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Tie S, He YD, Lázaro A, Inouye DW, Guo YH, Yang CF. Floral trait variation across individual plants within a population enhances defense capability to nectar robbing. PLANT DIVERSITY 2023; 45:315-325. [PMID: 37397606 PMCID: PMC10311112 DOI: 10.1016/j.pld.2022.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 11/01/2022] [Accepted: 11/07/2022] [Indexed: 07/04/2023]
Abstract
Floral trait variation may help pollinators and nectar robbers identify their target plants and, thus, lead to differential selection pressure for defense capability against floral antagonists. However, the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored. We investigated floral trait variation, pollination, and nectar robbing among individual plants in a population of the bumble bee-pollinated plant, Caryopteris divaricata, from which flowers are also robbed by bumble bees with varying intensity across individuals. We measured the variation in corolla tube length, nectar volume and sugar concentration among individual plants, and evaluated whether the variation were recognized by pollinators and robbers. We investigated the influence of nectar robbing on legitimate visitation and seed production per fruit. We found that the primary nectar robber (Bombus nobilis) preferred to forage on plants with long-tubed flowers, which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes. Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors (mainly B. picipes) and higher seed production. Nectar robbing significantly reduced seed production because it decreased pollinator visits. However, neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded. This finding suggests that floral trait variation might not be driven by pollinators. Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.
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Affiliation(s)
- Shuang Tie
- College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Yong-Deng He
- CAS Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Amparo Lázaro
- Global Change Research Group, Mediterranean Institute for Advanced Studies (IMEDEA; UIB-CSIC), Esporles, Balearic Islands, Spain
| | - David W. Inouye
- The Rocky Mountain Biological Laboratory, Post Office Box 519, Crested Butte, CO 81224, USA
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - You-Hao Guo
- College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Chun-Feng Yang
- CAS Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
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2
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Soininen JOS, Kytöviita M. Geranium sylvaticum increases pollination probability by sexually dimorphic flowers. Ecol Evol 2022; 12:e9670. [PMID: 36590340 PMCID: PMC9797467 DOI: 10.1002/ece3.9670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 12/10/2022] [Indexed: 12/29/2022] Open
Abstract
Sexual dimorphism is expressed as different morphologies between the sexes of a species. Dimorphism is pronounced in gynodioecious populations which consist of female and hermaphrodite individuals. The small size of female flowers in gynodioecious species is often explained by resource re-allocation to seed production instead of large flowers. However, pollinator attraction is critical to female fitness, and factors other than resource savings are needed to explain the small size of female flowers. We hypothesized that the floral size dimorphism in the perennial gynodioecious Geranium sylvaticum (L.) is adaptive in terms of pollination. To test this "pollination hypothesis," we video recorded the small female and large hermaphrodite G. sylvaticum flowers. We parameterized floral visitor behavior when visiting a flower and calculated pollination probabilities by a floral visitor as the probability of touching anther and stigma with the same body part. Pollination probability differed in terms of flower sex and pollinator species. Bumblebees had the highest pollination probability. The small female flowers were more likely to receive pollen via several pollinator groups than the large hermaphrodite flowers. The pollen display of hermaphrodites matched poorly with the stigma display of hermaphrodites, but well with that of females. Although the small size of female flowers is commonly explained by resource re-allocation, we show that sexual dimorphism in flower size may increase the main reproductive functions of the females and hermaphrodites. Dimorphism increases pollination probability in females and fathering probability of the hermaphrodites likely driving G. sylvaticum populations towards dioecy.
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Affiliation(s)
- Jaakko O. S. Soininen
- Department of Biological and Environmental Sciences, Faculty of Mathematics and ScienceUniversity of JyväskyläJyväskyläFinland
| | - Minna‐Maarit Kytöviita
- Department of Biological and Environmental Sciences, Faculty of Mathematics and ScienceUniversity of JyväskyläJyväskyläFinland
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Krishna S, Keasar T. Generalization of Foraging Experience Biases Bees Toward Flowers With Complex Morphologies. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.655086] [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
The importance of pollinators as selective agents for many floral traits is well established, but understanding their role in the evolution of complex floral shapes remains challenging. This is because pollinators often need much practice to efficiently handle morphologically complex flowers and extract their food rewards. What induces foragers to persistently visit and pollinate complex flowers despite their initial low profitability? We previously found that naive bumblebees, and unsuccessful feeding attempts of experienced ones, contribute to the pollination of complex flowers. Here we tested a complementary hypothesis, positing that successful foraging on flowers of one complex shape prepares pollinators to visit other species of different complex morphologies. We trained bumblebees to computer-controlled artificial flowers that were either simple, complex or both simple and complex. We then recorded their feeding choices and handling times on a second array of simple and complex flowers that had different shapes and required another handling technique. Bees trained on a single flower type (whether simple or complex) preferred flowers of the same type in the testing array. The foragers’ preferences after training on both flower types depended on the reward schedule during training: when both flower types rewarded equally, simple flowers were preferred at the test phase; when complex flowers provided higher reward during training, they became the preferred flower type during testing. These results suggest that successful foraging on complex flowers, especially when highly rewarding, can indeed induce insect pollinators to attempt additional flower species with other complex shapes.
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Bees and abstract concepts. Curr Opin Behav Sci 2021. [DOI: 10.1016/j.cobeha.2020.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Lichtenberg EM, Irwin RE, Bronstein JL. Bumble bees are constant to nectar-robbing behaviour despite low switching costs. Anim Behav 2020. [DOI: 10.1016/j.anbehav.2020.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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6
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Oberhauser FB, Czaczkes TJ. Tasting the unexpected: disconfirmation of expectations leads to lower perceived food value in an invertebrate. Biol Lett 2018; 14:20180440. [PMID: 30185610 PMCID: PMC6170749 DOI: 10.1098/rsbl.2018.0440] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 08/07/2018] [Indexed: 11/12/2022] Open
Abstract
To make sensible decisions, both humans and other animals must compare the available options against a reference point-either other options or previous experience. Options of higher quality than the reference are considered good value. However, many perceptible attributes of options are value-neutral, such as flower scent. Nonetheless, such value-neutral differences may be part of an expectation. Can a mismatch between the expectation and experience of value-neutral attributes affect perceived value? Consumer psychology theory and results suggest it can. To test this in a non-human animal, we manipulated a value-neutral aspect of a food source-its taste-while keeping its absolute value-its sweetness-the same. Individual ants (Lasius niger) were allowed to drink either lemon- or rosemary-flavoured 1 M sucrose. After three successive visits to the food, we switched the taste in the last, fourth, visit to induce a disconfirmation of expectations. In control trials, ants received the same taste on all four visits. Disconfirmed ants showed lower food acceptance and laid less pheromone on the way back to the nest, even though the molarity of the food was unchanged. As ants recruit nest-mates via pheromone depositions, fewer depositions indicate that the ants valued the food less. Thus, an expectation of value-neutral attributes can influence the perceived value of a resource. Such influences of value-neutral variables on value perception may affect how animals interact with and exploit their environment, and may contribute to phenomena such as flower constancy.
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Affiliation(s)
- F B Oberhauser
- Animal Comparative Economics Laboratory, Department of Zoology and Evolutionary Biology, University of Regensburg, Regensburg 93053, Germany
| | - T J Czaczkes
- Animal Comparative Economics Laboratory, Department of Zoology and Evolutionary Biology, University of Regensburg, Regensburg 93053, Germany
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Lichtenberg EM, Irwin RE, Bronstein JL. Costs and benefits of alternative food handling tactics help explain facultative exploitation of pollination mutualisms. Ecology 2018; 99:1815-1824. [PMID: 29800495 DOI: 10.1002/ecy.2395] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 03/24/2018] [Accepted: 04/11/2018] [Indexed: 11/05/2022]
Abstract
Many mutualisms are taken advantage of by organisms that take rewards from their partners but provide no benefit in return. In the absence of traits that limit exploitation, facultative exploiters (partners that can either exploit or cooperate) are widely predicted by mutualism theory to choose an exploitative strategy, potentially threatening mutualism stability. However, it is unknown whether facultative exploiters choose to exploit, and, if so, make this choice because it is the most beneficial strategy for them. We explored these questions in a subalpine plant-insect community in which individuals of several bumble bee species visit flowers both "legitimately" (entering via the flower opening, picking up and depositing pollen, and hence behaving mutualistically) and via nectar robbing (creating holes through corollas or using an existing hole, bypassing stigmas and anthers). We applied foraging theory to (1) quantify handling costs, benefits and foraging efficiencies incurred by three bumble bee species as they visited flowers legitimately or robbed nectar in cage experiments, and (2) determine whether these efficiencies matched the food handling tactics these bee species employed in the field. Relative efficiencies of legitimate and robbing tactics depended on the combination of bee and plant species. In some cases (Bombus mixtus visiting Corydalis caseana or Mertensia ciliata), the robbing tactic permitted more efficient nectar removal. As both mutualism and foraging theory would predict, in the field, B. mixtus visiting C. caseana were observed more frequently robbing than foraging legitimately. However, for Bombus flavifrons visiting M. ciliata, the expectation from mutualism theory did not hold: legitimate visitation was the more efficient tactic. Legitimate visitation to M. ciliata was in fact more frequently observed in free-flying B. flavifrons. Free-flying B. mixtus also frequently visited M. ciliata flowers legitimately. This may reflect lower nectar volumes in robbed than unrobbed flowers in the field. These results suggest that a foraging ecology perspective is informative to the choice of tactics facultative exploiters make. In contrast, the simple expectation that exploiters should always have an advantage, and hence could threaten mutualism persistence unless they are deterred or punished, may not be broadly applicable.
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Affiliation(s)
- Elinor M Lichtenberg
- Department of Ecology & Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721, USA
| | - Rebecca E Irwin
- Department of Applied Ecology, North Carolina State University, Raleigh, North Carolina, 27695, USA.,Rocky Mountain Biological Lab, Crested Butte, Colorado, 81224, USA
| | - Judith L Bronstein
- Department of Ecology & Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721, USA
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8
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Learning about larceny: experience can bias bumble bees to rob nectar. Behav Ecol Sociobiol 2018. [DOI: 10.1007/s00265-018-2478-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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9
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Schöner MG, Schöner CR, Ermisch R, Puechmaille SJ, Grafe TU, Tan MC, Kerth G. Stabilization of a bat-pitcher plant mutualism. Sci Rep 2017; 7:13170. [PMID: 29030597 PMCID: PMC5640698 DOI: 10.1038/s41598-017-13535-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 09/25/2017] [Indexed: 11/23/2022] Open
Abstract
Despite the long persistence of many mutualisms, it is largely unknown which mechanisms stabilize these interactions. This is especially true if only one mutualism partner can choose alternative partners while the other cannot, resulting in a power asymmetry. According to biological market theory the choosing partner should prefer the more dependent partner if the latter offers commodities of higher quality than its competitors. We tested this prediction using Bornean carnivorous pitcher plants (Nepenthes hemsleyana) that strongly rely on faecal nitrogen of bats (Kerivoula hardwickii) which roost inside the pitchers. The bats also roost in furled leaves of various plants. Surprisingly, during field observations the bats did not always choose N. hemsleyana pitchers despite their superior quality but were generally faithful either to pitchers or to furled leaves. In behavioural experiments 21% of the leaf-roosting bats switched to pitchers, while the majority of these bats and all pitcher-roosting individuals were faithful to the roost type in which we had found them. Genetic differentiation cannot explain this faithfulness, which likely results from different roosting traditions. Such traditions could have stabilizing or destabilizing effects on various mutualisms and should be investigated in more detail.
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Affiliation(s)
- Michael G Schöner
- Zoological Institute and Museum, University of Greifswald, Loitzer Straße 26, 17489, Greifswald, Germany.
| | - Caroline R Schöner
- Zoological Institute and Museum, University of Greifswald, Loitzer Straße 26, 17489, Greifswald, Germany
| | - Rebecca Ermisch
- Zoological Institute and Museum, University of Greifswald, Loitzer Straße 26, 17489, Greifswald, Germany
| | - Sébastien J Puechmaille
- Zoological Institute and Museum, University of Greifswald, Loitzer Straße 26, 17489, Greifswald, Germany
| | - T Ulmar Grafe
- Faculty of Science, Biology, University Brunei Darussalam, Tungku Link, Gadong, 1410, Brunei Darussalam
| | - Moi Chan Tan
- Faculty of Science, Biology, University Brunei Darussalam, Tungku Link, Gadong, 1410, Brunei Darussalam
| | - Gerald Kerth
- Zoological Institute and Museum, University of Greifswald, Loitzer Straße 26, 17489, Greifswald, Germany
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Bronstein JL, Barker JL, Lichtenberg EM, Richardson LL, Irwin RE. The behavioral ecology of nectar robbing: why be tactic constant? CURRENT OPINION IN INSECT SCIENCE 2017; 21:14-18. [PMID: 28822483 DOI: 10.1016/j.cois.2017.05.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 04/28/2017] [Accepted: 05/10/2017] [Indexed: 06/07/2023]
Abstract
How do animals forage for variable food resources? For animals foraging at flowers, floral constancy has provided a framework for understanding why organisms visit some flowers while bypassing others. We extend this framework to the flower-handling tactics that visitors employ. Nectar robbers remove nectar through holes bitten in flowers, often without pollinating. Many foragers can switch between robbing and visiting flowers legitimately to gain access to nectar. We document that even though individuals can switch foraging tactics, they often do not. We explore whether individuals exhibit constancy to either robbing or visiting legitimately, which we term tactic constancy. We then extend hypotheses of floral constancy to understand when and why visitors exhibit tactic constancy and raise questions for future research.
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Affiliation(s)
- Judith L Bronstein
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, United States.
| | - Jessica L Barker
- Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Elinor M Lichtenberg
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, United States
| | - Leif L Richardson
- Gund Institute for Ecological Economics, University of Vermont, Burlington, VT, United States
| | - Rebecca E Irwin
- Department of Applied Ecology, North Carolina State University, Raleigh, NC, United States
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Sands RJ, Rowntree JK. Interactions between the Bumblebee Bombus pascuorum and Red Clover (Trifolium pratense) Are Mediated by Plant Genetic Background. PLoS One 2016; 11:e0161327. [PMID: 27552193 PMCID: PMC4995044 DOI: 10.1371/journal.pone.0161327] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 08/03/2016] [Indexed: 12/01/2022] Open
Abstract
Wildflower mixes are often planted around field margins to provide forage for pollinators. Although seed for these mixtures is often wild-sourced, for species where agricultural cultivars are available, for example red clover (Trifolium pratense), cultivars can also be included. Previous evidence suggests that plant genetic background can have a strong influence on plant-arthropod interactions and therefore the provenance and genetic background of the plants included in wildflower mixes could impact plant-pollinator interactions. We tested the performance of five individual T. pratense cultivars against two commercially available wild-sourced T. pratense populations in terms of their ability to attract potential pollinator species (focusing on bumblebees) and their floral traits using greenhouse and garden experiments. The main bumblebee observed interacting with T. pratense was Bombus pascuorum and we found no difference in the absolute number of B. pascuorum visiting the cultivars or wild populations. However, we found variation among cultivars and between wild populations in their ability to attract bumblebees, which seems to be related to their relative investment in different floral traits. There was a positive relationship between biomass and number of inflorescences produced by the wild populations of T. pratense, which was not apparent for the cultivars. This suggests that artificial selection on the cultivars has changed the G-matrix of correlated traits. We show that agricultural cultivars of T. pratense can be as effective as wild populations at attracting pollinators such as bumblebees, but that the genetic background of both cultivars and wild populations can have a significant impact on the attractiveness of the plant to pollinators. We also show divergence in the correlated traits of T. pratense cultivars and wild populations that could lead to outbreeding depression if the plants interbreed.
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Affiliation(s)
- Richard J. Sands
- Centre for the Genetics of Ecosystem Services, Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Manchester, United Kingdom
| | - Jennifer K. Rowntree
- Centre for the Genetics of Ecosystem Services, Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Manchester, United Kingdom
- * E-mail:
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