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Garlovsky MD, Whittington E, Albrecht T, Arenas-Castro H, Castillo DM, Keais GL, Larson EL, Moyle LC, Plakke M, Reifová R, Snook RR, Ålund M, Weber AAT. Synthesis and Scope of the Role of Postmating Prezygotic Isolation in Speciation. Cold Spring Harb Perspect Biol 2024; 16:a041429. [PMID: 38151330 PMCID: PMC11444258 DOI: 10.1101/cshperspect.a041429] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
How barriers to gene flow arise and are maintained are key questions in evolutionary biology. Speciation research has mainly focused on barriers that occur either before mating or after zygote formation. In comparison, postmating prezygotic (PMPZ) isolation-a barrier that acts after gamete release but before zygote formation-is less frequently investigated but may hold a unique role in generating biodiversity. Here we discuss the distinctive features of PMPZ isolation, including the primary drivers and molecular mechanisms underpinning PMPZ isolation. We then present the first comprehensive survey of PMPZ isolation research, revealing that it is a widespread form of prezygotic isolation across eukaryotes. The survey also exposes obstacles in studying PMPZ isolation, in part attributable to the challenges involved in directly measuring PMPZ isolation and uncovering its causal mechanisms. Finally, we identify outstanding knowledge gaps and provide recommendations for improving future research on PMPZ isolation. This will allow us to better understand the nature of this often-neglected reproductive barrier and its contribution to speciation.
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Affiliation(s)
- Martin D Garlovsky
- Applied Zoology, Faculty of Biology, Technische Universität Dresden, Dresden 01062, Germany
| | | | - Tomas Albrecht
- Institute of Vertebrate Biology, Czech Academy of Sciences, Brno 60365, Czech Republic
- Department of Zoology, Faculty of Science, Charles University, Prague 128 00, Czech Republic
| | - Henry Arenas-Castro
- School of Biological Sciences, University of Queensland, St Lucia 4072, Queensland, Australia
| | - Dean M Castillo
- Department of Biological Sciences, Miami University, Hamilton, Ohio 45011, USA
| | - Graeme L Keais
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Erica L Larson
- Department of Biological Sciences, University of Denver, Denver, Colorado 80208, USA
| | - Leonie C Moyle
- Department of Biology, Indiana University Bloomington, Indiana 47405, USA
| | - Melissa Plakke
- Division of Science, Mathematics, and Technology, Governors State University, University Park, Illinois 60484, USA
| | - Radka Reifová
- Department of Zoology, Faculty of Science, Charles University, Prague 128 00, Czech Republic
| | - Rhonda R Snook
- Department of Zoology, Stockholm University, Stockholm 109 61, Sweden
| | - Murielle Ålund
- Department of Ecology and Genetics, Animal Ecology, Uppsala University, Uppsala 75236, Sweden
| | - Alexandra A-T Weber
- Department of Aquatic Ecology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf 8600, Zürich, Switzerland
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Lanzino M, Palermo AM, Pellegrino G. Pollination mechanism in Serapias with no pollinaria reconfiguration. AOB PLANTS 2023; 15:plad054. [PMID: 37899971 PMCID: PMC10601389 DOI: 10.1093/aobpla/plad054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 08/09/2023] [Indexed: 10/31/2023]
Abstract
Orchidaceae, one of the most numerous families in the world's flora, have evolved various pollination strategies to favour cross-pollination, such as deceptive pollination and pollinarium reconfiguration. Among the terrestrial orchids of the Mediterranean, only species belonging to the genus Serapias show a strategy defined as shelter imitation. The floral elements form a tubular structure that insects use during their resting phases. The purpose of this article was to clarify the mechanisms that guarantee pollination with particular attention to the morphological interactions between orchids and pollinators and whether pollinaria reconfiguration is necessary in the promotion of cross-pollination in Serapias. Breeding system experiments and hand-pollination treatments indicated that Serapias was highly self-compatible, shows low value of natural fruit set and is pollinator limited. Time-lapse photos showed that the pollinarium had no refolding of the stipe or caudicle after its removal from the flower. The morphology of the flower determined the attack of the pollinarium on the occiput/vertex of insect. When the insect left the flower, the pollinarium was unable to encounter the stigma. When the insect made a second visit to another flower, the pollen masses of the first pollinarium ended up on the stigma and at the same time, the insect picked up a second pollinarium. Our observations and analyses suggested that morphological interactions between flower and pollinator are crucial to the success of pollination and to prevent self-pollination and thus that pollinarium reconfiguration is unnecessary in shelter deceptive orchids, such as Serapias species, for the promotion of cross-pollination. Serapias represent a case of interactions between plant and pollinator; the formation of the tubular shape of the flower is an essential preadaptation for the development of resting site mimicry originating exclusively in Serapias among Mediterranean orchids.
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Affiliation(s)
- Micaela Lanzino
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Rende, Cosenza, Italy
| | - Anna Maria Palermo
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Rende, Cosenza, Italy
| | - Giuseppe Pellegrino
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036 Rende, Cosenza, Italy
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Pellegrino G, Mahmoudi M, Palermo AM. Pollen viability of Euro-Mediterranean orchids under different storage conditions: The possible effects of climate change. PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23:140-147. [PMID: 32967048 DOI: 10.1111/plb.13185] [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: 03/28/2020] [Accepted: 08/24/2020] [Indexed: 06/11/2023]
Abstract
The future impact of climate change and a warmer world is a matter of great concern. We therefore aimed to evaluate the effects of temperature on pollen viability and fruit set of Mediterranean orchids. The in vitro and controlled pollination experiments were performed to evaluate the ability of pollinia stored at lower and higher temperatures to germinate and produce fruits and seeds containing viable embryos. In all of the examined orchids, pollen stored at -20 °C remained fully viable for up to 3 years, reducing its percentage germination from year 4 onwards. Pollinia stored at higher temperatures had a drastic reduction in vitality after 2 days at 41-44 °C, while pollinia stored at 47-50 °C did not show any pollen tube growth. The different levels of pollen viability duration among the examined orchids can be related to their peculiar reproductive biology and pollination ecology. The germinability of pollinia stored at lower temperatures for long periods suggests that orchid pollinia can be conserved ex situ. In contrast, higher temperatures can have harmful effects on the vitality of pollen and consequently on reproductive success of the plants. To our knowledge, this is the first report demonstrating the effects of global change on orchid pollen, and on pollen ability to tolerate, or not, higher air temperatures. Although vegetative reproduction allows orchids to survive a few consecutive warm years, higher temperatures for several consecutive years can have dramatic effects on reproductive success of orchids.
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Affiliation(s)
- G Pellegrino
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, Rende, CS, Italy
| | - M Mahmoudi
- Faculté des Sciences de Tunis, Université de Tunis El-Manar, Tunis, Tunisia
- Laboratoire des écosystèmes pastoraux et valorisation des plantes spontanées et des micro-organismes associés, Institut des Régions Arides, Médenine, Tunisia
| | - A M Palermo
- Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, Rende, CS, Italy
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Liu R, Gao Y, Fan Z, Wang X, Xiao J, Zhang Q. Within-day temporal isolation of two species of Iris (Iridaceae) sharing the same pollinator. Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa032] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Abstract
Knowledge of factors driving reproductive isolation is essential to understand the process of speciation. To study the reproductive isolation of two closely related species with overlapping flowering seasons, Iris domestica and Iris dichotoma, we compared their reproductive system, floral biology and pollination biology. The results indicated that I. domestica was facultatively xenogamous, whereas I. dichotoma was facultatively autogamous. Although the two species differed significantly in floral colour, floral diameter, floral structure, nectar volume, flower opening and closing times, they shared the same diurnal pollinator, the honeybee Apis cerana. The frequency of pollination by A. cerana did not differ significantly between the two species, but honeybee pollination of I. domestica was more efficient compared with that of I. dichotoma. Despite the difference in floral structure between the two species, both species deposited pollen on the same parts of the body of honeybees. The temporal partitioning of within-day flowering times between I. domestica (from 07.15 to 08.15 h to 18.00 to 19.00 h) and I. dichotoma (from 15.45 to 16.15 h to 22.00 to 23.00 h), together with the time memory of honeybees, meant that the two species did not overlap in the time of their pollination, thus leading to temporal isolation as a major driver of reproductive isolation between the two species.
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Affiliation(s)
- Rong Liu
- Department of Landscape Architecture, Beijing Forestry University, Beijing, China
| | - Yike Gao
- Department of Landscape Architecture, Beijing Forestry University, Beijing, China
| | - Zhuping Fan
- Department of Landscape Architecture, Beijing Forestry University, Beijing, China
| | - Xinzi Wang
- Department of Landscape Architecture, Beijing Forestry University, Beijing, China
| | - Jianhua Xiao
- Department of Landscape Architecture, Beijing Forestry University, Beijing, China
| | - Qixiang Zhang
- Department of Landscape Architecture, Beijing Forestry University, Beijing, China
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Tao Z, Ren Z, Bernhardt P, Liang H, Li H, Zhao Y, Wang H, Li D. Does reproductive isolation reflect the segregation of color forms in Spiranthes sinensis (Pers.) Ames complex (Orchidaceae) in the Chinese Himalayas? Ecol Evol 2018; 8:5455-5469. [PMID: 29938065 PMCID: PMC6010815 DOI: 10.1002/ece3.4067] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 03/09/2018] [Accepted: 03/12/2018] [Indexed: 01/16/2023] Open
Abstract
Isolation between species, or taxa sharing a common lineage, depends primarily on the relative strengths of various reproductive barriers. Previous studies on reproductive isolation between orchids emphasized mechanical and ethological barriers in flowers of species showing food and/or sexual mimicry. In this study, we investigated and quantified a series of prepollination and postpollination barriers between pink and white forms of Spiranthes sinensis sl, a nectar-secreting complex. We generated ML trees based on trnS-G and matK to explore phylogenetic relationships in this species complex. Spiranthes sinensis sl segregated from some other congeners, but the white form constituted a distinct clade in relation to the pink form. The white form secreted 2-Phenylethanol as it is a single-scent compound and was pollinated almost exclusively by native, large-bodied Apis cerana and Bombus species (Apidae). Apis cerana showed a high floral constancy to this form. The scentless, pink form was pollinated primarily by smaller bees in the genera Ceratina (Apidae), and members of the family Halictidae, with infrequent visits by A. cerana and Bombus species. Fruit set and the production of large embryos following interform pollination treatments were significantly lower compared to intraform pollination results for the white form. Our results suggested that pollinator isolation, based on color and scent cues, may result in greater floral constancy in white populations when both forms are sympatric as two different, guilds of pollinators forage selectively preventing or reducing prospective gene flow. Postpollination barriers appear weaker than prepollination barriers but they also play a role in interform isolation, especially in the white form. Our findings suggest that floral color forms in S. sinensis do not represent an unbalanced polymorphism. Interpretations of the evolutionary status of these forms are discussed.
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Affiliation(s)
- Zhi‐Bin Tao
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
- Kunming College of Life SciencesUniversity of Chinese Academy of SciencesKunmingChina
| | - Zong‐Xin Ren
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | | | - Huan Liang
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
- Kunming College of Life SciencesUniversity of Chinese Academy of SciencesKunmingChina
| | - Hai‐Dong Li
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | - Yan‐Hui Zhao
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | - Hong Wang
- Key Laboratory for Plant Diversity and Biogeography of East AsiaKunming Institute of BotanyChinese Academy of SciencesKunmingChina
| | - De‐Zhu Li
- Germplasm Bank of Wild SpeciesKunming Institute of BotanyChinese Academy of SciencesKunmingChina
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Marques I, Loureiro J, Draper D, Castro M, Castro S. How much do we know about the frequency of hybridisation and polyploidy in the Mediterranean region? PLANT BIOLOGY (STUTTGART, GERMANY) 2018; 20 Suppl 1:21-37. [PMID: 28963818 DOI: 10.1111/plb.12639] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 09/25/2017] [Indexed: 06/07/2023]
Abstract
Natural hybridisation and polyploidy are currently recognised as drivers of biodiversity, despite early scepticism about their importance. The Mediterranean region is a biodiversity hotspot where geological and climatic events have created numerous opportunities for speciation through hybridisation and polyploidy. Still, our knowledge on the frequency of these mechanisms in the region is largely limited, despite both phenomena are frequently cited in studies of Mediterranean plants. We reviewed information available from biodiversity and cytogenetic databases to provide the first estimates of hybridisation and polyploidy frequency in the Mediterranean region. We also inspected the most comprehensive modern Mediterranean Flora (Flora iberica) to survey the frequency and taxonomic distribution of hybrids and polyploids in Iberian Peninsula. We found that <6% of Mediterranean plants were hybrids, although a higher frequency was estimated for the Iberian Peninsula (13%). Hybrids were concentrated in few families and in even fewer genera. The overall frequency of polyploidy (36.5%) was comparable with previous estimates in other regions; however our estimates increased when analysing the Iberian Peninsula (48.8%). A surprisingly high incidence of species harbouring two or more ploidy levels was also observed (21.7%). A review of the available literature also showed that the ecological factors driving emergence and establishment of new entities are still poorly studied in the Mediterranean flora, although geographic barriers seem to play a major role in polyploid complexes. Finally, this study reveals several gaps and limitations in our current knowledge about the frequency of hybridisation and polyploidy in the Mediterranean region. The obtained estimates might change in the future with the increasing number of studies; still, rather than setting the complete reality, we hope that this work triggers future studies on hybridisation and polyploidy in the Mediterranean region.
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Affiliation(s)
- I Marques
- Department of Agricultural and Environmental Sciences, High Polytechnic School of Huesca, University of Zaragoza, Huesca, Spain
| | - J Loureiro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - D Draper
- Centro de Ecologia, Evolução e Alterações Ambientais (cE3c), Universidade de Lisboa, Lisbon, Portugal
- UBC Botanical Garden & Centre for Plant Research, and Department of Botany, University of British Columbia, Vancouver, Canada
| | - M Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - S Castro
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- Botanic Garden of the University of Coimbra, Coimbra, Portugal
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7
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Baek YS, Royer SM, Broz AK, Covey PA, López-Casado G, Nuñez R, Kear PJ, Bonierbale M, Orillo M, van der Knaap E, Stack SM, McClure B, Chetelat RT, Bedinger PA. Interspecific reproductive barriers between sympatric populations of wild tomato species (Solanum section Lycopersicon). AMERICAN JOURNAL OF BOTANY 2016; 103:1964-1978. [PMID: 27864262 DOI: 10.3732/ajb.1600356] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 10/21/2016] [Indexed: 05/09/2023]
Abstract
PREMISE OF THE STUDY Interspecific reproductive barriers (IRBs) often prevent hybridization between closely related species in sympatry. In the tomato clade (Solanum section Lycopersicon), interspecific interactions between natural sympatric populations have not been evaluated previously. In this study, we assessed IRBs between members of the tomato clade from nine sympatric sites in Peru. METHODS Coflowering was assessed at sympatric sites in Peru. Using previously collected seeds from sympatric sites in Peru, we evaluated premating prezygotic (floral morphology), postmating prezygotic (pollen-tube growth), and postzygotic barriers (fruit and seed development) between sympatric species in common gardens. Pollen-tube growth and seed development were examined in reciprocal crosses between sympatric species. KEY RESULTS We confirmed coflowering of sympatric species at five sites in Peru. We found three types of postmating prezygotic IRBs during pollen-pistil interactions: (1) unilateral pollen-tube rejection between pistils of self-incompatible species and pollen of self-compatible species; (2) potential conspecific pollen precedence in a cross between two self-incompatible species; and (3) failure of pollen tubes to target ovules. In addition, we found strong postzygotic IRBs that prevented normal seed development in 11 interspecific crosses, resulting in seed-like structures containing globular embryos and aborted endosperm and, in some cases, overgrown endothelium. Viable seed and F1 hybrid plants were recovered from three of 19 interspecific crosses. CONCLUSIONS We have identified diverse prezygotic and postzygotic IRBs that would prevent hybridization between sympatric wild tomato species, but interspecific hybridization is possible in a few cases.
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Affiliation(s)
- You Soon Baek
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA
| | - Suzanne M Royer
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA
| | - Amanda K Broz
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA
| | - Paul A Covey
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA
| | - Gloria López-Casado
- Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA
| | - Reynaldo Nuñez
- Department of Horticulture and Crop Science, Ohio State University, Wooster, Ohio 44691, USA
| | - Philip J Kear
- Quality and Nutrition Laboratory, Centro Internacional de la Papa, Perú Postal 1558, Lima, Peru
| | - Merideth Bonierbale
- Quality and Nutrition Laboratory, Centro Internacional de la Papa, Perú Postal 1558, Lima, Peru
| | - Matilde Orillo
- Quality and Nutrition Laboratory, Centro Internacional de la Papa, Perú Postal 1558, Lima, Peru
| | - Esther van der Knaap
- Department of Horticulture and Crop Science, Ohio State University, Wooster, Ohio 44691, USA
- Department of Horticulture, University of Georgia, Athens, Georgia 30602, USA
| | - Stephen M Stack
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA
| | - Bruce McClure
- Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri 65211, USA
| | - Roger T Chetelat
- Department of Plant Sciences, University of California Davis, Davis, California 95616, USA
| | - Patricia A Bedinger
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA
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8
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Pellegrino G. Sympatric reinforcement of reproductive barriers between Neotinea tridentata and N. ustulata (Orchidaceae). JOURNAL OF PLANT RESEARCH 2016; 129:1061-1068. [PMID: 27502952 DOI: 10.1007/s10265-016-0855-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 07/03/2016] [Indexed: 06/06/2023]
Abstract
Reinforcement is the process by which selection favors traits that decrease mating between two incipient species in response to costly mating or the production of maladapted hybrids, causing the evolution of greater reproductive isolation between emerging species. I have studied a pair of orchids, Neotinea tridentata and N. ustulata, to examine the level of postmating pre- and post-zygotic isolating mechanisms that maintain these species, and the degree to which the boundary may still be permeable to gene flow. In this study, I performed pollen tube growth rate experiments and I investigated pre- and post-zygotic barriers by performing hand pollination experiments in order to evaluate fruit set, embryonate seed set and seed germination rates by intra- and interspecific crosses. Fruit set, the percentage of embryonate seeds and germinability of interspecific crosses were reduced compared to intraspecific pollinations, showing significant differences between sympatric and allopatric populations. While in allopatric populations the post-pollination isolation index ranged between 0.40 and 0.11, in sympatric populations orchid pairs showed total isolation due to post-pollination prezygotic barriers, guaranteed at the level of pollen-stigma interactions. Indeed, in sympatric populations, pollen tubes reached the ovary after 24 h in only 8 out of 45 plants; in the remaining cases, the pollen tubes did not enter the ovary, and thus no fruit set occurred. This pair of orchids is characterized by postmating pre-zygotic reproductive isolation in sympatric populations that prevents the formation of hybrids. This mechanism of speciation, starting in allopatry and triggering the reinforcement mechanisms of reproductive isolation in secondary sympatry, is the most likely explanation for the pattern of evolutionary transitions found in this pair of orchids.
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Affiliation(s)
- Giuseppe Pellegrino
- Department of Biology, Ecology and Earth Sciences, University of Calabria, via Bucci 6/B, 87036, Rende, CS, Italy.
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9
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Baack E, Melo MC, Rieseberg LH, Ortiz-Barrientos D. The origins of reproductive isolation in plants. THE NEW PHYTOLOGIST 2015; 207:968-84. [PMID: 25944305 DOI: 10.1111/nph.13424] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/16/2015] [Indexed: 05/23/2023]
Abstract
Reproductive isolation in plants occurs through multiple barriers that restrict gene flow between populations, but their origins remain uncertain. Work in the past decade has shown that postpollination barriers, such as the failure to form hybrid seeds or sterility of hybrid offspring, are often less strong than prepollination barriers. Evidence implicates multiple evolutionary forces in the origins of reproductive barriers, including mutation, stochastic processes and natural selection. Although adaptation to different environments is a common element of reproductive isolation, genomic conflicts also play a role, including female meiotic drive. The genetic basis of some reproductive barriers, particularly flower colour influencing pollinator behaviour, is well understood in some species, but the genetic changes underlying many other barriers, especially pollen-stylar interactions, are largely unknown. Postpollination barriers appear to accumulate at a faster rate in annuals compared with perennials, due in part to chromosomal rearrangements. Chromosomal changes can be important isolating barriers in themselves but may also reduce the recombination of genes contributing to isolation. Important questions for the next decade include identifying the evolutionary forces responsible for chromosomal rearrangements, determining how often prezygotic barriers arise due to selection against hybrids, and establishing the relative importance of genomic conflicts in speciation.
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Affiliation(s)
- Eric Baack
- Department of Biology, Luther College, Decorah, IA, 52101, USA
| | - Maria Clara Melo
- School of Biological Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
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10
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Luca A, Palermo AM, Bellusci F, Pellegrino G. Pollen competition between two sympatric Orchis species (Orchidaceae): the overtaking of conspecific of heterospecific pollen as a reproductive barrier. PLANT BIOLOGY (STUTTGART, GERMANY) 2015; 17:219-225. [PMID: 24889383 DOI: 10.1111/plb.12199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/26/2014] [Indexed: 06/03/2023]
Abstract
The frequency of hybrid formation in angiosperms depends on how and when heterospecific pollen is transferred to the stigma, and on the success of that heterospecific pollen at fertilising ovules. We applied pollen mixtures to stigmas to determine how pollen interactions affect siring success and the frequency of hybrid formation between two species of Mediterranean deceptive orchid. Plants of Orchis italica and O. anthropophora were pollinated with conspecific and heterospecific pollen (first conspecific pollen then heterospecific pollen and vice versa) and molecular analysis was used to check the paternity of the seeds produced. In this pair of Mediterranean orchids, competition between conspecific and heterospecific pollen functions as a post-pollination pre-zygotic barrier limiting the frequency of the formation of hybrids in nature. Flowers pollinated with heterospecific pollen can remain receptive for the arrival of conspecific pollen for a long time. There is always an advantage of conspecific pollen for fruit formation, whether it comes before or after heterospecific pollen, because it overtakes the heterospecific pollen. The conspecific pollen advantage exhibited in O. italica and O. anthropophora is likely to result from the reduced germination of heterospecific pollen or retarded growth of heterospecific pollen tubes in the stigma and ovary. Overall, the results indicate that our hybrid zone represents a phenomenon of little evolutionary consequence, and the conspecific pollen advantage maintains the genetic integrity of the parental species.
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Affiliation(s)
- A Luca
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Rende, Italy
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11
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Sonnleitner M, Weis B, Flatscher R, García PE, Suda J, Krejčíková J, Schneeweiss GM, Winkler M, Schönswetter P, Hülber K. Parental ploidy strongly affects offspring fitness in heteroploid crosses among three cytotypes of autopolyploid Jacobaea carniolica (Asteraceae). PLoS One 2013; 8:e78959. [PMID: 24265735 PMCID: PMC3827125 DOI: 10.1371/journal.pone.0078959] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/17/2013] [Indexed: 11/25/2022] Open
Abstract
Reproductive interactions among cytotypes in their contact zones determine whether these cytotypes can co-exist and form stable contact zones or not. In autopolyploids, heteroploid cross-compatibilities might depend on parental ploidy, but tests of this hypothesis in autopolyploid systems with more than two ploidies are lacking. Here, we study Jacobaea carniolica, which comprises diploid, tetraploid, and hexaploid individuals regularly forming contact zones. Seeds obtained from in situ cross-pollinations within and among cytotypes were subjected to DNA flow cytometry and greenhouse germination experiments. Hybrid fitness and parental effects on hybrid fitness were tested with regression models comparing fitness parameters of early life stages. Irrespective of the direction of crosses, seed viability and seedling survival in diploid-polyploid crosses were substantially lower than in tetraploid-hexaploid crosses. In contrast, seedling growth traits indicated neither transgressive character expression nor any selection against hybrid offspring. Congruent with a model of genome dosage effects, these traits differed between reciprocal crosses, especially of diploids and tetraploids, where trait values resembled those of the maternal parent. The strong effect of parental ploidy on offspring fitness in heteroploid crosses may cause contact zones involving exclusively polyploid cytotypes to be less stable over longer terms than those involving diploids and polyploids.
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Affiliation(s)
- Michaela Sonnleitner
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
- Department of Conservation Biology, Vegetation Ecology and Landscape Ecology, University of Vienna, Vienna, Austria
| | - Birgit Weis
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | - Ruth Flatscher
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
- Institute of Botany, University of Innsbruck, Innsbruck, Austria
| | - Pedro Escobar García
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | - Jan Suda
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice, Czech Republic
| | - Jana Krejčíková
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice, Czech Republic
| | - Gerald M. Schneeweiss
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | - Manuela Winkler
- Department of Systematic and Evolutionary Botany, University of Vienna, Vienna, Austria
| | | | - Karl Hülber
- Department of Conservation Biology, Vegetation Ecology and Landscape Ecology, University of Vienna, Vienna, Austria
- Vienna Institute for Nature Conservation & Analyses, Vienna, Austria
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Natalis LC, Wesselingh RA. Post-pollination barriers and their role in asymmetric hybridization in Rhinanthus (Orobanchaceae). AMERICAN JOURNAL OF BOTANY 2012; 99:1847-1856. [PMID: 23092992 DOI: 10.3732/ajb.1200085] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
PREMISE OF THE STUDY Several barriers against hybrid formation exist, and their combined action can affect the evolutionary outcomes of hybridization. To explain the asymmetrical introgression observed between two bumblebee-pollinated plant species (Rhinanthus angustifolius and R. minor), we focused on post-pollination barriers and ethological isolation of hybrids. METHODS We studied pollen competition in conspecific and heterospecific crosses on both species and analyzed germination rates of hybrid and pure seeds. We also measured bumblebee visitation rates to hybrids relative to their parents using potted Rhinanthus placed in populations of each parental species. KEY RESULTS In mixed pollinations, there was a conspecific siring advantage in both species, but no difference in pollen tube growth rates in either cross type. F(1) seeds with a R. angustifolius maternal plant germinated poorly, while those with R. minor as the maternal parent germinated better than pure seeds. Interestingly, bumblebees treated hybrids almost as equal to the background species and more often rejected the nonresident Rhinanthus. In a R. angustifolius background, bumblebees preferred R. angustifolius, but visited hybrids more often than R. minor. In contrast, visitation rates were similar on a R. minor background. CONCLUSIONS Our results suggest that hybridization rates in Rhinanthus remain low because of several leaky barriers that make R. minor the maternal parent of most F(1) offspring. Preference for R. angustifolius and the equal treatment of F(1) and background species by bumblebees induce a visitation pattern that directs gene flow toward R. angustifolius when this species predominates.
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Affiliation(s)
- Laurent C Natalis
- Biodiversity Research Centre, Earth and Life Institute, Université catholique de Louvain, Croix du Sud 4-5, Box L7.07.04, B-1348 Louvain-la-Neuve, Belgium.
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