiation of nectar traits according to geographical regions. In spurred orchids, the length of the spur impacted nectar traits. We recommend the development of studies on nectar chemistry in orchids, including a wider range of species (both in taxonomic and geographical contexts), as well as extending the analyses to other nectar components (such as amino acids and secondary metabolites). The nectar biome would be also worth investigating, since it could affect the chemical composition of nectar. This will enrich the understanding of the mechanisms of plants-pollinators interactions.
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Affiliation(s)
- Emilia Brzosko
- Faculty of Biology, University of Bialystok, Ciołkowskiego 1J, 15-245 Bialystok, Poland
| | - Paweł Mirski
- Faculty of Biology, University of Bialystok, Ciołkowskiego 1J, 15-245 Bialystok, Poland
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Essenberg CJ. Intraspecific relationships between floral signals and rewards with implications for plant fitness. AOB PLANTS 2021; 13:plab006. [PMID: 33708371 PMCID: PMC7937183 DOI: 10.1093/aobpla/plab006] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 01/11/2021] [Indexed: 06/12/2023]
Abstract
Within-species variation in traits such as petal size or colour often provides reliable information to pollinators about the rewards offered to them by flowers. In spite of potential disadvantages of allowing pollinators to discriminate against less-rewarding flowers, examples of informative floral signals are diverse in form and widely distributed across plant taxa, apparently having evolved repeatedly in different lineages. Although hypotheses about the adaptive value of providing reward information have been proposed and tested in a few cases, a unified effort to understand the evolutionary mechanisms favouring informative floral signals has yet to emerge. This review describes the diversity of ways in which floral signals can be linked with floral rewards within plant species and discusses the constraints and selective pressures on floral signal-reward relationships. It focuses particularly on how information about floral rewards can influence pollinator behaviour and how those behavioural changes may, in turn, affect plant fitness, selecting either for providing or withholding reward information. Most of the hypotheses about the evolution of floral signal-reward relationships are, as yet, untested, and the review identifies promising research directions for addressing these considerable gaps in knowledge. The advantages and disadvantages of sharing floral reward information with pollinators likely play an important role in floral trait evolution, and opportunities abound to further our understanding of this neglected aspect of floral signalling.
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Kessler D, Kallenbach M, Diezel C, Rothe E, Murdock M, Baldwin IT. How scent and nectar influence floral antagonists and mutualists. eLife 2015; 4:e07641. [PMID: 26132861 PMCID: PMC4530224 DOI: 10.7554/elife.07641] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Accepted: 06/30/2015] [Indexed: 02/01/2023] Open
Abstract
Many plants attract and reward pollinators with floral scents and nectar, respectively, but these traits can also incur fitness costs as they also attract herbivores. This dilemma, common to most flowering plants, could be solved by not producing nectar and/or scent, thereby cheating pollinators. Both nectar and scent are highly variable in native populations of coyote tobacco, Nicotiana attenuata, with some producing no nectar at all, uncorrelated with the tobacco's main floral attractant, benzylacetone. By silencing benzylacetone biosynthesis and nectar production in all combinations by RNAi, we experimentally uncouple these floral rewards/attractrants and measure their costs/benefits in the plant's native habitat and experimental tents. Both scent and nectar increase outcrossing rates for three, separately tested, pollinators and both traits increase oviposition by a hawkmoth herbivore, with nectar being more influential than scent. These results underscore that it makes little sense to study floral traits as if they only mediated pollination services.
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Affiliation(s)
- Danny Kessler
- Department of Molecular Ecology, Max-Planck Institute for Chemical Ecology, Jena, Germany
| | - Mario Kallenbach
- Department of Molecular Ecology, Max-Planck Institute for Chemical Ecology, Jena, Germany
| | - Celia Diezel
- Department of Molecular Ecology, Max-Planck Institute for Chemical Ecology, Jena, Germany
| | - Eva Rothe
- Department of Molecular Ecology, Max-Planck Institute for Chemical Ecology, Jena, Germany
| | - Mark Murdock
- Department of Molecular Ecology, Max-Planck Institute for Chemical Ecology, Jena, Germany
| | - Ian T Baldwin
- Department of Molecular Ecology, Max-Planck Institute for Chemical Ecology, Jena, Germany
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Jacquemyn H, Lenaerts M, Tyteca D, Lievens B. Microbial diversity in the floral nectar of seven Epipactis (Orchidaceae) species. Microbiologyopen 2013; 2:644-58. [PMID: 23836678 PMCID: PMC3948608 DOI: 10.1002/mbo3.103] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 05/23/2013] [Accepted: 05/28/2013] [Indexed: 11/16/2022] Open
Abstract
Floral nectar of animal-pollinated plants is commonly infested with microorganisms, yet little is known about the microorganisms inhabiting the floral nectar of orchids. In this study, we investigated microbial communities occurring in the floral nectar of seven Epipactis (Orchidaceae) species. Culturable bacteria and yeasts were isolated and identified by partially sequencing the small subunit (SSU) ribosomal RNA (rRNA) gene and the D1/D2 domains of the large subunit (LSU) rRNA gene, respectively. Using three different culture media, we found that bacteria were common inhabitants of the floral nectar of Epipactis. The most widely distributed bacterial operational taxonomic units (OTUs) in nectar of Epipactis were representatives of the family of Enterobacteriaceae, with an unspecified Enterobacteriaceae bacterium as the most common. In contrast to previous studies investigating microbial communities in floral nectar, very few yeast species (mainly of the genus Cryptococcus) were observed, and most of them occurred in very low densities. Total OTU richness (i.e., the number of bacterial and yeast OTUs per orchid species) varied between 4 and 20. Cluster analysis revealed that microbial communities of allogamous species differed from those of autogamous and facultatively autogamous species. This study extends previous efforts to identify microbial communities in floral nectar and indicates that the floral nectar of the orchids investigated mainly contained bacterial communities with moderate phylogenetic diversity.
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MESH Headings
- Bacteria/classification
- Bacteria/genetics
- Bacteria/growth & development
- Bacteria/isolation & purification
- Biodiversity
- Cluster Analysis
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Fungal/chemistry
- DNA, Fungal/genetics
- DNA, Ribosomal/chemistry
- DNA, Ribosomal/genetics
- Fungi/classification
- Fungi/genetics
- Fungi/growth & development
- Fungi/isolation & purification
- Genes, rRNA
- Molecular Sequence Data
- Orchidaceae/microbiology
- Phylogeny
- Plant Nectar
- RNA, Bacterial/genetics
- RNA, Fungal/genetics
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 18S/genetics
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
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Affiliation(s)
- Hans Jacquemyn
- Plant Conservation and Population Biology Biology Department, KU LeuvenKasteelpark Arenberg 31, B-3001, Heverlee, Belgium
| | - Marijke Lenaerts
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More University College, De Nayer Campus Department of Microbial and Molecular Systems (MS), KU Leuven AssociationB-2860, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research InstituteB-2860 Sint-Katelijne-Waver, Belgium
| | - Daniel Tyteca
- Biodiversity Research Centre Earth and Life Institute, Université catholique de LouvainB-1348, Louvain-la-Neuve, Belgium
| | - Bart Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More University College, De Nayer Campus Department of Microbial and Molecular Systems (MS), KU Leuven AssociationB-2860, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research InstituteB-2860 Sint-Katelijne-Waver, Belgium
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Brandenburg A, Kuhlemeier C, Bshary R. Hawkmoth pollinators decrease seed set of a low-nectar Petunia axillaris line through reduced probing time. Curr Biol 2012; 22:1635-9. [PMID: 22840518 DOI: 10.1016/j.cub.2012.06.058] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 06/04/2012] [Accepted: 06/19/2012] [Indexed: 11/15/2022]
Abstract
Although deception of floral pollinators is well known among orchids, the majority of animal-pollinated plants secure pollination by nectar rewards. The costs and benefits of nectar production remain poorly understood. Here, we developed a crossing design to introgress a low-nectar-volume locus of Petunia integrifolia into the genetic background of P. axillaris. The resulting introgression line resembled P. axillaris but produced only one-third of the nectar volume. When exposed simultaneously to low-nectar and wild-type P. axillaris plants, hawkmoth pollinators reduced their probing duration on low-nectar plants but otherwise did not show any signs of discrimination against these plants. However, reduced probing duration resulted in reduced seed production in the low-nectar plants despite their higher reproductive potential as evidenced by hand pollination. In line with this interpretation, we found a positive correlation between probing duration and seed set, and hawkmoth pollination of low-nectar plants that were manually supplemented with nectar to parental levels yielded seed sets similar to hand pollination. Thus, a simple self-serving pollinator behavior--the adjustment of probing time in response to nectar volume--may select against reducing nectar and protect many plant-pollinator mutualisms against a drift toward parasitism.
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Affiliation(s)
- Anna Brandenburg
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
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Pozo MI, de Vega C, Canto A, Herrera CM. Presence of yeasts in floral nectar is consistent with the hypothesis of microbial-mediated signaling in plant-pollinator interactions. PLANT SIGNALING & BEHAVIOR 2009; 4:1102-4. [PMID: 20009562 PMCID: PMC2819527 DOI: 10.4161/psb.4.11.9874] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Olfactory floral signals are significant factors in plant-pollinator mutualisms. Recently, unusual fermentation odors have been described in the nectar and flowers of some species. Since yeasts are common inhabitants of many angiosperms nectars, this raises the possibility that nectar yeasts may act as causal agents of fermentation odors in flowers and, therefore, as possible intermediate agents in plant signaling to pollinators. A recent field study has reported that nectar yeasts were quite frequent in floral nectar across three different regions in Europe and America, where they reached high densities (up to 10(5) cells/mm(3)). Yeast incidence in floral nectar differed widely across plant host species in all sampling sites. A detailed study currently in progress on one of the species surveyed in that study (Helleborus foetidus, Ranunculaceae) has detected that, in addition to interespecific differences in yeast incidence, there is also a strong component of variance in yeast abundance that takes place at the subindividual level (among flowers of the same plant, among nectaries of the same flower). If yeast metabolism is eventually proved to contribute significantly to floral scent, then multilevel patchiness in the distribution of nectar yeasts (among species, among individuals within species, and among flowers and nectaries of the same individual) might contribute to concomitant multilevel variation in plant signaling and, eventually, also in pollination success, pollen flow and plant fitness.
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Affiliation(s)
- María I Pozo
- Estación Biológica de Doñana, CSIC, Sevilla, Spain.
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