1
|
Soboleva ES, Kirilenko KM, Fedorova VS, Kokhanenko AA, Artemov GN, Sharakhov IV. Two Nested Inversions in the X Chromosome Differentiate the Dominant Malaria Vectors in Europe, Anopheles atroparvus and Anopheles messeae. INSECTS 2024; 15:312. [PMID: 38786868 PMCID: PMC11122324 DOI: 10.3390/insects15050312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/25/2024]
Abstract
The Maculipennis subgroup of malaria mosquitoes includes both dominant malaria vectors and non-vectors in Eurasia. Understanding the genetic factors, particularly chromosomal inversions, that differentiate Anopheles species can provide valuable insights for vector control strategies. Although autosomal inversions between the species in this subgroup have been characterized based on the chromosomal banding patterns, the number and positions of rearrangements in the X chromosome remain unclear due to the divergent banding patterns. Here, we identified two large X chromosomal inversions, approximately 13 Mb and 10 Mb in size, using fluorescence in situ hybridization. The inversion breakpoint regions were mapped by hybridizing 53 gene markers with polytene chromosomes of An. messeae. The DNA probes were designed based on gene sequences from the annotated An. atroparvus genome. The two nested inversions resulted in five syntenic blocks. Only two small syntenic blocks, which encompass 181 annotated genes in the An. atroparvus genome, changed their position and orientation in the X chromosome. The analysis of the An. atroparvus genome revealed an enrichment of gene ontology terms associated with immune system and mating behavior in the rearranged syntenic blocks. Additionally, the enrichment of DNA transposons was found in sequences homologous to three of the four breakpoint regions. This study demonstrates the successful application of the physical genome mapping approach to identify rearrangements that differentiate species in insects with polytene chromosomes.
Collapse
Affiliation(s)
- Evgenia S. Soboleva
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 36 Lenin Avenue, Tomsk 634050, Russia
| | - Kirill M. Kirilenko
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 36 Lenin Avenue, Tomsk 634050, Russia
| | - Valentina S. Fedorova
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 36 Lenin Avenue, Tomsk 634050, Russia
| | - Alina A. Kokhanenko
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 36 Lenin Avenue, Tomsk 634050, Russia
| | - Gleb N. Artemov
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 36 Lenin Avenue, Tomsk 634050, Russia
| | - Igor V. Sharakhov
- Laboratory of Ecology, Genetics and Environmental Protection, Tomsk State University, 36 Lenin Avenue, Tomsk 634050, Russia
- Department of Entomology, the Fralin Life Sciences Institute, Virginia Polytechnic Institute and State University, 360 West Campus Drive, Blacksburg, VA 24061, USA
| |
Collapse
|
2
|
Carpinteyro-Ponce J, Machado CA. The Complex Landscape of Structural Divergence Between the Drosophila pseudoobscura and D. persimilis Genomes. Genome Biol Evol 2024; 16:evae047. [PMID: 38482945 PMCID: PMC10980976 DOI: 10.1093/gbe/evae047] [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] [Accepted: 03/07/2024] [Indexed: 04/01/2024] Open
Abstract
Structural genomic variants are key drivers of phenotypic evolution. They can span hundreds to millions of base pairs and can thus affect large numbers of genetic elements. Although structural variation is quite common within and between species, its characterization depends upon the quality of genome assemblies and the proportion of repetitive elements. Using new high-quality genome assemblies, we report a complex and previously hidden landscape of structural divergence between the genomes of Drosophila persimilis and D. pseudoobscura, two classic species in speciation research, and study the relationships among structural variants, transposable elements, and gene expression divergence. The new assemblies confirm the already known fixed inversion differences between these species. Consistent with previous studies showing higher levels of nucleotide divergence between fixed inversions relative to collinear regions of the genome, we also find a significant overrepresentation of INDELs inside the inversions. We find that transposable elements accumulate in regions with low levels of recombination, and spatial correlation analyses reveal a strong association between transposable elements and structural variants. We also report a strong association between differentially expressed (DE) genes and structural variants and an overrepresentation of DE genes inside the fixed chromosomal inversions that separate this species pair. Interestingly, species-specific structural variants are overrepresented in DE genes involved in neural development, spermatogenesis, and oocyte-to-embryo transition. Overall, our results highlight the association of transposable elements with structural variants and their importance in driving evolutionary divergence.
Collapse
Affiliation(s)
| | - Carlos A Machado
- Department of Biology, University of Maryland, College Park, MD, USA
| |
Collapse
|
3
|
Li H, Berent E, Hadjipanteli S, Galey M, Muhammad-Lahbabi N, Miller DE, Crown KN. Heterozygous inversion breakpoints suppress meiotic crossovers by altering recombination repair outcomes. PLoS Genet 2023; 19:e1010702. [PMID: 37053290 PMCID: PMC10128924 DOI: 10.1371/journal.pgen.1010702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 04/25/2023] [Accepted: 03/15/2023] [Indexed: 04/15/2023] Open
Abstract
Heterozygous chromosome inversions suppress meiotic crossover (CO) formation within an inversion, potentially because they lead to gross chromosome rearrangements that produce inviable gametes. Interestingly, COs are also severely reduced in regions nearby but outside of inversion breakpoints even though COs in these regions do not result in rearrangements. Our mechanistic understanding of why COs are suppressed outside of inversion breakpoints is limited by a lack of data on the frequency of noncrossover gene conversions (NCOGCs) in these regions. To address this critical gap, we mapped the location and frequency of rare CO and NCOGC events that occurred outside of the dl-49 chrX inversion in D. melanogaster. We created full-sibling wildtype and inversion stocks and recovered COs and NCOGCs in the syntenic regions of both stocks, allowing us to directly compare rates and distributions of recombination events. We show that COs outside of the proximal inversion breakpoint are distributed in a distance-dependent manner, with strongest suppression near the inversion breakpoint. We find that NCOGCs occur evenly throughout the chromosome and, importantly, are not suppressed near inversion breakpoints. We propose a model in which COs are suppressed by inversion breakpoints in a distance-dependent manner through mechanisms that influence DNA double-strand break repair outcome but not double-strand break formation. We suggest that subtle changes in the synaptonemal complex and chromosome pairing might lead to unstable interhomolog interactions during recombination that permits NCOGC formation but not CO formation.
Collapse
Affiliation(s)
- Haosheng Li
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Erica Berent
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Savannah Hadjipanteli
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Miranda Galey
- Division of Genetic Medicine, Department of Pediatrics, University of Washington and Seattle Children's Hospital, Seattle, Washington, United States of America
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, United States of America
| | - Nigel Muhammad-Lahbabi
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Danny E Miller
- Division of Genetic Medicine, Department of Pediatrics, University of Washington and Seattle Children's Hospital, Seattle, Washington, United States of America
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, Washington, United States of America
- Brotman Baty Institute for Precision Medicine, University of Washington, Seattle, Washington, United States of America
| | - K Nicole Crown
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| |
Collapse
|
4
|
Ferreira PHN, Souza FHS, de Moraes RL, Perez MF, Sassi FDMC, Viana PF, Feldberg E, Ezaz T, Liehr T, Bertollo LAC, Cioffi MDB. The Genetic Differentiation of Pyrrhulina (Teleostei, Characiformes) Species is Likely Influenced by Both Geographical Distribution and Chromosomal Rearrangements. Front Genet 2022; 13:869073. [PMID: 35601496 PMCID: PMC9114635 DOI: 10.3389/fgene.2022.869073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
Allopatry is generally considered to be one of the main contributors to the remarkable Neotropical biodiversity. However, the role of chromosomal rearrangements including neo-sex chromosomes for genetic diversity is still poorly investigated and understood. Here, we assess the genetic divergence in five Pyrrhulina species using population genomics and combined the results with previously obtained cytogenetic data, highlighting that molecular genetic diversity is consistent with their chromosomal features. The results of a principal coordinate analysis (PCoA) indicated a clear difference among all species while showing a closer relationship of the ones located in the same geographical region. This was also observed in genetic structure analyses that only grouped P. australis and P. marilynae, which were also recovered as sister species in a species tree analysis. We observed a contradictory result for the relationships among the three species from the Amazon basin, as the phylogenetic tree suggested P. obermulleri and P. semifasciata as sister species, while the PCoA showed a high genetic difference between P. semifasciata and all other species. These results suggest a potential role of sex-related chromosomal rearrangements as reproductive barriers between these species.
Collapse
Affiliation(s)
- Pedro H. N. Ferreira
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Fernando H. S. Souza
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Renata L. de Moraes
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Manolo F. Perez
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Francisco de M. C. Sassi
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Patrik F. Viana
- Laboratório de Genética Animal, Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil
| | - Eliana Feldberg
- Laboratório de Genética Animal, Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, NSW, Australia
| | - Thomas Liehr
- Institute of Human Genetics, Friedrich Schiller University, University Hospital Jena, Jena, Germany
- *Correspondence: Thomas Liehr,
| | - Luiz A. C. Bertollo
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Marcelo de B. Cioffi
- Laboratório de Citogenética de Peixes, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| |
Collapse
|
5
|
Korunes KL, Machado CA, Noor MAF. Inversions shape the divergence of Drosophila pseudoobscura and Drosophila persimilis on multiple timescales. Evolution 2021; 75:1820-1834. [PMID: 34041743 DOI: 10.1111/evo.14278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/03/2021] [Accepted: 05/17/2021] [Indexed: 02/02/2023]
Abstract
By shaping meiotic recombination, chromosomal inversions can influence genetic exchange between hybridizing species. Despite the recognized importance of inversions in evolutionary processes such as divergence and speciation, teasing apart the effects of inversions over time remains challenging. For example, are their effects on sequence divergence primarily generated through creating blocks of linkage disequilibrium prespeciation or through preventing gene flux after speciation? We provide a comprehensive look into the influence of inversions on gene flow throughout the evolutionary history of a classic system: Drosophila pseudoobscura and Drosophila persimilis. We use extensive whole-genome sequence data to report patterns of introgression and divergence with respect to chromosomal arrangements. Overall, we find evidence that inversions have contributed to divergence patterns between D. pseudoobscura and D. persimilis over three distinct timescales: (1) segregation of ancestral polymorphism early in the speciation process, (2) gene flow after the split of D. pseudoobscura and D. persimilis, but prior to the split of D. pseudoobscura subspecies, and (3) recent gene flow between sympatric D. pseudoobscura and D. persimilis, after the split of D. pseudoobscura subspecies. We discuss these results in terms of our understanding of evolution in this classic system and provide cautions for interpreting divergence measures in other systems.
Collapse
Affiliation(s)
- Katharine L Korunes
- Department of Evolutionary Anthropology, Duke University, Durham, North Carolina, 27708
| | - Carlos A Machado
- Department of Biology, University of Maryland, College Park, Maryland, 20742
| | - Mohamed A F Noor
- Department of Biology, Duke University, Durham, North Carolina, 27708
| |
Collapse
|
6
|
Hill T, Unckless RL. Adaptation, ancestral variation and gene flow in a 'Sky Island' Drosophila species. Mol Ecol 2021; 30:83-99. [PMID: 33089581 PMCID: PMC7945764 DOI: 10.1111/mec.15701] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 09/28/2020] [Accepted: 10/08/2020] [Indexed: 02/06/2023]
Abstract
Over time, populations of species can expand, contract, fragment and become isolated, creating subpopulations that must adapt to local conditions. Understanding how species maintain variation after divergence as well as adapt to these changes in the face of gene flow is of great interest, especially as the current climate crisis has caused range shifts and frequent migrations for many species. Here, we characterize how a mycophageous fly species, Drosophila innubila, came to inhabit and adapt to its current range which includes mountain forests in south-western USA separated by large expanses of desert. Using population genomic data from more than 300 wild-caught individuals, we examine four populations to determine their population history in these mountain forests, looking for signatures of local adaptation. In this first extensive study, establishing D. innubila as a key genomic "Sky Island" model, we find D. innubila spread northwards during the previous glaciation period (30-100 KYA) and have recently expanded even further (0.2-2 KYA). D. innubila shows little evidence of population structure, consistent with a recent establishment and genetic variation maintained since before geographic stratification. We also find some signatures of recent selective sweeps in chorion proteins and population differentiation in antifungal immune genes suggesting differences in the environments to which flies are adapting. However, we find little support for long-term recurrent selection in these genes. In contrast, we find evidence of long-term recurrent positive selection in immune pathways such as the Toll signalling system and the Toll-regulated antimicrobial peptides.
Collapse
Affiliation(s)
- Tom Hill
- 4055 Haworth Hall, The Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045
| | - Robert L. Unckless
- 4055 Haworth Hall, The Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045
| |
Collapse
|
7
|
Fuller ZL, Koury SA, Leonard CJ, Young RE, Ikegami K, Westlake J, Richards S, Schaeffer SW, Phadnis N. Extensive Recombination Suppression and Epistatic Selection Causes Chromosome-Wide Differentiation of a Selfish Sex Chromosome in Drosophila pseudoobscura. Genetics 2020; 216:205-226. [PMID: 32732371 PMCID: PMC7463281 DOI: 10.1534/genetics.120.303460] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 07/27/2020] [Indexed: 11/18/2022] Open
Abstract
Sex-Ratio (SR) chromosomes are selfish X-chromosomes that distort Mendelian segregation and are commonly associated with inversions. These chromosomal rearrangements suppress recombination with Standard (ST) X-chromosomes and are hypothesized to maintain multiple alleles important for distortion in a single large haplotype. Here, we conduct a multifaceted study of the multiply inverted Drosophila pseudoobscura SR chromosome to understand the evolutionary history, genetic architecture, and present-day dynamics that shape this enigmatic selfish chromosome. The D. pseudoobscura SR chromosome has three nonoverlapping inversions of the right arm of the metacentric X-chromosome: basal, medial, and terminal. We find that 23 of 29 Mb of the D. pseudoobscuraX-chromosome right arm is highly differentiated between the Standard and SR arrangements, including a 6.6 Mb collinear region between the medial and terminal inversions. Although crossing-over is heavily suppressed on this chromosome arm, we discover it is not completely eliminated, with measured rates indicating recombination suppression alone cannot explain patterns of differentiation or the near-perfect association of the three SR chromosome inversions in nature. We then demonstrate the ancient basal and medial inversions of the SR chromosome contain genes sufficient to cause weak distortion. In contrast, the younger terminal inversion cannot distort by itself, but contains at least one modifier gene necessary for full manifestation of strong sex chromosome distortion. By parameterizing population genetic models for chromosome-wide linkage disequilibrium with our experimental results, we infer that strong selection acts to maintain the near-perfect association of SR chromosome inversions in present-day populations. Based on comparative genomic analyses, direct recombination experiments, segregation distortion assays, and population genetic modeling, we conclude the combined action of suppressed recombination and strong, ongoing, epistatic selection shape the D. pseudoobscura SR arrangement into a highly differentiated chromosome.
Collapse
Affiliation(s)
- Zachary L Fuller
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
- Department of Biological Sciences, Columbia University, New York, New York 10027
| | - Spencer A Koury
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | | | - Randee E Young
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
- Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706
| | - Kobe Ikegami
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Jonathan Westlake
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Stephen Richards
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, Texas 77030
| | - Stephen W Schaeffer
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Nitin Phadnis
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| |
Collapse
|
8
|
Jewell CP, Zhang SV, Gibson MJS, Tovar-Méndez A, McClure B, Moyle LC. Intraspecific Genetic Variation Underlying Postmating Reproductive Barriers between Species in the Wild Tomato Clade (Solanum sect. Lycopersicon). J Hered 2020; 111:216-226. [PMID: 32072169 DOI: 10.1093/jhered/esaa003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 02/11/2020] [Indexed: 12/29/2022] Open
Abstract
A goal of speciation genetics is to understand how the genetic components underlying interspecific reproductive barriers originate within species. Unilateral incompatibility (UI) is a postmating prezygotic barrier in which pollen rejection in the female reproductive tract (style) occurs in only one direction of an interspecific cross. Natural variation in the strength of UI has been observed among populations within species in the wild tomato clade. In some cases, molecular loci underlying self-incompatibility (SI) are associated with this variation in UI, but the mechanistic connection between these intra- and inter-specific pollen rejection behaviors is poorly understood in most instances. We generated an F2 population between SI and SC genotypes of a single species, Solanum pennellii, to examine the genetic basis of intraspecific variation in UI against other species, and to determine whether loci underlying SI are genetically associated with this variation. We found that F2 individuals vary in the rate at which UI rejection occurs. One large effect QTL detected for this trait co-localized with the SI-determining S-locus. Moreover, individuals that expressed S-RNase-the S-locus protein involved in SI pollen rejection-in their styles had much more rapid UI responses compared with those without S-RNase protein. Our analysis shows that intraspecific variation at mate choice loci-in this case at loci that prevent self-fertilization-can contribute to variation in the expression of interspecific isolation, including postmating prezygotic barriers. Understanding the nature of such intraspecific variation can provide insight into the accumulation of these barriers between diverging lineages.
Collapse
Affiliation(s)
| | - Simo V Zhang
- Department of Biology, Indiana University, Bloomington, IN
| | | | | | - Bruce McClure
- Department of Biochemistry, University of Missouri, Columbia, MO
| | - Leonie C Moyle
- Department of Biology, Indiana University, Bloomington, IN
| |
Collapse
|
9
|
Jewell CP, Zhang SV, Gibson MJS, Tovar-Méndez A, McClure B, Moyle LC. Intraspecific Genetic Variation Underlying Postmating Reproductive Barriers between Species in the Wild Tomato Clade (Solanum sect. Lycopersicon). J Hered 2020. [PMID: 32072169 DOI: 10.1101/718544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
A goal of speciation genetics is to understand how the genetic components underlying interspecific reproductive barriers originate within species. Unilateral incompatibility (UI) is a postmating prezygotic barrier in which pollen rejection in the female reproductive tract (style) occurs in only one direction of an interspecific cross. Natural variation in the strength of UI has been observed among populations within species in the wild tomato clade. In some cases, molecular loci underlying self-incompatibility (SI) are associated with this variation in UI, but the mechanistic connection between these intra- and inter-specific pollen rejection behaviors is poorly understood in most instances. We generated an F2 population between SI and SC genotypes of a single species, Solanum pennellii, to examine the genetic basis of intraspecific variation in UI against other species, and to determine whether loci underlying SI are genetically associated with this variation. We found that F2 individuals vary in the rate at which UI rejection occurs. One large effect QTL detected for this trait co-localized with the SI-determining S-locus. Moreover, individuals that expressed S-RNase-the S-locus protein involved in SI pollen rejection-in their styles had much more rapid UI responses compared with those without S-RNase protein. Our analysis shows that intraspecific variation at mate choice loci-in this case at loci that prevent self-fertilization-can contribute to variation in the expression of interspecific isolation, including postmating prezygotic barriers. Understanding the nature of such intraspecific variation can provide insight into the accumulation of these barriers between diverging lineages.
Collapse
Affiliation(s)
| | - Simo V Zhang
- Department of Biology, Indiana University, Bloomington, IN
| | | | | | - Bruce McClure
- Department of Biochemistry, University of Missouri, Columbia, MO
| | - Leonie C Moyle
- Department of Biology, Indiana University, Bloomington, IN
| |
Collapse
|
10
|
Gillespie RG, Bennett GM, De Meester L, Feder JL, Fleischer RC, Harmon LJ, Hendry AP, Knope ML, Mallet J, Martin C, Parent CE, Patton AH, Pfennig KS, Rubinoff D, Schluter D, Seehausen O, Shaw KL, Stacy E, Stervander M, Stroud JT, Wagner C, Wogan GOU. Comparing Adaptive Radiations Across Space, Time, and Taxa. J Hered 2020; 111:1-20. [PMID: 31958131 PMCID: PMC7931853 DOI: 10.1093/jhered/esz064] [Citation(s) in RCA: 95] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 10/28/2019] [Indexed: 01/02/2023] Open
Abstract
Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.
Collapse
Affiliation(s)
- Rosemary G Gillespie
- University of California, Berkeley, Essig Museum of Entomology & Department of Environmental Science, Policy, and Management, Berkeley, CA
| | - Gordon M Bennett
- University of California Merced, Life and Environmental Sciences Unit, Merced, CA
| | - Luc De Meester
- University of Leuven, Laboratory of Aquatic Ecology, Evolution and Conservation, Leuven, Belguim
| | - Jeffrey L Feder
- University of Notre Dame, Dept. of Biological Sciences, Notre Dame, IN
| | - Robert C Fleischer
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC
| | - Luke J Harmon
- University of Idaho, Dept. of Biological Sciences, Moscow, ID
| | | | | | | | - Christopher Martin
- University of California Berkeley, Integrative Biology and Museum of Vertebrate Zoology, Berkeley, CA
| | | | - Austin H Patton
- Washington State University, School of Biological Sciences, Pullman, WA
| | - Karin S Pfennig
- University of North Carolina at Chapel Hill, Department of Biology, Chapel Hill, NC
| | - Daniel Rubinoff
- University of Hawaiʻi at Manoa, Department of Plant and Environmental Protection Sciences, Honolulu, HI
| | | | - Ole Seehausen
- Institute of Ecology & Evolution, University of Bern, Bern, BE, Switzerland
- Center for Ecology, Evolution & Biogeochemistry, Eawag, Kastanienbaum, LU, Switzerland
| | - Kerry L Shaw
- Cornell University, Neurobiology and Behavior, Tower Road,, Ithaca, NY
| | - Elizabeth Stacy
- University of Nevada Las Vegas, School of Life Sciences, Las Vegas, NV
| | - Martin Stervander
- University of Oregon, Institute of Ecology and Evolution, Eugene, OR
| | - James T Stroud
- Washington University in Saint Louis, Biology, Saint Louis, MO
| | | | - Guinevere O U Wogan
- University of California Berkeley, Environmental Science Policy, and Management, Berkeley, CA
| |
Collapse
|
11
|
Fuller ZL, Koury SA, Phadnis N, Schaeffer SW. How chromosomal rearrangements shape adaptation and speciation: Case studies in Drosophila pseudoobscura and its sibling species Drosophila persimilis. Mol Ecol 2019; 28:1283-1301. [PMID: 30402909 PMCID: PMC6475473 DOI: 10.1111/mec.14923] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 09/30/2018] [Accepted: 10/09/2018] [Indexed: 01/01/2023]
Abstract
The gene arrangements of Drosophila have played a prominent role in the history of evolutionary biology from the original quantification of genetic diversity to current studies of the mechanisms for the origin and establishment of new inversion mutations within populations and their subsequent fixation between species supporting reproductive barriers. This review examines the genetic causes and consequences of inversions as recombination suppressors and the role that recombination suppression plays in establishing inversions in populations as they are involved in adaptation within heterogeneous environments. This often results in the formation of clines of gene arrangement frequencies among populations. Recombination suppression leads to the differentiation of the gene arrangements which may accelerate the accumulation of fixed genetic differences among populations. If these fixed mutations cause incompatibilities, then inversions pose important reproductive barriers between species. This review uses the evolution of inversions in Drosophila pseudoobscura and D. persimilis as a case study for how inversions originate, establish and contribute to the evolution of reproductive isolation.
Collapse
Affiliation(s)
- Zachary L. Fuller
- Department of Biology, The Pennsylvania State University, 208 Erwin W. Mueller Laboratory, University Park, PA 16802-5301
| | - Spencer A. Koury
- Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Nitin Phadnis
- Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Stephen W. Schaeffer
- Department of Biology, The Pennsylvania State University, 208 Erwin W. Mueller Laboratory, University Park, PA 16802-5301
| |
Collapse
|
12
|
Christmas MJ, Wallberg A, Bunikis I, Olsson A, Wallerman O, Webster MT. Chromosomal inversions associated with environmental adaptation in honeybees. Mol Ecol 2018; 28:1358-1374. [DOI: 10.1111/mec.14944] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 11/07/2018] [Accepted: 11/07/2018] [Indexed: 01/03/2023]
Affiliation(s)
- Matthew J. Christmas
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory Uppsala University Uppsala Sweden
| | - Andreas Wallberg
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory Uppsala University Uppsala Sweden
| | - Ignas Bunikis
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory Uppsala University Uppsala Sweden
| | - Anna Olsson
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory Uppsala University Uppsala Sweden
| | - Ola Wallerman
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory Uppsala University Uppsala Sweden
| | - Matthew T. Webster
- Department of Medical Biochemistry and Microbiology, Science for Life Laboratory Uppsala University Uppsala Sweden
| |
Collapse
|
13
|
Korunes KL, Noor MAF. Pervasive gene conversion in chromosomal inversion heterozygotes. Mol Ecol 2018; 28:1302-1315. [PMID: 30387889 DOI: 10.1111/mec.14921] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 09/27/2018] [Accepted: 10/22/2018] [Indexed: 12/30/2022]
Abstract
Chromosomal inversions shape recombination landscapes, and species differing by inversions may exhibit reduced gene flow in these regions of the genome. Though single crossovers within inversions are not usually recovered from inversion heterozygotes, the recombination barrier imposed by inversions is nuanced by noncrossover gene conversion. Here, we provide a genomewide empirical analysis of gene conversion rates both within species and in species hybrids. We estimate that gene conversion occurs at a rate of 1 × 10-5 to 2.5 × 10-5 converted sites per bp per generation in experimental crosses within Drosophila pseudoobscura and between D. pseudoobscura and its naturally hybridizing sister species D. persimilis. This analysis is the first direct empirical assessment of gene conversion rates within inversions of a species hybrid. Our data show that gene conversion rates in interspecies hybrids are at least as high as within-species estimates of gene conversion rates, and gene conversion occurs regularly within and around inverted regions of species hybrids, even near inversion breakpoints. We also found that several gene conversion events appeared to be mitotic rather than meiotic in origin. Finally, we observed that gene conversion rates are higher in regions of lower local sequence divergence, yet our observed gene conversion rates in more divergent inverted regions were at least as high as in less divergent collinear regions. Given our observed high rates of gene conversion despite the sequence differentiation between species, especially in inverted regions, gene conversion has the potential to reduce the efficacy of inversions as barriers to recombination over evolutionary time.
Collapse
|
14
|
Ross KG, Shoemaker D. Unexpected patterns of segregation distortion at a selfish supergene in the fire ant Solenopsis invicta. BMC Genet 2018; 19:101. [PMID: 30404617 PMCID: PMC6223060 DOI: 10.1186/s12863-018-0685-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 10/12/2018] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND The Sb supergene in the fire ant Solenopsis invicta determines the form of colony social organization, with colonies whose inhabitants bear the element containing multiple reproductive queens and colonies lacking it containing only a single queen. Several features of this supergene - including suppressed recombination, presence of deleterious mutations, association with a large centromere, and "green-beard" behavior - suggest that it may be a selfish genetic element that engages in transmission ratio distortion (TRD), defined as significant departures in progeny allele frequencies from Mendelian inheritance ratios. We tested this possibility by surveying segregation ratios in embryo progenies of 101 queens of the "polygyne" social form (3512 embryos) using three supergene-linked markers and twelve markers outside the supergene. RESULTS Significant departures from Mendelian ratios were observed at the supergene loci in 3-5 times more progenies than expected in the absence of TRD and than found, on average, among non-supergene loci. Also, supergene loci displayed the greatest mean deviations from Mendelian ratios among all study loci, although these typically were modest. A surprising feature of the observed inter-progeny variation in TRD was that significant deviations involved not only excesses of supergene alleles but also similarly frequent excesses of the alternate alleles on the homologous chromosome. As expected given the common occurrence of such "drive reversal" in this system, alleles associated with the supergene gain no consistent transmission advantage over their alternate alleles at the population level. Finally, we observed low levels of recombination and incomplete gametic disequilibrium across the supergene, including between adjacent markers within a single inversion. CONCLUSIONS Our data confirm the prediction that the Sb supergene is a selfish genetic element capable of biasing its own transmission during reproduction, yet counterselection for suppressor loci evidently has produced an evolutionary stalemate in TRD between the variant homologous haplotypes on the "social chromosome". Evidence implicates prezygotic segregation distortion as responsible for the TRD we document, with "true" meiotic drive the most likely mechanism. Low levels of recombination and incomplete gametic disequilibrium across the supergene suggest that selection does not preserve a single uniform supergene haplotype responsible for inducing polygyny.
Collapse
Affiliation(s)
- Kenneth G. Ross
- Department of Entomology, University of Georgia, Athens, GA USA
| | - DeWayne Shoemaker
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN USA
| |
Collapse
|
15
|
Fuller ZL, Leonard CJ, Young RE, Schaeffer SW, Phadnis N. Ancestral polymorphisms explain the role of chromosomal inversions in speciation. PLoS Genet 2018; 14:e1007526. [PMID: 30059505 PMCID: PMC6085072 DOI: 10.1371/journal.pgen.1007526] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/09/2018] [Accepted: 06/29/2018] [Indexed: 01/28/2023] Open
Abstract
Understanding the role of chromosomal inversions in speciation is a fundamental problem in evolutionary genetics. Here, we perform a comprehensive reconstruction of the evolutionary histories of the chromosomal inversions in Drosophila persimilis and D. pseudoobscura. We provide a solution to the puzzling origins of the selfish Sex-Ratio arrangement in D. persimilis and uncover surprising patterns of phylogenetic discordance on this chromosome. These patterns show that, contrary to widely held views, all fixed chromosomal inversions between D. persimilis and D. pseudoobscura were already present in their ancestral population long before the species split. Our results suggest that patterns of higher genomic divergence and an association of reproductive isolation genes with chromosomal inversions may be a direct consequence of incomplete lineage sorting of ancestral polymorphisms. These findings force a reconsideration of the role of chromosomal inversions in speciation, not as protectors of existing hybrid incompatibilities, but as fertile grounds for their formation.
Collapse
Affiliation(s)
- Zachary L. Fuller
- Department of Biology, Erwin W. Mueller Laboratories, The Pennsylvania State University, University Park, PA, United States of America
| | | | - Randee E. Young
- Department of Biology, University of Utah, Salt Lake City, UT, United States of America
| | - Stephen W. Schaeffer
- Department of Biology, Erwin W. Mueller Laboratories, The Pennsylvania State University, University Park, PA, United States of America
| | - Nitin Phadnis
- Department of Biology, University of Utah, Salt Lake City, UT, United States of America
| |
Collapse
|
16
|
Hill T, Betancourt AJ. Extensive exchange of transposable elements in the Drosophila pseudoobscura group. Mob DNA 2018; 9:20. [PMID: 29946370 PMCID: PMC6006672 DOI: 10.1186/s13100-018-0123-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/01/2018] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND As species diverge, so does their transposable element (TE) content. Within a genome, TE families may eventually become dormant due to host-silencing mechanisms, natural selection and the accumulation of inactive copies. The transmission of active copies from a TE families, both vertically and horizontally between species, can allow TEs to escape inactivation if it occurs often enough, as it may allow TEs to temporarily escape silencing in a new host. Thus, the contribution of horizontal exchange to TE persistence has been of increasing interest. RESULTS Here, we annotated TEs in five species with sequenced genomes from the D. pseudoobscura species group, and curated a set of TE families found in these species. We found that, compared to host genes, many TE families showed lower neutral divergence between species, consistent with recent transmission of TEs between species. Despite these transfers, there are differences in the TE content between species in the group. CONCLUSIONS The TE content is highly dynamic in the D. pseudoobscura species group, frequently transferring between species, keeping TEs active. This result highlights how frequently transposable elements are transmitted between sympatric species and, despite these transfers, how rapidly species TE content can diverge.
Collapse
Affiliation(s)
- Tom Hill
- The Department of Molecular Biosciences, University of Kansas, 4055 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS 66045 USA
| | - Andrea J. Betancourt
- Institute of Integrative Biology, University of Liverpool, Liverpool, L69 7ZB UK
| |
Collapse
|
17
|
Paczolt KA, Reinhardt JA, Wilkinson GS. Contrasting patterns of X-chromosome divergence underlie multiple sex-ratio polymorphisms in stalk-eyed flies. J Evol Biol 2017; 30:1772-1784. [PMID: 28688201 DOI: 10.1111/jeb.13140] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 06/27/2017] [Accepted: 07/04/2017] [Indexed: 11/28/2022]
Abstract
Sex-linked segregation distorters cause offspring sex ratios to differ from equality. Theory predicts that such selfish alleles may either go to fixation and cause extinction, reach a stable polymorphism or initiate an evolutionary arms race with genetic modifiers. The extent to which a sex ratio distorter follows any of these trajectories in nature is poorly known. Here, we used X-linked sequence and simple tandem repeat data for three sympatric species of stalk-eyed flies (Teleopsis whitei and two cryptic species of T. dalmanni) to infer the evolution of distorting X chromosomes. By screening large numbers of field and recently laboratory-bred flies, we found no evidence of males with strongly female-biased sex ratio phenotypes (SR) in one species but high frequencies of SR males in the other two species. In the two species with SR males, we find contrasting patterns of X-chromosome evolution. T. dalmanni-1 shows chromosome-wide differences between sex-ratio (XSR ) and standard (XST ) X chromosomes consistent with a relatively old sex-ratio haplotype based on evidence including genetic divergence, an inversion polymorphism and reduced recombination among XSR chromosomes relative to XST chromosomes. In contrast, we found no evidence of genetic divergence on the X between males with female-biased and nonbiased sex ratios in T. whitei. Taken with previous studies that found evidence of genetic suppression of sex ratio distortion in this clade, our results illustrate that sex ratio modification in these flies is undergoing recurrent evolution with diverse genomic consequences.
Collapse
Affiliation(s)
- K A Paczolt
- Department of Biology, University of Maryland College Park, College Park, MD, USA
| | - J A Reinhardt
- Department of Biology, SUNY Geneseo, Geneseo, NY, USA
| | - G S Wilkinson
- Department of Biology, University of Maryland College Park, College Park, MD, USA
| |
Collapse
|
18
|
Souza NA, Brazil RP, Araki AS. The current status of the Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) species complex. Mem Inst Oswaldo Cruz 2017; 112:161-174. [PMID: 28225906 PMCID: PMC5319373 DOI: 10.1590/0074-02760160463] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 01/13/2017] [Indexed: 11/23/2022] Open
Abstract
Lutzomyia longipalpis s.l. is a complex of sibling species and is
the principal vector of American visceral leishmaniasis. The present review
summarises the diversity of efforts that have been undertaken to elucidate the number
of unnamed species in this species complex and the phylogenetic relationships among
them. A wide variety of evidence, including chemical, behavioral and molecular
traits, suggests very recent speciation events and complex population structure in
this group. Although significant advances have been achieved to date, differential
vector capacity and the correlation between structure of parasite and vector
populations have yet to be elucidated. Furthermore, increased knowledge about recent
epidemiological changes, such as urbanisation, is essential for pursuing effective
strategies for sandfly control in the New World.
Collapse
Affiliation(s)
- Nataly A Souza
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório Interdisciplinar de Vigilância Entomológica em Diptera e Hemiptera, Rio de Janeiro, RJ, Brasil
| | - Reginaldo P Brazil
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Doenças Parasitárias, Rio de Janeiro, RJ, Brasil
| | - Alejandra S Araki
- Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Biologia Molecular de Insetos, Rio de Janeiro, RJ, Brasil
| |
Collapse
|
19
|
Davey JW, Barker SL, Rastas PM, Pinharanda A, Martin SH, Durbin R, McMillan WO, Merrill RM, Jiggins CD. No evidence for maintenance of a sympatric Heliconius species barrier by chromosomal inversions. Evol Lett 2017; 1:138-154. [PMID: 30283645 PMCID: PMC6122123 DOI: 10.1002/evl3.12] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 04/21/2017] [Accepted: 05/02/2017] [Indexed: 12/18/2022] Open
Abstract
Mechanisms that suppress recombination are known to help maintain species barriers by preventing the breakup of coadapted gene combinations. The sympatric butterfly species Heliconius melpomene and Heliconius cydno are separated by many strong barriers, but the species still hybridize infrequently in the wild, and around 40% of the genome is influenced by introgression. We tested the hypothesis that genetic barriers between the species are maintained by inversions or other mechanisms that reduce between-species recombination rate. We constructed fine-scale recombination maps for Panamanian populations of both species and their hybrids to directly measure recombination rate within and between species, and generated long sequence reads to detect inversions. We find no evidence for a systematic reduction in recombination rates in F1 hybrids, and also no evidence for inversions longer than 50 kb that might be involved in generating or maintaining species barriers. This suggests that mechanisms leading to global or local reduction in recombination do not play a significant role in the maintenance of species barriers between H. melpomene and H. cydno.
Collapse
Affiliation(s)
- John W. Davey
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
- Smithsonian Tropical Research InstituteGamboaPanama
| | - Sarah L. Barker
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
| | - Pasi M. Rastas
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
| | - Ana Pinharanda
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
- Smithsonian Tropical Research InstituteGamboaPanama
| | - Simon H. Martin
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
| | - Richard Durbin
- Wellcome Trust Sanger InstituteCambridgeCB10 1SAUnited Kingdom
| | | | - Richard M. Merrill
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
- Smithsonian Tropical Research InstituteGamboaPanama
| | - Chris D. Jiggins
- Department of ZoologyUniversity of CambridgeDowning StreetCambridgeCB2 3EJUnited Kingdom
- Smithsonian Tropical Research InstituteGamboaPanama
| |
Collapse
|
20
|
Holliday JA, Aitken SN, Cooke JEK, Fady B, González-Martínez SC, Heuertz M, Jaramillo-Correa JP, Lexer C, Staton M, Whetten RW, Plomion C. Advances in ecological genomics in forest trees and applications to genetic resources conservation and breeding. Mol Ecol 2017; 26:706-717. [PMID: 27997049 DOI: 10.1111/mec.13963] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 12/07/2016] [Accepted: 12/14/2016] [Indexed: 12/25/2022]
Abstract
Forest trees are an unparalleled group of organisms in their combined ecological, economic and societal importance. With widespread distributions, predominantly random mating systems and large population sizes, most tree species harbour extensive genetic variation both within and among populations. At the same time, demographic processes associated with Pleistocene climate oscillations and land-use change have affected contemporary range-wide diversity and may impinge on the potential for future adaptation. Understanding how these adaptive and neutral processes have shaped the genomes of trees species is therefore central to their management and conservation. As for many other taxa, the advent of high-throughput sequencing methods is expected to yield an understanding of the interplay between the genome and environment at a level of detail and depth not possible only a few years ago. An international conference entitled 'Genomics and Forest Tree Genetics' was held in May 2016, in Arcachon (France), and brought together forest geneticists with a wide range of research interests to disseminate recent efforts that leverage contemporary genomic tools to probe the population, quantitative and evolutionary genomics of trees. An important goal of the conference was to discuss how such data can be applied to both genome-enabled breeding and the conservation of forest genetic resources under land use and climate change. Here, we report discoveries presented at the meeting and discuss how the ecological genomic toolkit can be used to address both basic and applied questions in tree biology.
Collapse
Affiliation(s)
- Jason A Holliday
- Department of Forest Resources and Environmental Conservation, Virginia Tech, 304 Cheatham Hall, Blacksburg, VA 24061, USA
| | - Sally N Aitken
- Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC V6T1Z4, Canada
| | - Janice E K Cooke
- Department of Biological Sciences, University of Alberta, 5-108 Centennial Centre for Interdisciplinary Science, Edmonton, AB T6G2E9, Canada
| | - Bruno Fady
- Mediterranean Forest Ecology (URFM), Institut National de la Recherche Agronomique (INRA), Domaine St Paul, Site Agroparc, 84914 Avignon, France
| | | | - Myriam Heuertz
- BIOGECO, INRA, Universite de Bordeaux, 69 Route d'Arcachon, 33612 Cestas, France
| | - Juan-Pablo Jaramillo-Correa
- Institute of Ecology, Universidad Nacional Autonoma de Mexico (UNAM) Circuito Exterior s/n, Apartado Postal 70-275, 04510 Ciudad de México, Mexico City, Mexico
| | - Christian Lexer
- Department of Botany and Biodiversity Research, University of Vienna Faculty of Life SciencesRennweg 14, Room 217, A-1030, Vienna, Austria
| | - Margaret Staton
- Department of Entomology and Plant Pathology, University of Tennessee, 370 Plant Biotechnology Building, 2505 EJ Chapman Drive, Knoxville, TN 37996, USA
| | - Ross W Whetten
- Department of Forestry and Environmental Resources, North Carolina State University Jordan Hall Addition 5231, Raleigh, NC 27695, USA
| | - Christophe Plomion
- BIOGECO, INRA, Universite de Bordeaux, 69 Route d'Arcachon, 33612 Cestas, France
| |
Collapse
|
21
|
Abstract
We report genomes of two species of cactophilic Drosophila: Drosophila arizonae and D. navojoa These two are the closest relatives of D. mojavensis, forming the D. mojavensis cluster. D. mojavensis and D. arizonae diverged from D. navojoa ∼5.8 Mya, while the split between D. arizonae and D. mojavensis is more recent, at 1.5 Mya. Together the three genomes provide opportunities to examine genomic changes associated with speciation and host shifts in this ecologically defined group of flies. The three species are also separated by fixed inversion differences in three of their six chromosomes. While the levels of nucleotide divergence in the colinear chromosomes are significantly lower than in the inverted chromosomes, consistent with a past role of the inversions in preventing gene flow, the patterns differ among the inverted chromosomes when the locations of nucleotides inside or outside of the inversions are considered. For Muller element E, there is greater divergence external to the inversion breakpoints. For Muller A, the divergence is slightly higher inside the inversions, while for Muller B, the breakpoints and hence the difference in substitutions in relation to the inversions could not be determined. The differences among the inverted chromosomes, especially once the breakpoints are clearly established, could aid in dating the origins of the inversions.
Collapse
|
22
|
Owens GL, Baute GJ, Rieseberg LH. Revisiting a classic case of introgression: hybridization and gene flow in Californian sunflowers. Mol Ecol 2016; 25:2630-43. [DOI: 10.1111/mec.13569] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 01/26/2016] [Accepted: 01/28/2016] [Indexed: 01/09/2023]
Affiliation(s)
- Gregory L. Owens
- Department of Botany and Biodiversity Research Centre; University of British Columbia, University Blvd; Vancouver BC V6T 1Z4 Canada
| | - Gregory J. Baute
- Department of Botany and Biodiversity Research Centre; University of British Columbia, University Blvd; Vancouver BC V6T 1Z4 Canada
| | - Loren H. Rieseberg
- Department of Botany and Biodiversity Research Centre; University of British Columbia, University Blvd; Vancouver BC V6T 1Z4 Canada
- Department of Biology; Indiana University; Bloomington IN 47405 USA
| |
Collapse
|
23
|
Ortiz-Barrientos D, Engelstädter J, Rieseberg LH. Recombination Rate Evolution and the Origin of Species. Trends Ecol Evol 2016; 31:226-236. [PMID: 26831635 DOI: 10.1016/j.tree.2015.12.016] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/14/2015] [Accepted: 12/22/2015] [Indexed: 12/13/2022]
Abstract
A recipe for dissolving incipient species into a continuum of phenotypes is to recombine their genetic material. Therefore, students of speciation have become increasingly interested in the mechanisms by which recombination between locally adapted lineages is reduced. Evidence abounds that chromosomal rearrangements, via their suppression of recombination during meiosis in hybrids, play a major role in adaptation and speciation. By contrast, genic modifiers of recombination rates have been largely ignored in studies of speciation. We show how both types of reduction in recombination rates facilitate divergence in the face of gene flow, including the early stages of adaptive divergence, the persistence of species after secondary contact, and reinforcement.
Collapse
Affiliation(s)
- Daniel Ortiz-Barrientos
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland, Australia.
| | - Jan Engelstädter
- The University of Queensland, School of Biological Sciences, St. Lucia, Queensland, Australia
| | - Loren H Rieseberg
- University of British Columbia, Department of Botany, Vancouver, British Columbia, Canada; Indiana University, Biology Department, Bloomington, IN 47405-7005, USA
| |
Collapse
|
24
|
Sharakhov IV, Artemov GN, Sharakhova MV. Chromosome evolution in malaria mosquitoes inferred from physically mapped genome assemblies. J Bioinform Comput Biol 2016; 14:1630003. [PMID: 27021248 DOI: 10.1142/s0219720016300033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Polymorphic inversions in mosquitoes are distributed nonrandomly among chromosomes and are associated with ecological, behavioral, and physiological adaptations related to pathogen transmission. Despite their significance, the patterns and mechanism of genome rearrangements are not well understood. Recent sequencing and physical mapping of the genomes for 16 Anopheles mosquito species provided an opportunity to study chromosome evolution at the highest resolution. New studies revealed that fixed rearrangement accumulated [Formula: see text]3 times faster on the X chromosome than on autosomes. The highest densities of transposable elements (TEs) and satellites of different sizes have also been found on the X chromosome, suggesting a mechanism for the inversion generation. The high rate of X chromosome rearrangements is in sharp contrast with the paucity of polymorphic inversions on the X in the majority of anopheline species. This paper highlights the advances in understanding chromosome evolution in malaria vectors and discusses possible future directions in studying mechanisms and biological roles of genome rearrangements.
Collapse
Affiliation(s)
- Igor V Sharakhov
- 1 Department of Entomology, Virginia Tech, Blacksburg, Virginia 24061, USA.,2 Tomsk State University, Tomsk 634050, Russia
| | | | - Maria V Sharakhova
- 1 Department of Entomology, Virginia Tech, Blacksburg, Virginia 24061, USA.,2 Tomsk State University, Tomsk 634050, Russia
| |
Collapse
|
25
|
Takeuchi N, Cordero OX, Koonin EV, Kaneko K. Gene-specific selective sweeps in bacteria and archaea caused by negative frequency-dependent selection. BMC Biol 2015; 13:20. [PMID: 25928466 PMCID: PMC4410459 DOI: 10.1186/s12915-015-0131-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 03/13/2015] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Fixation of beneficial genes in bacteria and archaea (collectively, prokaryotes) is often believed to erase pre-existing genomic diversity through the hitchhiking effect, a phenomenon known as genome-wide selective sweep. Recent studies, however, indicate that beneficial genes spread through a prokaryotic population via recombination without causing genome-wide selective sweeps. These gene-specific selective sweeps seem to be at odds with the existing estimates of recombination rates in prokaryotes, which appear far too low to explain such phenomena. RESULTS We use mathematical modeling to investigate potential solutions to this apparent paradox. Most microbes in nature evolve in heterogeneous, dynamic communities, in which ecological interactions can substantially impact evolution. Here, we focus on the effect of negative frequency-dependent selection (NFDS) such as caused by viral predation (kill-the-winner dynamics). The NFDS maintains multiple genotypes within a population, so that a gene beneficial to every individual would have to spread via recombination, hence a gene-specific selective sweep. However, gene loci affected by NFDS often are located in variable regions of microbial genomes that contain genes involved in the mobility of selfish genetic elements, such as integrases or transposases. Thus, the NFDS-affected loci are likely to experience elevated rates of recombination compared with the other loci. Consequently, these loci might be effectively unlinked from the rest of the genome, so that NFDS would be unable to prevent genome-wide selective sweeps. To address this problem, we analyzed population genetic models of selective sweeps in prokaryotes under NFDS. The results indicate that NFDS can cause gene-specific selective sweeps despite the effect of locally elevated recombination rates, provided NFDS affects more than one locus and the basal rate of recombination is sufficiently low. Although these conditions might seem to contradict the intuition that gene-specific selective sweeps require high recombination rates, they actually decrease the effective rate of recombination at loci affected by NFDS relative to the per-locus basal level, so that NFDS can cause gene-specific selective sweeps. CONCLUSION Because many free-living prokaryotes are likely to evolve under NFDS caused by ubiquitous viruses, gene-specific selective sweeps driven by NFDS are expected to be a major, general phenomenon in prokaryotic populations.
Collapse
Affiliation(s)
- Nobuto Takeuchi
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan.
| | - Otto X Cordero
- Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.
| | - Eugene V Koonin
- National Institutes of Health, National Library of Medicine, National Center for Biotechnology Information, Bethesda, USA.
| | - Kunihiko Kaneko
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan.
| |
Collapse
|
26
|
Pratdesaba R, Segarra C, Aguadé M. Inferring the demographic history of Drosophila subobscura from nucleotide variation at regions not affected by chromosomal inversions. Mol Ecol 2015; 24:1729-41. [PMID: 25776124 DOI: 10.1111/mec.13155] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 03/09/2015] [Accepted: 03/11/2015] [Indexed: 11/29/2022]
Abstract
Drosophila subobscura presents a rich and complex chromosomal inversion polymorphism. It can thus be considered a model system (i) to study the mechanisms originating inversions and how inversions affect the levels and patterns of variation in the inverted regions and (ii) to study adaptation at both the single-gene and chromosomal inversion levels. It is therefore important to infer its demographic history as previous information indicated that its nucleotide variation is not at mutation-drift equilibrium. For that purpose, we sequenced 16 noncoding regions distributed across those parts of the J chromosome not affected by inversions in the studied population and possibly either by other selective events. The pattern of variation detected in these 16 regions is similar to that previously reported within different chromosomal arrangements, suggesting that the latter results would, thus, mainly reflect recent demographic events rather than the partial selective sweep imposed by the origin and frequency increase of inversions. Among the simple demographic models considered in our Approximate Bayesian Computation analysis of variation at the 16 regions, the model best supported by the data implies a population size expansion soon after the penultimate glacial period. This model constitutes a better null model, and it is therefore an important resource for subsequent studies aiming among others to uncover selective events across the species genome. Our results also highlight the importance of introducing the possibility of multiple hits in the coalescent simulations with an outgroup.
Collapse
Affiliation(s)
- Roser Pratdesaba
- Departament de Genètica, Facultat de Biologia and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Diagonal 643, 08028, Barcelona, Spain
| | | | | |
Collapse
|
27
|
Evidence for stabilizing selection on codon usage in chromosomal rearrangements of Drosophila pseudoobscura. G3-GENES GENOMES GENETICS 2014; 4:2433-49. [PMID: 25326424 PMCID: PMC4267939 DOI: 10.1534/g3.114.014860] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
There has been a renewed interest in investigating the role of stabilizing selection acting on genome-wide traits such as codon usage bias. Codon bias, when synonymous codons are used at unequal frequencies, occurs in a wide variety of taxa. Standard evolutionary models explain the maintenance of codon bias through a balance of genetic drift, mutation and weak purifying selection. The efficacy of selection is expected to be reduced in regions of suppressed recombination. Contrary to observations in Drosophila melanogaster, some recent studies have failed to detect a relationship between the recombination rate, intensity of selection acting at synonymous sites, and the magnitude of codon bias as predicted under these standard models. Here, we examined codon bias in 2798 protein coding loci on the third chromosome of D. pseudoobscura using whole-genome sequences of 47 individuals, representing five common third chromosome gene arrangements. Fine-scale recombination maps were constructed using more than 1 million segregating sites. As expected, recombination was demonstrated to be significantly suppressed between chromosome arrangements, allowing for a direct examination of the relationship between recombination, selection, and codon bias. As with other Drosophila species, we observe a strong mutational bias away from the most frequently used codons. We find the rate of synonymous and nonsynonymous polymorphism is variable between different amino acids. However, we do not observe a reduction in codon bias or the strength of selection in regions of suppressed recombination as expected. Instead, we find that the interaction between weak stabilizing selection and mutational bias likely plays a role in shaping the composition of synonymous codons across the third chromosome in D. pseudoobscura.
Collapse
|
28
|
Avila V, Marion de Procé S, Campos JL, Borthwick H, Charlesworth B, Betancourt AJ. Faster-X effects in two Drosophila lineages. Genome Biol Evol 2014; 6:2968-82. [PMID: 25323954 PMCID: PMC4224355 DOI: 10.1093/gbe/evu229] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Under certain circumstances, X-linked loci are expected to experience more adaptive substitutions than similar autosomal loci. To look for evidence of faster-X evolution, we analyzed the evolutionary rates of coding sequences in two sets of Drosophila species, the melanogaster and pseudoobscura clades, using whole-genome sequences. One of these, the pseudoobscura clade, contains a centric fusion between the ancestral X chromosome and the autosomal arm homologous to 3L in D. melanogaster. This offers an opportunity to study the same loci in both an X-linked and an autosomal context, and to compare these loci with those that are only X-linked or only autosomal. We therefore investigated these clades for evidence of faster-X evolution with respect to nonsynonymous substitutions, finding mixed results. Overall, there was consistent evidence for a faster-X effect in the melanogaster clade, but not in the pseudoobscura clade, except for the comparison between D. pseudoobscura and its close relative, Drosophila persimilis. An analysis of polymorphism data on a set of genes from D. pseudoobscura that evolve rapidly with respect to their protein sequences revealed no evidence for a faster-X effect with respect to adaptive protein sequence evolution; their rapid evolution is instead largely attributable to lower selective constraints. Faster-X evolution in the melanogaster clade was not related to male-biased gene expression; surprisingly, however, female-biased genes showed evidence for faster-X effects, perhaps due to their sexually antagonistic effects in males.
Collapse
Affiliation(s)
- Victoria Avila
- Institute of Evolutionary Biology, University of Edinburgh, United Kingdom Present address: Institute of Biological, Environmental and Rural Sciences, Abertystwyth University, Aberystwyth, United Kingdom
| | - Sophie Marion de Procé
- Institute of Evolutionary Biology, University of Edinburgh, United Kingdom Present address: MRC Human Genetics Unit, MRC IGMM, University of Edinburgh, Edinburgh, United Kingdom
| | - José L Campos
- Institute of Evolutionary Biology, University of Edinburgh, United Kingdom
| | - Helen Borthwick
- Institute of Evolutionary Biology, University of Edinburgh, United Kingdom
| | - Brian Charlesworth
- Institute of Evolutionary Biology, University of Edinburgh, United Kingdom
| | - Andrea J Betancourt
- Institute of Evolutionary Biology, University of Edinburgh, United Kingdom Present address: Institut for Populationsgenetik, Vetmeduni Vienna, Vienna, Austria
| |
Collapse
|
29
|
Genetic differentiation and evolutionary adaptation in Cryptomeria japonica. G3-GENES GENOMES GENETICS 2014; 4:2389-402. [PMID: 25320072 PMCID: PMC4267934 DOI: 10.1534/g3.114.013896] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Local adaptation of plant species is a central issue for survival during global climate change, especially for long-lived forest trees, with their lengthy regeneration time and spatially limited gene flow. Identification of loci and/or genomic regions associated with local adaptation is necessary for knowledge of both evolution and molecular breeding for climate change. Cryptomeria japonica is an important species for forestry in Japan; it has a broad natural distribution and can survive in a range of different environments. The genetic structure of 14 natural populations of this species was investigated using 3930 SNP markers. Populations on the Pacific Ocean side of Japan are clearly different from those on the Japan Sea side, as discussed in previous studies. Structure analysis and population network trees show that peripheral populations, including the most northerly and southerly ones, have unique features. We found that the genetic differentiation coefficient is low, FST = 0.05, although it must account for the presence of important genes associated with adaptation to specific environments. In total, 208 outlier loci were detected, of which 43 were associated with environmental variables. Four clumped regions of outlier loci were detected in the genome by linkage analysis. Linkage disequilibrium (LD) was quite high in these clumps of outlier loci, which were found in linkage groups (LGs) 2, 7, 10, and 11, especially between populations of two varieties, and when interchromosomal LD was also detected. The LG7 region is characteristic of the Yakushima population, which is a large, isolated, peripheral population occupying a specific environment resulting from isolation combined with volcanic activity in the region. The detected LD may provide strong evidence for selection between varieties.
Collapse
|
30
|
Feder JL, Flaxman SM, Egan SP, Comeault AA, Nosil P. Geographic Mode of Speciation and Genomic Divergence. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2013. [DOI: 10.1146/annurev-ecolsys-110512-135825] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jeffrey L. Feder
- Department of Biological Sciences,
- Environmental Change Initiative, and
- Advanced Diagnostics and Therapeutics, University of Notre Dame, Notre Dame, Indiana 46556; ,
| | - Samuel M. Flaxman
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado 80309;
| | - Scott P. Egan
- Department of Biological Sciences,
- Advanced Diagnostics and Therapeutics, University of Notre Dame, Notre Dame, Indiana 46556; ,
| | - Aaron A. Comeault
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S102TN, United Kingdom; ,
| | - Patrik Nosil
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S102TN, United Kingdom; ,
| |
Collapse
|
31
|
Myers EM, Harwell TI, Yale EL, Lamb AM, Frankino WA. Multifaceted, cross-generational costs of hybridization in sibling Drosophila species. PLoS One 2013; 8:e80331. [PMID: 24265807 PMCID: PMC3827178 DOI: 10.1371/journal.pone.0080331] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Accepted: 10/01/2013] [Indexed: 11/19/2022] Open
Abstract
Maladaptive hybridization, as determined by the pattern and intensity of selection against hybrid individuals, is an important factor contributing to the evolution of prezygotic reproductive isolation. To identify the consequences of hybridization between Drosophila pseudoobscura and D. persimilis, we estimated multiple fitness components for F1 hybrids and backcross progeny and used these to compare the relative fitness of parental species and their hybrids across two generations. We document many sources of intrinsic (developmental) and extrinsic (ecological) selection that dramatically increase the fitness costs of hybridization beyond the well-documented F1 male sterility in this model system. Our results indicate that the cost of hybridization accrues over multiple generations and reinforcement in this system is driven by selection against hybridization above and beyond the cost of hybrid male sterility; we estimate a fitness loss of >95% relative to the parental species across two generations of hybridization. Our findings demonstrate the importance of estimating hybridization costs using multiple fitness measures from multiple generations in an ecologically relevant context; so doing can reveal intense postzygotic selection against hybridization and thus, an enhanced role for reinforcement in the evolution of populations and diversification of species.
Collapse
Affiliation(s)
- Erin M. Myers
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Tiffany I. Harwell
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Elizabeth L. Yale
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Abigail M. Lamb
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - W. Anthony Frankino
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| |
Collapse
|
32
|
Multilocus analysis of divergence and introgression in sympatric and allopatric sibling species of the Lutzomyia longipalpis complex in Brazil. PLoS Negl Trop Dis 2013; 7:e2495. [PMID: 24147172 PMCID: PMC3798421 DOI: 10.1371/journal.pntd.0002495] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 09/08/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Lutzomyia longipalpis, the main vector of visceral leishmaniasis in Latin America, is a complex of sibling species. In Brazil, a number of very closely related sibling species have been revealed by the analyses of copulation songs, sex pheromones and molecular markers. However, the level of divergence and gene flow between the sibling species remains unclear. Brazilian populations of this vector can be divided in two main groups: one producing Burst-type songs and the Cembrene-1 pheromone and a second more diverse group producing various Pulse song subtypes and different pheromones. METHODOLOGY/PRINCIPAL FINDINGS We analyzed 21 nuclear loci in two pairs of Brazilian populations: two sympatric populations from the Sobral locality (1S and 2S) in northeastern Brazil and two allopatric populations from the Lapinha and Pancas localities in southeastern Brazil. Pancas and Sobral 2S are populations of the Burst/Cembrene-1 species while Lapinha and Sobral 1S are two putative incipient species producing the same pheromone and similar Pulse song subtypes. The multilocus analysis strongly suggests the occurrence of gene flow during the divergence between the sibling species, with different levels of introgression between loci. Moreover, this differential introgression is asymmetrical, with estimated gene flow being higher in the direction of the Burst/Cembrene-1 species. CONCLUSIONS/SIGNIFICANCE The results indicate that introgressive hybridization has been a crucial phenomenon in shaping the genome of the L. longipalpis complex. This has possible epidemiological implications and is particularly interesting considering the potential for increased introgression caused by man-made environmental changes and the current trend of leishmaniasis urbanization in Brazil.
Collapse
|
33
|
Ostberg CO, Hauser L, Pritchard VL, Garza JC, Naish KA. Chromosome rearrangements, recombination suppression, and limited segregation distortion in hybrids between Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) and rainbow trout (O. mykiss). BMC Genomics 2013; 14:570. [PMID: 23968234 PMCID: PMC3765842 DOI: 10.1186/1471-2164-14-570] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 08/16/2013] [Indexed: 12/03/2022] Open
Abstract
Background Introgressive hybridization is an important evolutionary process that can lead to the creation of novel genome structures and thus potentially new genetic variation for selection to act upon. On the other hand, hybridization with introduced species can threaten native species, such as cutthroat trout (Oncorhynchus clarkii) following the introduction of rainbow trout (O. mykiss). Neither the evolutionary consequences nor conservation implications of rainbow trout introgression in cutthroat trout is well understood. Therefore, we generated a genetic linkage map for rainbow-Yellowstone cutthroat trout (O. clarkii bouvieri) hybrids to evaluate genome processes that may help explain how introgression affects hybrid genome evolution. Results The hybrid map closely aligned with the rainbow trout map (a cutthroat trout map does not exist), sharing all but one linkage group. This linkage group (RYHyb20) represented a fusion between an acrocentric (Omy28) and a metacentric chromosome (Omy20) in rainbow trout. Additional mapping in Yellowstone cutthroat trout indicated the two rainbow trout homologues were fused in the Yellowstone genome. Variation in the number of hybrid linkage groups (28 or 29) likely depended on a Robertsonian rearrangement polymorphism within the rainbow trout stock. Comparison between the female-merged F1 map and a female consensus rainbow trout map revealed that introgression suppressed recombination across large genomic regions in 5 hybrid linkage groups. Two of these linkage groups (RYHyb20 and RYHyb25_29) contained confirmed chromosome rearrangements between rainbow and Yellowstone cutthroat trout indicating that rearrangements may suppress recombination. The frequency of allelic and genotypic segregation distortion varied among parents and families, suggesting few incompatibilities exist between rainbow and Yellowstone cutthroat trout genomes. Conclusions Chromosome rearrangements suppressed recombination in the hybrids. This result supports several previous findings demonstrating that recombination suppression restricts gene flow between chromosomes that differ by arrangement. Conservation of synteny and map order between the hybrid and rainbow trout maps and minimal segregation distortion in the hybrids suggest rainbow and Yellowstone cutthroat trout genomes freely introgress across chromosomes with similar arrangement. Taken together, these results suggest that rearrangements impede introgression. Recombination suppression across rearrangements could enable large portions of non-recombined chromosomes to persist within admixed populations.
Collapse
Affiliation(s)
- Carl O Ostberg
- U,S, Geological Survey, Western Fisheries Research Center, 6505 NE 65th Street, Seattle, WA 98115, USA.
| | | | | | | | | |
Collapse
|
34
|
Escudero M, Weber JA, Hipp AL. Species coherence in the face of karyotype diversification in holocentric organisms: the case of a cytogenetically variable sedge (Carex scoparia, Cyperaceae). ANNALS OF BOTANY 2013; 112:515-26. [PMID: 23723260 PMCID: PMC3718211 DOI: 10.1093/aob/mct119] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
BACKGROUND AND AIMS The sedge genus Carex, the most diversified angiosperm genus of the northern temperate zone, is renowned for its holocentric chromosomes and karyotype variability. The genus exhibits high variation in chromosome numbers both among and within species. Despite the possibility that this chromosome evolution may play a role in the high species diversity of Carex, population-level patterns of molecular and cytogenetic differentiation in the genus have not been extensively studied. METHODS Microsatellite variation (11 loci, 461 individuals) and chromosomal diversity (82 individuals) were investigated in 22 Midwestern populations of the North American sedge Carex scoparia and two Northeastern populations. KEY RESULTS Among Midwestern populations, geographic distance is the most important predictor of genetic differentiation. Within populations, inbreeding is high and chromosome variation explains a significant component of genetic differentiation. Infrequent dispersal among populations separated by >100 km explains an important component of molecular genetic and cytogenetic diversity within populations. However, karyotype variation and correlation between genetic and chromosomal variation persist within populations even when putative migrants based on genetic data are excluded. CONCLUSIONS These findings demonstrate dispersal and genetic connectivity among widespread populations that differ in chromosome numbers, explaining the phenomenon of genetic coherence in this karyotypically diverse sedge species. More generally, the study suggests that traditional sedge taxonomic boundaries demarcate good species even when those species encompass a high range of chromosomal diversity. This finding is important evidence as we work to document the limits and drivers of biodiversity in one of the world's largest angiosperm genera.
Collapse
Affiliation(s)
- Marcial Escudero
- The Morton Arboretum, 4100 Illinois Route 53, Lisle, IL 60532-1293, USA
- Pablo de Olavide University, Carretera de Utrera km 1 SN, Seville 41013, Spain
| | - Jaime A. Weber
- The Morton Arboretum, 4100 Illinois Route 53, Lisle, IL 60532-1293, USA
| | - Andrew L. Hipp
- The Morton Arboretum, 4100 Illinois Route 53, Lisle, IL 60532-1293, USA
- The Field Museum, 1400 S. Lake Shore Drive, Chicago, IL 60605-2496, USA
- For correspondence. E-mail
| |
Collapse
|
35
|
Mamidi S, Rossi M, Moghaddam SM, Annam D, Lee R, Papa R, McClean PE. Demographic factors shaped diversity in the two gene pools of wild common bean Phaseolus vulgaris L. Heredity (Edinb) 2013; 110:267-76. [PMID: 23169559 PMCID: PMC3668653 DOI: 10.1038/hdy.2012.82] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Revised: 05/31/2012] [Accepted: 06/29/2012] [Indexed: 11/09/2022] Open
Abstract
Wild common bean (Phaseolus vulgaris L.) is distributed throughout the Americas from Mexico to northern Argentina. Within this range, the species is divided into two gene pools (Andean and Middle American) along a latitudinal gradient. The diversity of 24 wild common bean genotypes from throughout the geographic range of the species was described by using sequence data from 13 loci. An isolation-migration model was evaluated using a coalescent analysis to estimate multiple demographic parameters. Using a Bayesian approach, Andean and Middle American subpopulations with high percentage of parentages were observed. Over all loci, the Middle American gene pool was more diverse than the Andean gene pool (π(sil)=0.0089 vs 0.0068). The two subpopulations were strongly genetically differentiated over all loci (F(st)=0.29). It is estimated that the two current wild gene pools diverged from a common ancestor ∼111 000 years ago. Subsequently, each gene pool underwent a bottleneck immediately after divergence and lasted ∼40 000 years. The Middle American bottleneck population size was ∼46% of the ancestral population size, whereas the Andean was 26%. Continuous asymmetric gene flow was detected between the two gene pools with a larger number of migrants entering Middle American gene pool from the Andean gene pool. These results suggest that because of the complex population structure associated with the ancestral divergence, subsequent bottlenecks in each gene pool, gene pool-specific domestication and intense selection within each gene pool by breeders; association mapping would best be practised within each common bean gene pool.
Collapse
Affiliation(s)
- S Mamidi
- Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND, USA
- Department of Plant Sciences, North Dakota State University, Fargo, ND, USA
| | - M Rossi
- Dipartimento di Scienze Agrarie, Alimentari ed Ambientali, Università Politecnica delle Marche, Ancona, Italy
| | - S M Moghaddam
- Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND, USA
- Department of Plant Sciences, North Dakota State University, Fargo, ND, USA
| | - D Annam
- Department of Statistics, North Dakota State University, Fargo, ND, USA
| | - R Lee
- Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND, USA
- Department of Plant Sciences, North Dakota State University, Fargo, ND, USA
| | - R Papa
- Dipartimento di Scienze Agrarie, Alimentari ed Ambientali, Università Politecnica delle Marche, Ancona, Italy
- Cereal Research Centre, Agricultural Research Council (CRA-CER), Foggia, Italy
| | - P E McClean
- Genomics and Bioinformatics Program, North Dakota State University, Fargo, ND, USA
- Department of Plant Sciences, North Dakota State University, Fargo, ND, USA
| |
Collapse
|
36
|
McGaugh SE, Heil CSS, Manzano-Winkler B, Loewe L, Goldstein S, Himmel TL, Noor MAF. Recombination modulates how selection affects linked sites in Drosophila. PLoS Biol 2012; 10:e1001422. [PMID: 23152720 PMCID: PMC3496668 DOI: 10.1371/journal.pbio.1001422] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 10/05/2012] [Indexed: 11/18/2022] Open
Abstract
Recombination rate in Drosophila species shapes the impact of selection in the genome and is positively correlated with nucleotide diversity. One of the most influential observations in molecular evolution has been a strong association between local recombination rate and nucleotide polymorphisms across the genome. This is interpreted as evidence for ubiquitous natural selection. The alternative explanation, that recombination is mutagenic, has been rejected by the absence of a similar association between local recombination rate and nucleotide divergence between species. However, many recent studies show that recombination rates are often very different even in closely related species, questioning whether an association between recombination rate and divergence between species has been tested satisfactorily. To circumvent this problem, we directly surveyed recombination across approximately 43% of the D. pseudoobscura physical genome in two separate recombination maps and 31% of the D. miranda physical genome, and we identified both global and local differences in recombination rate between these two closely related species. Using only regions with conserved recombination rates between and within species and accounting for multiple covariates, our data support the conclusion that recombination is positively related to diversity because recombination modulates Hill–Robertson effects in the genome and not because recombination is predominately mutagenic. Finally, we find evidence for dips in diversity around nonsynonymous substitutions. We infer that at least some of this reduction in diversity resulted from selective sweeps and examine these dips in the context of recombination rate. Individuals within a species differ in the DNA sequences of their genes. This sequence variation affects how well individuals survive or reproduce and is transmitted to their offspring. Genes near each other on individual chromosomes tend to be passed to offspring together—neighboring genes are unlikely to be separated by exchanges of genetic material derived from different parents during meiotic recombination. When genes are inherited together, however, the evolutionary forces acting on one gene can interfere with variation at its neighbors. Thus, variation at multiple genes can be lost if natural selection acts on one gene in close proximity. Recombination can prevent or reduce this loss of variation, but previous tests of this phenomenon failed to account for recombination rate differences between species. In this study, we show that some parts of the genome differ in recombination rate between two species of fruit fly, Drosophila pseudoobscura and D. miranda. Avoiding an assumption made in previous studies, we then examine sequence variation within and between fly species in those parts of the genome that have conserved recombination rates. Based on the results, we conclude that recombination indeed preserves variation within species that would otherwise have been eliminated by natural selection.
Collapse
Affiliation(s)
- Suzanne E McGaugh
- Biology Department, Duke University, Durham, North Carolina, United States of America.
| | | | | | | | | | | | | |
Collapse
|
37
|
Flaxman SM, Feder JL, Nosil P. Spatially explicit models of divergence and genome hitchhiking. J Evol Biol 2012; 25:2633-50. [DOI: 10.1111/jeb.12013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 08/24/2012] [Accepted: 09/09/2012] [Indexed: 12/11/2022]
Affiliation(s)
- S. M. Flaxman
- Department of Ecology and Evolutionary Biology; University of Colorado; Boulder CO USA
| | - J. L. Feder
- Department of Biological Sciences; University of Notre Dame; Notre Dame IN USA
| | - P. Nosil
- Department of Ecology and Evolutionary Biology; University of Colorado; Boulder CO USA
| |
Collapse
|
38
|
Sun Y, Corcoran P, Menkis A, Whittle CA, Andersson SGE, Johannesson H. Large-scale introgression shapes the evolution of the mating-type chromosomes of the filamentous ascomycete Neurospora tetrasperma. PLoS Genet 2012; 8:e1002820. [PMID: 22844246 PMCID: PMC3406010 DOI: 10.1371/journal.pgen.1002820] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 05/17/2012] [Indexed: 12/14/2022] Open
Abstract
The significance of introgression as an evolutionary force shaping natural populations is well established, especially in animal and plant systems. However, the abundance and size of introgression tracts, and to what degree interspecific gene flow is the result of adaptive processes, are largely unknown. In this study, we present medium coverage genomic data from species of the filamentous ascomycete Neurospora, and we use comparative genomics to investigate the introgression landscape at the genomic level in this model genus. We revealed one large introgression tract in each of the three investigated phylogenetic lineages of Neurospora tetrasperma (sizes of 5.6 Mbp, 5.2 Mbp, and 4.1 Mbp, respectively). The tract is located on the chromosome containing the locus conferring sexual identity, the mating-type (mat) chromosome. The region of introgression is confined to the region of suppressed recombination and is found on one of the two mat chromosomes (mat a). We used Bayesian concordance analyses to exclude incomplete lineage sorting as the cause for the observed pattern, and multilocus genealogies from additional species of Neurospora show that the introgression likely originates from two closely related, freely recombining, heterothallic species (N. hispaniola and N. crassa/N. perkinsii). Finally, we investigated patterns of molecular evolution of the mat chromosome in Neurospora, and we show that introgression is correlated with reduced level of molecular degeneration, consistent with a shorter time of recombination suppression. The chromosome specific (mat) and allele specific (mat a) introgression reported herein comprise the largest introgression tracts reported to date from natural populations. Furthermore, our data contradicts theoretical predictions that introgression should be less likely on sex-determining chromosomes. Taken together, the data presented herein advance our general understanding of introgression as a force shaping eukaryotic genomes. Introgression is a process by which genetic material from one species becomes infiltrated into another, genetically distinct species. Introgression usually occurs via sexual reproduction: individuals of two species mate and produce a hybrid offspring, then the offspring repeatedly backcross with one of the parental species. Introgression has long been recognized as a key process in evolution, as it may contribute to speciation, diversification, and adaptation to new environments. The importance and prevalence of introgression has been well established in plant and animal systems, and in this study we use a fungal model system, Neurospora, to study the introgression at the genomic level. We gathered genomic data from six genomes, and by comparative genomics we revealed genetic transfer of DNA regions of unprecedentedly large sizes, covering over 50% of the mating-type chromosomes, and used phylogenetic analyses to reveal the origin and direction of the transfer. Introgression was found solely on the mating-type chromosomes, which contradicts theoretical predictions for sex-determining chromosomes. We argue that this unexpected pattern is due to the fact that fungi do not have differentiated sexes (female/male) and thereby are free from sex-biased evolutionary forces. Instead, we suggest that introgression between fungal species may result in reinvigoration of genomic regions exposed to suppressed recombination.
Collapse
Affiliation(s)
- Yu Sun
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
| | - Pádraic Corcoran
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
| | - Audrius Menkis
- Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Carrie A. Whittle
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
| | | | - Hanna Johannesson
- Department of Evolutionary Biology, Uppsala University, Uppsala, Sweden
- * E-mail:
| |
Collapse
|
39
|
Guerrero RF, Rousset F, Kirkpatrick M. Coalescent patterns for chromosomal inversions in divergent populations. Philos Trans R Soc Lond B Biol Sci 2012; 367:430-8. [PMID: 22201172 DOI: 10.1098/rstb.2011.0246] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Chromosomal inversions allow genetic divergence of locally adapted populations by reducing recombination between chromosomes with different arrangements. Divergence between populations (or hybridization between species) is expected to leave signatures in the neutral genetic diversity of the inverted region. Quantitative expectations for these patterns, however, have not been obtained. Here, we develop coalescent models of neutral sites linked to an inversion polymorphism in two locally adapted populations. We consider two scenarios of local adaptation: selection on the inversion breakpoints and selection on alleles inside the inversion. We find that ancient inversion polymorphisms cause genetic diversity to depart dramatically from neutral expectations. Other situations, however, lead to patterns that may be difficult to detect; important determinants are the age of the inversion and the rate of gene flux between arrangements. We also study inversions under genetic drift, finding that they produce patterns similar to locally adapted inversions of intermediate age. Our results are consistent with empirical observations, and provide the foundation for quantitative analyses of the roles that inversions have played in speciation.
Collapse
Affiliation(s)
- Rafael F Guerrero
- Section of Integrative Biology, University of Texas, Austin, TX 78712, USA.
| | | | | |
Collapse
|
40
|
McGaugh SE, Noor MAF. Genomic impacts of chromosomal inversions in parapatric Drosophila species. Philos Trans R Soc Lond B Biol Sci 2012; 367:422-9. [PMID: 22201171 DOI: 10.1098/rstb.2011.0250] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Chromosomal inversions impact genetic variation and facilitate speciation in part by reducing recombination in heterokaryotypes. We generated multiple whole-genome shotgun sequences of the parapatric species pair Drosophila pseudoobscura and Drosophila persimilis and their sympatric outgroup (Drosophila miranda) and compared the average pairwise differences for neutral sites within, just outside and far outside of the three large inversions. Divergence between D. pseudoobscura and D. persimilis is high inside the inversions and in the suppressed recombination regions extending 2.5 Mb outside of inversions, but significantly lower in collinear regions further from the inversions. We observe little evidence of decreased divergence predicted to exist in the centre of inversions, suggesting that gene flow through double crossovers or gene conversion is limited within the inversion, or selection is acting within the inversion to maintain divergence in the face of gene flow. In combination with past studies, we provide evidence that inversions in this system maintain areas of high divergence in the face of hybridization, and have done so for a substantial period of time. The left arm of the X chromosome and chromosome 2 inversions appear to have arisen in the lineage leading to D. persimilis approximately 2 Ma, near the time of the split of D. persimilis-D. pseudoobscura-D. miranda, but likely fixed within D. persimilis much more recently, as diversity within D. persimilis is substantially reduced inside and near these two inversions. We also hypothesize that the inversions in D. persimilis may provide an empirical example of the 'mixed geographical mode' theory of inversion origin and fixation, whereby allopatry and secondary contact both play a role.
Collapse
Affiliation(s)
- Suzanne E McGaugh
- Biology Department, Duke University, Box 90388, Durham, NC 27708, USA.
| | | |
Collapse
|
41
|
Abstract
Chromosomal inversions are thought to play a special role in local adaptation, through dramatic suppression of recombination, which favors the maintenance of locally adapted alleles. However, relatively few inversions have been characterized in population genomic data. On the basis of single-nucleotide polymorphism (SNP) genotyping across a large panel of Zea mays, we have identified an ∼50-Mb region on the short arm of chromosome 1 where patterns of polymorphism are highly consistent with a polymorphic paracentric inversion that captures >700 genes. Comparison to other taxa in Zea and Tripsacum suggests that the derived, inverted state is present only in the wild Z. mays subspecies parviglumis and mexicana and is completely absent in domesticated maize. Patterns of polymorphism suggest that the inversion is ancient and geographically widespread in parviglumis. Cytological screens find little evidence for inversion loops, suggesting that inversion heterozygotes may suffer few crossover-induced fitness consequences. The inversion polymorphism shows evidence of adaptive evolution, including a strong altitudinal cline, a statistical association with environmental variables and phenotypic traits, and a skewed haplotype frequency spectrum for inverted alleles.
Collapse
|
42
|
|
43
|
Grath S, Parsch J. Rate of amino acid substitution is influenced by the degree and conservation of male-biased transcription over 50 myr of Drosophila evolution. Genome Biol Evol 2012; 4:346-59. [PMID: 22321769 PMCID: PMC3318448 DOI: 10.1093/gbe/evs012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2012] [Indexed: 12/18/2022] Open
Abstract
Sex-biased gene expression (i.e., the differential expression of genes between males and females) is common among sexually reproducing species. However, genes often differ in their sex-bias classification or degree of sex bias between species. There is also an unequal distribution of sex-biased genes (especially male-biased genes) between the X chromosome and the autosomes. We used whole-genome expression data and evolutionary rate estimates for two different Drosophilid lineages, melanogaster and obscura, spanning an evolutionary time scale of around 50 Myr to investigate the influence of sex-biased gene expression and chromosomal location on the rate of molecular evolution. In both lineages, the rate of protein evolution correlated positively with the male/female expression ratio. Genes with highly male-biased expression, genes expressed specifically in male reproductive tissues, and genes with conserved male-biased expression over long evolutionary time scales showed the fastest rates of evolution. An analysis of sex-biased gene evolution in both lineages revealed evidence for a "fast-X" effect in which the rate of evolution was greater for X-linked than for autosomal genes. This pattern was particularly pronounced for male-biased genes. Genes located on the obscura "neo-X" chromosome, which originated from a recent X-autosome fusion, showed rates of evolution that were intermediate between genes located on the ancestral X-chromosome and the autosomes. This suggests that the shift to X-linkage led to an increase in the rate of molecular evolution.
Collapse
Affiliation(s)
- Sonja Grath
- Institute for Evolution and Biodiversity, University of Muenster (WWU), Germany.
| | | |
Collapse
|
44
|
Muir G, Dixon CJ, Harper AL, Filatov DA. Dynamics of drift, gene flow, and selection during speciation in Silene. Evolution 2012; 66:1447-58. [PMID: 22519783 DOI: 10.1111/j.1558-5646.2011.01529.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanics of speciation with gene flow are still unclear. Disparity among genes in population differentiation (F(ST)) between diverging species is often interpreted as evidence for semipermeable species boundaries, with selection preventing "key" genes from introgressing despite ongoing gene flow. However, F(ST) can remain high before it reaches equilibrium between the lineage sorting of species divergence and the homogenizing effects of gene flow (via secondary contact). Thus, when interpreting F(ST), the dynamics of drift, gene flow, and selection need to be taken into account. We illustrate this view with a multigenic analyses of gene flow and selection in three closely related Silene species, S. latifolia, S. dioica, and S. diclinis. We report that although S. diclinis appears to have evolved in allopatry, isolation with (bidirectional) gene flow between S. latifolia and S. dioica is likely, perhaps as a result of parapatric speciation followed by more extensive sympatry. Interestingly, we detected the signatures of apparently independent instances of positive selection at the same locus in S. latifolia and S. dioica. Despite gene flow between the species, the adaptive alleles have not crossed the species boundary, suggesting that this gene has independently undergone species-specific (diversifying or parallel) selection.
Collapse
Affiliation(s)
- Graham Muir
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, United Kingdom.
| | | | | | | |
Collapse
|
45
|
Sambatti JB, Strasburg JL, Ortiz-Barrientos D, Baack EJ, Rieseberg LH. RECONCILING EXTREMELY STRONG BARRIERS WITH HIGH LEVELS OF GENE EXCHANGE IN ANNUAL SUNFLOWERS. Evolution 2012; 66:1459-73. [DOI: 10.1111/j.1558-5646.2011.01537.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
46
|
Ecological genomics of Anopheles gambiae along a latitudinal cline: a population-resequencing approach. Genetics 2011; 190:1417-32. [PMID: 22209907 DOI: 10.1534/genetics.111.137794] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The association between fitness-related phenotypic traits and an environmental gradient offers one of the best opportunities to study the interplay between natural selection and migration. In cases in which specific genetic variants also show such clinal patterns, it may be possible to uncover the mutations responsible for local adaptation. The malaria vector, Anopheles gambiae, is associated with a latitudinal cline in aridity in Cameroon; a large inversion on chromosome 2L of this mosquito shows large differences in frequency along this cline, with high frequencies of the inverted karyotype present in northern, more arid populations and an almost complete absence of the inverted arrangement in southern populations. Here we use a genome resequencing approach to investigate patterns of population divergence along the cline. By sequencing pools of individuals from both ends of the cline as well as in the center of the cline- where the inversion is present in intermediate frequency- we demonstrate almost complete panmixia across collinear parts of the genome and high levels of differentiation in inverted parts of the genome. Sequencing of separate pools of each inversion arrangement in the center of the cline reveals large amounts of gene flux (i.e., gene conversion and double crossovers) even within inverted regions, especially away from the inversion breakpoints. The interplay between natural selection, migration, and gene flux allows us to identify several candidate genes responsible for the match between inversion frequency and environmental variables. These results, coupled with similar conclusions from studies of clinal variation in Drosophila, point to a number of important biological functions associated with local environmental adaptation.
Collapse
|
47
|
Stevison LS, Hoehn KB, Noor MAF. Effects of inversions on within- and between-species recombination and divergence. Genome Biol Evol 2011; 3:830-41. [PMID: 21828374 PMCID: PMC3171675 DOI: 10.1093/gbe/evr081] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Chromosomal inversions disrupt recombination in heterozygotes by both reducing crossing-over within inverted regions and increasing it elsewhere in the genome. The reduction of recombination in inverted regions facilitates the maintenance of hybridizing species, as outlined by various models of chromosomal speciation. We present a comprehensive comparison of the effects of inversions on recombination rates and on nucleotide divergence. Within an inversion differentiating Drosophila pseudoobscura and Drosophila persimilis, we detected one double recombinant among 9,739 progeny from F1 hybrids screened, consistent with published double-crossover frequencies observed within species. Despite similar rates of exchange within and between species, we found no sequence-based evidence of ongoing gene exchange between species within this inversion, but significant exchange was inferred within species. We also observed greater differentiation at regions near inversion breakpoints between species versus within species. Moreover, we observed strong “interchromosomal effect” (higher recombination in inversion heterozygotes between species) with up to 9-fold higher recombination rates along collinear segments of chromosome two in hybrids. Further, we observed that regions most susceptible to changes in recombination rates corresponded to regions with lower recombination rates in homokaryotypes. Finally, we showed that interspecies nucleotide divergence is lower in regions with greater increases in recombination rate, potentially resulting from greater interspecies exchange. Overall, we have identified several similarities and differences between inversions segregating within versus between species in their effects on recombination and divergence. We conclude that these differences are most likely due to lower frequency of heterokaryotypes and to fitness consequences from the accumulation of various incompatibilities between species. Additionally, we have identified possible effects of inversions on interspecies gene exchange that had not been considered previously.
Collapse
|
48
|
Servedio MR, Van Doorn GS, Kopp M, Frame AM, Nosil P. Magic traits in speciation: ‘magic’ but not rare? Trends Ecol Evol 2011; 26:389-97. [PMID: 21592615 DOI: 10.1016/j.tree.2011.04.005] [Citation(s) in RCA: 372] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 04/05/2011] [Accepted: 04/11/2011] [Indexed: 12/29/2022]
Affiliation(s)
- Maria R Servedio
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
| | | | | | | | | |
Collapse
|
49
|
McDermott SR, Noor MAF. Genetics of hybrid male sterility among strains and species in the Drosophila pseudoobscura species group. Evolution 2011; 65:1969-78. [PMID: 21729052 PMCID: PMC3132132 DOI: 10.1111/j.1558-5646.2011.01256.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Taxa in the early stages of speciation may bear intraspecific allelic variation at loci conferring barrier traits in hybrids such as hybrid sterility. Additionally, hybridization may spread alleles that confer barrier traits to other taxa. Historically, few studies examine within- and between-species variation at loci conferring reproductive isolation. Here, we test for allelic variation within Drosophila persimilis and within the Bogota subspecies of D. pseudoobscura at regions previously shown to contribute to hybrid male sterility. We also test whether D. persimilis and the USA subspecies of D. pseudoobscura share an allele conferring hybrid sterility in a D. pseudoobscura bogotana genetic background. All loci conferred similar hybrid sterility effects across all strains studied, although we detected some statistically significant quantitative effect variation among D. persimilis alleles of some hybrid incompatibility QTLs. We also detected allelism between D. persimilis and D. pseudoobscura USA at a second chromosome hybrid sterility QTL. We hypothesize that either the QTL is ancestral in D. persimilis and D. pseudoobscura USA and lost in D. pseudoobscura bogotana, or gene flow transferred the QTL from D. persimilis to D. pseudoobscura USA. We discuss our findings in the context of population features that may contribute to variation in hybrid incompatibilities.
Collapse
Affiliation(s)
- Shannon R McDermott
- University Program in Genetics and Genomics, and Biology Department, Duke University, Durham, North Carolina 27708, USA.
| | | |
Collapse
|
50
|
Carneiro M, Blanco-Aguiar JA, Villafuerte R, Ferrand N, Nachman MW. Speciation in the European rabbit (Oryctolagus cuniculus): islands of differentiation on the X chromosome and autosomes. Evolution 2011; 64:3443-60. [PMID: 20666840 DOI: 10.1111/j.1558-5646.2010.01092.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Studies of gene flow between closely related taxa can provide insight into the genetic basis of speciation. To evaluate the importance of the X chromosome in reproductive isolation between subspecies of the European rabbit and to study the genomic scale over which islands of differentiation extend, we resequenced a total of 34 loci distributed along the X chromosome and chromosome 14. Previous studies based on few markers suggested that loci in centromeric regions were highly differentiated between rabbit subspecies, whereas loci in telomeric regions were less differentiated. Here, we confirmed this finding but also discovered remarkable variation in levels of differentiation among loci, with F(ST) values from nearly 0 to 1. Analyses using isolation-with-migration models suggest that this range appears to be largely explained by differential levels of gene flow among loci. The X chromosome was significantly more differentiated than the autosomes. On chromosome 14, differentiation decayed very rapidly at increasing distances from the centromere, but on the X chromosome distinct islands of differentiation encompassing several megabases were observed both at the centromeric region and along the chromosome arms. These findings support the idea that the X chromosome plays an important role in reproductive isolation between rabbit subspecies. These results also demonstrate the mosaic nature of the genome at species boundaries.
Collapse
Affiliation(s)
- Miguel Carneiro
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661, Vairão, Portugal.
| | | | | | | | | |
Collapse
|