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Gaczorek TS, Marszałek M, Dudek K, Arntzen JW, Wielstra B, Babik W. Interspecific introgression of MHC genes in Triturus newts: Evidence from multiple contact zones. Mol Ecol 2023; 32:867-880. [PMID: 36458894 PMCID: PMC10108261 DOI: 10.1111/mec.16804] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 11/03/2022] [Accepted: 11/29/2022] [Indexed: 12/04/2022]
Abstract
The major histocompatibility complex (MHC) genes are central to the adaptive immune response in vertebrates. Selection generally maintains high MHC variation because the spectrum of recognized pathogens depends on MHC polymorphism. Novel alleles favoured by selection originate by interallelic recombination or de novo mutations but may also be acquired by introgression from related species. However, the extent and prevalence of MHC introgression remain an open question. In this study, we tested for MHC introgression in six hybrid zones formed by six Triturus newt species. We sequenced and genotyped the polymorphic second exons of the MHC class I and II genes and compared their interspecific similarity at various distances from the centre of the hybrid zone. We found evidence for introgression of both MHC classes in the majority of examined hybrid zones, with support for a more substantial class I introgression. Furthermore, the overall MHC allele sharing outside of hybrid zones was elevated between pairs of Triturus species with abutting ranges, regardless of the phylogenetic distance between them. No effect of past hybrid zone movement on MHC allele sharing was found. Finally, using previously published genome-wide data, we demonstrated that MHC introgression was more extensive than genome-wide introgression, supporting its adaptive potential. Our study thus provides evidence for the prevalence of MHC introgression across multiple Triturus hybrid zones, indicating that MHC introgression between divergent hybridizing species may be widespread and adaptive.
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Affiliation(s)
- Tomasz S Gaczorek
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
| | - Marzena Marszałek
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
| | - Katarzyna Dudek
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
| | - Jan W Arntzen
- Naturalis Biodiversity Center, Leiden, The Netherlands.,Institute of Biology, Leiden University, Leiden, The Netherlands
| | - Ben Wielstra
- Naturalis Biodiversity Center, Leiden, The Netherlands.,Institute of Biology, Leiden University, Leiden, The Netherlands
| | - Wiesław Babik
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
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2
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Million KM, Lively CM. Trans‐specific polymorphism and the convergent evolution of supertypes in major histocompatibility complex class II genes in darters (
Etheostoma
). Ecol Evol 2022; 12:e8485. [PMID: 36311547 PMCID: PMC9601779 DOI: 10.1002/ece3.8485] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 11/30/2021] [Accepted: 12/01/2021] [Indexed: 12/24/2022] Open
Abstract
Major Histocompatibility Complex (MHC) genes are one of the most polymorphic gene groups known in vertebrates. MHC genes also exhibit allelic variants that are shared among taxa, referred to as trans‐specific polymorphism (TSP). The role that selection plays in maintaining such high diversity within species, as well as TSP, is an ongoing discussion in biology. In this study, we used deep‐sequencing techniques to characterize MHC class IIb gene diversity in three sympatric species of darters. We found at least 5 copies of the MHC gene in darters, with 126 genetic variants encoding 122 unique amino acid sequences. We identified four supertypes based on the binding properties of proteins encoded by the sequences. Although each species had a unique pool of variants, many variants were shared between species pairs and across all three species. Phylogenetic analysis showed that the variants did not group together monophyletically based on species identity or on supertype. An expanded phylogenetic analysis showed that some darter alleles grouped together with alleles from other percid fishes. Our findings show that TSP occurs in darters, which suggests that balancing selection is acting at the genotype level. Supertypes, however, are most likely evolving convergently, as evidenced by the fact that alleles do not form monophyletic groups based on supertype. Our research demonstrates that selection may be acting differently on MHC genes at the genotype and supertype levels, selecting for the maintenance of high genotypic diversity while driving the convergent evolution of similar MHC phenotypes across different species.
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Affiliation(s)
- Kara M. Million
- Department of Biology Indiana University Bloomington Indiana USA
| | - Curtis M. Lively
- Department of Biology Indiana University Bloomington Indiana USA
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3
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Moran BM, Payne C, Langdon Q, Powell DL, Brandvain Y, Schumer M. The genomic consequences of hybridization. eLife 2021; 10:e69016. [PMID: 34346866 PMCID: PMC8337078 DOI: 10.7554/elife.69016] [Citation(s) in RCA: 84] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 07/09/2021] [Indexed: 12/29/2022] Open
Abstract
In the past decade, advances in genome sequencing have allowed researchers to uncover the history of hybridization in diverse groups of species, including our own. Although the field has made impressive progress in documenting the extent of natural hybridization, both historical and recent, there are still many unanswered questions about its genetic and evolutionary consequences. Recent work has suggested that the outcomes of hybridization in the genome may be in part predictable, but many open questions about the nature of selection on hybrids and the biological variables that shape such selection have hampered progress in this area. We synthesize what is known about the mechanisms that drive changes in ancestry in the genome after hybridization, highlight major unresolved questions, and discuss their implications for the predictability of genome evolution after hybridization.
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Affiliation(s)
- Benjamin M Moran
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
| | - Cheyenne Payne
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
| | - Quinn Langdon
- Department of Biology, Stanford UniversityStanfordUnited States
| | - Daniel L Powell
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
| | - Yaniv Brandvain
- Department of Ecology, Evolution & Behavior and Plant and Microbial Biology, University of MinnesotaMinneapolisUnited States
| | - Molly Schumer
- Department of Biology, Stanford UniversityStanfordUnited States
- Centro de Investigaciones Científicas de las Huastecas “Aguazarca”HidalgoMexico
- Hanna H. Gray Fellow, Howard Hughes Medical InstituteStanfordUnited States
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4
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Rendón-Anaya M, Wilson J, Sveinsson S, Fedorkov A, Cottrell J, Bailey MES, Ruņģis D, Lexer C, Jansson S, Robinson KM, Street NR, Ingvarsson PK. Adaptive introgression facilitate adaptation to high latitudes in European aspen (Populus tremula L.). Mol Biol Evol 2021; 38:5034-5050. [PMID: 34329481 PMCID: PMC8557470 DOI: 10.1093/molbev/msab229] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Understanding local adaptation has become a key research area given the ongoing climate challenge and the concomitant requirement to conserve genetic resources. Perennial plants, such as forest trees, are good models to study local adaptation given their wide geographic distribution, largely outcrossing mating systems, and demographic histories. We evaluated signatures of local adaptation in European aspen (Populus tremula) across Europe by means of whole-genome resequencing of a collection of 411 individual trees. We dissected admixture patterns between aspen lineages and observed a strong genomic mosaicism in Scandinavian trees, evidencing different colonization trajectories into the peninsula from Russia, Central and Western Europe. As a consequence of the secondary contacts between populations after the last glacial maximum, we detected an adaptive introgression event in a genome region of ∼500 kb in chromosome 10, harboring a large-effect locus that has previously been shown to contribute to adaptation to the short growing seasons characteristic of Northern Scandinavia. Demographic simulations and ancestry inference suggest an Eastern origin—probably Russian—of the adaptive Nordic allele which nowadays is present in a homozygous state at the north of Scandinavia. The strength of introgression and positive selection signatures in this region is a unique feature in the genome. Furthermore, we detected signals of balancing selection, shared across regional populations, that highlight the importance of standing variation as a primary source of alleles that facilitate local adaptation. Our results, therefore, emphasize the importance of migration–selection balance underlying the genetic architecture of key adaptive quantitative traits.
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Affiliation(s)
- Martha Rendón-Anaya
- Linnean Centre for Plant Biology, Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Science, Uppsala, Sweden
| | - Jonathan Wilson
- Linnean Centre for Plant Biology, Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Science, Uppsala, Sweden
| | | | - Aleksey Fedorkov
- Institute of Biology, Komi Science Center, Russian Academy of Sciences, Syktyvkar, Russia
| | - Joan Cottrell
- Forest Research, Northern Research Station, Roslin, UK
| | - Mark E S Bailey
- School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Dainis Ruņģis
- Genetic Resource Centre, Latvian State Forest Research Institute "Silava", LV2169 Salaspils, Latvia
| | - Christian Lexer
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Stefan Jansson
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - Kathryn M Robinson
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - Nathaniel R Street
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - Pär K Ingvarsson
- Linnean Centre for Plant Biology, Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Science, Uppsala, Sweden
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5
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Hybridization increases population variation during adaptive radiation. Proc Natl Acad Sci U S A 2019; 116:23216-23224. [PMID: 31659024 DOI: 10.1073/pnas.1913534116] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Adaptive radiations are prominent components of the world's biodiversity. They comprise many species derived from one or a small number of ancestral species in a geologically short time that have diversified into a variety of ecological niches. Several authors have proposed that introgressive hybridization has been important in the generation of new morphologies and even new species, but how that happens throughout evolutionary history is not known. Interspecific gene exchange is expected to have greatest impact on variation if it occurs after species have diverged genetically and phenotypically but before genetic incompatibilities arise. We use a dated phylogeny to infer that populations of Darwin's finches in the Galápagos became more variable in morphological traits through time, consistent with the hybridization hypothesis, and then declined in variation after reaching a peak. Some species vary substantially more than others. Phylogenetic inferences of hybridization are supported by field observations of contemporary hybridization. Morphological effects of hybridization have been investigated on the small island of Daphne Major by documenting changes in hybridizing populations of Geospiza fortis and Geospiza scandens over a 30-y period. G. scandens showed more evidence of admixture than G. fortis Beaks of G. scandens became progressively blunter, and while variation in length increased, variation in depth decreased. These changes imply independent effects of introgression on 2, genetically correlated, beak dimensions. Our study shows how introgressive hybridization can alter ecologically important traits, increase morphological variation as a radiation proceeds, and enhance the potential for future evolution in changing environments.
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Abstract
In this perspective, we evaluate the explanatory power of the neutral theory of molecular evolution, 50 years after its introduction by Kimura. We argue that the neutral theory was supported by unreliable theoretical and empirical evidence from the beginning, and that in light of modern, genome-scale data, we can firmly reject its universality. The ubiquity of adaptive variation both within and between species means that a more comprehensive theory of molecular evolution must be sought.
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Affiliation(s)
- Andrew D Kern
- Department of Genetics, Rutgers University, Piscataway, NJ
| | - Matthew W Hahn
- Department of Biology and Department of Computer Science, Indiana University Bloomington, IN
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7
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Koenig D, Hagmann J, Li R, Bemm F, Slotte T, Neuffer B, Wright SI, Weigel D. Long-term balancing selection drives evolution of immunity genes in Capsella. eLife 2019; 8:e43606. [PMID: 30806624 PMCID: PMC6426441 DOI: 10.7554/elife.43606] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 02/26/2019] [Indexed: 12/14/2022] Open
Abstract
Genetic drift is expected to remove polymorphism from populations over long periods of time, with the rate of polymorphism loss being accelerated when species experience strong reductions in population size. Adaptive forces that maintain genetic variation in populations, or balancing selection, might counteract this process. To understand the extent to which natural selection can drive the retention of genetic diversity, we document genomic variability after two parallel species-wide bottlenecks in the genus Capsella. We find that ancestral variation preferentially persists at immunity related loci, and that the same collection of alleles has been maintained in different lineages that have been separated for several million years. By reconstructing the evolution of the disease-related locus MLO2b, we find that divergence between ancient haplotypes can be obscured by referenced based re-sequencing methods, and that trans-specific alleles can encode substantially diverged protein sequences. Our data point to long-term balancing selection as an important factor shaping the genetics of immune systems in plants and as the predominant driver of genomic variability after a population bottleneck.
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Affiliation(s)
- Daniel Koenig
- Department of Molecular BiologyMax Planck Institute for Developmental BiologyTübingenGermany
| | - Jörg Hagmann
- Department of Molecular BiologyMax Planck Institute for Developmental BiologyTübingenGermany
| | - Rachel Li
- Department of Molecular BiologyMax Planck Institute for Developmental BiologyTübingenGermany
| | - Felix Bemm
- Department of Molecular BiologyMax Planck Institute for Developmental BiologyTübingenGermany
| | - Tanja Slotte
- Department of Ecology,Environment, and Plant SciencesStockholm UniversityStockholmSweden
| | - Barbara Neuffer
- Department of BiologyUniversity of OsnabrückOsnabrückGermany
| | - Stephen I Wright
- Department of Ecology and Evolutionary BiologyUniversity of TorontoTorontoCanada
| | - Detlef Weigel
- Department of Molecular BiologyMax Planck Institute for Developmental BiologyTübingenGermany
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8
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Mable BK, Brysting AK, Jørgensen MH, Carbonell AKZ, Kiefer C, Ruiz-Duarte P, Lagesen K, Koch MA. Adding Complexity to Complexity: Gene Family Evolution in Polyploids. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00114] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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9
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Nevado B, Contreras-Ortiz N, Hughes C, Filatov DA. Pleistocene glacial cycles drive isolation, gene flow and speciation in the high-elevation Andes. THE NEW PHYTOLOGIST 2018; 219:779-793. [PMID: 29862512 DOI: 10.1111/nph.15243] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/30/2018] [Indexed: 05/10/2023]
Abstract
Mountain ranges are amongst the most species-rich habitats, with many large and rapid evolutionary radiations. The tempo and mode of diversification in these systems are key unanswered questions in evolutionary biology. Here we study the Andean Lupinus radiation to understand the processes driving very rapid diversification in montane systems. We use genomic and transcriptomic data of multiple species and populations, and apply phylogenomic and demographic analyses to test whether diversification proceeded without interspecific gene flow - as expected if Andean orogeny and geographic isolation were the main drivers of diversification - or if diversification was accompanied by gene flow, in which case other processes were probably involved. We uncover several episodes of gene flow between species, including very recent events likely to have been prompted by changes in habitat connectivity during Pleistocene glacial cycles. Furthermore, we find that gene flow between species was heterogeneously distributed across the genome. We argue that exceptionally fast diversification of Andean Lupinus was partly a result of Late Pleistocene glacial cycles, with associated cycles of expansion and contraction driving geographic isolation or secondary contact of species. Furthermore, heterogeneous gene flow across the genome suggests a role for selection and ecological speciation in rapid diversification in this system.
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Affiliation(s)
- Bruno Nevado
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Natalia Contreras-Ortiz
- Laboratorio de Botánica y Sistemática, Departamento de Ciencias Biológicas, Universidad de los Andes, Apartado Aéreo, 4976, Bogotá, Colombia
- Jardín Botánico de Bogotá 'José Celestino Mutis', Avenida Calle 63 No. 68-95, Bogotá DC, Colombia
| | - Colin Hughes
- Department of Systematic & Evolutionary Botany, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland
| | - Dmitry A Filatov
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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10
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Schrider DR, Ayroles J, Matute DR, Kern AD. Supervised machine learning reveals introgressed loci in the genomes of Drosophila simulans and D. sechellia. PLoS Genet 2018; 14:e1007341. [PMID: 29684059 PMCID: PMC5933812 DOI: 10.1371/journal.pgen.1007341] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 05/03/2018] [Accepted: 03/28/2018] [Indexed: 12/30/2022] Open
Abstract
Hybridization and gene flow between species appears to be common. Even though it is clear that hybridization is widespread across all surveyed taxonomic groups, the magnitude and consequences of introgression are still largely unknown. Thus it is crucial to develop the statistical machinery required to uncover which genomic regions have recently acquired haplotypes via introgression from a sister population. We developed a novel machine learning framework, called FILET (Finding Introgressed Loci via Extra-Trees) capable of revealing genomic introgression with far greater power than competing methods. FILET works by combining information from a number of population genetic summary statistics, including several new statistics that we introduce, that capture patterns of variation across two populations. We show that FILET is able to identify loci that have experienced gene flow between related species with high accuracy, and in most situations can correctly infer which population was the donor and which was the recipient. Here we describe a data set of outbred diploid Drosophila sechellia genomes, and combine them with data from D. simulans to examine recent introgression between these species using FILET. Although we find that these populations may have split more recently than previously appreciated, FILET confirms that there has indeed been appreciable recent introgression (some of which might have been adaptive) between these species, and reveals that this gene flow is primarily in the direction of D. simulans to D. sechellia. Understanding the extent to which species or diverged populations hybridize in nature is crucially important if we are to understand the speciation process. Accordingly numerous research groups have developed methodology for finding the genetic evidence of such introgression. In this report we develop a supervised machine learning approach for uncovering loci which have introgressed across species boundaries. We show that our method, FILET, has greater accuracy and power than competing methods in discovering introgression, and in addition can detect the directionality associated with the gene flow between species. Using whole genome sequences from Drosophila simulans and Drosophila sechellia we show that FILET discovers quite extensive introgression between these species that has occurred mostly from D. simulans to D. sechellia. Our work highlights the complex process of speciation even within a well-studied system and points to the growing importance of supervised machine learning in population genetics.
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Affiliation(s)
- Daniel R. Schrider
- Department of Genetics, Rutgers University, Piscataway, New Jersey, United States of America
- Human Genetics Institute of New Jersey, Rutgers University, Piscataway, New Jersey, United States of America
- * E-mail:
| | - Julien Ayroles
- Ecology and Evolutionary Biology Department, Princeton University, Princeton, New Jersey, United States of America
- Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Daniel R. Matute
- Biology Department, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Andrew D. Kern
- Department of Genetics, Rutgers University, Piscataway, New Jersey, United States of America
- Human Genetics Institute of New Jersey, Rutgers University, Piscataway, New Jersey, United States of America
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