1
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Nevado B, Chapman MA, Brennan AC, Clark JW, Wong ELY, Batstone T, McCarthy SA, Tracey A, Torrance J, Sims Y, Abbott RJ, Filatov D, Hiscock SJ. Genomic changes and stabilization following homoploid hybrid speciation of the Oxford ragwort Senecio squalidus. Curr Biol 2024:S0960-9822(24)01085-6. [PMID: 39260362 DOI: 10.1016/j.cub.2024.08.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 06/10/2024] [Accepted: 08/07/2024] [Indexed: 09/13/2024]
Abstract
Oxford ragwort (Senecio squalidus) is one of only two homoploid hybrid species known to have originated very recently, so it is a unique model for determining genomic changes and stabilization following homoploid hybrid speciation. Here, we provide a chromosome-level genome assembly of S. squalidus with 95% of the assembly contained in the 10 longest scaffolds, corresponding to its haploid chromosome number. We annotated 30,249 protein-coding genes and estimated that ∼62% of the genome consists of repetitive elements. We then characterized genome-wide patterns of linkage disequilibrium, polymorphism, and divergence in S. squalidus and its two parental species, finding that (1) linkage disequilibrium is highly heterogeneous, with a region on chromosome 4 showing increased values across all three species but especially in S. squalidus; (2) regions harboring genetic incompatibilities between the two parental species tend to be large, show reduced recombination, and have lower polymorphism in S. squalidus; (3) the two parental species have an unequal contribution (70:30) to the genome of S. squalidus, with long blocks of parent-specific ancestry supporting a very rapid stabilization of the hybrid lineage after hybrid formation; and (4) genomic regions with major parent ancestry exhibit an overrepresentation of loci with evidence for divergent selection occurring between the two parental species on Mount Etna. Our results show that both genetic incompatibilities and natural selection play a role in determining genome-wide reorganization following hybrid speciation and that patterns associated with homoploid hybrid speciation-typically seen in much older systems-can evolve very quickly following hybridization.
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Affiliation(s)
- Bruno Nevado
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK; cE3c, Centre for Ecology, Evolution and Environmental Changes & CHANGE - Global Change and Sustainability Institute, Faculty of Sciences, University of Lisbon, Lisbon 1749-016, Portugal; Department of Animal Biology, Faculty of Sciences, University of Lisbon, Lisbon 1749-016, Portugal.
| | - Mark A Chapman
- School of Biological Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Adrian C Brennan
- Biosciences Department, University of Durham, Durham DH1 3LE, UK
| | - James W Clark
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK; Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath BA2 7AY, UK
| | - Edgar L Y Wong
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Tom Batstone
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Bath BA2 7AY, UK
| | | | - Alan Tracey
- Wellcome Sanger Institute, Cambridge CB10 1SA, UK
| | | | - Ying Sims
- Wellcome Sanger Institute, Cambridge CB10 1SA, UK
| | - Richard J Abbott
- School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - Dmitry Filatov
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK
| | - Simon J Hiscock
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK; University of Oxford Botanic Garden and Arboretum, Rose Lane, Oxford OX1 4AZ, UK
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2
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Long Z, Rieseberg LH. Documenting homoploid hybrid speciation. Mol Ecol 2024:e17412. [PMID: 38780141 DOI: 10.1111/mec.17412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 04/11/2024] [Accepted: 04/30/2024] [Indexed: 05/25/2024]
Abstract
Homoploid hybrid speciation is challenging to document because hybridization can lead to outcomes other than speciation. Thus, some authors have argued that establishment of homoploid hybrid speciation should include evidence that reproductive barriers isolating the hybrid neo-species from its parental species were derived from hybridization. While this criterion is difficult to satisfy, several recent papers have successfully employed a common pipeline to identify candidate genes underlying such barriers and (in one case) to validate their function. We describe this pipeline, its application to several plant and animal species and what we have learned about homoploid hybrid speciation as a consequence. We argue that - given the ubiquity of admixture and the polygenic basis of reproductive isolation - homoploid hybrid speciation could be much more common and more protracted than suggested by earlier conceptual arguments and theoretical studies.
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Affiliation(s)
- Zhiqin Long
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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3
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Feller AF, Peichel CL, Seehausen O. Testing for a role of postzygotic incompatibilities in rapidly speciated Lake Victoria cichlids. Evolution 2024; 78:652-664. [PMID: 38288653 DOI: 10.1093/evolut/qpae007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/22/2023] [Accepted: 01/29/2024] [Indexed: 03/27/2024]
Abstract
Intrinsic postzygotic hybrid incompatibilities are usually due to negative epistatic interactions between alleles from different parental genomes. While such incompatibilities are thought to be uncommon in speciation with gene flow, they may be important if such speciation results from a hybrid population. Here we aimed to test this idea in the endemic cichlid fishes of Lake Victoria. Hundreds of species have evolved within the lake in <15k years from hybrid progenitors. While the importance of prezygotic barriers to gene flow is well established in this system, the possible relevance of postzygotic genetic incompatibilities is unknown. We inferred the presence of negative epistatic interactions from systematic patterns of genotype ratio distortions in experimental crosses and wild samples. We then compared the positions of putative incompatibility loci to regions of high genetic differentiation between sympatric sister species and between members of clades that may have arisen in the early history of this radiation, and further determined if the loci showed fixed differences between the closest living relatives of the lineages ancestral to the hybrid progenitors. Overall, we find little evidence for a major role of intrinsic postzygotic incompatibilities in the Lake Victoria radiation. However, we find putative incompatibility loci significantly more often coinciding with islands of genetic differentiation between species that separated early in the radiation than between the younger sister species, consistent with the hypothesis that such variants segregated in the hybrid swarm and were sorted between species in the early speciation events.
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Affiliation(s)
- Anna F Feller
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution and Biogeochemistry, Eawag Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States
- Arnold Arboretum of Harvard University, Boston, MA, United States
| | - Catherine L Peichel
- Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Ole Seehausen
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution and Biogeochemistry, Eawag Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
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4
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Bock DG, Cai Z, Elphinstone C, González-Segovia E, Hirabayashi K, Huang K, Keais GL, Kim A, Owens GL, Rieseberg LH. Genomics of plant speciation. PLANT COMMUNICATIONS 2023; 4:100599. [PMID: 37050879 PMCID: PMC10504567 DOI: 10.1016/j.xplc.2023.100599] [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: 01/26/2023] [Revised: 03/21/2023] [Accepted: 04/06/2023] [Indexed: 06/19/2023]
Abstract
Studies of plants have been instrumental for revealing how new species originate. For several decades, botanical research has complemented and, in some cases, challenged concepts on speciation developed via the study of other organisms while also revealing additional ways in which species can form. Now, the ability to sequence genomes at an unprecedented pace and scale has allowed biologists to settle decades-long debates and tackle other emerging challenges in speciation research. Here, we review these recent genome-enabled developments in plant speciation. We discuss complications related to identification of reproductive isolation (RI) loci using analyses of the landscape of genomic divergence and highlight the important role that structural variants have in speciation, as increasingly revealed by new sequencing technologies. Further, we review how genomics has advanced what we know of some routes to new species formation, like hybridization or whole-genome duplication, while casting doubt on others, like population bottlenecks and genetic drift. While genomics can fast-track identification of genes and mutations that confer RI, we emphasize that follow-up molecular and field experiments remain critical. Nonetheless, genomics has clarified the outsized role of ancient variants rather than new mutations, particularly early during speciation. We conclude by highlighting promising avenues of future study. These include expanding what we know so far about the role of epigenetic and structural changes during speciation, broadening the scope and taxonomic breadth of plant speciation genomics studies, and synthesizing information from extensive genomic data that have already been generated by the plant speciation community.
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Affiliation(s)
- Dan G Bock
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Zhe Cai
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Cassandra Elphinstone
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Eric González-Segovia
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | | | - Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Graeme L Keais
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Amy Kim
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Gregory L Owens
- Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
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5
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Wang D, Sun Y, Lei W, Zhu H, Wang J, Bi H, Feng S, Liu J, Ru D. Backcrossing to different parents produced two distinct hybrid species. Heredity (Edinb) 2023; 131:145-155. [PMID: 37264213 PMCID: PMC10382510 DOI: 10.1038/s41437-023-00630-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 05/23/2023] [Accepted: 05/23/2023] [Indexed: 06/03/2023] Open
Abstract
Repeated homoploid hybrid speciation (HHS) events with the same parental species have rarely been reported. In this study, we used population transcriptome data to test paraphyly and HHS events in the conifer Picea brachytyla. Our analyses revealed non-sister relationships for two lineages of P. brachytyla, with the southern lineage being placed within the re-circumscribed P. likiangensis species complex (PLSC) and P. brachytyla sensu stricto (s.s.) consisted solely of the northern lineage, forming a distinct clade that is paratactic to both the PLSC and P. wilsonii. Our phylogenetic and coalescent analyses suggested that P. brachytyla s.s. arose from HHS between the ancestor of the PLSC before its diversification and P. wilsonii through an intermediate hybrid lineage at an early stage and backcrossing to the ancestral PLSC. Additionally, P. purpurea shares the same parents and an extinct lineage with P. brachytyla s.s. but backcrossing to the other parent, P. wilsonii at a later stage. We reveal the first case that backcrossing to different parents of the same extinct hybrid lineage produced two different hybrid species. Our results highlight the existence of more reticulate evolution during species diversification in the spruce genus and more complex homoploid hybrid events than previously identified.
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Affiliation(s)
- Donglei Wang
- Key Laboratory for Bio-resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, PR China
| | - Yongshuai Sun
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China
| | - Weixiao Lei
- State Key Laboratory of Grassland Agro-ecosystem, College of Ecology, Lanzhou University, Lanzhou, 730000, China
| | - Hui Zhu
- State Key Laboratory of Grassland Agro-ecosystem, College of Ecology, Lanzhou University, Lanzhou, 730000, China
| | - Ji Wang
- Key Laboratory for Bio-resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, PR China
| | - Hao Bi
- Key Laboratory for Bio-resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, PR China
| | - Shuo Feng
- State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xi'ning, Qinghai, China
| | - Jianquan Liu
- Key Laboratory for Bio-resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, PR China.
- State Key Laboratory of Grassland Agro-ecosystem, College of Ecology, Lanzhou University, Lanzhou, 730000, China.
| | - Dafu Ru
- Key Laboratory for Bio-resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, PR China.
- State Key Laboratory of Grassland Agro-ecosystem, College of Ecology, Lanzhou University, Lanzhou, 730000, China.
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6
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Stull GW, Pham KK, Soltis PS, Soltis DE. Deep reticulation: the long legacy of hybridization in vascular plant evolution. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023; 114:743-766. [PMID: 36775995 DOI: 10.1111/tpj.16142] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 02/02/2023] [Accepted: 02/07/2023] [Indexed: 05/27/2023]
Abstract
Hybridization has long been recognized as a fundamental evolutionary process in plants but, until recently, our understanding of its phylogenetic distribution and biological significance across deep evolutionary scales has been largely obscure. Over the past decade, genomic and phylogenomic datasets have revealed, perhaps not surprisingly, that hybridization, often associated with polyploidy, has been common throughout the evolutionary history of plants, particularly in various lineages of flowering plants. However, phylogenomic studies have also highlighted the challenges of disentangling signals of ancient hybridization from other sources of genomic conflict (in particular, incomplete lineage sorting). Here, we provide a critical review of ancient hybridization in vascular plants, outlining well-documented cases of ancient hybridization across plant phylogeny, as well as the challenges unique to documenting ancient versus recent hybridization. We provide a definition for ancient hybridization, which, to our knowledge, has not been explicitly attempted before. Further documenting the extent of deep reticulation in plants should remain an important research focus, especially because published examples likely represent the tip of the iceberg in terms of the total extent of ancient hybridization. However, future research should increasingly explore the macroevolutionary significance of this process, in terms of its impact on evolutionary trajectories (e.g. how does hybridization influence trait evolution or the generation of biodiversity over long time scales?), as well as how life history and ecological factors shape, or have shaped, the frequency of hybridization across geologic time and plant phylogeny. Finally, we consider the implications of ubiquitous ancient hybridization for how we conceptualize, analyze, and classify plant phylogeny. Networks, as opposed to bifurcating trees, represent more accurate representations of evolutionary history in many cases, although our ability to infer, visualize, and use networks for comparative analyses is highly limited. Developing improved methods for the generation, visualization, and use of networks represents a critical future direction for plant biology. Current classification systems also do not generally allow for the recognition of reticulate lineages, and our classifications themselves are largely based on evidence from the chloroplast genome. Updating plant classification to better reflect nuclear phylogenies, as well as considering whether and how to recognize hybridization in classification systems, will represent an important challenge for the plant systematics community.
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Affiliation(s)
- Gregory W Stull
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20013, USA
| | - Kasey K Pham
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Pamela S Soltis
- Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611, USA
| | - Douglas E Soltis
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
- Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611, USA
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7
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Wong ELY, Nevado B, Hiscock SJ, Filatov DA. Rapid evolution of hybrid breakdown following recent divergence with gene flow in Senecio species on Mount Etna, Sicily. Heredity (Edinb) 2023; 130:40-52. [PMID: 36494489 PMCID: PMC9814926 DOI: 10.1038/s41437-022-00576-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 11/07/2022] [Accepted: 11/08/2022] [Indexed: 12/13/2022] Open
Abstract
How do nascent species evolve reproductive isolation during speciation with on-going gene flow? How do hybrid lineages become stabilised hybrid species? While commonly used genomic approaches provide an indirect way to identify species incompatibility factors, synthetic hybrids generated from interspecific crosses allow direct pinpointing of phenotypic traits involved in incompatibilities and the traits that are potentially adaptive in hybrid species. Here we report the analysis of phenotypic variation and hybrid breakdown in crosses between closely-related Senecio aethnensis and S. chrysanthemifolius, and their homoploid hybrid species, S. squalidus. The two former species represent a likely case of recent (<200 ky) speciation with gene flow driven by adaptation to contrasting conditions of high- and low-elevations on Mount Etna, Sicily. As these species form viable and fertile hybrids, it remains unclear whether they have started to evolve reproductive incompatibility. Our analysis represents the first study of phenotypic variation and hybrid breakdown involving multiple Senecio hybrid families. It revealed wide range of variation in multiple traits, including the traits previously unrecorded in synthetic hybrids. Leaf shape, highly distinct between S. aethnensis and S. chrysanthemifolius, was extremely variable in F2 hybrids, but more consistent in S. squalidus. Our study demonstrates that interspecific incompatibilities can evolve rapidly despite on-going gene flow between the species. Further work is necessary to understand the genetic bases of these incompatibilities and their role in speciation with gene flow.
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Affiliation(s)
- Edgar L. Y. Wong
- grid.4991.50000 0004 1936 8948Department of Biology, University of Oxford, Oxford, UK ,grid.507705.0Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
| | - Bruno Nevado
- grid.4991.50000 0004 1936 8948Department of Biology, University of Oxford, Oxford, UK ,grid.9983.b0000 0001 2181 4263Centre for Ecology, Evolution and Environmental Changes, University of Lisbon, Lisbon, Portugal
| | - Simon J. Hiscock
- grid.4991.50000 0004 1936 8948Department of Biology, University of Oxford, Oxford, UK ,Oxford Botanic Garden and Arboretum, Oxford, UK
| | - Dmitry A. Filatov
- grid.4991.50000 0004 1936 8948Department of Biology, University of Oxford, Oxford, UK
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Barone G, Domina G, Bartolucci F, Galasso G, Peruzzi L. A Nomenclatural and Taxonomic Revision of the Senecio squalidus Group (Asteraceae). PLANTS (BASEL, SWITZERLAND) 2022; 11:plants11192597. [PMID: 36235463 PMCID: PMC9572006 DOI: 10.3390/plants11192597] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 09/26/2022] [Accepted: 09/29/2022] [Indexed: 05/27/2023]
Abstract
Senecio squalidus (Asteraceae) currently includes nine subspecies distributed in North and Central Europe and in the Mediterranean basin. Within this taxonomic aggregate, many species have been described, but research on their nomenclatural types is incomplete. A complete nomenclatural survey of 19 names belonging to this taxonomically critical group was carried out. Fourteen lectotypes are here designated. The nomenclatural analysis, complemented by field investigations in the type localities of the taxa described in the Central Mediterranean, allowed us to accept 10 species. Accordingly, we proposed here a new name and a new missing combination at a specific level: S. aknoulensis and S. calabrus.
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Affiliation(s)
- Giulio Barone
- Department of Architecture, University of Palermo, Viale delle Scienze, bldg. 14., I-90128 Palermo, Italy
| | - Gianniantonio Domina
- Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze, bldg. 4., I-90128 Palermo, Italy
| | - Fabrizio Bartolucci
- Floristic Research Center of the Apennines, University of Camerino—Gran Sasso and Monti della Laga National Park, San Colombo, Barisciano, I-67021 L’Aquila, Italy
| | - Gabriele Galasso
- Section of Botany, Natural History Museum of Milan, Corso Venezia 55, I-20121 Milano, Italy
| | - Lorenzo Peruzzi
- PLANTSEED Lab, Department of Biology, University of Pisa, Via Luca Ghini 13., I-56126 Pisa, Italy
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9
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Shapiro JA. What we have learned about evolutionary genome change in the past 7 decades. Biosystems 2022; 215-216:104669. [DOI: 10.1016/j.biosystems.2022.104669] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/23/2022] [Accepted: 03/23/2022] [Indexed: 12/12/2022]
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10
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Wong ELY, Hiscock SJ, Filatov DA. The Role of Interspecific Hybridisation in Adaptation and Speciation: Insights From Studies in Senecio. FRONTIERS IN PLANT SCIENCE 2022; 13:907363. [PMID: 35812981 PMCID: PMC9260247 DOI: 10.3389/fpls.2022.907363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 06/03/2022] [Indexed: 05/08/2023]
Abstract
Hybridisation is well documented in many species, especially plants. Although hybrid populations might be short-lived and do not evolve into new lineages, hybridisaiton could lead to evolutionary novelty, promoting adaptation and speciation. The genus Senecio (Asteraceae) has been actively used to unravel the role of hybridisation in adaptation and speciation. In this article, we first briefly describe the process of hybridisation and the state of hybridisation research over the years. We then discuss various roles of hybridisation in plant adaptation and speciation illustrated with examples from different Senecio species, but also mention other groups of organisms whenever necessary. In particular, we focus on the genomic and transcriptomic consequences of hybridisation, as well as the ecological and physiological aspects from the hybrids' point of view. Overall, this article aims to showcase the roles of hybridisation in speciation and adaptation, and the research potential of Senecio, which is part of the ecologically and economically important family, Asteraceae.
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Affiliation(s)
- Edgar L. Y. Wong
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
- *Correspondence: Edgar L. Y. Wong,
| | - Simon J. Hiscock
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
- Oxford Botanic Garden and Arboretum, Oxford, United Kingdom
| | - Dmitry A. Filatov
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
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11
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12
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Triguero-Piñero P, de Vega C, Aparicio A, Albaladejo RG. Isolation of microsatellite markers for the endemic Phlomis lychnitis (Lamiaceae). Mol Biol Rep 2021; 48:8233-8238. [PMID: 34617241 DOI: 10.1007/s11033-021-06730-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/28/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND Phlomis lychnitis is a mostly endemic species of the Iberian Peninsula that frequently hybridizes with the narrow endemic P. crinita subsp. malacitana in southern Spain. Whenever they coexist they form homoploid hybrid zones. Unlike hybridization at the polyploid level, the process of hybridization at the homoploid level is much less well known. METHODS AND RESULTS In this study we report the development of 22 microsatellite markers through next-generation sequencing technologies for P. lychnitis. We characterize the genetic diversity for two populations of this species for the 10 markers that resulted to be polymorphic. Further, we check the transferability of these polymorphic markers to one population of P. crinita subsp. malacitana to verify the potential use of these markers for hybridization studies. The values of expected heterozygosity for P. lychnitis were higher than in P. crinita subsp. malacitana, and the three analyzed populations displayed negative values for the inbreeding coefficient which is compatible with the frequent instances of hybridization and introgression between species. CONCLUSIONS This set of polymorphic markers are useful for further studies aiming at a deeper understanding of the homoploid hybrid process between these species. Additionally, this is the first panel of microsatellite markers developed for the genus Phlomis, a genus very rich in endemic species and with medicinal properties that could benefit from the use of these new markers.
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Affiliation(s)
- Paloma Triguero-Piñero
- Departamento de Biología Vegetal y Ecología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González no 2, 41012, Seville, Spain
| | - Clara de Vega
- Departamento de Biología Vegetal y Ecología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González no 2, 41012, Seville, Spain
| | - Abelardo Aparicio
- Departamento de Biología Vegetal y Ecología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González no 2, 41012, Seville, Spain
| | - Rafael G Albaladejo
- Departamento de Biología Vegetal y Ecología, Facultad de Farmacia, Universidad de Sevilla, c/Profesor García González no 2, 41012, Seville, Spain.
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13
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Wang Z, Jiang Y, Bi H, Lu Z, Ma Y, Yang X, Chen N, Tian B, Liu B, Mao X, Ma T, DiFazio SP, Hu Q, Abbott RJ, Liu J. Hybrid speciation via inheritance of alternate alleles of parental isolating genes. MOLECULAR PLANT 2021; 14:208-222. [PMID: 33220509 DOI: 10.1016/j.molp.2020.11.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/11/2020] [Accepted: 11/13/2020] [Indexed: 05/21/2023]
Abstract
It is increasingly realized that homoploid hybrid speciation (HHS), which involves no change in chromosome number, is an important mechanism of speciation. HHS will likely increase in frequency as ecological and geographical barriers between species are continuing to be disrupted by human activities. HHS requires the establishment of reproductive isolation between a hybrid and its parents, but the underlying genes and genetic mechanisms remain largely unknown. In this study, we reveal by integrated approaches that reproductive isolation originates in one homoploid hybrid plant species through the inheritance of alternate alleles at genes that determine parental premating isolation. The parent species of this hybrid species are reproductively isolated by differences in flowering time and survivorship on soils containing high concentrations of iron. We found that the hybrid species inherits alleles of parental isolating major genes related to flowering time from one parent and alleles of major genes related to iron tolerance from the other parent. In this way, it became reproductively isolated from one parent by the difference in flowering time and from the other by habitat adaptation (iron tolerance). These findings and further modeling results suggest that HHS may occur relatively easily via the inheritance of alternate parental premating isolating genes and barriers.
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Affiliation(s)
- Zefu Wang
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Yuanzhong Jiang
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Hao Bi
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Zhiqiang Lu
- State Key Laboratory of Grassland Agro-Ecosystem, Innovation Institute of Ecology and Life Sciences, Lanzhou University, Lanzhou 730000, China; CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China
| | - Yazhen Ma
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Xiaoyue Yang
- State Key Laboratory of Grassland Agro-Ecosystem, Innovation Institute of Ecology and Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Ningning Chen
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Bin Tian
- State Key Laboratory of Grassland Agro-Ecosystem, Innovation Institute of Ecology and Life Sciences, Lanzhou University, Lanzhou 730000, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry and Grassland Administration, Southwest Forestry University, Kunming 650224, China
| | - Bingbing Liu
- Institute of Loess Plateau, Shanxi University, Taiyuan 030006, China
| | - Xingxing Mao
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Tao Ma
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China
| | - Stephen P DiFazio
- Department of Biology, West Virginia University, Morgantown, WV 25606, USA
| | - Quanjun Hu
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China.
| | - Richard J Abbott
- School of Biology, University of St Andrews, St Andrews KY16 9TH, UK.
| | - Jianquan Liu
- Key Laboratory for Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences & State Key Lab of Hydraulics & Mountain River Engineering, Sichuan University, Chengdu 610065, China; State Key Laboratory of Grassland Agro-Ecosystem, Innovation Institute of Ecology and Life Sciences, Lanzhou University, Lanzhou 730000, China.
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14
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Gao Y, Harris AJ, Li H, Gao X. Hybrid Speciation and Introgression Both Underlie the Genetic Structures and Evolutionary Relationships of Three Morphologically Distinct Species of Lilium (Liliaceae) Forming a Hybrid Zone Along an Elevational Gradient. FRONTIERS IN PLANT SCIENCE 2020; 11:576407. [PMID: 33365039 PMCID: PMC7750405 DOI: 10.3389/fpls.2020.576407] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 11/02/2020] [Indexed: 05/28/2023]
Abstract
We studied hybrid interactions of Lilium meleagrinum, Lilium gongshanense, and Lilium saluenense using an integrative approach combining population genetics, fieldwork, and phenological research. These three species occur along an elevational gradient, with L. meleagrinum occurring at lower elevations, L. saluenense at higher elevations, and L. gongshanense between them. The species show strong morphological differentiation despite there being no clear environmental barriers to gene flow among them. Lilium gongshanense is likely to have a hybrid origin based on our prior work, but its progenitors remain uncertain. We sought to determine whether gene flow occurs among these three parapatric species, and, if so, whether L. gongshanense is a hybrid of L. meleagrinum and/or L. saluenense. We analyzed data from multiple chloroplast genes and spacers, nuclear internal transcribed spacer (ITS), and 18 nuclear Expressed Sequence Tag-Simple Sequence Repeat (EST-SSR) microsatellites for accessions of the three species representing dense population-level sampling. We also inferred phenology by examining species in the field and using herbarium specimens. We found that there are only two types of chloroplast genomes shared among the three species and that L. gongshanense forms two distinct groups with closest links to other species of Lilium based on ITS. Taken together, L. gongshanense is unlikely to be a hybrid species resulting from a cross between L. meleagrinum and L. saluenense, but gene flow is occurring among the three species. The gene flow is likely to be rare according to evidence from all molecular datasets, and this is corroborated by detection of only one putative hybrid individual in the field and asynchronous phenology. We suspect that the rarity of hybridization events among the species facilitates their continued genetic separation.
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Affiliation(s)
- Yundong Gao
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - AJ Harris
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Huaicheng Li
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
- Institut für Biologie, Freie Universität Berlin, Berlin, Germany
| | - Xinfen Gao
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
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15
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Nevado B, Harris SA, Beaumont MA, Hiscock SJ. Rapid homoploid hybrid speciation in British gardens: The origin of Oxford ragwort (
Senecio squalidus
). Mol Ecol 2020; 29:4221-4233. [DOI: 10.1111/mec.15630] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 08/21/2020] [Accepted: 08/26/2020] [Indexed: 01/17/2023]
Affiliation(s)
- Bruno Nevado
- Department of Plant Sciences University of Oxford Oxford UK
| | | | | | - Simon J. Hiscock
- Department of Plant Sciences University of Oxford Oxford UK
- Oxford Botanic Garden and Arboretum Oxford UK
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16
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Sun Y, Lu Z, Zhu X, Ma H. Genomic basis of homoploid hybrid speciation within chestnut trees. Nat Commun 2020; 11:3375. [PMID: 32632155 PMCID: PMC7338469 DOI: 10.1038/s41467-020-17111-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 06/09/2020] [Indexed: 12/30/2022] Open
Abstract
Hybridization can drive speciation. We examine the hypothesis that Castanea henryi var. omeiensis is an evolutionary lineage that originated from hybridization between two near-sympatric diploid taxa, C. henryi var. henryi and C. mollissima. We produce a high-quality genome assembly for mollissima and characterize evolutionary relationships among related chestnut taxa. Our results show that C. henryi var. omeiensis has a mosaic genome but has accumulated divergence in all 12 chromosomes. We observe positive correlation between admixture proportions and recombination rates across the genome. Candidate barrier genomic regions, which isolate var. henryi and mollissima, are re-assorted in the hybrid lineage. We further find that the putative barrier segments concentrate in genomic regions with less recombination, suggesting that interaction between natural selection and recombination shapes the evolution of hybrid genomes during hybrid speciation. This study highlights that reassortment of parental barriers is an important mechanism in generating biodiversity. Chinese chestnut is widely cultivated for nut production and harbors value as a genetic resource for restoration of American and European chestnut trees destroyed by chestnut blight. Here, the authors reveal the genomic basis of homoploid hybrid speciation within Castanea spp. and find the nonrandom distribution of reproductive barrier loci based on a high-quality reference genome.
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Affiliation(s)
- Yongshuai Sun
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China. .,Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China.
| | - Zhiqiang Lu
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China.,Center for Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China
| | - Xingfu Zhu
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China
| | - Hui Ma
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China
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17
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Walter GM, Abbott RJ, Brennan AC, Bridle JR, Chapman M, Clark J, Filatov D, Nevado B, Ortiz-Barrientos D, Hiscock SJ. Senecio as a model system for integrating studies of genotype, phenotype and fitness. THE NEW PHYTOLOGIST 2020; 226:326-344. [PMID: 31951018 DOI: 10.1111/nph.16434] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 12/17/2019] [Indexed: 05/24/2023]
Abstract
Two major developments have made it possible to use examples of ecological radiations as model systems to understand evolution and ecology. First, the integration of quantitative genetics with ecological experiments allows detailed connections to be made between genotype, phenotype, and fitness in the field. Second, dramatic advances in molecular genetics have created new possibilities for integrating field and laboratory experiments with detailed genetic sequencing. Combining these approaches allows evolutionary biologists to better study the interplay between genotype, phenotype, and fitness to explore a wide range of evolutionary processes. Here, we present the genus Senecio (Asteraceae) as an excellent system to integrate these developments, and to address fundamental questions in ecology and evolution. Senecio is one of the largest and most phenotypically diverse genera of flowering plants, containing species ranging from woody perennials to herbaceous annuals. These Senecio species exhibit many growth habits, life histories, and morphologies, and they occupy a multitude of environments. Common within the genus are species that have hybridized naturally, undergone polyploidization, and colonized diverse environments, often through rapid phenotypic divergence and adaptive radiation. These diverse experimental attributes make Senecio an attractive model system in which to address a broad range of questions in evolution and ecology.
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Affiliation(s)
- Greg M Walter
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
| | - Richard J Abbott
- School of Biology, University of St Andrews, St Andrews, Fife, KY16 9TH, UK
| | - Adrian C Brennan
- School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE, UK
| | - Jon R Bridle
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
| | - Mark Chapman
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - James Clark
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Dmitry Filatov
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Bruno Nevado
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | | | - Simon J Hiscock
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
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18
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Abstract
Introgressive hybridization can affect the evolution of populations in several important ways. It may retard or reverse divergence of species, enable the development of novel traits, enhance the potential for future evolution by elevating levels of standing variation, create new species, and alleviate inbreeding depression in small populations. Most of what is known of contemporary hybridization in nature comes from the study of pairs of species, either coexisting in the same habitat or distributed parapatrically and separated by a hybrid zone. More rarely, three species form an interbreeding complex (triad), reported in vertebrates, insects, and plants. Often, one species acts as a genetic link or conduit for the passage of genes (alleles) between two others that rarely, if ever, hybridize. Demographic and genetic consequences are unknown. Here we report results of a long-term study of interbreeding Darwin's finches on Daphne Major island, Galápagos. Geospiza fortis acted as a conduit for the passage of genes between two others that have never been observed to interbreed on Daphne: Geospiza fuliginosa, a rare immigrant, and Geospiza scandens, a resident. Microsatellite gene flow from G. fortis into G. scandens increased in frequency during 30 y of favorable ecological conditions, resulting in genetic and morphological convergence. G. fortis, G. scandens, and the derived dihybrids and trihybrids experienced approximately equal fitness. Especially relevant to young adaptive radiations, where species differ principally in ecology and behavior, these findings illustrate how new combinations of genes created by hybridization among three species can enhance the potential for evolutionary change.
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19
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Wong ELY, Nevado B, Osborne OG, Papadopulos AST, Bridle JR, Hiscock SJ, Filatov DA. Strong divergent selection at multiple loci in two closely related species of ragworts adapted to high and low elevations on Mount Etna. Mol Ecol 2019; 29:394-412. [PMID: 31793091 DOI: 10.1111/mec.15319] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 11/28/2019] [Accepted: 11/28/2019] [Indexed: 12/20/2022]
Abstract
Recently diverged species present particularly informative systems for studying speciation and maintenance of genetic divergence in the face of gene flow. We investigated speciation in two closely related Senecio species, S. aethnensis and S. chrysanthemifolius, which grow at high and low elevations, respectively, on Mount Etna, Sicily and form a hybrid zone at intermediate elevations. We used a newly generated genome-wide single nucleotide polymorphism (SNP) dataset from 192 individuals collected over 18 localities along an elevational gradient to reconstruct the likely history of speciation, identify highly differentiated SNPs, and estimate the strength of divergent selection. We found that speciation in this system involved heterogeneous and bidirectional gene flow along the genome, and species experienced marked population size changes in the past. Furthermore, we identified highly-differentiated SNPs between the species, some of which are located in genes potentially involved in ecological differences between species (such as photosynthesis and UV response). We analysed the shape of these SNPs' allele frequency clines along the elevational gradient. These clines show significantly variable coincidence and concordance, indicative of the presence of multifarious selective forces. Selection against hybrids is estimated to be very strong (0.16-0.78) and one of the highest reported in literature. The combination of strong cumulative selection across the genome and previously identified intrinsic incompatibilities probably work together to maintain the genetic and phenotypic differentiation between these species - pointing to the importance of considering both intrinsic and extrinsic factors when studying divergence and speciation.
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Affiliation(s)
- Edgar L Y Wong
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Bruno Nevado
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Owen G Osborne
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | | | - Jon R Bridle
- School of Biological Sciences, University of Bristol, Bristol, UK
| | - Simon J Hiscock
- Department of Plant Sciences, University of Oxford, Oxford, UK
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