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Larue C, Petit RJ. Harmful self-pollination drives gynodioecy in European chestnut, a self-incompatible tree. AMERICAN JOURNAL OF BOTANY 2024; 111:e16329. [PMID: 38708705 DOI: 10.1002/ajb2.16329] [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: 10/25/2023] [Revised: 02/27/2024] [Accepted: 03/04/2024] [Indexed: 05/07/2024]
Abstract
PREMISE Gynodioecy is a rare sexual system in which two genders (sensu Lloyd, 1980), cosexuals and females, coexist. To survive, female plants must compensate for their lack of siring capacity and male attractiveness. In European chestnut (Castanea sativa), an outcrossing tree, self-pollination reduces fruit set in cosexual individuals because of late-acting self-incompatibility and early inbreeding depression. Could this negative sexual interaction explain the presence of females in this species? METHODS We studied gender variation in wild populations of European chestnut. In addition, we compared fruit set (the proportion of flowers giving fruits) and other key female fitness components as well as reproductive allocation between genders. We then performed emasculation experiments in cosexual trees, by removing nectar-producing fertile male inflorescences. We also removed sterile but nectar-producing male inflorescences from female trees, as a control. RESULTS We found a highly variable proportion of male-sterile individuals in the wild in European chestnut. In the experimental plot, trees from each gender had similar size, flower density, and burr set, but different fruit set. Removing nectar-producing male inflorescences from branches or entire trees increased fruit set in cosexual but not in female trees. CONCLUSIONS These results show that self-pollination impairs fruit set in cosexual trees. Female trees avoid these problems as they do not produce pollen but continue to attract pollinators thanks to their rewarding male-sterile inflorescences, resulting in a much higher fruit set than in cosexuals. This demonstrates that even outcrossed plants can benefit from the cessation of self-pollination, to the point that unisexuality can evolve.
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Affiliation(s)
- Clément Larue
- Univ. Bordeaux, INRAE, Biogeco, Cestas, 33610, France
- INVENIO, Maison Jeannette, Douville, 24140, France
| | - Rémy J Petit
- Univ. Bordeaux, INRAE, Biogeco, Cestas, 33610, France
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Chen KH, Pannell JR. Unisexual flowers as a resolution to intralocus sexual conflict in hermaphrodites. Proc Biol Sci 2023; 290:20232137. [PMID: 38018108 PMCID: PMC10685137 DOI: 10.1098/rspb.2023.2137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 11/01/2023] [Indexed: 11/30/2023] Open
Abstract
In dioecious populations, males and females may evolve different trait values to increase fitness through their respective sexual functions. Because hermaphrodites express both sexual functions, resolving sexual conflict is potentially more difficult for them. Here, we show that hermaphrodite plants can partially resolve sexual conflict by expressing different trait values in different male and female modules (e.g. different flowers, inflorescences, branches etc.). We analysed the flowering phenology, sex allocation and selection gradients on floral traits of flowers of the andromonoecious plant Pulsatilla alpina, which produces both bisexual and male flowers. Our results indicate that strong protogyny prevents early bisexual flowers from profiting from high siring opportunities early in the reproductive season at a time when male flowers could achieve high siring success. The production of unisexual male flowers thus resolves this sexual conflict because it allows the flowers to express their male function without waiting until after the female function has been performed. Our study illustrates the resolution of sexual conflict arising from phenological constraints via modular divergence in sex allocation. We discuss the extent to which modular variation in sex allocation in the context of other sexual systems may be similarly explained.
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Affiliation(s)
- Kai-Hsiu Chen
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
| | - John R. Pannell
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015 Lausanne, Switzerland
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Tel-Zur N. Preventing self-fertilization: Insights from Ziziphus species. FRONTIERS IN PLANT SCIENCE 2023; 14:1226502. [PMID: 37662155 PMCID: PMC10471802 DOI: 10.3389/fpls.2023.1226502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Accepted: 08/02/2023] [Indexed: 09/05/2023]
Abstract
The fitness of self-progeny individuals is inferior to that of their outcrossed counterparts, resulting in a reduction in a plant population's ability to survive and reproduce. To prevent self-fertilization, angiosperms with hermaphrodite flowers may exploit a variety of mechanisms, including synchronous dichogamy and self-incompatibility. Synchronous dichogamy involves two flowering morphs, with strict within-morph synchronization, thereby preventing not only autogamy and geitonogamy but also intra-morph mating. Self-fertilization is also prevented by self-incompatibility, a genetic mechanism that allows the identification and rejection of "self" pollen, thereby preventing both autogamy and geitonogamy. Here, I seek to provide a perspective of flowering in Ziziphus species exhibiting both synchronous (i.e., "Early" morph flowers open in the morning and "Late" morph flowers open in the afternoon) protandrous dichogamy (i.e., pollen dispersal before the stigma becomes receptive) and self-incompatibility.
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Song B, Sun L, Barrett SCH, Moles AT, Luo YH, Armbruster WS, Gao YQ, Zhang S, Zhang ZQ, Sun H. Global analysis of floral longevity reveals latitudinal gradients and biotic and abiotic correlates. THE NEW PHYTOLOGIST 2022; 235:2054-2065. [PMID: 35611604 DOI: 10.1111/nph.18271] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/12/2022] [Indexed: 06/15/2023]
Abstract
The length of time a flower remains open and functional - floral longevity - governs important reproductive processes influencing pollination and mating and varies considerably among angiosperm species. However, little is known about large-scale biogeographic patterns and the correlates of floral longevity. Using published data on floral longevity from 818 angiosperm species in 134 families and 472 locations world-wide, we present the first global quantification of the latitudinal pattern of floral longevity and the relationships between floral longevity and a range of biotic and abiotic factors. Floral longevity exhibited a significant phylogenetic signal and was longer at higher latitudes in both northern and southern hemispheres, even after accounting for elevation. This latitudinal variation was associated with several biotic and abiotic variables. The mean temperature of the flowering season had the highest predictive power for floral longevity, followed by pollen number per flower. Surprisingly, compatibility status, flower size, pollination mode, and growth form had no significant effects on flower longevity. Our results suggest that physiological processes associated with floral maintenance play a key role in explaining latitudinal variation in floral longevity across global ecosystems, with potential implications for floral longevity under global climate change and species distributions.
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Affiliation(s)
- Bo Song
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- Yunnan International Joint Laboratory for Biodiversity of Central Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Lu Sun
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Angela T Moles
- Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Ya-Huang Luo
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - W Scott Armbruster
- School of Biological Sciences, University of Portsmouth, Portsmouth, PO1 2DY, UK
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA
| | - Yong-Qian Gao
- Yunnan Forestry Technological College, Kunming, 650224, China
| | - Shuang Zhang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Zhi-Qiang Zhang
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Institute of Biodiversity, School of Ecology and Environmental Science, Yunnan University, Kunming, 650504, China
| | - Hang Sun
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
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Olito C, Vries CD. The demographic costs of sexually antagonistic selection in partially selfing populations. Am Nat 2022; 200:401-418. [DOI: 10.1086/720419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Lee KJ, Caruso CM. Plasticity in floral longevity and sex-phase duration of Lobelia siphilitica in response to simulated pollinator declines. AMERICAN JOURNAL OF BOTANY 2022; 109:526-534. [PMID: 35253215 DOI: 10.1002/ajb2.1837] [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: 09/10/2021] [Revised: 02/14/2022] [Accepted: 02/17/2022] [Indexed: 06/14/2023]
Abstract
PREMISE Pollinator declines can reduce the quantity and quality of pollination services, resulting in less pollen deposited on flowers and lower seed production by plants. In response to these reductions, plant species that cannot autonomously self-pollinate and thus are dependent on pollinators to set seed could plastically adjust their floral traits. Such plasticity could increase the opportunity for outcross pollination directly, as well as indirectly by affecting inflorescence traits. METHODS To test whether plants can respond to pollinator declines by plastically adjusting their floral traits, we simulated declines by experimentally reducing pollinator access to Lobelia siphilitica plants and measuring two traits of early- and late-season flowers: (1) floral longevity; and (2) sex-phase duration. To test whether plasticity in these floral traits affected inflorescence traits, we measured daily display size and phenotypic gender. RESULTS We found that experimentally reducing pollination did not affect female-phase duration, but did extend the male-phase duration of early-season flowers by 13% and the longevity of late-season flowers by 12.8%. However, plants with an extended male phase did not have a more male-biased phenotypic gender, and plants with an extended floral longevity did not have a larger daily display. CONCLUSIONS Our results suggest that plants can respond to pollinator declines by plastically adjusting both the longevity and sex-phase duration of their flowers. If this plasticity increases the opportunity for outcross pollination, then it could be one mechanism by which pollinator-dependent plant species maintain seed production as pollinators decline.
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Affiliation(s)
- Kiana J Lee
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Calabrese A, Weeks SC. Testing a behavioral model for the maintenance of androdioecy as a result of sexual conflict in the clam shrimp
Eulimnadia dahli. Ethology 2022. [DOI: 10.1111/eth.13266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Tonnabel J. Digest: Sexual conflict as a novel hypothesis for the evolution of gynodioecy. Evolution 2021; 75:557-558. [PMID: 33393130 DOI: 10.1111/evo.14161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 12/23/2020] [Indexed: 01/25/2023]
Abstract
Can sexual conflict over the length of male versus female maturity phases within hermaphroditic flowers promote the evolution of gynodioecy? Wang et al. found that hermaphroditic plants of Cyananthus delavayi exhibited a plastic response to a failure in pollen removal, which compromised seed production by reducing the duration of the female maturity phase to the benefit of the male phase. Sexual conflict over sex-specific temporal maturity may bring about sufficient fertility differences between hermaphrodites and females to promote the evolution of gynodioecy.
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Affiliation(s)
- Jeanne Tonnabel
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier, France
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