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Simón-Porcar V, Escudero M, Santos-Gally R, Sauquet H, Schönenberger J, Johnson SD, Arroyo J. Convergent evolutionary patterns of heterostyly across angiosperms support the pollination-precision hypothesis. Nat Commun 2024; 15:1237. [PMID: 38336937 PMCID: PMC10858259 DOI: 10.1038/s41467-024-45118-0] [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: 02/14/2023] [Accepted: 01/12/2024] [Indexed: 02/12/2024] Open
Abstract
Since the insights by Charles Darwin, heterostyly, a floral polymorphism with morphs bearing stigmas and anthers at reciprocal heights, has become a model system for the study of natural selection. Based on his archetypal heterostylous flower, including regular symmetry, few stamens and a tube, Darwin hypothesised that heterostyly evolved to promote outcrossing through efficient pollen transfer between morphs involving different areas of a pollinator's body, thus proposing his seminal pollination-precision hypothesis. Here we update the number of heterostylous and other style-length polymorphic taxa to 247 genera belonging to 34 families, notably expanding known cases by 20%. Using phylogenetic and comparative analyses across the angiosperms, we show numerous independent origins of style-length polymorphism associated with actinomorphic, tubular flowers with a low number of sex organs, stamens fused to the corolla, and pollination by long-tongued insects. These associations provide support for the Darwinian pollination-precision hypothesis as a basis for convergent evolution of heterostyly across angiosperms.
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Affiliation(s)
- Violeta Simón-Porcar
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, E-41080, Sevilla, Spain.
- School of Life Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa.
| | - Marcial Escudero
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, E-41080, Sevilla, Spain
| | | | - Hervé Sauquet
- National Herbarium of New South Wales, Royal Botanic Gardens and Domain Trust, Sydney, NSW, Australia
| | - Jürg Schönenberger
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, 1030, Vienna, Austria
| | - Steven D Johnson
- School of Life Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa
| | - Juan Arroyo
- Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, E-41080, Sevilla, Spain.
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Kay KM, Zepeda AM, Raguso RA. Experimental sympatry reveals geographic variation in floral isolation by hawkmoths. ANNALS OF BOTANY 2019; 123:405-413. [PMID: 30032166 PMCID: PMC6344223 DOI: 10.1093/aob/mcy143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 07/06/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND AND AIMS Under a widely accepted model of pollinator-driven speciation, geographic variation in pollinator assemblage drives floral divergence and automatically causes reproductive isolation. Yet it is unclear whether divergent floral adaptation initially confers strong reproductive isolation, or whether that comes at later stages of speciation and requires other forms of reproductive isolation. This study uses a pair of recently diverged, interfertile and parapatric species in the genus Clarkia to determine whether adaptation to hawkmoths, a novel pollinator functional group, would automatically confer floral isolation upon sympatric contact. METHODS First, genetically based differences in floral traits between C. breweri and C. concinna that would be maintained upon migration are quantified. Then scenarios of experimental sympatry are constructed in which arrays of flowers are exposed to the novel pollinator, the hawkmoth Hyles lineata, and pollinator preference and heterospecific pollen transfer are assessed. Source populations from across the ranges of each species are used to understand how geographic variation in floral traits within species may affect floral isolation. KEY RESULTS Although H. lineata has never been observed visiting C. concinna in the wild, it regularly moves between species in experimental floral arrays. Hawkmoth preference and heterospecific pollen transfer vary both among moths and among geographic source locations of C. concinna. The strength of floral isolation in this system is related to variation in flower size, especially hypanthium tube width, and nectar reward among C. concinna forms. CONCLUSIONS Although C. breweri has adopted a novel hawkmoth pollination system, both ethological and mechanical floral isolation by hawkmoths are incomplete and vary according to the specific phenotype of the C. concinna source population. The results suggest that strong floral isolation is not automatically conferred by a pollinator shift and may require additional evolution of deterrent floral traits and habitat isolation that reduces the immediate spatial co-occurrence of young species.
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Affiliation(s)
- Kathleen M Kay
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
| | - Aubrey M Zepeda
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
| | - Robert A Raguso
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, USA
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Spencer V, Kim M. Re“CYC”ling molecular regulators in the evolution and development of flower symmetry. Semin Cell Dev Biol 2018; 79:16-26. [DOI: 10.1016/j.semcdb.2017.08.052] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 07/28/2017] [Indexed: 11/27/2022]
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Armbruster WS, Bolstad GH, Hansen TF, Keller B, Conti E, Pélabon C. The measure and mismeasure of reciprocity in heterostylous flowers. THE NEW PHYTOLOGIST 2017; 215:906-917. [PMID: 28556899 DOI: 10.1111/nph.14604] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 03/31/2017] [Indexed: 06/07/2023]
Abstract
The goal of biological measurement is to capture underlying biological phenomena in numerical form. The reciprocity index applied to heterostylous flowers is meant to measure the degree of correspondence between fertile parts of opposite sex on complementary (inter-compatible) morphs, reflecting the correspondence of locations of pollen placement on, and stigma contact with, pollinators. Pollen of typical heterostylous flowers can achieve unimpeded fertilization only on opposite-morph flowers. Thus, the implicit goal of this measurement is to assess the likelihood of 'legitimate' pollinations between compatible morphs, and hence reproductive fitness. Previous reciprocity metrics fall short of this goal on both empirical and theoretical grounds. We propose a new measure of reciprocity based on theory that relates floral morphology to reproductive fitness. This method establishes a scale based on adaptive inaccuracy, a measure of the fitness cost of the deviation of phenotypes in a population from the optimal phenotype. Inaccuracy allows the estimation of independent contributions of maladaptive bias (mean departure from optimum) and imprecision (within-population variance) to the phenotypic mismatch (inaccuracy) of heterostylous morphs on a common scale. We illustrate this measure using data from three species of Primula (Primulaceae).
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Affiliation(s)
- 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
| | - Geir H Bolstad
- Norwegian Institute for Nature Research (NINA), Trondheim, NO-7485, Norway
| | - Thomas F Hansen
- Department of Biology, CEES & Evogene, University of Oslo, PB1016, Oslo, 0316, Norway
| | - Barbara Keller
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, Zürich, 8008, Switzerland
| | - Elena Conti
- Department of Systematic and Evolutionary Botany, University of Zürich, Zollikerstrasse 107, Zürich, 8008, Switzerland
| | - Christophe Pélabon
- Institute of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway
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Keller B, de Vos JM, Schmidt‐Lebuhn AN, Thomson JD, Conti E. Both morph- and species-dependent asymmetries affect reproductive barriers between heterostylous species. Ecol Evol 2016; 6:6223-44. [PMID: 27648239 PMCID: PMC5016645 DOI: 10.1002/ece3.2293] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/03/2016] [Accepted: 06/07/2016] [Indexed: 12/13/2022] Open
Abstract
The interaction between floral traits and reproductive isolation is crucial to explaining the extraordinary diversity of angiosperms. Heterostyly, a complex floral polymorphism that optimizes outcrossing, evolved repeatedly and has been shown to accelerate diversification in primroses, yet its potential influence on isolating mechanisms remains unexplored. Furthermore, the relative contribution of pre- versus postmating barriers to reproductive isolation is still debated. No experimental study has yet evaluated the possible effects of heterostyly on pre- and postmating reproductive mechanisms. We quantify multiple reproductive barriers between the heterostylous Primula elatior (oxlip) and P. vulgaris (primrose), which readily hybridize when co-occurring, and test whether traits of heterostyly contribute to reproductive barriers in unique ways. We find that premating isolation is key for both species, while postmating isolation is considerable only for P. vulgaris; ecogeographic isolation is crucial for both species, while phenological, seed developmental, and hybrid sterility barriers are also important in P. vulgaris, implicating sympatrically higher gene flow into P. elatior. We document for the first time that, in addition to the aforementioned species-dependent asymmetries, morph-dependent asymmetries affect reproductive barriers between heterostylous species. Indeed, the interspecific decrease of reciprocity between high sexual organs of complementary floral morphs limits interspecific pollen transfer from anthers of short-styled flowers to stigmas of long-styled flowers, while higher reciprocity between low sexual organs favors introgression over isolation from anthers of long-styled flowers to stigmas of short-styled flowers. Finally, intramorph incompatibility persists across species boundaries, but is weakened in long-styled flowers of P. elatior, opening a possible backdoor to gene flow through intramorph pollen transfer between species. Therefore, patterns of gene flow across species boundaries are likely affected by floral morph composition of adjacent populations. To summarize, our study highlights the general importance of premating isolation and newly illustrates that both morph- and species-dependent asymmetries shape boundaries between heterostylous species.
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Affiliation(s)
- Barbara Keller
- Department of Systematic and Evolutionary BotanyUniversity of ZürichZollikerstrasse 1078008ZürichSwitzerland
| | - Jurriaan M. de Vos
- Department of Ecology and Evolutionary BiologyBrown University80 Waterman StreetBox G‐WProvidenceRhode Island02912USA
- Present address: Comparative Plant and Fungal Biology DepartmentRoyal Botanic GardensKewRichmondSurreyTW9 3AE UK
| | | | - James D. Thomson
- Ecology and Evolutionary Biology DepartmentUniversity of Toronto25 Harbord St.TorontoOntarioM5S 3G5Canada
| | - Elena Conti
- Department of Systematic and Evolutionary BotanyUniversity of ZürichZollikerstrasse 1078008ZürichSwitzerland
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Kameyama Y, Watanabe M, Kurosawa H, Nishimori T, Matsue D, Takyu M. Seasonal changes in pollen limitation and femaleness along the snowmelt gradient in a distylous alpine herb, Primula modesta. Ecol Evol 2015; 5:5352-5363. [PMID: 30151137 PMCID: PMC6102533 DOI: 10.1002/ece3.1803] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/14/2015] [Accepted: 10/03/2015] [Indexed: 11/16/2022] Open
Abstract
Flowering phenology of alpine plants is strongly determined by the timing of snowmelt, and the conditions of pollination of widely distributed plants vary greatly during their flowering season. We examined the reproductive success of the distylous alpine herb, Primula modesta, along the snowmelt gradient under natural conditions, and compared it with the result of artificial pollination experiments. In addition, the compositions and visit frequencies of pollinators to the flower of P. modesta were examined during the flowering period. The pin and thrum plants of P. modesta growing at the same site have an equal ability to produce seeds if a sufficient amount of legitimate pollen grains are deposited on the stigma surface. However, under natural conditions, their seed‐set success was often (even if not always) restricted by pollen limitation, and the functional gender of the pin and thrum plants biased to the female and male, respectively, associated with their growing sites. These variations were not ascribed to resource limitation nor biased morph ratio but to the seasonal changes in pollination situations, a replacement of pollinator types from long‐ to short‐tongued pollinators resulted in unidirectional pollen transfer from long stamens (thrum plants) to long styles (pin plants). The functional gender specialization may enhance the evolution of dioecy from heterostyly, but the severe pollen limitation may cause the breakdown of heterostyly into homostyly. To consider the evolutionary pathway of heterostylous plants, an accumulation of the empirical data is required demonstrating how phenological synchrony between plants and pollinators is decided and to what degree this relationship is stable over years, along with estimates of selection and gene flow in individual plants.
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Affiliation(s)
- Yoshiaki Kameyama
- Faculty of Regional Environment Science Tokyo University of Agriculture Tokyo 156-8502 Japan
| | - Manami Watanabe
- Faculty of Regional Environment Science Tokyo University of Agriculture Tokyo 156-8502 Japan.,Present address: OTA Floriculture Auction Co., Ltd. Tokyo 143-0001 Japan
| | - Hideki Kurosawa
- Faculty of Regional Environment Science Tokyo University of Agriculture Tokyo 156-8502 Japan.,Present address: Tamamura-machi Sawa-gun Gunma 370-1105 Japan
| | - Takuya Nishimori
- Faculty of Regional Environment Science Tokyo University of Agriculture Tokyo 156-8502 Japan.,Present address: OTA Floriculture Auction Co., Ltd. Tokyo 143-0001 Japan
| | - Daisuke Matsue
- Faculty of Regional Environment Science Tokyo University of Agriculture Tokyo 156-8502 Japan.,Present address: Hakone Botanical Garden of Wetlands Kanagawa 205-0631 Japan
| | - Masaaki Takyu
- Faculty of Regional Environment Science Tokyo University of Agriculture Tokyo 156-8502 Japan
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Chung H, Carroll SB. Wax, sex and the origin of species: Dual roles of insect cuticular hydrocarbons in adaptation and mating. Bioessays 2015; 37:822-30. [PMID: 25988392 PMCID: PMC4683673 DOI: 10.1002/bies.201500014] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Evolutionary changes in traits that affect both ecological divergence and mating signals could lead to reproductive isolation and the formation of new species. Insect cuticular hydrocarbons (CHCs) are potential examples of such dual traits. They form a waxy layer on the cuticle of the insect to maintain water balance and prevent desiccation, while also acting as signaling molecules in mate recognition and chemical communication. Because the synthesis of these hydrocarbons in insect oenocytes occurs through a common biochemical pathway, natural or sexual selection on one role may affect the other. In this review, we explore how ecological divergence in insect CHCs can lead to divergence in mating signals and reproductive isolation. We suggest that the evolution of insect CHCs may be ripe models for understanding ecological speciation.
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Affiliation(s)
- Henry Chung
- Howard Hughes Medical Institute and Laboratory of Molecular Biology, University of Wisconsin, WI, USA
| | - Sean B Carroll
- Howard Hughes Medical Institute and Laboratory of Molecular Biology, University of Wisconsin, WI, USA
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