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Göttlinger T, Lohaus G. Origin and Function of Amino Acids in Nectar and Nectaries of Pitcairnia Species with Particular Emphasis on Alanine and Glutamine. PLANTS (BASEL, SWITZERLAND) 2023; 13:23. [PMID: 38202331 PMCID: PMC10780904 DOI: 10.3390/plants13010023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/08/2023] [Accepted: 12/18/2023] [Indexed: 01/12/2024]
Abstract
Floral nectar contains sugars and numerous other compounds, including amino acids, but little is known about their function and origin in nectar. Therefore, the amino acid, sugar, and inorganic ion concentrations, as well as the activity of alanine aminotransferase (AlaAT) and glutamine synthetase (GS) in nectar, nectaries, and leaves were analyzed in 30 Pitcairnia species. These data were compared with various floral traits, the pollinator type, and the phylogenetic relationships of the species to find possible causes for the high amino acid concentrations in the nectar of some species. The highest concentrations of amino acids (especially alanine) in nectar were found in species with reddish flowers. Furthermore, the concentration of amino acids in nectar and nectaries is determined through analyzing flower color/pollination type rather than phylogenetic relations. This study provides new insights into the origin of amino acids in nectar. The presence of almost all amino acids in nectar is mainly due to their transport in the phloem to the nectaries, with the exception of alanine, which is partially produced in nectaries. In addition, active regulatory mechanisms are required in nectaries that retain most of the amino acids and allow the selective secretion of specific amino acids, such as alanine.
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Affiliation(s)
- Thomas Göttlinger
- Molecular Plant Science and Plant Biochemistry, University of Wuppertal, 42119 Wuppertal, Germany;
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Lustofin K, Świątek P, Miranda VFO, Płachno BJ. Phylogenetical Position versus Pollination Syndromes: Floral Trichomes of Central American and Mexican Pinguicula. Int J Mol Sci 2023; 24:ijms24098423. [PMID: 37176130 PMCID: PMC10179228 DOI: 10.3390/ijms24098423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Revised: 04/27/2023] [Accepted: 04/29/2023] [Indexed: 05/15/2023] Open
Abstract
Central American and Mexican Pinguicula species are characterized by enormous divergence in size and color of flowers and are pollinated by butterflies, flies, bees, and hummingbirds. It is known that floral trichomes are key characters in plant-pollinator interaction. The main aim of our study was to verify our hypothesis that the distribution and diversity of non-glandular and glandular trichomes are related to the pollinator syndromes rather than the phylogenetic relationships. The studied sample consisted of Central American and Mexican species. In our study, we relied on light microscopy and scanning electron microscopy with a phylogenetic perspective based on ITS DNA sequences. The flower morphology of species pollinated by butterflies and hummingbirds was similar in contrast to species pollinated by flies and bees. Species pollinated by butterflies and hummingbirds contained low diversity of non-glandular trichomes, which occurred mostly in the tube and basal part of the spur. Surprisingly, in P. esseriana and P. mesophytica, non-glandular trichomes also occurred at the base of lower lip petals. In the case of species pollinated by flies/bees, we observed a high variety of non-glandular trichomes, which occurred on the surface of corolla petals, in the tube, and at the entrance to the spur. Furthermore, we did not identify any non-glandular trichomes in the spur. The capitate glandular trichomes were of similar morphology in all examined species. There were minor differences in the shape of the trichome head, as well as the length and the number of stalk cells. The distribution and the diversity of non-glandular and glandular trichomes and pollinator syndromes were mapped onto a phylogenetic reconstruction of the genus. Most micromorphological characters appear to be associated more with floral adaptation to pollinators and less with phylogeny.
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Affiliation(s)
- Krzysztof Lustofin
- Department of Plant Cytology and Embryology, Institute of Botany, Faculty of Biology, Jagiellonian University in Cracow, 9 Gronostajowa St., 30-387 Cracow, Poland
- Doctoral School of Exact and Natural Sciences, Jagiellonian University, 30-348 Cracow, Poland
| | - Piotr Świątek
- Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, 9 Bankowa St., 40-007 Katowice, Poland
| | - Vitor F O Miranda
- Laboratory of Plant Systematics, School of Agricultural and Veterinarian Sciences, São Paulo State University (Unesp), Jaboticabal 14884-900, Brazil
| | - Bartosz J Płachno
- Department of Plant Cytology and Embryology, Institute of Botany, Faculty of Biology, Jagiellonian University in Cracow, 9 Gronostajowa St., 30-387 Cracow, Poland
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Brzosko E, Bajguz A, Burzyńska J, Chmur M. Does Reproductive Success in Natural and Anthropogenic Populations of Generalist Epipactis helleborine Depend on Flower Morphology and Nectar Composition? Int J Mol Sci 2023; 24:4276. [PMID: 36901705 PMCID: PMC10001846 DOI: 10.3390/ijms24054276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 02/17/2023] [Accepted: 02/18/2023] [Indexed: 02/24/2023] Open
Abstract
The purpose of our study was to determine the role of flower structure and nectar composition in shaping the reproductive success (RS) of the generalist orchid Epipactis helleborine in natural and anthropogenic populations. We supposed that the distinct character of two groups of habitats creates different conditions for plant-pollinator relationships, thus influencing reproductive success in E. helleborine populations. Both pollinaria removal (PR) and fruiting (FRS) were differentiated between the populations. On average, FRS was almost two times higher in the anthropogenic than in the natural populations. The difference between the two population groups in PR was smaller but still statistically significant. RS parameters were correlated with some floral display and flower traits. Floral display influenced RS only in three anthropogenic populations. Flower traits had a weak influence on RS (10 of the 192 cases analyzed). The more important trait in shaping RS was nectar chemistry. The nectar of E. helleborine is relatively diluted with a lower sugar concentration in the anthropogenic than in the natural populations. In the natural populations, domination of sucrose over hexoses was found, while in the anthropogenic populations, hexoses were more abundant and the participation of sugars was balanced. In some populations, sugars influenced RS. In E. helleborine nectar, 20 proteogenic and 7 non-proteogenic amino acids (AAs) were found with a clear domination of glutamic acid. We noted relationships between some AAs and RS, but distinct AAs shaped RS in different populations, and their impact was independent of their participation. Our results indicate that the flower structure and nectar composition of E. helleborine reflect its generalistic character and meet the requirements of a wide range of pollinators. Simultaneously, the differentiation of flower traits suggests a variation in pollinator assemblages in particular populations. Knowledge about the factors influencing RS in distinct habitats helps to understand the evolutionary potential of species and to understand mechanisms and processes crucial for shaping interactions between plants and pollinators.
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Affiliation(s)
- Emilia Brzosko
- Department of Biology and Plant Ecology, Faculty of Biology, University of Bialystok, Ciolkowskiego 1J, 15-245 Bialystok, Poland
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Balduino HDK, Tunes P, Giordano E, Guarnieri M, Machado SR, Nepi M, Guimarães E. To each their own! Nectar plasticity within a flower mediates distinct ecological interactions. AOB PLANTS 2023; 15:plac067. [PMID: 36751365 PMCID: PMC9893873 DOI: 10.1093/aobpla/plac067] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 12/29/2022] [Indexed: 06/18/2023]
Abstract
Nuptial and extranuptial nectaries are involved in interactions with different animal functional groups. Nectar traits involved in pollination mutualisms are well known. However, we know little about those traits involved in other mutualisms, such as ant-plant interactions, especially when both types of nectaries are in the same plant organ, the flower. Here we investigated if when two types of nectaries are exploited by distinct functional groups of floral visitors, even being within the same plant organ, the nectar secreted presents distinct features that fit animal requirements. We compared nectar secretion dynamics, floral visitors and nectar chemical composition of both nuptial and extranuptial nectaries in natural populations of the liana Amphilophium mansoanum (Bignoniaceae). For that we characterized nectar sugar, amino acid and specialized metabolite composition by high-performance liquid chromatography. Nuptial nectaries were visited by three medium- and large-sized bee species and extranuptial nectaries were visited mainly by ants, but also by cockroaches, wasps and flies. Nuptial and extranuptial nectar differed regarding volume, concentration, milligrams of sugars per flower and secretion dynamics. Nuptial nectar was sucrose-dominated, with high amounts of γ-aminobutyric acid and β-aminobutyric acid and with theophylline-like alkaloid, which were all exclusive of nuptial nectar. Whereas extranuptial nectar was hexose-rich, had a richer and less variable amino acid chemical profile, with high amounts of serine and alanine amino acids and with higher amounts of the specialized metabolite tyramine. The nectar traits from nuptial and extranuptial nectaries differ in energy amount and nutritional value, as well as in neuroactive specialized metabolites. These differences seem to match floral visitors' requirements, since they exclusively consume one of the two nectar types and may be exerting selective pressures on the composition of the respective resources of interest.
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Affiliation(s)
- Hannelise de Kassia Balduino
- Graduate Course in Plant Biology, São Paulo State University, 18618-689 Botucatu, Brazil
- Laboratory of Ecology and Evolution of Plant-Animal Interactions, Institute of Biosciences, São Paulo State University, 18618-689 Botucatu, Brazil
| | - Priscila Tunes
- Laboratory of Ecology and Evolution of Plant-Animal Interactions, Institute of Biosciences, São Paulo State University, 18618-689 Botucatu, Brazil
| | - Emanuele Giordano
- Laboratory of Analytical Methods for Chemical Ecology - Plant Reproductive Biology, Department of Life Sciences, University of Siena, 53100 Siena, Italy
| | - Massimo Guarnieri
- Laboratory of Analytical Methods for Chemical Ecology - Plant Reproductive Biology, Department of Life Sciences, University of Siena, 53100 Siena, Italy
| | - Silvia Rodrigues Machado
- Laboratory of Plant Anatomy, Institute of Biosciences, São Paulo State University, 18618-689 Botucatu, Brazil
| | - Massimo Nepi
- Laboratory of Analytical Methods for Chemical Ecology - Plant Reproductive Biology, Department of Life Sciences, University of Siena, 53100 Siena, Italy
- National Biodiversity Future Center (NBFC), 90133 Palermo, Italy
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Göttlinger T, Lohaus G. Comparative analyses of the metabolite and ion concentrations in nectar, nectaries, and leaves of 36 bromeliads with different photosynthesis and pollinator types. FRONTIERS IN PLANT SCIENCE 2022; 13:987145. [PMID: 36092434 PMCID: PMC9459329 DOI: 10.3389/fpls.2022.987145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/08/2022] [Indexed: 06/15/2023]
Abstract
Floral nectar contains mainly sugars as well as smaller amounts of amino acids and further compounds. The nectar composition varies between different plant species and it is related to the pollination type of the plant. In addition to this, other factors can influence the composition. Nectar is produced in and secreted from nectaries. A few models exist to explain the origin of nectar for dicotyl plant species, a complete elucidation of the processes, however, has not yet been achieved. This is particularly true for monocots or plant species with CAM photosynthesis. To get closer to such an elucidation, nectar, nectaries, and leaves of 36 bromeliad species were analyzed for sugars, starch, amino acids, and inorganic ions. The species studied include different photosynthesis types (CAM/C3), different pollination types (trochilophilous/chiropterophilous), or different live forms. The main sugars in nectar and nectaries were glucose, fructose, and sucrose, the total sugar concentration was about twofold higher in nectar than in nectaries, which suggests that sugars are actively transported from the nectaries into the nectar. The composition of amino acids in nectar is already determined in the nectaries, but the concentration is much lower in nectar than in nectaries, which suggests selective retention of amino acids during nectar secretion. The same applies to inorganic ions. Statistical analyses showed that the photosynthesis type and the pollination type can explain more data variation in nectar than in nectaries and leaves. Furthermore, the pollinator type has a stronger influence on the nectar or nectary composition than the photosynthesis type. Trochilophilous C3 plants showed significant correlations between the nitrate concentration in leaves and the amino acid concentration in nectaries and nectar. It can be assumed that the more nitrate is taken up, the more amino acids are synthesized in leaves and transported to the nectaries and nectar. However, chiropterophilous C3 plants show no such correlation, which means that the secretion of amino acids into the nectar is regulated by further factors. The results help understand the physiological properties that influence nectaries and nectar as well as the manner of metabolite and ion secretion from nectaries to nectar.
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Roguz K, Hill L, Koethe S, Lunau K, Roguz A, Zych M. Visibility and attractiveness of Fritillaria (Liliaceae) flowers to potential pollinators. Sci Rep 2021; 11:11006. [PMID: 34040041 PMCID: PMC8155214 DOI: 10.1038/s41598-021-90140-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 05/05/2021] [Indexed: 02/04/2023] Open
Abstract
Visual floral characters play an important role in shaping plant-pollinator interactions. The genus Fritillaria L. (Liliaceae), comprising approximately 140 species, is described as displaying a remarkable variety of flower colours and sizes. Despite this variation in visual floral traits of fritillaries, little is known about the potential role of these features in shaping plant-pollinator interactions. Here, we seek to clarify the role of visual attraction in species offering a robust food reward for pollinators early in the spring, which is the case for Fritillaria. We also searched for potential tendencies in the evolution of floral traits crucial for plant-pollinator communication. The generality of species with green and purple flowers may indicate an influence of environmental factors other than pollinators. The flowers of the studied species seem to be visible but not very visually attractive to potential pollinators. The food rewards are hidden within the nodding perianth, and both traits are conserved among fritillaries. Additionally, visual floral traits are not good predictors of nectar properties. When in the flowers, pollinators are navigated by nectar guides in the form of contrasting nectary area colouration. Flower colour does not serve as a phenotypic filter against illegitimate pollinators-red and orange bird-pollinated fritillaries are visible to bees.
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Affiliation(s)
- Katarzyna Roguz
- Botanic Garden, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | | | - Sebastian Koethe
- Institute of Sensory Ecology, Faculty of Biology, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Klaus Lunau
- Institute of Sensory Ecology, Faculty of Biology, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
| | - Agata Roguz
- National Information Processing Institute, Al. Niepodległości 188 B, 00-608, Warszawa, Poland
| | - Marcin Zych
- Botanic Garden, Faculty of Biology, University of Warsaw, Warsaw, Poland
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Álvarez-Pérez S, Tsuji K, Donald M, Van Assche A, Vannette RL, Herrera CM, Jacquemyn H, Fukami T, Lievens B. Nitrogen Assimilation Varies Among Clades of Nectar- and Insect-Associated Acinetobacters. MICROBIAL ECOLOGY 2021; 81:990-1003. [PMID: 33404822 DOI: 10.1007/s00248-020-01671-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/20/2020] [Indexed: 06/12/2023]
Abstract
Floral nectar is commonly colonized by yeasts and bacteria, whose growth largely depends on their capacity to assimilate nutrient resources, withstand high osmotic pressures, and cope with unbalanced carbon-to-nitrogen ratios. Although the basis of the ecological success of these microbes in the harsh environment of nectar is still poorly understood, it is reasonable to assume that they are efficient nitrogen scavengers that can consume a wide range of nitrogen sources in nectar. Furthermore, it can be hypothesized that phylogenetically closely related strains have more similar phenotypic characteristics than distant relatives. We tested these hypotheses by investigating the growth performance on different nitrogen-rich substrates of a collection of 82 acinetobacters isolated from nectar and honeybees, representing members of five species (Acinetobacter nectaris, A. boissieri, A. apis, and the recently described taxa A. bareti and A. pollinis). We also analyzed possible links between growth performance and phylogenetic affiliation of the isolates, while taking into account their geographical origin. Results demonstrated that the studied isolates could utilize a wide variety of nitrogen sources, including common metabolic by-products of yeasts (e.g., ammonium and urea), and that phylogenetic relatedness was associated with the variation in nitrogen assimilation among the studied acinetobacters. Finally, nutrient source and the origin (sample type and country) of isolates also predicted the ability of the acinetobacters to assimilate nitrogen-rich compounds. Overall, these results demonstrate inter-clade variation in the potential of the acinetobacters as nitrogen scavengers and suggest that nutritional dependences might influence interactions between bacteria and yeasts in floral nectar.
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Affiliation(s)
- Sergio Álvarez-Pérez
- Department of Microbial and Molecular Systems, Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), KU Leuven, B-3001, Leuven, Belgium.
- Department of Animal Health, Complutense University of Madrid, 28040, Madrid, Spain.
| | - Kaoru Tsuji
- Center for Ecological Research, Kyoto University, Hirano 2, Otsu, Shiga, 520-2113, Japan
| | - Marion Donald
- Department of BioSciences, Rice University, Houston, TX, 77005, USA
| | - Ado Van Assche
- Department of Microbial and Molecular Systems, Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), KU Leuven, B-3001, Leuven, Belgium
| | - Rachel L Vannette
- Department of Entomology and Nematology, University of California Davis, Davis, CA, 95616, USA
| | | | - Hans Jacquemyn
- Biology Department, Laboratory of Plant Conservation and Population Biology, KU Leuven, B-3001, Leuven, Belgium
| | - Tadashi Fukami
- Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Bart Lievens
- Department of Microbial and Molecular Systems, Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), KU Leuven, B-3001, Leuven, Belgium.
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Roguz K, Hill L, Roguz A, Zych M. Evolution of Bird and Insect Flower Traits in Fritillaria L. (Liliaceae). FRONTIERS IN PLANT SCIENCE 2021; 12:656783. [PMID: 33868353 PMCID: PMC8044542 DOI: 10.3389/fpls.2021.656783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/03/2021] [Indexed: 05/27/2023]
Abstract
Pollinators are often perceived as a primary selective agent influencing flower traits such as colour, size, and nectar properties. The genus Fritillaria L. (Liliaceae), comprising approximately 150 species, is described as generally insect pollinated. However, there are at least three exceptions: two hummingbird-pollinated North American species and one passerine-pollinated Asian species. Despite this variation in pollination, little is known about flower traits that may accompany this shift in fritillaries. In this study, we aimed to assess the attractiveness of the floral traits for (new) pollinators and track the evolution of flowers traits in the context of a shift in the principal pollinator. Therefore, we studied 14 flower traits related to the pollination in 60 Fritillaria species and traced the evolutionary trajectory of these traits. We used a phylogenetic tree of the genus, based on five DNA markers (matK, rpl16, and rbcL, 18S, and ITS) to reconstruct the ancestral state of studied flower traits. The results show that in bird-pollinated species several new traits evolved. For example, flower colouration, nectar sugar, and amino acid concentration and composition fulfil the criteria of ornithophilous flowers, although flower traits do not exclude insect pollinators in bird-pollinated fritillaries. Interestingly, we recorded potential reversals from bird to insect pollination. Our analysis, showing a broad study of flower traits among closely related species in the context of pollinator shift, serves as a starting point for future work exploring the genetic and physiological mechanisms controlling flower traits in the genus Fritillaria.
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Affiliation(s)
- Katarzyna Roguz
- Botanic Garden, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | | | | | - Marcin Zych
- Botanic Garden, Faculty of Biology, University of Warsaw, Warsaw, Poland
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Evolutionary and Ecological Considerations on Nectar-Mediated Tripartite Interactions in Angiosperms and Their Relevance in the Mediterranean Basin. PLANTS 2021; 10:plants10030507. [PMID: 33803275 PMCID: PMC7999006 DOI: 10.3390/plants10030507] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/22/2021] [Accepted: 03/03/2021] [Indexed: 11/16/2022]
Abstract
The Mediterranean basin hosts a high diversity of plants and bees, and it is considered one of the world's biodiversity hotspots. Insect pollination, i.e., pollen transfer from male reproductive structures to conspecific female ones, was classically thought to be a mutualistic relationship that links these two groups of organisms, giving rise to an admirable and complex network of interactions. Although nectar is often involved in mediating these interactions, relatively little is known about modifications in its chemical traits during the evolution of plants. Here, we examine how the current sucrose-dominated floral nectar of most Mediterranean plants could have arisen in the course of evolution of angiosperms. The transition from hexose-rich to sucrose-rich nectar secretion was probably triggered by increasing temperature and aridity during the Cretaceous period, when most angiosperms were radiating. This transition may have opened new ecological niches for new groups of insects that were co-diversifying with angiosperms and for specific nectar-dwelling yeasts that originated later (i.e., Metschnikowiaceae). Our hypothesis embeds recent discoveries in nectar biology, such as the involvement of nectar microbiota and nectar secondary metabolites in shaping interactions with pollinators, and it suggests a complex, multifaceted ecological and evolutionary scenario that we are just beginning to discover.
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Intraspecific Variation in Nectar Chemistry and Its Implications for Insect Visitors: The Case of the Medicinal Plant, Polemonium Caeruleum L. PLANTS 2020; 9:plants9101297. [PMID: 33019586 PMCID: PMC7600102 DOI: 10.3390/plants9101297] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/25/2020] [Accepted: 09/28/2020] [Indexed: 11/17/2022]
Abstract
Floral nectar, being a primary reward for insect visitors, is a key factor in shaping plant–pollinator interactions. However, little is known about the variability in nectar traits, which could potentially affect pollinators and the reproduction of the species. We investigated intraspecific variation in nectar traits in 14 populations of a Red-listed plant, Polemonium caeruleum. Populations varied in terms of the proportion of self-compatible and self-incompatible individuals, and insect communities visiting flowers. Using HPLC, we determined the nectar sugar and amino acid (AA) composition and concentration. We also recorded some basic habitat parameters, which could influence nectar chemistry. In seven selected populations, we investigated the taxonomic composition of the insects visiting flowers. Our observations revealed significant intraspecific variability in nectar chemistry in P. caeruleum. Nectar production was male-biased, with male-phase flowers secreting sucrose- and AA-rich nectar. An analysis revealed that variability in P. caeruleum nectar may be slightly shaped by environmental factors. The studied nectar characters, especially sugars, had little effect on insects visiting flowers. We argue that variation in nectar traits in this generalist plant is a matter of random genetic drift or “adaptive wandering” rather than directional specialization and adaptation in the most effective and abundant group of pollinators.
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