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Francisco A, Ascensão L. Osmophore Structure and Labellum Micromorphology in Ophrys speculum (Orchidaceae): New Interpretations of Floral Features and Implications for a Specific Sexually Deceptive Pollination Interaction. PLANTS (BASEL, SWITZERLAND) 2024; 13:1413. [PMID: 38794483 PMCID: PMC11125028 DOI: 10.3390/plants13101413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 05/12/2024] [Accepted: 05/14/2024] [Indexed: 05/26/2024]
Abstract
Pollination by sexual deception specifically attracts male insects, through the floral scent and particular morphological features of the flower that serve as visual and tactile stimuli. The unique bond between the Ophrys speculum orchid and the male Dasyscolia ciliata wasp primarily stems from a few distinctive semiochemicals that mimic the female wasp's sex pheromone, although the floral scent comprises a variety of compounds. An osmophore producing highly volatile compounds has been documented in four close relatives of O. speculum and is now being also investigated in this species. Given the existing debates regarding the structure of the labellum and stigmatic cavity in O. speculum, this study details their micromorphology. Additionally, comparisons of O. speculum flowers and female D. ciliata wasps under stereomicroscopy and scanning electron microscopy are conducted to seek new evidence of visual and tactile mimicry. The findings confirm that (i) an osmophore is present at the apical margin of the labellum in O. speculum flowers; (ii) the labellum features a distinct basal field homologous to those found in other Ophrys species; and (iii) the basal labellum region closely mimics the female wasp's thorax and wings. The implications of these novel floral features are discussed within an evolutionary context.
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Affiliation(s)
- Ana Francisco
- Centro de Estudos do Ambiente e do Mar (CESAM Lisboa), Faculdade de Ciências da Universidade de Lisboa (FCUL), C2, Campo Grande, 1749-016 Lisboa, Portugal
| | - Lia Ascensão
- Centro de Estudos do Ambiente e do Mar (CESAM Lisboa), Faculdade de Ciências da Universidade de Lisboa (FCUL), C2, Campo Grande, 1749-016 Lisboa, Portugal
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2
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Anghelescu NE, Balogh L, Balogh M, Kigyossy N, Georgescu MI, Petra SA, Toma F, Peticila AG. Gymnadenia winkeliana-A New Orchid Species to Romanian Flora. PLANTS (BASEL, SWITZERLAND) 2024; 13:1363. [PMID: 38794434 PMCID: PMC11125076 DOI: 10.3390/plants13101363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 04/11/2024] [Accepted: 05/08/2024] [Indexed: 05/26/2024]
Abstract
A novel species, Gymnadenia winkeliana, has been identified in the Bucegi Natural Park ROSCI0013, located in the Southern Carpathians of Central Romania. Two moderately sized populations of Gymnadenia winkeliana, totalling 120-140 individuals, were discovered inhabiting the alpine grasslands of the park, situated 2.000 m above sea level. To describe this newly found population as comprehensively as possible, 44 vegetative and floral organs/organ parts were directly studied and measured from living plants. Special attention was focused on the characteristics that proved to have taxonomic significance, particularly those involving distinctive details in the morphology of the leaves, perianth, labellum and gynostemium. A total of 223 characteristics were analysed encompassing the morphology of every organ of the plant, cytology and breeding system. Furthermore, comprehensive taxonomic treatment and description, accompanied by colour photographs illustrating the holotype, are provided. Voucher specimens were deposited at the Herbarium of the University of Agriculture and Veterinary Medicine, Bucharest (USAMVB Herbarium barcode: 40102, NEA); Gymnadenia winkeliana, a (micro)endemic species, is characterized as a putative allogamous, facultatively apomict that significantly differs from other Gymnadenia R.Br. species found in Romania. Notably, it distinguishes itself through its smaller habitus (reaching heights of up to 8-10 cm), its two-coloured, rounded/hemispherical inflorescence displaying a gradient of pink hues in an acropetal fashion (ranging from whitish-pink at the base to vivid-pink at the topmost flowers), and its limited distribution in high-altitude areas, encompassing approximately 8-10 km2 in the central area of the Bucegi Natural Park. This species has been under observation since 2005, with observed population numbers showing a significant increase over time, from ca. 50-55 (counted at the time of its discovery) to 120-140 individuals (counted in June 2023). Additionally, comprehensive information regarding the habitat, ecology, phenology and IUCN conservation assessments of Gymnadenia winkeliana are provided, including maps illustrating its distribution.
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Affiliation(s)
- Nora E. Anghelescu
- Faculty of Horticulture, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 Marasti Blvd, District 1, 011464 Bucharest, Romania
| | - Lori Balogh
- Association “Comori de pe Valea Prahovei”, 106100 Sinaia, Romania
| | - Mihaela Balogh
- Association “Comori de pe Valea Prahovei”, 106100 Sinaia, Romania
| | | | - Mihaela I. Georgescu
- Faculty of Horticulture, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 Marasti Blvd, District 1, 011464 Bucharest, Romania
| | - Sorina A. Petra
- Faculty of Horticulture, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 Marasti Blvd, District 1, 011464 Bucharest, Romania
| | - Florin Toma
- Faculty of Horticulture, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 Marasti Blvd, District 1, 011464 Bucharest, Romania
| | - Adrian G. Peticila
- Faculty of Horticulture, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 59 Marasti Blvd, District 1, 011464 Bucharest, Romania
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Mahilkar A, Nagendra P, Venkataraman P, Deshmukh S, Saini S. Rapid evolution of pre-zygotic reproductive barriers in allopatric populations. Microbiol Spectr 2023; 11:e0195023. [PMID: 37787555 PMCID: PMC10714765 DOI: 10.1128/spectrum.01950-23] [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: 05/09/2023] [Accepted: 08/14/2023] [Indexed: 10/04/2023] Open
Abstract
IMPORTANCE A population diversifies into two or more species-such a process is known as speciation. In sexually reproducing microorganisms, which barriers arise first-pre-mating or post-mating? In this work, we quantify the relative strengths of these barriers and demonstrate that pre-mating barriers arise first in allopatrically evolving populations of yeast, Saccharomyces cerevisiae. These defects arise because of the altered kinetics of mating of the participating groups. Thus, our work provides an understanding of how adaptive changes can lead to diversification among microbial populations.
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Affiliation(s)
- Anjali Mahilkar
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Powai, Maharashtra, India
| | - Prachitha Nagendra
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Powai, Maharashtra, India
| | - Pavithra Venkataraman
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Powai, Maharashtra, India
| | - Saniya Deshmukh
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Powai, Maharashtra, India
| | - Supreet Saini
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, Powai, Maharashtra, India
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4
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Coughlan JM. The role of hybrid seed inviability in angiosperm speciation. AMERICAN JOURNAL OF BOTANY 2023; 110:1-14. [PMID: 36801827 DOI: 10.1002/ajb2.16135] [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: 08/27/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 05/11/2023]
Abstract
Understanding which reproductive barriers contribute to speciation is essential to understanding the diversity of life on earth. Several contemporary examples of strong hybrid seed inviability (HSI) between recently diverged species suggest that HSI may play a fundamental role in plant speciation. Yet, a broader synthesis of HSI is needed to clarify its role in diversification. Here, I review the incidence and evolution of HSI. Hybrid seed inviability is common and evolves rapidly, suggesting that it may play an important role early in speciation. The developmental mechanisms that underlie HSI involve similar developmental trajectories in endosperm, even between evolutionarily deeply diverged incidents of HSI. In hybrid endosperm, HSI is often accompanied by whole-scale gene misexpression, including misexpression of imprinted genes which have a key role in endosperm development. I explore how an evolutionary perspective can clarify the repeated and rapid evolution of HSI. In particular, I evaluate the evidence for conflict between maternal and paternal interests in resource allocation to offspring (i.e., parental conflict). I highlight that parental conflict theory generates explicit predictions regarding the expected hybrid phenotypes and genes responsible for HSI. While much phenotypic evidence supports a role of parental conflict in the evolution of HSI, an understanding of the underlying molecular mechanisms of this barrier is essential to test parental conflict theory. Lastly, I explore what factors may influence the strength of parental conflict in natural plant populations as an explanation for why rates of HSI may differ between plant groups and the consequences of strong HSI in secondary contact.
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Affiliation(s)
- Jenn M Coughlan
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06511, USA
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5
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Osmolovsky I, Shifrin M, Gamliel I, Belmaker J, Sapir Y. Eco-Geography and Phenology Are the Major Drivers of Reproductive Isolation in the Royal Irises, a Species Complex in the Course of Speciation. PLANTS (BASEL, SWITZERLAND) 2022; 11:3306. [PMID: 36501345 PMCID: PMC9739335 DOI: 10.3390/plants11233306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 10/30/2022] [Accepted: 11/25/2022] [Indexed: 06/17/2023]
Abstract
The continuous nature of speciation implies that different species are found at different stages of divergence, from no- to complete reproductive isolation. This process and its underlying mechanisms are best viewed in incipient species. Moreover, the species complex can offer unique insight into how reproductive isolation (RI) has evolved. The royal irises (Iris section Oncocyclus) are a young group of species in the course of speciation, providing an ideal system for speciation study. We quantified pre- and post-zygotic reproductive barriers between the eight Israeli species of this complex and estimated the total RI among them. We tested for both pre-pollination and post-pollination reproductive barriers. Pre-pollination barriers, i.e., eco-geographic divergence and phenological differentiation were the major contributors to RI among the Iris species. On the other hand, post-pollination barriers, namely pollen-stigma interactions, fruit set, and seed viability had negligible contributions to total RI. The strength of RI was not uniform across the species complex, suggesting that species may have diverged at different rates. Overall, this study in a young, recently diverged group of species provides insight into the first steps of speciation, suggesting a crucial role of the pre-zygotic barriers.
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Affiliation(s)
- Inna Osmolovsky
- The Botanical Garden, School of Plant Science and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Mariana Shifrin
- The Botanical Garden, School of Plant Science and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Inbal Gamliel
- School of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Jonathan Belmaker
- School of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Yuval Sapir
- The Botanical Garden, School of Plant Science and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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6
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Reproductive character displacement allows two sexually deceptive orchids to coexist and attract the same specific pollinator. Evol Ecol 2022. [DOI: 10.1007/s10682-021-10149-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AbstractAn increased divergence in characters between species in secondary contact can be shaped by selection against competition for a common resource (ecological character displacement, ECD) or against maladapted hybridization (reproductive character displacement, RCD). These selective pressures can act between incipient species (reinforcement) or well-separated species that already completed the speciation process, but that can still hybridize and produce maladapted hybrids. Here, we investigated two well-separated sexually deceptive orchid species that, unusually, share their specific pollinator. Sympatric individuals of these species are more divergent than allopatric ones in floral characters involved in a mechanical isolating barrier, a pattern suggestive of RCD. To experimentally test this scenario, we built an artificial sympatric population with allopatric individuals. We measured flower characters, genotyped the offspring in natural and artificial sympatry and estimated fertility of hybrids. Different from naturally sympatric individuals, allopatric individuals in artificial sympatry hybridized widely. Hybrids showed lower pollination success and seed viability than parentals. Character displacement did not affect plant pollination success. These findings suggest that RCD evolved between these species to avoid hybridization and that selection on reinforcement may be very strong even in plants with highly specialized pollination.
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Morgan EJ, Čertner M, Lučanová M, Deniz U, Kubíková K, Venon A, Kovářík O, Lafon Placette C, Kolář F. Disentangling the components of triploid block and its fitness consequences in natural diploid-tetraploid contact zones of Arabidopsis arenosa. THE NEW PHYTOLOGIST 2021; 232:1449-1462. [PMID: 33768528 DOI: 10.1111/nph.17357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 03/15/2021] [Indexed: 06/12/2023]
Abstract
Hybrid seed inviability (HSI) is an important mechanism of reproductive isolation and speciation. HSI varies in strength among populations of diploid species but it remains to be tested whether similar processes affect natural variation in HSI within ploidy-variable species (triploid block). Here we used extensive endosperm, seed and F1 -hybrid phenotyping to explore HSI variation within a diploid-autotetraploid species. By leveraging 12 population pairs from three ploidy contact zones, we tested for the effect of interploidy crossing direction (parent of origin), ploidy divergence and spatial arrangement in shaping reproductive barriers in a naturally relevant context. We detected strong parent-of-origin effects on endosperm development, F1 germination and survival, which was also reflected in the rates of triploid formation in the field. Endosperm cellularization failure was least severe and F1 -hybrid performance was slightly better in the primary contact zone, with genetically closest diploid and tetraploid lineages. We demonstrated overall strong parent-of-origin effects on HSI in a ploidy variable species, which translate to fitness effects and contribute to interploidy reproductive isolation in a natural context. Subtle intraspecific variation in these traits suggests the fitness consequences of HSI are predominantly a constitutive property of the species regardless of the evolutionary background of its populations.
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Affiliation(s)
- Emma J Morgan
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Martin Čertner
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
- Institute of Botany of the Czech Academy of Sciences, Zámek 1, Průhonice, CZ-252 43, Czech Republic
| | - Magdalena Lučanová
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
- Institute of Botany of the Czech Academy of Sciences, Zámek 1, Průhonice, CZ-252 43, Czech Republic
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 31, České Budějovice, CZ-370 05, Czech Republic
| | - Utku Deniz
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Kateřina Kubíková
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Anthony Venon
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Oleg Kovářík
- Datamole Inc., Vítězné Náměstí 2, Prague, CZ-160 00, Czech Republic
| | - Clément Lafon Placette
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
| | - Filip Kolář
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01, Czech Republic
- Institute of Botany of the Czech Academy of Sciences, Zámek 1, Průhonice, CZ-252 43, Czech Republic
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Sato Y, Fujiwara S, Egas M, Matsuda T, Gotoh T. Patterns of reproductive isolation in a haplodiploid mite, Amphitetranychus viennensis: prezygotic isolation, hybrid inviability and hybrid sterility. BMC Ecol Evol 2021; 21:177. [PMID: 34551724 PMCID: PMC8459536 DOI: 10.1186/s12862-021-01896-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 08/23/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Evolution of reproductive isolation is an important process, generating biodiversity and driving speciation. To better understand this process, it is necessary to investigate factors underlying reproductive isolation through various approaches but also in various taxa. Previous studies, mainly focusing on diploid animals, supported the prevalent view that reproductive barriers evolve gradually as a by-product of genetic changes accumulated by natural selection by showing a positive relationship between the degree of reproductive isolation and genetic distance. Haplodiploid animals are expected to generate additional insight into speciation, but few studies investigated the prevalent view in haplodiploid animals. In this study, we investigate whether the relationship also holds in a haplodiploid spider mite, Amphitetranychus viennensis (Zacher). RESULTS We sampled seven populations of the mite in the Palaearctic region, measured their genetic distance (mtDNA) and carried out cross experiments with all combinations. We analyzed how lack of fertilization rate (as measure of prezygotic isolation) as well as hybrid inviability and hybrid sterility (as measures of postzygotic isolation) varies with genetic distance. We found that the degree of reproductive isolation varies among cross combinations, and that all three measures of reproductive isolation have a positive relationship with genetic distance. Based on the mtDNA marker, lack of fertilization rate, hybrid female inviability and hybrid female sterility were estimated to be nearly complete (99.0-99.9% barrier) at genetic distances of 0.475-0.657, 0.150-0.209 and 0.145-0.210, respectively. Besides, we found asymmetries in reproductive isolation. CONCLUSIONS The prevalent view on the evolution of reproductive barriers is supported in the haplodiploid spider mite we studied here. According to the estimated minimum genetic distance for total reproductive isolation in parent population crosses in this study and previous work, a genetic distance of 0.15-0.21 in mtDNA (COI) appears required for speciation in spider mites. Variations and asymmetries in the degree of reproductive isolation highlight the importance of reinforcement of prezygotic reproductive isolation through incompatibility and the importance of cytonuclear interactions for reproductive isolation in haplodiploid spider mites.
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Affiliation(s)
- Yukie Sato
- Faculty of Life and Environmental Science/Mountain Science Center, University of Tsukuba, Ibaraki, 305-8577, Japan
| | - Satoshi Fujiwara
- Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Ami, Ibaraki, 300-0393, Japan
| | - Martijn Egas
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
| | - Tomoko Matsuda
- Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Ami, Ibaraki, 300-0393, Japan.,Nihon BioData Corporation, Kawasaki, Kanagawa, 213-0012, Japan
| | - Tetsuo Gotoh
- Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Ami, Ibaraki, 300-0393, Japan. .,Faculty of Economics, Ryutsu Keizai University, Ryugasaki, Ibaraki, 301-8555, Japan.
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9
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Bersweden L, Viruel J, Schatz B, Harland J, Gargiulo R, Cowan RS, Calevo J, Juan A, Clarkson JJ, Leitch AR, Fay MF. Microsatellites and petal morphology reveal new patterns of admixture in Orchis hybrid zones. AMERICAN JOURNAL OF BOTANY 2021; 108:1388-1404. [PMID: 34418070 DOI: 10.1002/ajb2.1710] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 02/20/2021] [Accepted: 02/23/2021] [Indexed: 05/23/2023]
Abstract
PREMISE The genetic structure of hybrid zones provides insight into the potential for gene flow to occur between plant taxa. Four closely related European orchid species (Orchis anthropophora, O. militaris, O. purpurea, and O. simia) hybridize when they co-occur. We aimed to characterize patterns of hybridization in O. militaris-O. purpurea, O. purpurea-O. simia, and O. anthropophora-O. simia hybrid zones using molecular and morphological data. METHODS We used 11 newly isolated nuclear microsatellites to genotype 695 individuals collected from seven hybrid zones and six allopatric parental populations in France. Geometric morphometric analysis was conducted using 15 labellum landmarks to capture the main aspects of petal shape. RESULTS Backcrossing was asymmetric toward O. militaris in multiple O. militaris-O. purpurea hybrid zones. Hybrids in O. purpurea-O. simia and O. anthropophora-O. simia hybrid zones were largely limited to F1 and F2 generations, but further admixture had occurred. These patterns were reflected in labellum geometric morphometric data, which correlated strongly with nuclear microsatellite data in all three species combinations. CONCLUSIONS The coexistence of parental and admixed individuals in these Orchis hybrid zones implies they are likely to be tension zones being maintained by a balance between gene flow into the hybrid zone and selection acting against admixed individuals. The pattern of admixture in the three species combinations suggests intrinsic selection acting on the hybrids is weaker in more closely related taxa.
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Affiliation(s)
- Leif Bersweden
- Jodrell Laboratory, Royal Botanic Gardens, Kew TW9 3DS, UK
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Juan Viruel
- Jodrell Laboratory, Royal Botanic Gardens, Kew TW9 3DS, UK
| | - Bertrand Schatz
- Centre for Ecology and Evolution, University of Montpellier, Montpellier 34090, France
| | - Joanna Harland
- Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | | | - Robyn S Cowan
- Jodrell Laboratory, Royal Botanic Gardens, Kew TW9 3DS, UK
| | - Jacopo Calevo
- Department of Life Sciences and Systems Biology, University of Turin, Turin 10125, Italy
| | - Ana Juan
- Department of Environmental Sciences & Natural Resources, University of Alicante, San Vicente, Alicante 03690, Spain
| | | | - Andrew R Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Michael F Fay
- Jodrell Laboratory, Royal Botanic Gardens, Kew TW9 3DS, UK
- School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia
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10
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Cozzolino S, Scopece G, Lussu M, Cortis P, Schiestl FP. Do floral and ecogeographic isolation allow the co-occurrence of two ecotypes of Anacamptis papilionacea (Orchidaceae)? Ecol Evol 2021; 11:9917-9931. [PMID: 34367549 PMCID: PMC8328454 DOI: 10.1002/ece3.7432] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/10/2021] [Accepted: 02/18/2021] [Indexed: 11/08/2022] Open
Abstract
Ecotypes are relatively frequent in flowering plants and considered central in ecological speciation as local adaptation can promote the insurgence of reproductive isolation. Without geographic isolation, gene flow usually homogenizes the allopatrically generated phenotypic and ecological divergences, unless other forms of reproductive isolation keep them separated. Here, we investigated two orchid ecotypes with marked phenotypic floral divergence that coexist in contact zones. We found that the two ecotypes show different ecological habitat preferences with one being more climatically restricted than the other. The ecotypes remain clearly morphologically differentiated both in allopatry and in sympatry and differed in diverse floral traits. Despite only slightly different flowering times, the two ecotypes achieved floral isolation thanks to different pollination strategies. We found that both ecotypes attract a wide range of insects, but the ratio of male/female attracted by the two ecotypes was significantly different, with one ecotype mainly attracts male pollinators, while the other mainly attracts female pollinators. As a potential consequence, the two ecotypes show different pollen transfer efficiency. Experimental plots with pollen staining showed a higher proportion of intra- than interecotype movements confirming floral isolation between ecotypes in sympatry while crossing experiments excluded evident postmating barriers. Even if not completely halting the interecotypes pollen flow in sympatry, such incipient switch in pollination strategy between ecotypes may represent a first step on the path toward evolution of sexual mimicry in Orchidinae.
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Affiliation(s)
| | - Giovanni Scopece
- Department of BiologyUniversity Federico II of NaplesNapoliItaly
| | - Michele Lussu
- Department of Life and Environmental SciencesUniversity of CagliariCagliariItaly
- Istituto Regionale per la Floricoltura (IRF)SanremoItaly
| | - Pierluigi Cortis
- Department of Life and Environmental SciencesUniversity of CagliariCagliariItaly
| | - Florian P. Schiestl
- Department of Systematic and Evolutionary Botany and Botanical GardensUniversity of ZurichZurichSwitzerland
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11
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Liang J, Hodge JM, Sharakhov IV. Asymmetric Phenotypes of Sterile Hybrid Males From Reciprocal Crosses Between Species of the Anopheles gambiae Complex. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.660207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Haldane’s rule of speciation states that sterility or inviability affects the heterogametic sex of inter-species hybrids. Darwin’s corollary to Haldane’s rule implies that there are asymmetric phenotypes in inter-species hybrids from reciprocal crosses. Studying the phenotypes of F1 hybrids among closely related species of malaria mosquitoes can assist researchers in identifying the genetic factors and molecular mechanisms of speciation. To characterize phenotypes of sterile hybrid males in the Anopheles gambiae complex, we performed crosses between laboratory strains of An. merus and either An. gambiae or An. coluzzii. The reproductive tracts had normal external morphology in hybrid males from crosses between female An. merus and male An. gambiae or An. coluzzii. Despite being sterile, these males could copulate with females for a normal period of time and could transfer a mating plug to induce female oviposition and monogamy. In contrast, the entire reproductive tracts in hybrid males from crosses between female An. gambiae or An. coluzzii and male An. merus were severely underdeveloped. These males had atrophic testes and reduced somatic organs of the reproductive system including male accessary glands and ejaculatory duct. In addition, hybrid males with underdeveloped reproductive tracts displayed a shorter copulation time with females and failed to induce female oviposition and monogamy due to their inability to form and transfer a plug to females during mating. The asymmetry of the phenotypes associated with hybrid male sterility suggests that different genetic factors and molecular mechanisms are responsible for reproductive isolation in reciprocal crosses among species of the An. gambiae complex.
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12
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Tripp EA, Dexter KG, Stone HB. Reproductive character displacement and potential underlying drivers in a species-rich and florally diverse lineage of tropical angiosperms ( Ruellia; Acanthaceae). Ecol Evol 2021; 11:4719-4730. [PMID: 33976842 PMCID: PMC8093712 DOI: 10.1002/ece3.7371] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 12/05/2020] [Accepted: 12/10/2020] [Indexed: 11/08/2022] Open
Abstract
Reproductive character displacement is a pattern whereby sympatric lineages diverge more in reproductive character morphology than allopatric lineages. This pattern has been observed in many plant species, but comparably few have sought to disentangle underlying mechanisms. Here, in a diverse lineage of Neotropical plants (Ruellia; Acanthaceae), we present evidence of reproductive character displacement in a macroevolutionary framework (i.e., among species) and document mechanistic underpinnings. In a series of interspecific hand pollinations in a controlled glasshouse environment, we found that crosses between species that differed more in overall flower size, particularly in style length, were significantly less likely to produce viable seeds. Further, species pairs that failed to set seed were more likely to have sympatric distributions in nature. Competition for pollinators and reinforcement to avoid costly interspecific mating could both result in these patterns and are not mutually exclusive processes. Our results add to growing evidence that reproductive character displacement contributes to exceptional floral diversity of angiosperms.
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Affiliation(s)
- Erin A. Tripp
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderCOUSA
- Museum of Natural HistoryUniversity of ColoradoBoulderCOUSA
| | - Kyle G. Dexter
- School of GeoSciencesUniversity of EdinburghEdinburghUK
- Royal Botanic Garden EdinburghEdinburghUK
| | - Heather B. Stone
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderCOUSA
- Museum of Natural HistoryUniversity of ColoradoBoulderCOUSA
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Matute DR, Cooper BS. Comparative studies on speciation: 30 years since Coyne and Orr. Evolution 2021; 75:764-778. [PMID: 33491225 PMCID: PMC8247902 DOI: 10.1111/evo.14181] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 12/28/2022]
Abstract
Understanding the processes of population divergence and speciation remains a core question in evolutionary biology. For nearly a hundred years evolutionary geneticists have characterized reproductive isolation (RI) mechanisms and specific barriers to gene flow required for species formation. The seminal work of Coyne and Orr provided the first comprehensive comparative analysis of speciation. By combining phylogenetic hypotheses and species range data with estimates of genetic divergence and multiple mechanisms of RI across Drosophila, Coyne and Orr's influential meta-analyses answered fundamental questions and motivated new analyses that continue to push the field forward today. Now 30 years later, we revisit the five questions addressed by Coyne and Orr, identifying results that remain well supported and others that seem less robust with new data. We then consider the future of speciation research, with emphasis on areas where novel methods and data motivate potential progress. While the literature remains biased towards Drosophila and other model systems, we are enthusiastic about the future of the field.
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Affiliation(s)
- Daniel R. Matute
- Biology DepartmentUniversity of North CarolinaChapel HillNorth Carolina27510
| | - Brandon S. Cooper
- Division of Biological SciencesUniversity of MontanaMissoulaMontana59812
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14
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Bateman RM, Rudall PJ, Murphy ARM, Cowan RS, Devey DS, Peréz-Escobar OA. Whole plastomes are not enough: phylogenomic and morphometric exploration at multiple demographic levels of the bee orchid clade Ophrys sect. Sphegodes. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:654-681. [PMID: 33449086 DOI: 10.1093/jxb/eraa467] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 12/15/2020] [Indexed: 05/21/2023]
Abstract
Plastid sequences have long dominated phylogeny reconstruction at all time depths, predicated on a usually untested assumption that they accurately represent the evolutionary histories of phenotypically circumscribed species. We combined detailed in situ morphometrics (124 plants) and whole-plastome sequencing through genome skimming (71 plants) in order to better understand species-level diversity and speciation in arguably the most challenging monophyletic group within the taxonomically controversial, pseudo-copulatory bee orchid genus Ophrys. Using trees and ordinations, we interpreted the data at four nested demographic levels-macrospecies, mesospecies, microspecies, and local population-seeking the optimal level for bona fide species. Neither morphological nor molecular discontinuities are evident at any level below macrospecies, the observed overlap among taxa suggesting that both mesospecies and microspecies reflect arbitrary division of a continuum of variation. Plastomes represent geographic location more strongly than taxonomic assignment and correlate poorly with morphology, suggesting widespread plastid capture and possibly post-glacial expansion from multiple southern refugia. As they are rarely directly involved in the speciation process, plastomes depend on extinction of intermediate lineages to provide phylogenetic signal and so cannot adequately document evolutionary radiations. The popular 'ethological' evolutionary model recognizes as numerous 'ecological species' (microspecies) lineages perceived as actively diverging as a result of density-dependent selection on very few features that immediately dictate extreme pollinator specificity. However, it is assumed rather than demonstrated that the many microspecies are genuinely diverging. We conversely envisage a complex four-dimensional reticulate network of lineages, generated locally and transiently through a wide spectrum of mechanisms, but each unlikely to maintain an independent evolutionary trajectory long enough to genuinely speciate by escaping ongoing gene flow. The frequent but localized microevolution that characterizes the Ophrys sphegodes complex is often convergent and rarely leads to macroevolution. Choosing between the contrasting 'discontinuity' and 'ethology' models will require next-generation sequencing of nuclear genomes plus ordination of corresponding morphometric matrices, seeking the crucial distinction between retained ancestral polymorphism-consistent with lineage divergence-and polymorphisms reflecting gene flow through 'hybridization'-more consistent with lineage convergence.
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15
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Arida BL, Scopece G, Machado RM, Moraes AP, Forni-Martins E, Pinheiro F. Reproductive barriers and fertility of two neotropical orchid species and their natural hybrid. Evol Ecol 2021. [DOI: 10.1007/s10682-020-10095-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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16
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Capó M, Borràs J, Perelló-Suau S, Rita J, Cursach J. Ecological factors affecting the fitness of the threatened orchid Anacamptis robusta (Orchidaceae): Habitat disturbance, interactions with a co-flowering rewarding orchid and hybridization events. PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23:121-129. [PMID: 32896978 DOI: 10.1111/plb.13179] [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: 07/16/2020] [Accepted: 08/24/2020] [Indexed: 06/11/2023]
Abstract
The food-deceptive species Anacamptis robusta is threatened in the Balearic Islands, and its habitat has recently been transformed through human disturbance. This study investigated how human disturbance affects the reproductive output of A. robusta and how its fitness is affected by competition with rewarding relatives, fungal infections and hybridization processes. To evaluate the impact of habitat loss on plant fitness, data on reproductive measures were obtained in two well-conserved subpopulations and the unique disturbed subpopulation. Photo-trapping cameras were installed to determine the floral visitation rate. All flowering individuals in 2019 were georeferenced using differential GPS to examine the influence of geospatial patterns on the reproductive success of A. robusta. In addition, hand-pollination treatments were performed to evaluate the hybridization between A. coriophora and A. robusta and the origin of A. × albuferensis. The human-disturbed subpopulation of A. robusta had a lower fruit set success than the subpopulations in well-conserved areas. The presence of A. coriophora is negatively affecting the reproductive output of A. robusta. Moreover, A. robusta can only act as the pollen donor during hybridization. The complexity of the ecological system, which is enhanced by the strong pollinator dependence of the threatened species, must be considered when making conservation decisions. Although human disturbance directly affects plant population stability, other ecological issues must be considered, such as pollinator interaction, interspecific competition for pollinators, fungal infection and hybridization events.
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Affiliation(s)
- M Capó
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
| | - J Borràs
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
| | - S Perelló-Suau
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
| | - J Rita
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
| | - J Cursach
- Laboratory of Botany, Research Group on Plant Biology under Mediterranean Conditions, Department of Biology, University of Balearic Islands, Palma, Spain
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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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18
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Baguette M, Bertrand JAM, Stevens VM, Schatz B. Why are there so many bee-orchid species? Adaptive radiation by intra-specific competition for mnesic pollinators. Biol Rev Camb Philos Soc 2020; 95:1630-1663. [PMID: 32954662 DOI: 10.1111/brv.12633] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 06/09/2020] [Accepted: 06/15/2020] [Indexed: 01/08/2023]
Abstract
Adaptive radiations occur mostly in response to environmental variation through the evolution of key innovations that allow emerging species to occupy new ecological niches. Such biological innovations may play a major role in niche divergence when emerging species are engaged in reciprocal ecological interactions. To demonstrate coevolution is a difficult task; only a few studies have confirmed coevolution as driver of speciation and diversification. Herein we review current knowledge about bee orchid (Ophrys spp.) reproductive biology. We propose that the adaptive radiation of the Mediterranean orchid genus Ophrys, comprising several hundred species, is due to coevolutionary dynamics between these plants and their pollinators. We suggest that pollination by sexual swindling used by Ophrys orchids is the main driver of this coevolution. Flowers of each Ophrys species mimic a sexually receptive female of one particular insect species, mainly bees. Male bees are first attracted by pseudo-pheromones emitted by Ophrys flowers that are similar to the sexual pheromones of their females. Males then are lured by the flower shape, colour and hairiness, and attempt to copulate with the flower, which glues pollen onto their bodies. Pollen is later transferred to the stigma of another flower of the same Ophrys species during similar copulation attempts. In contrast to rewarding pollination strategies, Ophrys pollinators appear to be parasitized. Here we propose that this apparent parasitism is in fact a coevolutionary relationship between Ophrys and their pollinators. For plants, pollination by sexual swindling could ensure pollination efficiency and specificity, and gene flow among populations. For pollinators, pollination by sexual swindling could allow habitat matching and inbreeding avoidance. Pollinators might use the pseudo-pheromones emitted by Ophrys to locate suitable habitats from a distance within complex landscapes. In small populations, male pollinators would disperse once they have memorized the local diversity of sexual pseudo-pheromone bouquets or if all Ophrys flowers are fertilized and thus repel pollinators via production of repulsive pheromones that mimic those produced by fertilized female bees. We propose the following evolutionary scenario: Ophrys radiation is driven by strong intra-specific competition among Ophrys individuals for the attraction of species-specific pollinators, which is a consequence of the high cognitive abilities of pollinators. Male bees record the pheromone signatures of kin or of previously courted partners to avoid further copulation attempts, thereby inducing strong selection on Ophrys for variation in odour bouquets emitted by individual flowers. The resulting odour bouquets could by chance correspond to pseudo-pheromones of the females of another bee species, and thus attract a new pollinator. If such pollinator shifts occur simultaneously in several indivuals, pollen exchanges might occur and initiate speciation. To reinforce the attraction of the new pollinator and secure prezygotic isolation, the following step is directional selection on flower phenotypes (shape, colour and hairiness) towards a better match with the body of the pollinator's female. Pollinator shift and the resulting prezygotic isolation is adaptive for new Ophrys species because they may benefit from competitor-free space for limited pollinators. We end our review by proritizing several critical research avenues.
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Affiliation(s)
- Michel Baguette
- Institut Systématique, Evolution, Biodiversité (ISYEB), UMR 7205 Museum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, F-75005, Paris, France.,Centre National de la Recherche Scientifique and Université Paul Sabatier Toulouse III, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, F-09200, Moulis, France
| | - Joris A M Bertrand
- LGDP (Laboratoire Génome et Développement des Plantes) UMR5096, Université de Perpignan Via Domitia -CNRS, F-66860, Perpignan, France
| | - Virginie M Stevens
- Centre National de la Recherche Scientifique and Université Paul Sabatier Toulouse III, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, F-09200, Moulis, France
| | - Bertrand Schatz
- CEFE (Centre d'Ecologie Fonctionnelle et Evolutive) UMR 5175, CNRS - Université de Montpellier - Université Paul Valéry - EPHE, 1919 Route de Mende, 34293, Montpellier, France
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19
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Misiewicz TM, Simmons TS, Fine PVA. The contribution of multiple barriers to reproduction between edaphically divergent lineages in the Amazonian tree Protium subserratum (Burseraceae). Ecol Evol 2020; 10:6646-6663. [PMID: 32724539 PMCID: PMC7381562 DOI: 10.1002/ece3.6396] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/30/2020] [Accepted: 04/22/2020] [Indexed: 11/09/2022] Open
Abstract
Disentangling the strength and importance of barriers to reproduction that arise between diverging lineages is central to our understanding of species origin and maintenance. To date, the vast majority of studies investigating the importance of different barriers to reproduction in plants have focused on short-lived temperate taxa while studies of reproductive isolation in trees and tropical taxa are rare. Here, we systematically examine multiple barriers to reproduction in an Amazonian tree, Protium subserratum (Burseraceae) with diverging lineages of soil specialist ecotypes. Using observational, molecular, distributional, and experimental data, we aimed to quantify the contributions of individual prezygotic and postzygotic barriers including ecogeographic isolation, flowering phenology, pollinator assemblage, pollen adhesion, pollen germination, pollen tube growth, seed development, and hybrid fitness to total reproductive isolation between the ecotypes. We were able to identify five potential barriers to reproduction including ecogeographic isolation, phenological differences, differences in pollinator assemblages, differential pollen adhesion, and low levels of hybrid seed development. We demonstrate that ecogeographic isolation is a strong and that a combination of intrinsic and extrinsic prezygotic and postzygotic barriers may be acting to maintain near complete reproductive isolation between edaphically divergent populations of the tropical tree, P. subserratum.
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Affiliation(s)
- Tracy M. Misiewicz
- Department of Integrative Biology, University and Jepson HerbariaUniversity of CaliforniaBerkeleyCAUSA
| | - Tracey S. Simmons
- Department of Biological SciencesSan Jose State UniversitySan JoseCAUSA
| | - Paul V. A. Fine
- Department of Integrative Biology, University and Jepson HerbariaUniversity of CaliforniaBerkeleyCAUSA
- Department of Integrative BiologyEssig Museum of EntomologyUniversity and Jepson HerbariaUniversity of CaliforniaBerkeleyCAUSA
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20
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Chin TA, Cáceres CE, Cristescu ME. The evolution of reproductive isolation in Daphnia. BMC Evol Biol 2019; 19:216. [PMID: 31775606 PMCID: PMC6880586 DOI: 10.1186/s12862-019-1542-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 11/15/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The process by which populations evolve to become new species involves the emergence of various reproductive isolating barriers (RIB). Despite major advancements in understanding this complex process, very little is known about the order in which RIBs evolve or their relative contribution to the total restriction of gene flow during various stages of speciation. This is mainly due to the difficulties of studying reproductive isolation during the early stages of species formation. This study examines ecological and non-ecological RIB within and between Daphnia pulex and Daphnia pulicaria, two recently diverged species that inhabit distinct habitats and exhibit an unusual level of intraspecific genetic subdivision. RESULTS We find that while ecological prezygotic barriers are close to completion, none of the non-ecological barriers can restrict gene flow between D. pulex and D. pulicaria completely when acting alone. Surprisingly, we also identified high levels of postzygotic reproductive isolation in 'conspecific' interpopulation crosses of D. pulex. CONCLUSIONS While the ecological prezygotic barriers are prevalent during the mature stages of speciation, non-ecological barriers likely dominated the early stages of speciation. This finding indicates the importance of studying the very early stages of speciation and suggests the contribution of postzygotic isolation in initiating the process of speciation.
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Affiliation(s)
- Tiffany A Chin
- Department of Biology, McGill University, 1205 ave Docteur Penfield, Montreal, Quebec, H3A 1B1, Canada.
| | - Carla E Cáceres
- School of Integrative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Melania E Cristescu
- Department of Biology, McGill University, 1205 ave Docteur Penfield, Montreal, Quebec, H3A 1B1, Canada
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21
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Wróblewska A, Szczepaniak L, Bajguz A, Jędrzejczyk I, Tałałaj I, Ostrowiecka B, Brzosko E, Jermakowicz E, Mirski P. Deceptive strategy in Dactylorhiza orchids: multidirectional evolution of floral chemistry. ANNALS OF BOTANY 2019; 123:1005-1016. [PMID: 30753414 PMCID: PMC6589506 DOI: 10.1093/aob/mcz003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 01/03/2019] [Indexed: 05/06/2023]
Abstract
BACKGROUND AND AIMS The deception strategies of orchids remain poorly understood, especially in regard to the chemical compounds emitted from their flowers and their interaction with various taxonomic groups of pollinators. We investigated the phylogenetic relationships and compared the variation of floral chemical compounds between food-deceptive Dactylorhiza taxa (D. incarnata var. incarnata and D. incarnata var. ochroleuca, D. fuchsii and D. majalis) from populations in north-eastern Poland. We propose a model of the evolution of deception based on floral chemical signals in this genus. METHODS A Bayesian approach based on polymorphic plastid DNA (trnL, trnF and psbC-trnK), internal transcribed spacer (ITS) sequences and flow cytometry data was applied to confirm the taxonomic status of the studied orchids. We also identified and classified the pollinators and flower visitors in each Dactylorhiza population to the taxonomic level and compared our results with literature data. The chemical composition of pentane and diethyl ether extracts from the flowers was analysed by gas chromatography-mass spectrometry. Variation of the floral chemical components was visualized by non-metric multidimensional scaling based on Bray-Curtis dissimilarity. KEY RESULTS The genetic distinctiveness of D. incarnata, D. fuchsii and D. majalis was confirmed. No hybrids between them were found, but the chloroplast DNA (cpDNA), ITS haplotypes and flow cytometry showed genetic similarity between D. incarnata var. incarnata and D. incarnata var. ochroleuca. We determined that Apis mellifera (Hymenoptera) was the only shared pollinator of these taxa. Strangalia attenuata and Alosterna tabacicolor (Coleoptera) and Volucella pellucens and V. bombylans (Hymenoptera) were observed pollinating D. fuchsii. Visualization of the emission rates of the 61 floral chemical compounds detected from pentane extracts (mainly hydrocarbons and aldehydes) and the 51 from diethyl extracts (with abundant groups of benzenoids and non-aromatic acids) strongly differentiated D. incarnata, D. fuchsii and D. majalis, while those of the two varieties of D. incarnata (var. incarnata and var. ochroleuca) were almost identical. CONCLUSIONS While the genetic data clearly supported the distinct lineages of D. incarnata, D. fuchsii and D. majalis, the patterns of emission of their flower chemical compounds were more complex within the series of shared compounds (alkanes and aldehydes) and taxon-specific compounds (benzenoids and esters). Their floral bouquet can influence the sexual, social and feeding behaviour of pollinators in different ways. We observed that the floral chemical compounds attracted both shared and species-specific pollinators to Dactylorhiza, confirming the multidirectional character of floral chemical signals in these food-deceptive taxa. Reduction of species-specific pollination levels in Dactylorhiza orchid taxa may promote hybridization between them.
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Affiliation(s)
- Ada Wróblewska
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
- For correspondence. E-mail
| | - Lech Szczepaniak
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Chemistry, Białystok, Poland
| | - Andrzej Bajguz
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
| | - Iwona Jędrzejczyk
- Laboratory of Molecular Biology and Cytometry, Department of Plant Genetics, Physiology and Biotechnology, UTP University of Science and Technology, Bydgoszcz, Poland
| | - Izabela Tałałaj
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
| | - Beata Ostrowiecka
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
| | - Emilia Brzosko
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
| | - Edyta Jermakowicz
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
| | - Paweł Mirski
- University of Bialystok, Faculty of Biology and Chemistry, Institute of Biology, Białystok, Poland
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22
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Liao WJ, Zhu BR, Li YF, Li XM, Zeng YF, Zhang DY. A comparison of reproductive isolation between two closely related oak species in zones of recent and ancient secondary contact. BMC Evol Biol 2019; 19:70. [PMID: 30841907 PMCID: PMC6404273 DOI: 10.1186/s12862-019-1399-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Accepted: 02/22/2019] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Much of the debate over the evolutionary consequences of hybridization on genetic divergence and speciation results from the breakdown or reinforcement of reproductive barriers in secondary hybrid zones. Among hybrid populations established for different lengths of time following secondary contact, stronger reproductive barriers are generally expected to occur in zones with longer contact. However, in plants no detailed investigation of recent and ancient zones of secondary contact has been conducted despite the importance of such a comparative study. Here, we compare pre- and postzygotic reproductive barriers between two closely related oak species, Quercus mongolica and Q. liaotungensis, in such a situation. RESULTS The recorded flowering times of both species overlapped in both contact zones. The fruit set at 10 and 30 days after interspecific hand pollination was not significantly lower than that after intraspecific pollination whenever Q. mongolica or Q. liaotungensis comprised the maternal parents in both populations. These results indicated that neither prezygotic phenological barriers nor interspecific incompatibility could have resulted in the reproductive isolation between the two species in both hybrid zones. However, the proportion of hybrid seeds produced by both species in the ancient zone was significantly lower than that recorded in the recent zone of secondary contact. In addition, the proportion of hybrid seeds simulated to form, assuming both random mating and an absence of postpollination barriers, was significantly higher than that detected in the ancient contact zone but not in the recent contact zone. These results suggest stronger early-acting postzygotic isolation between the two oak species in the ancient relative to the recent contact zone. CONCLUSIONS Our comparative study demonstrated that postzygotic barriers during seed maturity were the main contributing factor to total reproductive isolation, particularly in the ancient contact zone, which aided species delimitation. In the recently formed secondary contact zone, pre- and postzygotic barriers were not well developed, and a high frequency of natural hybridization was evident. To our knowledge this study provides the first comparison of reproductive isolation between the ancient and recent secondary contact zones in plants and helps to clarify the evolutionary consequences of hybridization in a temporal context.
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Affiliation(s)
- Wan-Jin Liao
- State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875 China
| | - Bi-Ru Zhu
- State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875 China
| | - Yue-Fei Li
- State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875 China
| | - Xiao-Meng Li
- State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875 China
| | - Yan-Fei Zeng
- Key Laboratory of Tree Breeding and Cultivation of the State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091 China
| | - Da-Yong Zhang
- State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875 China
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Caruso CM, Eisen KE, Martin RA, Sletvold N. A meta-analysis of the agents of selection on floral traits. Evolution 2018; 73:4-14. [PMID: 30411337 DOI: 10.1111/evo.13639] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 10/23/2018] [Accepted: 10/24/2018] [Indexed: 01/03/2023]
Abstract
Floral traits are hypothesized to evolve primarily in response to selection by pollinators. However, selection can also be mediated by other environmental factors. To understand the relative importance of pollinator-mediated selection and its variation among trait and pollinator types, we analyzed directional selection gradients on floral traits from experiments that manipulated the environment to identify agents of selection. Pollinator-mediated selection was stronger than selection by other biotic factors (e.g., herbivores), but similar in strength to selection by abiotic factors (e.g., soil water), providing partial support for the hypothesis that floral traits evolve primarily in response to pollinators. Pollinator-mediated selection was stronger on pollination efficiency traits than on other trait types, as expected if efficiency traits affect fitness via interactions with pollinators, but other trait types also affect fitness via other environmental factors. In addition to varying among trait types, pollinator-mediated selection varied among pollinator taxa: selection was stronger when bees, long-tongued flies, or birds were the primary visitors than when the primary visitors were Lepidoptera or multiple animal taxa. Finally, reducing pollinator access to flowers had a relatively small effect on selection on floral traits, suggesting that anthropogenic declines in pollinator populations would initially have modest effects on floral evolution.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Katherine E Eisen
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.,Current Address: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14853
| | - Ryan A Martin
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Nina Sletvold
- Department of Ecology and Genetics, Uppsala University, Uppsala, 751 05, Sweden
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Bundus JD, Wang D, Cutter AD. Genetic basis to hybrid inviability is more complex than hybrid male sterility in Caenorhabditis nematodes. Heredity (Edinb) 2018; 121:169-182. [PMID: 29626207 PMCID: PMC6039526 DOI: 10.1038/s41437-018-0069-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 01/22/2018] [Accepted: 02/11/2018] [Indexed: 12/31/2022] Open
Abstract
Hybrid male sterility often evolves before female sterility or inviability of hybrids, implying that the accumulation of divergence between separated lineages should lead hybrid male sterility to have a more polygenic basis. However, experimental evidence is mixed. Here, we use the nematodes Caenorhabditis remanei and C. latens to characterize the underlying genetic basis of asymmetric hybrid male sterility and hybrid inviability. We demonstrate that hybrid male sterility is consistent with a simple genetic basis, involving a single X-autosome incompatibility. We also show that hybrid inviability involves more genomic compartments, involving diverse nuclear-nuclear incompatibilities, a mito-nuclear incompatibility, and maternal effects. These findings demonstrate that male sensitivity to genetic perturbation may be genetically simple compared to hybrid inviability in Caenorhabditis and motivates tests of generality for the genetic architecture of hybrid incompatibility across the breadth of phylogeny.
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Affiliation(s)
- Joanna D Bundus
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Donglin Wang
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Asher D Cutter
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada.
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25
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Liang H, Ren ZX, Tao ZB, Zhao YH, Bernhardt P, Li DZ, Wang H. Impact of pre- and post-pollination barriers on pollen transfer and reproductive isolation among three sympatric Pedicularis (Orobanchaceae) species. PLANT BIOLOGY (STUTTGART, GERMANY) 2018; 20:662-673. [PMID: 29673012 DOI: 10.1111/plb.12833] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 04/11/2018] [Indexed: 06/08/2023]
Abstract
Pedicularis is the largest genus in the Orobanchaceae (>300) with many species co-occurring and co-blooming in subalpine to alpine meadows in the Himalayas. Although it is well known that different Pedicularis species place pollen on different parts of the same bumblebee's body, thus reducing interspecific pollen transfer, it is not known whether post-pollination components also contribute to reproductive isolation (RI). In this study, we quantified the individual strengths and absolute contributions of six pre- and post-pollination components of RI between three sympatric species in two pairs; Pedicularis gruina × Pedicularis tenuisecta (gru × ten) and Pedicularis comptoniifolia × Pedicularis tenuisecta (com × ten). All three Pedicularis species shared the same Bombus species. Individual foragers showed a high, but incomplete, floral constancy for each species. Therefore, pre-pollination barriers were potentially 'leaky' as Bombus species showed a low but consistent frequency of interspecific visitation. The RI strength of pre-pollination was lower in com × ten than in gru × ten. In contrast, post-pollination barriers completely blocked gene flow between both sets of species pairs. Two post-pollination recognition sites were identified. Late acting rejection of interspecific pollen tube growth occurred in com♀ × ten♂, while seeds produced in bi-directional crosses of gru × ten failed to germinate. We propose that, although floral isolation based on pollen placement on pollinators in the genus Pedicularis is crucial to avoid interspecific pollen transfer, the importance of this mode of interspecific isolation may be exaggerated. Post-pollination barriers may play even larger roles for currently established populations of co-blooming and sympatric species in this huge genus in the Himalayas.
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Affiliation(s)
- H Liang
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
- Kunming College of Life Sciences, University of Chinese Academy of Sciences, Kunming, China
| | - Z-X Ren
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - Z-B Tao
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
- Kunming College of Life Sciences, University of Chinese Academy of Sciences, Kunming, China
| | - Y-H Zhao
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - P Bernhardt
- Department of Biology, Saint Louis University, St. Louis, MI, USA
| | - D-Z Li
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - H Wang
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
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26
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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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27
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Suni SS, Hopkins R. The relationship between postmating reproductive isolation and reinforcement in Phlox. Evolution 2018; 72:1387-1398. [PMID: 29774945 DOI: 10.1111/evo.13507] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 04/09/2018] [Accepted: 04/14/2018] [Indexed: 02/06/2023]
Abstract
The process of speciation involves the accumulation of reproductive isolation (RI) between diverging lineages. Selection can favor increased RI via the process of reinforcement, whereby costs to hybridization impose selection for increased prezygotic RI. Reinforcement results in phenotypic divergence within at least one taxon, as a result of costly hybridization between sympatric taxa. The strength of selection driving reinforcement is determined by the cost of hybridization and the frequency of hybridization. We investigated the cost of hybridization by quantifying postmating RI barriers among Phlox species that comprise one of the best-studied cases of reinforcement. We determined if the strength of RI differs among lineages that have and have not undergone reinforcement, how much variability there is within species in RI, and whether RI is associated with phylogenetic relatedness. We found high RI for the species that underwent phenotypic divergence due to reinforcement; however, RI was also high between other species pairs. We found extensive variability in RI among individuals within species, and no evidence that the strength of RI was associated with phylogenetic relatedness. We suggest that phenotypic divergence due to reinforcement is associated with the frequency of hybridization and introgression, and not the cost of hybridization in this clade.
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Affiliation(s)
- Sevan S Suni
- The Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA 02131
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA
- Present Address: The University of San Francisco, 2130 Fulton Street, San Francisco, CA 94117
| | - Robin Hopkins
- The Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA 02131
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA
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Christie K, Strauss SY. Along the speciation continuum: Quantifying intrinsic and extrinsic isolating barriers across five million years of evolutionary divergence in California jewelflowers. Evolution 2018; 72:1063-1079. [DOI: 10.1111/evo.13477] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Accepted: 02/27/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Kyle Christie
- Department of Evolution and Ecology and Center for Population Biology University of California One Shields Avenue Davis California 95616
| | - Sharon Y. Strauss
- Department of Evolution and Ecology and Center for Population Biology University of California One Shields Avenue Davis California 95616
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29
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Sato Y, Sakamoto H, Gotoh T, Saito Y, Chao JT, Egas M, Mochizuki A. Patterns of reproductive isolation in a haplodiploid - strong post-mating, prezygotic barriers among three forms of a social spider mite. J Evol Biol 2018; 31:866-881. [DOI: 10.1111/jeb.13270] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 03/13/2018] [Accepted: 03/15/2018] [Indexed: 12/31/2022]
Affiliation(s)
- Yukie Sato
- Sugadaira Research Station; Mountain Science Center; University of Tsukuba; Ueda Nagano Japan
- Institute for Agro-Environmental Sciences; NARO; Tsukuba Ibaraki Japan
| | - Hironori Sakamoto
- Laboratory of Applied Entomology and Zoology; Faculty of Agriculture; Ibaraki University; Ami Ibaraki Japan
- Organization for University Research Initiatives; Waseda University; Shinjuku-ku Tokyo Japan
| | - Tetsuo Gotoh
- Laboratory of Applied Entomology and Zoology; Faculty of Agriculture; Ibaraki University; Ami Ibaraki Japan
| | - Yutaka Saito
- Research Faculty of Agriculture; Hokkaido University; Kita-ku Sapporo Hokkaido Japan
| | - Jung-Tai Chao
- Division of Forest Protection; Taiwan Forestry Research Institute; Taipei Taiwan
| | - Martijn Egas
- Institute for Biodiversity and Ecosystem Dynamics; University of Amsterdam; Amsterdam The Netherlands
| | - Atsushi Mochizuki
- Institute for Agro-Environmental Sciences; NARO; Tsukuba Ibaraki Japan
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30
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Roberts WR, Roalson EH. Phylogenomic analyses reveal extensive gene flow within the magic flowers (Achimenes). AMERICAN JOURNAL OF BOTANY 2018; 105:726-740. [PMID: 29702729 DOI: 10.1002/ajb2.1058] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 02/02/2018] [Indexed: 06/08/2023]
Abstract
PREMISE OF THE STUDY The Neotropical Gesneriaceae is a lineage known for its colorful and diverse flowers, as well as an extensive history of intra- and intergeneric hybridization, particularly among Achimenes (the magic flowers) and other members of subtribe Gloxiniinae. Despite numerous studies seeking to elucidate the evolutionary relationships of these lineages, relatively few have sought to infer specific patterns of gene flow despite evidence of widespread hybridization. METHODS To explore the utility of phylogenomic data for reassessing phylogenetic relationships and inferring patterns of gene flow among species of Achimenes, we sequenced 12 transcriptomes. We used a variety of methods to infer the species tree, examine gene tree discordance, and infer patterns of gene flow. KEY RESULTS Phylogenomic analyses resolve clade relationships at the crown of the lineage with strong support. In contrast to previous analyses, we recovered strong support for several new relationships despite a significant amount of gene tree discordance. We present evidence for at least two introgression events between two species pairs that share pollinators, and suggest that the species status of Achimenes admirabilis be reexamined. CONCLUSIONS Our study demonstrates the utility of transcriptome data for phylogenomic analyses, and inferring patterns of gene flow despite gene tree discordance. Moreover, these data provide another example of prevalent interspecific gene flow among Neotropical plants that share pollinators.
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Affiliation(s)
- Wade R Roberts
- Molecular Plant Sciences Graduate Program, Washington State University, Pullman, Washington, 99164-1030, USA
- School of Biological Sciences, Washington State University, Pullman, Washington, 99164-4236, USA
| | - Eric H Roalson
- Molecular Plant Sciences Graduate Program, Washington State University, Pullman, Washington, 99164-1030, USA
- School of Biological Sciences, Washington State University, Pullman, Washington, 99164-4236, USA
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31
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Turissini DA, McGirr JA, Patel SS, David JR, Matute DR. The Rate of Evolution of Postmating-Prezygotic Reproductive Isolation in Drosophila. Mol Biol Evol 2018; 35:312-334. [PMID: 29048573 PMCID: PMC5850467 DOI: 10.1093/molbev/msx271] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Reproductive isolation is an intrinsic aspect of species formation. For that reason, the identification of the precise isolating traits, and the rates at which they evolve, is crucial to understanding how species originate and persist. Previous work has measured the rates of evolution of prezygotic and postzygotic barriers to gene flow, yet no systematic analysis has studied the rates of evolution of postmating-prezygotic (PMPZ) barriers. We measured the magnitude of two barriers to gene flow that act after mating occurs but before fertilization. We also measured the magnitude of a premating barrier (female mating rate in nonchoice experiments) and two postzygotic barriers (hybrid inviability and hybrid sterility) for all pairwise crosses of all nine known extant species within the melanogaster subgroup. Our results indicate that PMPZ isolation evolves faster than hybrid inviability but slower than premating isolation. Next, we partition postzygotic isolation into different components and find that, as expected, hybrid sterility evolves faster than hybrid inviability. These results lend support for the hypothesis that, in Drosophila, reproductive isolation mechanisms (RIMs) that act early in reproduction (or in development) tend to evolve faster than those that act later in the reproductive cycle. Finally, we tested whether there was evidence for reinforcing selection at any RIM. We found no evidence for generalized evolution of reproductive isolation via reinforcement which indicates that there is no pervasive evidence of this evolutionary process. Our results indicate that PMPZ RIMs might have important evolutionary consequences in initiating speciation and in the persistence of new species.
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Affiliation(s)
- David A Turissini
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Joseph A McGirr
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Sonali S Patel
- Department of Biology, University of North Carolina, Chapel Hill, NC
| | - Jean R David
- Laboratoire Evolution, Génomes, Comportement, Ecologie (EGCE) CNRS, IRD, Univ. Paris-sud, Université Paris-Saclay, 91198 Gif sur Yvette, France
- Institut de Systématique, Evolution, Biodiversité, UMR 7205, CNRS, MNHN, UPMC, EPHE, Muséum National d’Histoire Naturelle, Sorbonne Universités, rue Buffon, 75005, Paris, France
| | - Daniel R Matute
- Department of Biology, University of North Carolina, Chapel Hill, NC
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Bateman RM, Sramkó G, Paun O. Integrating restriction site-associated DNA sequencing (RAD-seq) with morphological cladistic analysis clarifies evolutionary relationships among major species groups of bee orchids. ANNALS OF BOTANY 2018; 121:85-105. [PMID: 29325077 PMCID: PMC5786241 DOI: 10.1093/aob/mcx129] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 10/02/2017] [Indexed: 05/03/2023]
Abstract
BACKGROUND AND AIMS Bee orchids (Ophrys) have become the most popular model system for studying reproduction via insect-mediated pseudo-copulation and for exploring the consequent, putatively adaptive, evolutionary radiations. However, despite intensive past research, both the phylogenetic structure and species diversity within the genus remain highly contentious. Here, we integrate next-generation sequencing and morphological cladistic techniques to clarify the phylogeny of the genus. METHODS At least two accessions of each of the ten species groups previously circumscribed from large-scale cloned nuclear ribosomal internal transcibed spacer (nrITS) sequencing were subjected to restriction site-associated sequencing (RAD-seq). The resulting matrix of 4159 single nucleotide polymorphisms (SNPs) for 34 accessions was used to construct an unrooted network and a rooted maximum likelihood phylogeny. A parallel morphological cladistic matrix of 43 characters generated both polymorphic and non-polymorphic sets of parsimony trees before being mapped across the RAD-seq topology. KEY RESULTS RAD-seq data strongly support the monophyly of nine out of ten groups previously circumscribed using nrITS and resolve three major clades; in contrast, supposed microspecies are barely distinguishable. Strong incongruence separated the RAD-seq trees from both the morphological trees and traditional classifications; mapping of the morphological characters across the RAD-seq topology rendered them far more homoplastic. CONCLUSIONS The comparatively high level of morphological homoplasy reflects extensive convergence, whereas the derived placement of the fusca group is attributed to paedomorphic simplification. The phenotype of the most recent common ancestor of the extant lineages is inferred, but it post-dates the majority of the character-state changes that typify the genus. RAD-seq may represent the high-water mark of the contribution of molecular phylogenetics to understanding evolution within Ophrys; further progress will require large-scale population-level studies that integrate phenotypic and genotypic data in a cogent conceptual framework.
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Affiliation(s)
- Richard M Bateman
- Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, UK
- For correspondence. E-mail
| | - Gábor Sramkó
- Department of Botany, University of Debrecen, Egyetem, Debrecen, Hungary
- MTA-DE ‘Lendület’ Evolutionary Phylogenomics Research Group, Egyetem, Debrecen, Hungary
| | - Ovidiu Paun
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg, Vienna, Austria
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Esposito F, Vereecken NJ, Gammella M, Rinaldi R, Laurent P, Tyteca D. Characterization of sympatric Platanthera bifolia and Platanthera chlorantha (Orchidaceae) populations with intermediate plants. PeerJ 2018; 6:e4256. [PMID: 29379684 PMCID: PMC5787349 DOI: 10.7717/peerj.4256] [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: 09/19/2017] [Accepted: 12/20/2017] [Indexed: 12/25/2022] Open
Abstract
Platanthera bifolia and P. chlorantha are terrestrial and rewarding orchids with a wide Eurasian distribution. Although genetically closely related, they exhibit significant morphological, phenological and ecological differences that maintain reproductive isolation between the species. However, where both species co-occur, individuals with intermediate phenotypic traits, often considered as hybrids, are frequently observed. Here, we combined neutral genetic markers (AFLPs), morphometrics and floral scent analysis (GC-MS) to investigate two mixed Platanthera populations where morphologically intermediate plants were found. Self-pollination experiments revealed a low level of autogamy and artificial crossings combined with assessments of fruit set and seed viability, showed compatibility between the two species. The results of the genetic analyses showed that morphologically intermediate plants had similar genetic patterns as the P. bifolia group. These results are corroborated also by floral scent analyses, which confirmed a strong similarity in floral scent composition between intermediate morphotypes and P. bifolia. Therefore, this study provided a much more detailed picture of the genetic structure of a sympatric zone between two closely allied species and supports the hypothesis that intermediate morphotypes in sympatry could reflect an adaptive evolution in response to local pollinator-mediated selection.
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Affiliation(s)
- Fabiana Esposito
- Earth and Life Institute—Biodiversity Research Centre, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Nicolas J. Vereecken
- Agroecology Lab, Brussels Bioengineering School, Université libre de Bruxelles (ULB), Brussels, Belgium
| | | | - Rosita Rinaldi
- Department of Biology, University of Naples Federico II, Napoli, Italy
| | - Pascal Laurent
- Unit of General Chemistry, Université Libre de Bruxelles, Brussels, Belgium
| | - Daniel Tyteca
- Earth and Life Institute—Biodiversity Research Centre, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
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Abreu JA, Hawkins JA, Cotrim H, Fay MF, Hidalgo O, Pellicer J. Ophrys fusca and Ophrys dyris (Orchidaceae) – constancy of tetraploidy amongst populations in Central Portugal. ACTA ACUST UNITED AC 2017. [DOI: 10.1080/20423489.2017.1408185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- J. A. Abreu
- Centre for Ecology, Evolution and Evironmental Changes (CE3C), Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
- Conservation Science, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, UK
- School of Biological Sciences, University of Reading, Whiteknights, Reading, Berkshire RG6 6BX, UK
| | - J. A. Hawkins
- School of Biological Sciences, University of Reading, Whiteknights, Reading, Berkshire RG6 6BX, UK
| | - H. Cotrim
- Centre for Ecology, Evolution and Evironmental Changes (CE3C), Faculty of Sciences, University of Lisbon, 1749-016 Lisbon, Portugal
| | - M. F. Fay
- Conservation Science, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS, UK
- School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia
| | - O. Hidalgo
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey, TW3 3DS, UK
| | - J. Pellicer
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey, TW3 3DS, UK
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35
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Fantinato E, Del Vecchio S, Baltieri M, Fabris B, Buffa G. Are food-deceptive orchid species really functionally specialized for pollinators? Ecol Res 2017. [DOI: 10.1007/s11284-017-1501-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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36
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Scopece G, Juillet N, Lexer C, Cozzolino S. Fluctuating selection across years and phenotypic variation in food-deceptive orchids. PeerJ 2017; 5:e3704. [PMID: 28852594 PMCID: PMC5572944 DOI: 10.7717/peerj.3704] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 07/27/2017] [Indexed: 11/20/2022] Open
Abstract
Nectarless flowers that deceive pollinators offer an opportunity to study asymmetric plant-insect interactions. Orchids are a widely used model for studying these interactions because they encompass several thousand species adopting deceptive pollination systems. High levels of intra-specific phenotypic variation have been reported in deceptive orchids, suggesting a reduced consistency of pollinator-mediated selection on their floral traits. Nevertheless, several studies report on widespread directional selection mediated by pollinators even in these deceptive orchids. In this study we test the hypothesis that the observed selection can fluctuate across years in strength and direction thus likely contributing to the phenotypic variability of this orchid group. We performed a three-year study estimating selection differentials and selection gradients for nine phenotypic traits involved in insect attraction in two Mediterranean orchid species, namely Orchis mascula and O. pauciflora, both relying on a well-described food-deceptive pollination strategy. We found weak directional selection and marginally significant selection gradients in the two investigated species with significant intra-specific differences in selection differentials across years. Our data do not link this variation with a specific environmental cause, but our results suggest that pollinator-mediated selection in food-deceptive orchids can change in strength and in direction over time. In perennial plants, such as orchids, different selection differentials in the same populations in different flowering seasons can contribute to the maintenance of phenotypic variation often reported in deceptive orchids.
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Affiliation(s)
- Giovanni Scopece
- Department of Biology, University of Naples Federico II, Naples, Italy
| | - Nicolas Juillet
- UMR Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Université de la Réunion, Pôle de Protection des Plantes, Saint Pierre, La Réunion, France
| | - Christian Lexer
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
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37
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Huang BH, Huang CW, Huang CL, Liao PC. Continuation of the genetic divergence of ecological speciation by spatial environmental heterogeneity in island endemic plants. Sci Rep 2017; 7:5465. [PMID: 28710389 PMCID: PMC5511155 DOI: 10.1038/s41598-017-05900-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 06/06/2017] [Indexed: 01/11/2023] Open
Abstract
Divergent selection plays a critical role not only as a speciation driver but also in maintaining post-speciation divergence. In the absence of direct evidence, ancestral interspecific gene flow between incipient species can reflect ancient selective pressure for ecological speciation. In the present study, two late-Pleistocene diverged species endemic to Taiwan, Scutellaria playfairii and S. tashiroi, were spatially and ecologically partitioned with partial overlap. Multilocus genome-scan analyses and in silico evaluation revealed ancestral interspecific gene flow but distinct genetic compositions, implying that adaptive divergence contributed to their speciation. Ecological niche modeling and principal component analysis suggested incomplete divergent niches between the two species; the species distribution is therefore consistent with Hutchinson's metaphor of multidimensional hypervolume niches rather than attributable to a single factor. Constraint ordination analysis supported this inference of a combination of variables explaining the genetic structure. The rare occurrence of hybrids in the sympatric population suggested hybrid breakdown, providing further evidence of divergent selection blocking gene flow. The correlation of environmental variables with integrated genetic components demonstrated that environmental heterogeneity maintains the species and population differentiation. This study highlights the importance of environmental heterogeneity and divergent selection for the rapid speciation and recent diversification of island plants.
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Affiliation(s)
- Bing-Hong Huang
- Department of Life Science, National Taiwan Normal University, Taipei, 11677, Taiwan
| | - Chih-Wei Huang
- Department of Life Science, National Taiwan Normal University, Taipei, 11677, Taiwan
| | - Chia-Lung Huang
- Department of Life Science, National Taiwan Normal University, Taipei, 11677, Taiwan
| | - Pei-Chun Liao
- Department of Life Science, National Taiwan Normal University, Taipei, 11677, Taiwan.
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38
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Gervasi DDL, Selosse MA, Sauve M, Francke W, Vereecken NJ, Cozzolino S, Schiestl FP. Floral scent and species divergence in a pair of sexually deceptive orchids. Ecol Evol 2017; 7:6023-6034. [PMID: 28808562 PMCID: PMC5551101 DOI: 10.1002/ece3.3147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 04/14/2017] [Accepted: 05/17/2017] [Indexed: 01/08/2023] Open
Abstract
Speciation is typically accompanied by the formation of isolation barriers between lineages. Commonly, reproductive barriers are separated into pre‐ and post‐zygotic mechanisms that can evolve with different speed. In this study, we measured the strength of different reproductive barriers in two closely related, sympatric orchids of the Ophrys insectifera group, namely Ophrys insectifera and Ophrys aymoninii to infer possible mechanisms of speciation. We quantified pre‐ and post‐pollination barriers through observation of pollen flow, by performing artificial inter‐ and intraspecific crosses and analyzing scent bouquets. Additionally, we investigated differences in mycorrhizal fungi as a potential extrinsic factor of post‐zygotic isolation. Our results show that floral isolation mediated by the attraction of different pollinators acts apparently as the sole reproductive barrier between the two orchid species, with later‐acting intrinsic barriers seemingly absent. Also, the two orchids share most of their fungal mycorrhizal partners in sympatry, suggesting little or no importance of mycorrhizal symbiosis in reproductive isolation. Key traits underlying floral isolation were two alkenes and wax ester, present predominantly in the floral scent of O. aymoninii. These compounds, when applied to flowers of O. insectifera, triggered attraction and a copulation attempt of the bee pollinator of O. aymoninii and thus led to the (partial) breakdown of floral isolation. Based on our results, we suggest that adaptation to different pollinators, mediated by floral scent, underlies species isolation in this plant group. Pollinator switches may be promoted by low pollination success of individuals in dense patches of plants, an assumption that we also confirmed in our study.
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Affiliation(s)
- Daniel D L Gervasi
- Department of Systematic and Evolutionary Botany University of Zürich Zürich Switzerland
| | - Marc-Andre Selosse
- Institut de Systématique, Évolution, Biodiversité (ISYEB)UMR 7205 CNRS MNHN UPMC EPHE Muséum national d'Histoire naturelle Sorbonne Universités Paris France.,Department of Plant Taxonomy and Nature Conservation University of Gdansk Gdańsk Poland
| | - Mathieu Sauve
- Institut de Systématique, Évolution, Biodiversité (ISYEB)UMR 7205 CNRS MNHN UPMC EPHE Muséum national d'Histoire naturelle Sorbonne Universités Paris France
| | - Wittko Francke
- Institute of Organic Chemistry University of Hamburg Hamburg Germany
| | - Nicolas J Vereecken
- Agroecology and Pollination Group Landscape Ecology and Plant Production Systems Université libre de Bruxelles (ULB) Brussels Belgium
| | | | - Florian P Schiestl
- Department of Systematic and Evolutionary Botany University of Zürich Zürich Switzerland
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39
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Kostyun JL, Moyle LC. Multiple strong postmating and intrinsic postzygotic reproductive barriers isolate florally diverse species of Jaltomata (Solanaceae). Evolution 2017; 71:1556-1571. [PMID: 28432763 PMCID: PMC5502772 DOI: 10.1111/evo.13253] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/31/2017] [Indexed: 12/22/2022]
Abstract
Divergence in phenotypic traits often contributes to premating isolation between lineages, but could also promote isolation at postmating stages. Phenotypic differences could directly result in mechanical isolation or hybrids with maladapted traits; alternatively, when alleles controlling these trait differences pleiotropically affect other components of development, differentiation could indirectly produce genetic incompatibilities in hybrids. Here, we determined the strength of nine postmating and intrinsic postzygotic reproductive barriers among 10 species of Jaltomata (Solanaceae), including species with highly divergent floral traits. To evaluate the relative importance of floral trait diversification for the strength of these postmating barriers, we assessed their relationship to floral divergence, genetic distance, geographical context, and ecological differences, using conventional tests and a new linear-mixed modeling approach. Despite close evolutionary relationships, all species pairs showed moderate to strong isolation. Nonetheless, floral trait divergence was not a consistent predictor of the strength of isolation; instead this was best explained by genetic distance, although we found evidence for mechanical isolation in one species, and a positive relationship between floral trait divergence and fruit set isolation across species pairs. Overall, our data indicate that intrinsic postzygotic isolation is more strongly associated with genome-wide genetic differentiation, rather than floral divergence.
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Affiliation(s)
- Jamie L. Kostyun
- Department of Biology, Indiana University, Bloomington, Indiana
47405, USA
| | - Leonie C. Moyle
- Department of Biology, Indiana University, Bloomington, Indiana
47405, USA
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40
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Cuervo M, Rakosy D, Martel C, Schulz S, Ayasse M. Sexual Deception in the Eucera-Pollinated Ophrys leochroma: A Chemical Intermediate between Wasp- and Andrena-Pollinated Species. J Chem Ecol 2017; 43:469-479. [PMID: 28536987 DOI: 10.1007/s10886-017-0848-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 03/13/2017] [Accepted: 04/24/2017] [Indexed: 10/19/2022]
Abstract
Ophrys flowers mimic sex pheromones of attractive females of their pollinators and attract males, which attempt to copulate with the flower and thereby pollinate it. Virgin females and orchid flowers are known to use the same chemical compounds in order to attract males. The composition of the sex pheromone and its floral analogue, however, vary between pollinator genera. Wasp-pollinated Ophrys species attract their pollinators by using polar hydroxy acids, whereas Andrena-pollinated species use a mixture of non-polar hydrocarbons. The phylogeny of Ophrys shows that its evolution was marked by episodes of rapid diversification coinciding with shifts to different pollinator groups: from wasps to Eucera and consequently to Andrena and other bees. To gain further insights, we studied pollinator attraction in O. leochroma in the context of intra- and inter-generic pollinator shifts, radiation, and diversification in the genus Ophrys. Our model species, O. leochroma, is pollinated by Eucera kullenbergi males and lies in the phylogeny between the wasp and Andrena-pollinated species; therefore, it is a remarkable point to understand pollinator shifts. We collected surface extracts of attractive E. kullenbergi females and labellum extracts of O. leochroma and analyzed them by using gas chromatography with electroantennographic detection (GC-EAD) and gas chromatography coupled with mass spectrometry (GC-MS). We also performed field bioassays. Our results show that O. leochroma mimics the sex pheromone of its pollinator's female by using aldehydes, alcohols, fatty acids, and non-polar compounds (hydrocarbons). Therefore, in terms of the chemistry of pollinator attraction, Eucera-pollinated Ophrys species might represent an intermediate stage between wasp- and Andrena-pollinated orchid species.
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Affiliation(s)
- Monica Cuervo
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Helmholtzstraße 10-1, Containerstadt, 89081, Ulm, Germany.
| | - Demetra Rakosy
- Department of Integrative Zoology, University of Vienna, Althanstraße 14, 1090, Vienna, Austria
| | - Carlos Martel
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Helmholtzstraße 10-1, Containerstadt, 89081, Ulm, Germany
| | - Stefan Schulz
- Institute of Organic Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106, Braunschweig, Germany
| | - Manfred Ayasse
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Helmholtzstraße 10-1, Containerstadt, 89081, Ulm, Germany
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41
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Murúa M, Espíndola A, González A, Medel R. Pollinators and crossability as reproductive isolation barriers in two sympatric oil-rewarding Calceolaria (Calceolariaceae) species. Evol Ecol 2017. [DOI: 10.1007/s10682-017-9894-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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42
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Bateman RM, Molnár V A, Sramkó G. In situ morphometric survey elucidates the evolutionary systematics of the Eurasian Himantoglossum clade (Orchidaceae: Orchidinae). PeerJ 2017; 5:e2893. [PMID: 28168103 PMCID: PMC5289109 DOI: 10.7717/peerj.2893] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 12/09/2016] [Indexed: 12/17/2022] Open
Abstract
Background and Aims The charismatic Himantoglossum s.l. clade of Eurasian orchids contains an unusually large proportion of taxa that are of controversial circumscriptions and considerable conservation concern. Whereas our previously published study addressed the molecular phylogenetics and phylogeography of every named taxon within the clade, here we use detailed morphometric data obtained from the same populations to compare genotypes with associated phenotypes, in order to better explore taxonomic circumscription and character evolution within the clade. Methods Between one and 12 plants found in 25 populations that encompassed the entire distribution of the Himantoglossum s.l. clade were measured in situ for 51 morphological characters. Results for 45 of those characters were subjected to detailed multivariate and univariate analyses. Key Results Multivariate analyses readily separate subgenus Barlia and subgenus Comperia from subgenus Himantoglossum, and also the early-divergent H. formosum from the less divergent remainder of subgenus Himantoglossum. The sequence of divergence of these four lineages is confidently resolved. Our experimental approach to morphometric character analysis demonstrates clearly that phenotypic evolution within Himantoglossum is unusually multi-dimensional. Conclusions Degrees of divergence between taxa shown by morphological analyses approximate those previously shown using molecular analyses. Himantoglossum s.l. is readily divisible into three subgenera. The three sections of subgenus Himantoglossum—hircinum, caprinum and formosum—are arrayed from west to east with only limited geographical overlap. At this taxonomic level, their juxtaposition combines with conflict between contrasting datasets to complicate attempts to distinguish between clinal variation and the discontinuities that by definition separate bona fide species. All taxa achieve allogamy via food deceit and have only weak pollinator specificity. Artificial crossing demonstrates that intrinsic sterility barriers are weak. Although we have found evidence of gene flow among and within the three sections of subgenus Himantoglossum, reports of natural hybrids are surprisingly rare, probably because putative parents are sufficiently similar to questionably warrant the status of species. Phenological separation and increased xeromorphy characterise the origin of subgenus Barlia. Several individual morphological characters show evidence of parallel acquisition, and loss of features is especially frequent in floral markings among members of section caprinum. Detailed patterns of gain and loss demonstrate that several different categories of flower markings are inherited independently. Along with the dimensions of labellar lobes, these pigmentation characters have been over-emphasised in previous taxonomic treatments. Increased plant vigour was a crucial element of the origin of the genus, but vegetative characters underwent remarkably little subsequent evolution. Attempts to reconstruct hypothetical ancestors at internal nodes of the phylogeny are weakened by (a) uncertain placement of Steveniella as sister to Himantoglossum s.l. and (b) uncertain relationships among subtly different putative species within section caprinum. Nonetheless, heterochronic/allometric trends, ultimately limited by functional constraints, clearly dictate transitions between contrasting flower sizes and complex labellum shapes.
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Affiliation(s)
| | - Attila Molnár V
- Department of Botany, University of Debrecen , Debrecen , Hungary
| | - Gábor Sramkó
- Department of Botany, University of Debrecen, Debrecen, Hungary; MTA-DE "Lendület" Evolutionary Phylogenomics Research Group, Debrecen, Hungary
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43
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Spiraling Complexity: A Test of the Snowball Effect in a Computational Model of RNA Folding. Genetics 2016; 206:377-388. [PMID: 28007889 DOI: 10.1534/genetics.116.196030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 03/03/2017] [Indexed: 01/07/2023] Open
Abstract
Genetic incompatibilities can emerge as a byproduct of genetic divergence. According to Dobzhansky and Muller, an allele that fixes in one population may be incompatible with an allele at a different locus in another population when the two alleles are brought together in hybrids. Orr showed that the number of Dobzhansky-Muller incompatibilities (DMIs) should accumulate faster than linearly-i.e., snowball-as two lineages diverge. Several studies have attempted to test the snowball effect using data from natural populations. One limitation of these studies is that they have focused on predictions of the Orr model, but not on its underlying assumptions. Here, we use a computational model of RNA folding to test both predictions and assumptions of the Orr model. Two populations are allowed to evolve in allopatry on a holey fitness landscape. We find that the number of inviable introgressions (an indicator for the number of DMIs) snowballs, but does so more slowly than expected. We show that this pattern is explained, in part, by the fact that DMIs can disappear after they have arisen, contrary to the assumptions of the Orr model. This occurs because DMIs become progressively more complex (i.e., involve alleles at more loci) as a result of later substitutions. We also find that most DMIs involve >2 loci, i.e., they are complex. Reproductive isolation does not snowball because DMIs do not act independently of each other. We conclude that the RNA model supports the central prediction of the Orr model that the number of DMIs snowballs, but challenges other predictions, as well as some of its underlying assumptions.
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44
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Lackey ACR, Boughman JW. Evolution of reproductive isolation in stickleback fish. Evolution 2016; 71:357-372. [PMID: 27901265 DOI: 10.1111/evo.13114] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 10/15/2016] [Accepted: 10/24/2016] [Indexed: 12/21/2022]
Abstract
To understand how new species form and what causes their collapse, we examined how reproductive isolation evolves during the speciation process, considering species pairs with little to extensive divergence, including a recently collapsed pair. We estimated many reproductive barriers in each of five sets of stickleback fish species pairs using our own data and decades of previous work. We found that the types of barriers important early in the speciation process differ from those important late. Two premating barriers-habitat and sexual isolation-evolve early in divergence and remain two of the strongest barriers throughout speciation. Premating isolation evolves before postmating isolation, and extrinsic isolation is far stronger than intrinsic. Completing speciation, however, may require postmating intrinsic incompatibilities. Reverse speciation in one species pair was characterized by significant loss of sexual isolation. We present estimates of barrier strengths before and after collapse of a species pair; such detail regarding the loss of isolation has never before been documented. Additionally, despite significant asymmetries in individual barriers, which can limit speciation, total isolation was essentially symmetric between species. Our study provides important insight into the order of barrier evolution and the relative importance of isolating barriers during speciation and tests fundamental predictions of ecological speciation.
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Affiliation(s)
- Alycia C R Lackey
- Department of Integrative Biology, Michigan State University, East Lansing, Michigan.,Ecology, Evolutionary Biology, and Behavior Program, Michigan State University, East Lansing, Michigan.,BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, Michigan.,Department of Biological Sciences, Watershed Studies Institute, Murray State University, 2112 Biology Building, Murray, State University, Murray, Kentucky, 42071
| | - Janette W Boughman
- Department of Integrative Biology, Michigan State University, East Lansing, Michigan.,Ecology, Evolutionary Biology, and Behavior Program, Michigan State University, East Lansing, Michigan.,BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, Michigan
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45
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Pellegrino G, Bellusci F, Palermo AM. Who helps whom? Pollination strategy of Iris tuberosa and its relationship with a sexually deceptive orchid. JOURNAL OF PLANT RESEARCH 2016; 129:1051-1059. [PMID: 27480219 DOI: 10.1007/s10265-016-0853-9] [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: 11/23/2015] [Accepted: 03/23/2016] [Indexed: 06/06/2023]
Abstract
Reproductive success of plants may be affected by interactions with co-flowering species either negatively, through competition for pollinators, or positively, by means of a magnet species effect and floral mimicry. In this study, potential interactions between Iris tuberosa, a rewarding species, and Ophrys fusca, a sexually deceptive orchid, were explored in four populations in southern Italy. In each population plots showing different ratios of the examined species were arranged in the field, and in each plot the number of pollinators and fruit set were assessed. In addition, flower size and floral hydrocarbons produced by the two species were analysed. Morphological and scent data pointed out that flower size and aliphatic compounds did not differ significantly between the two species. Interestingly, both species shared tricosane and 11-nonacosene, electrophysiologically active compounds in the shared dominant pollinator Adrena. We have found that fruit production and number of pollinators in I. tuberosa varied significantly among plots, while percentage of capsules and number of pollinators of O. fusca captured showed no significant differences across plots. These results suggested, that the presence of O. fusca contributes differentially to pollinator attraction, and thus, to total reproductive success of I. tuberosa, according to a different ratio of aggregation. These findings suggest that I. tuberosa profits from the greater abundance of insects attracted by the presence of orchid specimens, and that a sexually deceptive orchid may be a magnet species in pollination strategy.
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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.
| | - Francesca Bellusci
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Via Bucci 6/B, 87036, Rende, CS, Italy
| | - Anna Maria Palermo
- Department of Biology, Ecology and Earth Sciences, University of Calabria, Via Bucci 6/B, 87036, Rende, CS, Italy
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46
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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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47
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Barnard‐Kubow KB, So N, Galloway LF. Cytonuclear incompatibility contributes to the early stages of speciation. Evolution 2016; 70:2752-2766. [DOI: 10.1111/evo.13075] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 09/08/2016] [Accepted: 09/17/2016] [Indexed: 12/20/2022]
Affiliation(s)
| | - Nina So
- Department of Biology University of Virginia Charlottesville Virginia 22904
- Current Address: Doctoral Program in Neurobiology and Behavior Columbia University New York NY 10027
| | - Laura F. Galloway
- Department of Biology University of Virginia Charlottesville Virginia 22904
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48
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Jacquemyn H, van der Meer S, Brys R. The impact of hybridization on long-term persistence of polyploid Dactylorhiza species. AMERICAN JOURNAL OF BOTANY 2016; 103:1829-1837. [PMID: 27793859 DOI: 10.3732/ajb.1600274] [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: 07/21/2016] [Accepted: 09/13/2016] [Indexed: 06/06/2023]
Abstract
PREMISE OF THE STUDY Hybridization may pose severe threats to the long-term survival of the parental taxa through introgression and the formation of hybrid swarms. However, when the resulting hybrids show strong male and female sterility, backcrossing and introgression are unlikely to occur, but the parental species may suffer from reduced male and female fitness. METHODS We assessed the impact of hybridization on the long-term persistence of two food-deceptive orchids in the genus Dactylorhiza (the common Dactylorhiza maculata and the rare D. sphagnicola). The extent of hybridization was investigated using both molecular markers and morphometric measurements. To determine the strength of postmating reproductive isolation, hand pollinations were conducted between pure and hybrid individuals. Finally, fruit set and seed viability of open-pollinated plants were determined in sympatric and allopatric populations to investigate the impact of hybridization on the reproductive output of the pure parental species. KEY RESULTS Our results showed that postmating reproductive isolation was weak and that hybridization occurred frequently within the studied sympatric population. Although hybrids were characterized by very low female fitness, mainly because of strongly reduced seed viability, backcrossing appeared to occur and was asymmetric toward the rare D. sphagnicola. Fruit set and seed viability of open-pollinated plants were also significantly lower in the sympatric population than in the allopatric populations, indicating that hybridization and ongoing introgression incurred fitness costs in the pure parental species. CONCLUSIONS Overall, our results suggest that extensive hybridization can affect the long-term viability of the parental species through the combined effect of introgression following interspecific hybrid fertilization and reduced fitness of the parental species.
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Affiliation(s)
- Hans Jacquemyn
- KU Leuven, Biology Department, Plant Population and Conservation Biology, Kasteelpark Arenberg 31, B-3001 Heverlee, Belgium
| | - Sascha van der Meer
- KU Leuven, Biology Department, Plant Population and Conservation Biology, Kasteelpark Arenberg 31, B-3001 Heverlee, Belgium
| | - Rein Brys
- Research Institute for Nature and Forest, Kliniekstraat 25, B-1070 Brussels, Belgium
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Vallejo-Marín M, Hiscock SJ. Hybridization and hybrid speciation under global change. THE NEW PHYTOLOGIST 2016; 211:1170-87. [PMID: 27214560 DOI: 10.1111/nph.14004] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 04/07/2016] [Indexed: 05/24/2023]
Abstract
Contents 1170 I. 1170 II. 1172 III. 1175 IV. 1180 V. 1183 1184 References 1184 SUMMARY: An unintended consequence of global change is an increase in opportunities for hybridization among previously isolated lineages. Here we illustrate how global change can facilitate the breakdown of reproductive barriers and the formation of hybrids, drawing on the flora of the British Isles for insight. Although global change may ameliorate some of the barriers preventing hybrid establishment, for example by providing new ecological niches for hybrids, it will have limited effects on environment-independent post-zygotic barriers. For example, genic incompatibilities and differences in chromosome numbers and structure within hybrid genomes are unlikely to be affected by global change. We thus speculate that global change will have a larger effect on eroding pre-zygotic barriers (eco-geographical isolation and phenology) than post-zygotic barriers, shifting the relative importance of these two classes of reproductive barriers from what is usually seen in naturally produced hybrids where pre-zygotic barriers are the largest contributors to reproductive isolation. Although the long-term fate of neo-hybrids is still to be determined, the massive impact of global change on the dynamics and distribution of biodiversity generates an unprecedented opportunity to study large numbers of unpredicted, and often replicated, hybridization 'experiments', allowing us to peer into the birth and death of evolutionary lineages.
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Affiliation(s)
- Mario Vallejo-Marín
- Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Simon J Hiscock
- University of Oxford Botanic Garden, Rose Lane, Oxford, OX1 4AZ, UK
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50
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Pegoraro L, Cafasso D, Rinaldi R, Cozzolino S, Scopece G. Habitat preference and flowering-time variation contribute to reproductive isolation between diploid and autotetraploid Anacamptis pyramidalis. J Evol Biol 2016; 29:2070-2082. [PMID: 27369842 DOI: 10.1111/jeb.12930] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 06/22/2016] [Accepted: 06/27/2016] [Indexed: 11/29/2022]
Abstract
Tetraploid lineages are typically reproductively isolated from their diploid ancestors by post-zygotic isolation via triploid sterility. Nevertheless, polyploids often also exhibit ecological divergence that could contribute to reproductive isolation from diploid ancestors. In this study, we disentangled the contribution of different forms of reproductive isolation between sympatric diploid and autotetraploid individuals of the food-deceptive orchid Anacamptis pyramidalis by quantifying the strength of seven reproductive barriers: three prepollination, one post-pollination prezygotic and three post-zygotic. The overall reproductive isolation between the two cytotypes was found very high, with a preponderant contribution of two prepollination barriers, that is phenological and microhabitat differences. Although the contribution of post-zygotic isolation (triploid sterility) is confirmed in our study, these results highlight that prepollination isolation, not necessarily involving pollinator preference, can represent a strong component of reproductive isolation between different cytotypes. Thus, in the context of polyploidy as quantum speciation, that generates reproductive isolation via triploid sterility, ecological divergence can strengthen the reproductive isolation between cytotypes, reducing the waste of gametes in low fitness interploidy crosses and thus favouring the initial establishment of the polyploid lineage. Under this light, speciation by polyploidy involves ecological processes and should not be strictly considered as a nonecological form of speciation.
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Affiliation(s)
- L Pegoraro
- Department of Biology, University of Padua, Padua, Italy
| | - D Cafasso
- Department of Biology, University Federico II of Naples, Naples, Italy
| | - R Rinaldi
- Department of Biology, University Federico II of Naples, Naples, Italy
| | - S Cozzolino
- Department of Biology, University Federico II of Naples, Naples, Italy
| | - G Scopece
- Department of Biology, University Federico II of Naples, Naples, Italy.
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