1
|
Bladen J, Nam HJ, Phadnis N. Transformation of meiotic drive into hybrid sterility in Drosophila. Genetics 2024:iyae133. [PMID: 39196789 DOI: 10.1093/genetics/iyae133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Accepted: 07/05/2024] [Indexed: 08/30/2024] Open
Abstract
Hybrid male sterility is one of the fastest evolving intrinsic reproductive barriers between recently isolated populations. A leading explanation for the evolution of hybrid male sterility involves genomic conflicts with meiotic drivers in the male germline. There are, however, few examples directly linking meiotic drive to hybrid sterility. In this study, we report that the Sex-Ratio chromosome of Drosophila pseudoobscura, which causes X-chromosome drive within the USA subspecies, causes near-complete male sterility when it is moved into the genetic background of the Bogota subspecies. In addition, we show that this new form of sterility is genetically distinct from the sterility of F1 hybrid males in crosses between USA males and Bogota females. Our observations provide a tractable study system where noncryptic drive within species is transformed into strong hybrid sterility between very young subspecies.
Collapse
Affiliation(s)
- Jackson Bladen
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Hyuck-Jin Nam
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Nitin Phadnis
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| |
Collapse
|
2
|
Bladen J, Nam HJ, Phadnis N. Transformation of meiotic drive into hybrid sterility in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.10.593569. [PMID: 38798315 PMCID: PMC11118531 DOI: 10.1101/2024.05.10.593569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Hybrid male sterility is one of the fastest evolving intrinsic reproductive barriers between recently isolated populations. A leading explanation for the evolution of hybrid male sterility involves genomic conflicts with meiotic drivers in the male germline. There are, however, few examples directly linking meiotic drive to hybrid sterility. Here, we report that the Sex-Ratio chromosome of Drosophila pseudoobscura, which causes X-chromosome drive within the USA subspecies, causes near complete male sterility when moved into the genetic background of the Bogota subspecies. In addition, we show that this new form of sterility is genetically distinct from the sterility of F1 hybrid males in crosses between USA males and Bogota females. Our observations provide a tractable study system where non-cryptic drive within species is transformed into strong hybrid sterility between very young subspecies.
Collapse
Affiliation(s)
- Jackson Bladen
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Hyuck-Jin Nam
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Nitin Phadnis
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| |
Collapse
|
3
|
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
|
4
|
Benites P, Zaldívar-Riverón A, Meza-Lázaro RN, Samacá-Sáenz E, Gutiérrez-Rodríguez J, Hernández-López A. Multiple introgression events during the diversification history of the edible mexican grasshopper genus sphenarium (orthoptera: pyrgomorphidae). Mol Phylogenet Evol 2023; 183:107774. [PMID: 36972795 DOI: 10.1016/j.ympev.2023.107774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 03/07/2023] [Accepted: 03/22/2023] [Indexed: 03/29/2023]
Abstract
Speciation with gene flow often leads to ambiguous phylogenetic reconstructions, reticulate patterns of relatedness and conflicting nuclear versus mitochondrial (mt) lineages. Here we employed a fragment of the COI mtDNA gene and nuclear genome-wide data (3RAD) to assess the diversification history of Sphenarium, an orthopteran genus of great economic importance in Mexico that is presumed to have experienced hybridisation events in some of its species. We carried out separate phylogenetic analyses to evaluate the existence of mito-nuclear discordance in the species relationships, and also assessed the genomic diversity and population genomic structure and investigated the existence of interspecific introgression and species limits of the taxa involved based on the nuclear dataset. The species delineation analyses discriminated all the currently recognised species, but also supported the existence of four undescribed species. The mt and nuclear topologies had four discordant species relationships that can be explained by mt introgression, where the mt haplotypes of S. purpurascens appear to have replaced those of S. purpurascens A and B, S. variabile and S. zapotecum. Moreover, our analyses supported the existence of nuclear introgression events between four species pairs that are distributed in the Sierra Madre del Sur province in southeast Mexico, with three of them occurring in the Tehuantepec Isthmus region. Our study highlights the relevance of genomic data to address the relative importance of allopatric isolation versus gene flow in speciation.
Collapse
Affiliation(s)
- Pilar Benites
- Colección Nacional de Insectos, Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito Exterior s/n, Cd. Universitaria, Copilco, Coyoacán, A. P. 70-233, C. P. 04510, Ciudad de México, México
| | - Alejandro Zaldívar-Riverón
- Colección Nacional de Insectos, Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito Exterior s/n, Cd. Universitaria, Copilco, Coyoacán, A. P. 70-233, C. P. 04510, Ciudad de México, México
| | - Rubi N Meza-Lázaro
- Colección Nacional de Insectos, Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito Exterior s/n, Cd. Universitaria, Copilco, Coyoacán, A. P. 70-233, C. P. 04510, Ciudad de México, México
| | - Ernesto Samacá-Sáenz
- Colección Nacional de Insectos, Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito Exterior s/n, Cd. Universitaria, Copilco, Coyoacán, A. P. 70-233, C. P. 04510, Ciudad de México, México; Instituto de Investigaciones Biomédicas, Departamento de Biología Celular y Fisiología, Universidad Nacional Autónoma de México, 3er Circuito Exterior s/n, Cd. Universitaria, Coyoacán, 04510 Ciudad de México, México
| | | | - Antonio Hernández-López
- Escuela Nacional de Estudios Superiores Unidad León, Universidad Nacional Autónoma de México, Guanajuato, México
| |
Collapse
|
5
|
Banker SE, Bonhomme F, Nachman MW. Bidirectional introgression between Mus musculus domesticus and Mus spretus. Genome Biol Evol 2022; 14:6509516. [PMID: 35038727 PMCID: PMC8784167 DOI: 10.1093/gbe/evab288] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2021] [Indexed: 11/24/2022] Open
Abstract
Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles—including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Collapse
Affiliation(s)
- Sarah E Banker
- Department of Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - François Bonhomme
- Institut des Sciences de l'Evolution, Université de Montpellier, Montpellier, France
| | - Michael W Nachman
- Department of Integrative Biology and Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, 94720, USA
| |
Collapse
|
6
|
Bauer DuMont VL, White SL, Zinshteyn D, Aquadro CF. Molecular population genetics of Sex-lethal ( Sxl) in the Drosophila melanogaster species group: a locus that genetically interacts with Wolbachia pipientis in Drosophila melanogaster. G3 GENES|GENOMES|GENETICS 2021; 11:6296609. [PMID: 34849818 PMCID: PMC8496275 DOI: 10.1093/g3journal/jkab197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 06/01/2021] [Indexed: 11/13/2022]
Abstract
Abstract
Sex-lethal (Sxl) is the sex determination switch in Drosophila, and also plays a critical role in germ-line stem cell daughter differentiation in Drosophila melanogaster. Three female-sterile alleles at Sxl in D. melanogaster were previously shown to genetically interact to varying degrees with the maternally inherited endosymbiont Wolbachia pipientis. Given this genetic interaction and W. pipientis’ ability to manipulate reproduction in Drosophila, we carried out a careful study of both the population genetics (within four Drosophila species) and molecular evolutionary analysis (across 20 Drosophila species) of Sxl. Consistent with earlier studies, we find that selective constraint has played a prominent role in Sxl’s molecular evolution within Drosophila, but we also observe patterns that suggest both episodic bursts of protein evolution and recent positive selection at Sxl. The episodic nature of Sxl’s protein evolution is discussed in light of its genetic interaction with W. pipientis.
Collapse
Affiliation(s)
| | - Simone L White
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Daniel Zinshteyn
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Charles F Aquadro
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| |
Collapse
|
7
|
How Important Are Structural Variants for Speciation? Genes (Basel) 2021; 12:genes12071084. [PMID: 34356100 PMCID: PMC8305853 DOI: 10.3390/genes12071084] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/04/2021] [Accepted: 07/14/2021] [Indexed: 12/11/2022] Open
Abstract
Understanding the genetic basis of reproductive isolation is a central issue in the study of speciation. Structural variants (SVs); that is, structural changes in DNA, including inversions, translocations, insertions, deletions, and duplications, are common in a broad range of organisms and have been hypothesized to play a central role in speciation. Recent advances in molecular and statistical methods have identified structural variants, especially inversions, underlying ecologically important traits; thus, suggesting these mutations contribute to adaptation. However, the contribution of structural variants to reproductive isolation between species—and the underlying mechanism by which structural variants most often contribute to speciation—remain unclear. Here, we review (i) different mechanisms by which structural variants can generate or maintain reproductive isolation; (ii) patterns expected with these different mechanisms; and (iii) relevant empirical examples of each. We also summarize the available sequencing and bioinformatic methods to detect structural variants. Lastly, we suggest empirical approaches and new research directions to help obtain a more complete assessment of the role of structural variants in speciation.
Collapse
|
8
|
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
|
9
|
Abstract
The detection of introgression from genomic data is transforming our view of species and the origins of adaptive variation. Among the most widely used approaches to detect introgression is the so-called ABBA-BABA test or D-statistic, which identifies excess allele sharing between nonsister taxa. Part of the appeal of D is its simplicity, but this also limits its informativeness, particularly about the timing and direction of introgression. Here we present a simple extension, D frequency spectrum or DFS, in which D is partitioned according to the frequencies of derived alleles. We use simulations over a large parameter space to show how DFS carries information about various factors. In particular, recent introgression reliably leads to a peak in DFS among low-frequency derived alleles, whereas violation of model assumptions can lead to a lack of signal at low frequencies. We also reanalyze published empirical data from six different animal and plant taxa, and interpret the results in the light of our simulations, showing how DFS provides novel insights. We currently see DFS as a descriptive tool that will augment both simple and sophisticated tests for introgression, but in the future it may be usefully incorporated into probabilistic inference frameworks.
Collapse
Affiliation(s)
- Simon H Martin
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - William Amos
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
10
|
Rakotoarivelo AR, O’Donoghue P, Bruford MW, Moodley Y. An ancient hybridization event reconciles mito-nuclear discordance among spiral-horned antelopes. J Mammal 2019. [DOI: 10.1093/jmammal/gyz089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Abstract
The spiral-horned antelopes (genus Tragelaphus) are among the most phenotypically diverse of all large mammals, and evolved in Africa during an adaptive radiation that began in the late Miocene, around 6 million years ago. Tragelaphus was able to exploit the habitat heterogeneity created by Plio-Pleistocene paleoclimatic fluctuations and tectonic processes to eventually occupy almost every habitat type in present day sub-Saharan Africa. The smallest of the spiral-horned antelopes, the bushbuck (T. scriptus), is also widely distributed across Africa, but is genetically divided into polyphyletic Scriptus and Sylvaticus mitochondrial (mt)DNA superlineages that inhabit opposite halves of the continent, suggesting the convergent evolution of independent bushbuck species. In this study, we provide a species tree reconstruction for the genus Tragelaphus and show that Scriptus and Sylvaticus are reciprocally monophyletic at nuclear DNA loci, comprising a single species across its African range. Given that mtDNA will sort into species-specific lineages more quickly than nuclear DNA, only an ancient interspecific hybridization event between a female from a now-extinct Tragelaphus species and a proto-Scriptus bushbuck male can reconcile the mito-nuclear incongruence. This extinct species diverged from the nyala (T. angasii) in the Pliocene about 4.1 million years ago. This study adds to an increasing body of evidence that suggests interspecific hybridization may be more common than previously thought.
Collapse
Affiliation(s)
- Andrinajoro R Rakotoarivelo
- Department of Zoology, University of Venda, Thohoyandou, Republic of South Africa
- Natiora Ahy, Lot Bis, Ampahibe, Antananarivo, Madagascar
| | | | - Michael W Bruford
- Cardiff School of Biosciences, Sir Martin Evans Building, Cardiff University, Museum Avenue, Cardiff, United Kingdom
| | - Yoshan Moodley
- Department of Zoology, University of Venda, Thohoyandou, Republic of South Africa
| |
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
|
Díaz F, Luís A. Lima A, Nakamura AM, Fernandes F, Sobrinho I, de Brito RA. Evidence for Introgression Among Three Species of the Anastrepha fraterculus Group, a Radiating Species Complex of Fruit Flies. Front Genet 2018; 9:359. [PMID: 30250479 PMCID: PMC6139333 DOI: 10.3389/fgene.2018.00359] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 08/21/2018] [Indexed: 12/13/2022] Open
Abstract
Introgression should no longer be considered as rare a phenomenon as once thought, since several studies have recently documented gene flow between closely related and radiating species. Here, we investigated evolutionary relationships among three closely related species of fruit flies of the Anastrepha fraterculus group (Anastrepha fraterculus, A. obliqua and A. sororcula). We sequenced a set of 20 genes and implemented a combined populational and phylogenetic inference with a model selection approach by an ABC framework in order to elucidate the demographic history of these species. The phylogenetic histories inferred from most genes showed a great deal of discordance and substantial shared polymorphic variation. The analysis of several population and speciation models reveal that this shared variation is better explained by introgression rather than convergence by parallel mutation or incomplete lineage sorting. Our results consistently showed these species evolving under an isolation with migration model experiencing a continuous and asymmetrical pattern of gene flow involving all species pairs, even though still showed a more closely related relationship between A. fraterculus and A. sororcula when compared with A. obliqua. This suggests that these species have been exchanging genes since they split from their common ancestor ∼2.6 MYA ago. We also found strong evidence for recent population expansion that appears to be consequence of anthropic activities affecting host crops of fruit flies. These findings point that the introgression here found may have been driven by genetic drift and not necessary by selection, which has implications for tracking and managing fruit flies.
Collapse
Affiliation(s)
- Fernando Díaz
- Department of Entomology, University of Arizona, Tucson, AZ, United States
| | - André Luís A. Lima
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Aline M. Nakamura
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Fernanda Fernandes
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Iderval Sobrinho
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Reinaldo A. de Brito
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, Brazil
| |
Collapse
|
13
|
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
|
14
|
Reeve J, Ortiz-Barrientos D, Engelstädter J. The evolution of recombination rates in finite populations during ecological speciation. Proc Biol Sci 2017; 283:rspb.2016.1243. [PMID: 27798297 DOI: 10.1098/rspb.2016.1243] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 10/04/2016] [Indexed: 11/12/2022] Open
Abstract
Recombination can impede ecological speciation with gene flow by mixing locally adapted genotypes with maladapted migrant genotypes from a divergent population. In such a scenario, suppression of recombination can be selectively favoured. However, in finite populations evolving under the influence of random genetic drift, recombination can also facilitate adaptation by reducing Hill-Robertson interference between loci under selection. In this case, increased recombination rates can be favoured. Although these two major effects on recombination have been studied individually, their joint effect on ecological speciation with gene flow remains unexplored. Using a mathematical model, we investigated the evolution of recombination rates in two finite populations that exchange migrants while adapting to contrasting environments. Our results indicate a two-step dynamic where increased recombination is first favoured (in response to the Hill-Robertson effect), and then disfavoured, as the cost of recombining locally with maladapted migrant genotypes increases over time (the maladaptive gene flow effect). In larger populations, a stronger initial benefit for recombination was observed, whereas high migration rates intensify the long-term cost of recombination. These dynamics may have important implications for our understanding of the conditions that facilitate incipient speciation with gene flow and the evolution of recombination in finite populations.
Collapse
Affiliation(s)
- James Reeve
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Daniel Ortiz-Barrientos
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jan Engelstädter
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| |
Collapse
|
15
|
Davis JS, Castillo DM, Moyle LC. Remating responses are consistent with male postcopulatory manipulation but not reinforcement in D. pseudoobscura. Ecol Evol 2017; 7:507-515. [PMID: 28116047 PMCID: PMC5243186 DOI: 10.1002/ece3.2628] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/21/2016] [Accepted: 10/25/2016] [Indexed: 11/05/2022] Open
Abstract
Reinforcement occurs when hybridization between closely related lineages produces low-fitness offspring, prompting selection for elevated reproductive isolation specifically in areas of sympatry. Both premating and postmating prezygotic behaviors have been shown to be the target of reinforcing selection, but it remains unclear whether remating behaviors experience reinforcement, although they can also influence offspring identity and limit formation of hybrids. Here, we evaluated evidence for reinforcing selection on remating behaviors in Drosophila pseudoobscura, by comparing remating traits in females from populations historically allopatric and sympatric with Drosophila persimilis. We found that the propensity to remate was not higher in sympatric females, compared to allopatric females, regardless of whether the first mated male was heterospecific or conspecific. Moreover, remating behavior did not contribute to interspecific reproductive isolation among any population; that is, females showed no higher propensity to remate following a heterospecific first mating than following a conspecific first mating. Instead, we found that females are less likely to remate after initial matings with unfamiliar males, regardless of species identity. This is consistent with one scenario of postmating sexual conflict in which females are poorly defended against postcopulatory manipulation by males with whom they have not coevolved. Our results are generally inconsistent with reinforcement on remating traits and suggest that this behavior might be more strongly shaped by the consequences of local antagonistic male-female interactions than interactions with heterospecifics.
Collapse
|
16
|
Ritz KR, Noor MAF. Mistaken Identity: Another Bias in the Use of Relative Genetic Divergence Measures for Detecting Interspecies Introgression. PLoS One 2016; 11:e0165032. [PMID: 27760228 PMCID: PMC5070774 DOI: 10.1371/journal.pone.0165032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 10/05/2016] [Indexed: 11/18/2022] Open
Abstract
Measures of genetic divergence have long been used to identify evolutionary processes operating within and between species. However, recent reviews have described a bias in the use of relative divergence measures towards incorrectly identifying genomic regions that are seemingly immune to introgression. Here, we present a novel and opposite bias of relative divergence measures: misidentifying regions of introgression between sister species. We examine two distinct haplotypes of intermediate frequency within Drosophila pseudoobscura at the DPSX009 locus. One of these haplotypes had lower relative divergence than another to sister species D. persimilis. Although we and others initially presumed one haplotype have spread via introgression between D. pseudoobscura and D. persimilis, absolute divergence measures and individual sequence analysis suggest that haplotype structuring occurred as the result of within-species processes. The potential for this type of misinference may occur with any haplotype that recently spread within a species. We conclude that absolute measures of genetic divergence are necessary for confirming putative regions of introgression.
Collapse
Affiliation(s)
- Kathryn R. Ritz
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- * E-mail:
| | - Mohamed A. F. Noor
- Department of Biology, Duke University, Durham, North Carolina, United States of America
| |
Collapse
|
17
|
Mardiros XB, Park R, Clifton B, Grewal G, Khizar AK, Markow TA, Ranz JM, Civetta A. Postmating Reproductive isolation between strains of Drosophila willistoni. Fly (Austin) 2016; 10:162-71. [PMID: 27268100 PMCID: PMC5036932 DOI: 10.1080/19336934.2016.1197448] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Speciation can occur through the presence of reproductive isolation barriers that impede mating, restrict cross-fertilization, or render inviable/sterile hybrid progeny. The D. willistoni subgroup is ideally suited for studies of speciation, with examples of both allopatry and sympatry, a range of isolation barriers, and the availability of one species complete genome sequence to facilitate genetic studies of divergence. D. w. willistoni has the largest geographic distribution among members of the Drosophila willistoni subgroup, spanning from Argentina to the southern United States, including the Caribbean islands. A subspecies of D. w. willistoni, D. w. quechua, is geographically separated by the Andes mountain range and has evolved unidirectional sterility, in that only male offspring of D. w. quechua females × D. w. willistoni males are sterile. Whether D. w. willistoni flies residing east of the Andes belong to one or more D. willistoni subspecies remains unresolved. Here we perform fecundity assays and show that F1 hybrid males produced from crosses between different strains found in Central America, North America, and northern Caribbean islands are reproductively isolated from South American and southern Caribbean island strains as a result of unidirectional hybrid male sterility. Our results show the existence of a reproductive isolation barrier between the northern and southern strains and suggest a subdivision of the previously identified D. willistoni willistoni species into 2 new subspecies.
Collapse
Affiliation(s)
- Xian B Mardiros
- a Department of Biology , University of Winnipeg , Winnipeg , Canada
| | - Ronni Park
- b Department of Ecology and Evolutionary Biology , University of California Irvine , Irvine , California , USA
| | - Bryan Clifton
- b Department of Ecology and Evolutionary Biology , University of California Irvine , Irvine , California , USA
| | - Gurman Grewal
- a Department of Biology , University of Winnipeg , Winnipeg , Canada
| | - Amina K Khizar
- a Department of Biology , University of Winnipeg , Winnipeg , Canada
| | - Therese A Markow
- c Division of Biological Sciences ; University of California , San Diego, La Jolla , California , USA
| | - José M Ranz
- b Department of Ecology and Evolutionary Biology , University of California Irvine , Irvine , California , USA
| | - Alberto Civetta
- a Department of Biology , University of Winnipeg , Winnipeg , Canada
| |
Collapse
|
18
|
Záveská E, Fér T, Šída O, Marhold K, Leong-Škorničková J. Hybridization among distantly related species: Examples from the polyploid genus Curcuma (Zingiberaceae). Mol Phylogenet Evol 2016; 100:303-321. [PMID: 27090448 DOI: 10.1016/j.ympev.2016.04.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Revised: 04/08/2016] [Accepted: 04/12/2016] [Indexed: 01/17/2023]
Abstract
Discerning relationships among species evolved by reticulate and/or polyploid evolution is not an easy task, although it is widely discussed. The economically important genus Curcuma (ca. 120 spp.; Zingiberaceae), broadly distributed in tropical SE Asia, is a particularly interesting example of a group of palaeopolyploid origin whose evolution is driven mainly by hybridization and polyploidization. Although a phylogeny and a new infrageneric classification of Curcuma, based on commonly used molecular markers (ITS and cpDNA), have recently been proposed, significant evolutionary questions remain unresolved. We applied a multilocus approach and a combination of modern analytical methods to this genus to distinguish causes of gene tree incongruence and to identify hybrids and their parental species. Five independent regions of nuclear DNA (DCS, GAPDH, GLOBOSA3, LEAFY, ITS) and four non-coding cpDNA regions (trnL-trnF, trnT-trnL, psbA-trnH and matK), analysed as a single locus, were employed to construct a species tree and hybrid species trees using (*)BEAST and STEM-hy. Detection of hybridogenous species in the dataset was also conducted using the posterior predictive checking approach as implemented in JML. The resulting species tree outlines the relationships among major evolutionary lineages within Curcuma, which were previously unresolved or which conflicted depending upon whether they were based on ITS or cpDNA markers. Moreover, by using the additional markers in tests of plausible topologies of hybrid species trees for C. vamana, C. candida, C. roscoeana and C. myanmarensis suggested by previous molecular and morphological evidence, we found strong evidence that all the species except C. candida are of subgeneric hybrid origin.
Collapse
Affiliation(s)
- Eliška Záveská
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic.
| | - Tomáš Fér
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
| | - Otakar Šída
- Department of Botany, National Museum in Prague, Prague, Czech Republic
| | - Karol Marhold
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic; Institute of Botany, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | | |
Collapse
|
19
|
Hu XS, Filatov DA. The large-X effect in plants: increased species divergence and reduced gene flow on the Silene X-chromosome. Mol Ecol 2016; 25:2609-19. [PMID: 26479725 DOI: 10.1111/mec.13427] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 10/12/2015] [Accepted: 10/15/2015] [Indexed: 12/25/2022]
Abstract
The disproportionately large involvement of the X-chromosome in the isolation of closely related species (the large-X effect) has been reported for many animals, where X-linked genes are mostly hemizygous in the heterogametic sex. The expression of deleterious recessive mutations is thought to drive the frequent involvement of the X-chromosome in hybrid sterility, as well as to reduce interspecific gene flow for X-linked genes. Here, we evaluate the role of the X-chromosome in the speciation of two closely related plant species - the white and red campions (Silene latifolia and S. dioica) - that hybridize widely across Europe. The two species evolved separate sexes and sex chromosomes relatively recently (~10(7) years), and unlike most animal species, most X-linked genes have intact Y-linked homologs. We demonstrate that the X-linked genes show a very small and insignificant amount of interspecific gene flow, while gene flow involving autosomal loci is significant and sufficient to homogenize the gene pools of the two species. These findings are consistent with the hypothesis of the large-X effect in Silene and comprise the first report of this effect in plants. Nonhemizygosity of many X-linked genes in Silene males indicates that exposure of recessive mutations to selection may not be essential for the occurrence of the large-X effect. Several possible causes of the large-X effect in Silene are discussed.
Collapse
Affiliation(s)
- Xin-Sheng Hu
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX13RB, UK
| | - Dmitry A Filatov
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX13RB, UK
| |
Collapse
|
20
|
Beck EA, Thompson AC, Sharbrough J, Brud E, Llopart A. Gene flow between Drosophila yakuba and Drosophila santomea in subunit V of cytochrome c oxidase: A potential case of cytonuclear cointrogression. Evolution 2015; 69:1973-86. [PMID: 26155926 PMCID: PMC5042076 DOI: 10.1111/evo.12718] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Revised: 06/13/2015] [Accepted: 06/16/2015] [Indexed: 12/11/2022]
Abstract
Introgression is the effective exchange of genetic information between species through natural hybridization. Previous genetic analyses of the Drosophila yakuba—D. santomea hybrid zone showed that the mitochondrial genome of D. yakuba had introgressed into D. santomea and completely replaced its native form. Since mitochondrial proteins work intimately with nuclear‐encoded proteins in the oxidative phosphorylation (OXPHOS) pathway, we hypothesized that some nuclear genes in OXPHOS cointrogressed along with the mitochondrial genome. We analyzed nucleotide variation in the 12 nuclear genes that form cytochrome c oxidase (COX) in 33 Drosophila lines. COX is an OXPHOS enzyme composed of both nuclear‐ and mitochondrial‐encoded proteins and shows evidence of cytonuclear coadaptation in some species. Using maximum‐likelihood methods, we detected significant gene flow from D. yakuba to D. santomea for the entire COX complex. Interestingly, the signal of introgression is concentrated in the three nuclear genes composing subunit V, which shows population migration rates significantly greater than the background level of introgression in these species. The detection of introgression in three proteins that work together, interact directly with the mitochondrial‐encoded core, and are critical for early COX assembly suggests this could be a case of cytonuclear cointrogression.
Collapse
Affiliation(s)
- Emily A Beck
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, Iowa, 52242
| | - Aaron C Thompson
- The Department of Biology, The University of Iowa, Iowa City, IA, 52242
| | - Joel Sharbrough
- The Department of Biology, The University of Iowa, Iowa City, IA, 52242
| | - Evgeny Brud
- The Department of Biology, The University of Iowa, Iowa City, IA, 52242
| | - Ana Llopart
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, Iowa, 52242. .,The Department of Biology, The University of Iowa, Iowa City, IA, 52242.
| |
Collapse
|
21
|
Gante HF, Doadrio I, Alves MJ, Dowling TE. Semi-permeable species boundaries in Iberian barbels (Barbus and Luciobarbus, Cyprinidae). BMC Evol Biol 2015; 15:111. [PMID: 26066794 PMCID: PMC4465174 DOI: 10.1186/s12862-015-0392-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 05/28/2015] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND The evolution of species boundaries and the relative impact of selection and gene flow on genomic divergence are best studied in populations and species pairs exhibiting various levels of divergence along the speciation continuum. We studied species boundaries in Iberian barbels, Barbus and Luciobarbus, a system of populations and species spanning a wide degree of genetic relatedness, as well as geographic distribution and range overlap. We jointly analyze multiple types of molecular markers and morphological traits to gain a comprehensive perspective on the nature of species boundaries in these cyprinid fishes. RESULTS Intraspecific molecular and morphological differentiation is visible among many populations. Genomes of all sympatric species studied are porous to gene flow, even if they are not sister species. Compared to their allopatric counterparts, sympatric representatives of different species share alleles and show an increase in all measures of nucleotide polymorphism (S, Hd, K, π and θ). High molecular diversity is particularly striking in L. steindachneri from the Tejo and Guadiana rivers, which co-varies with other sympatric species. Interestingly, different nuclear markers introgress across species boundaries at various levels, with distinct impacts on population trees. As such, some loci exhibit limited introgression and population trees resemble the presumed species tree, while alleles at other loci introgress more freely and population trees reflect geographic affinities and interspecific gene flow. Additionally, extent of introgression decreases with increasing genetic divergence in hybridizing species pairs. CONCLUSIONS We show that reproductive isolation in Iberian Barbus and Luciobarbus is not complete and species boundaries are semi-permeable to (some) gene flow, as different species (including non-sister) are exchanging genes in areas of sympatry. Our results support a speciation-with-gene-flow scenario with heterogeneous barriers to gene flow across the genome, strengthening with genetic divergence. This is consistent with observations coming from other systems and supports the notion that speciation is not instantaneous but a gradual process, during which different species are still able to exchange some genes, while selection prevents gene flow at other loci. We also provide evidence for a hybrid origin of a barbel ecotype, L. steindachneri, suggesting that ecology plays a key role in species coexistence and hybridization in Iberian barbels. This ecotype with intermediate, yet variable, molecular, morphological, trophic and ecological characteristics is the local product of introgressive hybridization of L. comizo with up to three different species (with L. bocagei in the Tejo, with L. microcephalus and L. sclateri in the Guadiana). In spite of the homogenizing effects of ongoing gene flow, species can still be discriminated using a combination of morphological and molecular markers. Iberian barbels are thus an ideal system for the study of species boundaries, since they span a wide range of genetic divergences, with diverse ecologies and degrees of sympatry.
Collapse
Affiliation(s)
- Hugo F Gante
- School of Life Sciences, Arizona State University, 85287-4601, Tempe, AZ, USA.
- Museu Nacional de História Natural e da Ciência, Centre for Ecology, Evolution and Environmental Changes (Ce3C), Universidade de Lisboa, Rua da Escola Politécnica 58, 1250-102, Lisbon, Portugal.
- Current address: Zoological Institute, University of Basel, 4051, Basel, Switzerland.
| | - Ignacio Doadrio
- Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, c/José Gutiérrez Abascal 2, 28006, Madrid, Spain.
| | - Maria Judite Alves
- Museu Nacional de História Natural e da Ciência, Centre for Ecology, Evolution and Environmental Changes (Ce3C), Universidade de Lisboa, Rua da Escola Politécnica 58, 1250-102, Lisbon, Portugal.
| | - Thomas E Dowling
- School of Life Sciences, Arizona State University, 85287-4601, Tempe, AZ, USA.
- Current address: Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, 48202, Detroit, MI, USA.
| |
Collapse
|
22
|
Gredler JN, Hish AJ, Noor MAF. Temporal Stability of Molecular Diversity Measures in Natural Populations of Drosophila pseudoobscura and Drosophila persimilis. J Hered 2015; 106:407-11. [PMID: 25969560 DOI: 10.1093/jhered/esv027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 04/16/2015] [Indexed: 11/12/2022] Open
Abstract
Many molecular ecological and evolutionary studies sample wild populations at a single point in time, but that data represents genetic variation from a potentially unrepresentative snapshot in time. Variation across time in genetic parameters may occur quickly in species that produce multiple generations of offspring per year. Here, we compare genetic diversity in wild caught populations of Drosophila persimilis and Drosophila pseudoobscura collected 16 years apart at the same time of year and same site at 4 X-linked and 2 mitochondrial loci to assess genetic stability. We found no major changes in nucleotide diversity in either species, but we observed a drastic shift in Tajima's D between D. pseudoobscura timepoints at 1 locus associated with increased abundance of a set of related haplotypes. Our data also suggests that D. persimilis may have recently accelerated its demographic expansion. While the changes we observed were modest, this study reinforces the importance of considering potential temporal variation in genetic parameters within single populations over short evolutionary timescales.
Collapse
|
23
|
Liu L, Xi Z, Wu S, Davis CC, Edwards SV. Estimating phylogenetic trees from genome-scale data. Ann N Y Acad Sci 2015; 1360:36-53. [DOI: 10.1111/nyas.12747] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Liang Liu
- Department of Statistics; University of Georgia; Athens Georgia
- Institute of Bioinformatics; University of Georgia; Athens Georgia
| | - Zhenxiang Xi
- Department of Organismic and Evolutionary Biology; Harvard University; Cambridge Massachusetts
| | - Shaoyuan Wu
- Department of Biochemistry and Molecular Biology & Tianjin Key Laboratory of Medical Epigenetics, School of Basic Medical Sciences; Tianjin Medical University; Tianjin China
| | - Charles C. Davis
- Department of Organismic and Evolutionary Biology; Harvard University; Cambridge Massachusetts
| | - Scott V. Edwards
- Department of Organismic and Evolutionary Biology; Harvard University; Cambridge Massachusetts
| |
Collapse
|
24
|
Geneva AJ, Muirhead CA, Kingan SB, Garrigan D. A new method to scan genomes for introgression in a secondary contact model. PLoS One 2015; 10:e0118621. [PMID: 25874895 PMCID: PMC4396994 DOI: 10.1371/journal.pone.0118621] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 01/21/2015] [Indexed: 12/20/2022] Open
Abstract
Secondary contact between divergent populations or incipient species may result in the exchange and introgression of genomic material. We develop a simple DNA sequence measure, called Gmin, which is designed to identify genomic regions experiencing introgression in a secondary contact model. Gmin is defined as the ratio of the minimum between-population number of nucleotide differences in a genomic window to the average number of between-population differences. Although it is conceptually simple, one advantage of Gmin is that it is computationally inexpensive relative to model-based methods for detecting gene flow and it scales easily to the level of whole-genome analysis. We compare the sensitivity and specificity of Gmin to those of the widely used index of population differentiation, FST, and suggest a simple statistical test for identifying genomic outliers. Extensive computer simulations demonstrate that Gmin has both greater sensitivity and specificity for detecting recent introgression than does FST. Furthermore, we find that the sensitivity of Gmin is robust with respect to both the population mutation and recombination rates. Finally, a scan of Gmin across the X chromosome of Drosophila melanogaster identifies candidate regions of introgression between sub-Saharan African and cosmopolitan populations that were previously missed by other methods. These results show that Gmin is a biologically straightforward, yet powerful, alternative to FST, as well as to more computationally intensive model-based methods for detecting gene flow.
Collapse
Affiliation(s)
- Anthony J. Geneva
- Department of Biology, University of Rochester, Rochester, New York, United States of America
| | - Christina A. Muirhead
- Department of Biology, University of Rochester, Rochester, New York, United States of America
- Ronin Institute, Montclair, New Jersey, United States of America
| | - Sarah B. Kingan
- Department of Biology, University of Rochester, Rochester, New York, United States of America
| | - Daniel Garrigan
- Department of Biology, University of Rochester, Rochester, New York, United States of America
- * E-mail:
| |
Collapse
|
25
|
Gao Z, Przeworski M, Sella G. Footprints of ancient-balanced polymorphisms in genetic variation data from closely related species. Evolution 2015; 69:431-46. [PMID: 25403856 PMCID: PMC4335603 DOI: 10.1111/evo.12567] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 10/28/2014] [Indexed: 01/17/2023]
Abstract
When long-lasting, balancing selection can lead to “trans-species” polymorphisms
that are shared by two or more species identical by descent. In such cases, the gene genealogy at
the selected site clusters by allele instead of by species, and nearby neutral sites also have
unusual genealogies because of linkage. While this scenario is expected to leave discernible
footprints in genetic variation data, the specific patterns remain poorly characterized. Motivated
by recent findings in primates, we focus on the case of a biallelic polymorphism under ancient
balancing selection and derive approximations for summaries of the polymorphism data from two
species. Specifically, we characterize the length of the segment that carries most of the
footprints, the expected number of shared neutral single nucleotide polymorphisms (SNPs), and the
patterns of allelic associations among them. We confirm the accuracy of our approximations by
coalescent simulations. We further show that for humans and chimpanzees—more generally, for
pairs of species with low genetic diversity levels—these patterns are highly unlikely to be
generated by neutral recurrent mutations. We discuss the implications for the design and
interpretation of genome scans for ancient balanced polymorphisms in primates and other taxa.
Collapse
Affiliation(s)
- Ziyue Gao
- Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, Illinois, 60637.
| | | | | |
Collapse
|
26
|
Llopart A, Herrig D, Brud E, Stecklein Z. Sequential adaptive introgression of the mitochondrial genome in Drosophila yakuba and Drosophila santomea. Mol Ecol 2014; 23:1124-36. [PMID: 24460929 PMCID: PMC4260671 DOI: 10.1111/mec.12678] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 01/09/2014] [Accepted: 01/15/2014] [Indexed: 01/29/2023]
Abstract
Interspecific hybridization provides the unique opportunity for species to tap into genetic variation present in a closely related species and potentially take advantage of beneficial alleles. It has become increasingly clear that when hybridization occurs, mitochondrial DNA (mtDNA) often crosses species boundaries, raising the possibility that it could serve as a recurrent target of natural selection and source of species' adaptations. Here we report the sequences of 46 complete mitochondrial genomes of Drosophila yakuba and Drosophila santomea, two sister species known to produce hybrids in nature (∼3%). At least two independent events of mtDNA introgression are uncovered in this study, including an early invasion of the D. yakuba mitochondrial genome that fully replaced the D. santomea mtDNA native haplotypes and a more recent, ongoing event centred in the hybrid zone. Interestingly, this recent introgression event bears the signature of Darwinian natural selection, and the selective haplotype can be found at low frequency in Africa mainland populations of D. yakuba. We put forward the possibility that, because the effective population size of D. santomea is smaller than that of D. yakuba, the faster accumulation of mildly deleterious mutations associated with Muller's ratchet in the former species may have facilitated the replacement of the mutationally loaded mitochondrial genome of D.
Collapse
Affiliation(s)
- Ana Llopart
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA; Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA, 52242, USA
| | | | | | | |
Collapse
|
27
|
The speciation continuum: population structure, gene flow, and maternal ancestry in the Simulium arcticum complex (Diptera: Simuliidae). Mol Phylogenet Evol 2014; 78:43-55. [PMID: 24821619 DOI: 10.1016/j.ympev.2014.05.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 04/15/2014] [Accepted: 05/01/2014] [Indexed: 12/27/2022]
Abstract
Comparative analyses of populations at different stages of divergence can yield insights into the process of speciation. We assess population structure, gene flow, and maternal ancestry at five locations containing sympatric members of the Simulium arcticum complex at different stages of chromosome divergence. We analyze both nuclear and mitochondrial DNA markers, including 11 microsatellite loci, as well as COI, COII, cytb, and ND4 gene sequences. Simulium negativum, representing the later stages of divergence, shows both nuclear and mitochondrial differentiation when compared with allopatric and sympatric chromosomal forms, as well as both low contemporary and historical gene flow in sympatry. At intermediate stages of chromosome divergence, populations differ at nuclear, but not mitochondrial, loci in allopatry and sympatry. In one comparison of intermediate stage chromosomal forms (S. arcticum sensu stricto and S. apricarium), populations demonstrate low contemporary, but higher historical, gene flow in sympatry. In a second sympatric comparison (S. arcticum s. s. and S. brevicercum), both contemporary and historical gene flow are high. All analyses of sympatric populations at the earliest stages of chromosome divergence demonstrate panmixia; yet, some nuclear differentiation in allopatry is apparent. These findings suggest that molecular divergence is tracking chromosome divergence along a chromosomally-defined continuum of speciation in black flies.
Collapse
|
28
|
Sargsyan O. An analytical framework in the general coalescent tree setting for analyzing polymorphisms created by two mutations. J Math Biol 2014; 70:913-56. [DOI: 10.1007/s00285-014-0785-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 04/01/2014] [Indexed: 11/30/2022]
|
29
|
Navascués M, Legrand D, Campagne C, Cariou ML, Depaulis F. Distinguishing migration from isolation using genes with intragenic recombination: detecting introgression in the Drosophila simulans species complex. BMC Evol Biol 2014; 14:89. [PMID: 24762206 PMCID: PMC4022370 DOI: 10.1186/1471-2148-14-89] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 04/03/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Determining the presence or absence of gene flow between populations is the target of some statistical methods in population genetics. Until recently, these methods either avoided the use of recombining genes, or treated recombination as a nuisance parameter. However, genes with recombination contribute additional information for the detection of gene flow (i.e. through linkage disequilibrium). METHODS We present three summary statistics based on the spatial arrangement of fixed differences, and shared and exclusive polymorphisms that are sensitive to the presence and direction of gene flow. Power and false positive rate for tests based on these statistics are studied by simulation. RESULTS The application of these tests to populations from the Drosophila simulans species complex yielded results consistent with migration between D. simulans and its two endemic sister species D. mauritiana and D. sechellia, and between populations D. mauritiana on the islands of the Mauritius and Rodrigues. CONCLUSIONS We demonstrate the sensitivity of the developed statistics to the presence and direction of gene flow, and characterize their power as a function of differentiation level and recombination rate. The properties of these statistics make them especially suitable for analyzing high-throughput sequencing data or for their integration within the approximate Bayesian computation framework.
Collapse
Affiliation(s)
| | | | | | | | - Frantz Depaulis
- UMR 7625 Écologie et Évolution (CNRS/École Normale Supérieure/Université Pierre et Marie Curie), Paris, France.
| |
Collapse
|
30
|
Evidence that natural selection on codon usage in Drosophila pseudoobscura varies across codons. G3-GENES GENOMES GENETICS 2014; 4:681-92. [PMID: 24531731 PMCID: PMC4059240 DOI: 10.1534/g3.114.010488] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Like other species of Drosophila, Drosophila pseudoobscura has a distinct bias toward the usage of C- and G-ending codons. Previous studies have indicated that this bias is due, at least in part, to natural selection. Codon bias clearly differs among amino acids (and other codon classes) in Drosophila, which may reflect differences in the intensity of selection on codon usage. Ongoing natural selection on synonymous codon usage should be reflected in the shapes of the site frequency spectra of derived states at polymorphic positions. Specifically, regardless of other demographic effects on the spectrum, it should be shifted toward higher values for changes from less-preferred to more-preferred codons, and toward lower values for the converse. If the intensity of natural selection is increased, shifts in the site frequency spectra should be more pronounced. A total of 33,729 synonymous polymorphic sites on Chromosome 2 in D. pseudoobscura were analyzed. Shifts in the site frequency spectra are consistent with differential intensity of natural selection on codon usage, with stronger shifts associated with higher codon bias. The shifts, in general, are greater for polymorphic synonymous sites than for polymorphic intron sites, also consistent with natural selection. However, unlike observations in D. melanogaster, codon bias is not reduced in areas of low recombination in D. pseudoobscura; the site frequency spectrum signal for selection on codon usage remains strong in these regions. However, diversity is reduced, as expected. It is possible that estimates of low recombination reflect a recent change in recombination rate.
Collapse
|
31
|
Kol-Maimon H, Ghanim M, Franco JC, Mendel Z. Evidence for gene flow between two sympatric mealybug species (Insecta; Coccoidea; Pseudococcidae). PLoS One 2014; 9:e88433. [PMID: 24523894 PMCID: PMC3921159 DOI: 10.1371/journal.pone.0088433] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 01/07/2014] [Indexed: 11/27/2022] Open
Abstract
Occurrence of inter-species hybrids in natural populations might be evidence of gene flow between species. In the present study we found evidence of gene flow between two sympatric, genetically related scale insect species--the citrus mealybug Planococcus citri (Risso) and the vine mealybug Planococcus ficus (Signoret). These species can be distinguished by morphological, behavioral, and molecular traits. We employed the sex pheromones of the two respective species to study their different patterns of male attraction. We also used nuclear ITS2 (internal transcribed spacer 2) and mitochondrial COI (Cytochrome c oxidase sub unit 1) DNA sequences to characterize populations of the two species, in order to demonstrate the outcome of a possible gene flow between feral populations of the two species. Our results showed attraction to P. ficus pheromones of all tested populations of P. citri males but not vice versa. Furthermore, ITS2 sequences revealed the presence of 'hybrid females' among P. citri populations but not among those of P. ficus. 'hybrid females' from P. citri populations identified as P. citri females according to COI sequences. We offer two hypotheses for these results. 1) The occurrence of phenotypic and genotypic traits of P. ficus in P. citri populations may be attributed to both ancient and contemporary gene flow between their populations; and 2) we cannot rule out that an ancient sympatric speciation by which P. ficus emerged from P. citri might have led to the present situation of shared traits between these species. In light of these findings we also discuss the origin of the studied species and the importance of the pherotype phenomenon as a tool with which to study genetic relationships between congener scale insects.
Collapse
Affiliation(s)
- Hofit Kol-Maimon
- Department of Entomology, Volcani Center (ARO), Bet Dagan, Israel
| | - Murad Ghanim
- Department of Entomology, Volcani Center (ARO), Bet Dagan, Israel
| | - José Carlos Franco
- Departamento de Ciências e Engenharia de Biossistemas/Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, Portugal
| | - Zvi Mendel
- Department of Entomology, Volcani Center (ARO), Bet Dagan, Israel
| |
Collapse
|
32
|
Larracuente AM, Clark AG. Recent selection on the Y-to-dot translocation in Drosophila pseudoobscura. Mol Biol Evol 2014; 31:846-56. [PMID: 24390701 DOI: 10.1093/molbev/msu002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Drosophila pseudoobscura dot chromosome acquired genes from the ancestral Drosophila Y chromosome in a Y-to-dot translocation event that occurred between 12.7 and 20.8 Ma. The formerly Y-linked genes mostly retained their testis-specific expression but shrank drastically in size, mostly through intron reduction, since becoming part of the dot chromosome in this species. We investigated the impact of this translocation on the evolution of the both the Y-to-dot translocated region and the original segments of the dot chromosome in D. pseudoobscura. Our survey of polymorphism and divergence across the chromosome reveals a reduction in variation, a deletion polymorphism segregating at high frequency, and a shift in the frequency spectra, all consistent with a history of recent selective sweeps in the Y-to-dot translocated region but not on the rest of the dot chromosome. We do find evidence for recombination primarily as gene conversion on the dot chromosome; however, predicted recombination events are restricted to the part of the dot chromosome outside the translocation. It therefore appears that recombination has resulted in a degree of decoupling between the ancestral Y region and the conserved region of the dot chromosome.
Collapse
|
33
|
Herrig DK, Modrick AJ, Brud E, Llopart A. Introgression in the Drosophila subobscura--D. Madeirensis sister species: evidence of gene flow in nuclear genes despite mitochondrial differentiation. Evolution 2013; 68:705-19. [PMID: 24152112 PMCID: PMC4255303 DOI: 10.1111/evo.12295] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Accepted: 10/15/2013] [Indexed: 12/19/2022]
Abstract
Species hybridization, and thus the potential for gene flow, was once viewed as reproductive mistake. However, recent analysis based on large datasets and newly developed models suggest that gene exchange is not as rare as originally suspected. To investigate the history and speciation of the closely related species Drosophila subobscura, D. madeirensis, and D. guanche, we obtained polymorphism and divergence data for 26 regions throughout the genome, including the Y chromosome and mitochondrial DNA. We found that the D. subobscura X/autosome ratio of silent nucleotide diversity is significantly smaller than the 0.75 expected under neutrality. This pattern, if held genomewide, may reflect a faster accumulation of beneficial mutations on the X chromosome than on autosomes. We also detected evidence of gene flow in autosomal regions, while sex chromosomes remain distinct. This is consistent with the large X effect on hybrid male sterility seen in this system and the presence of two X chromosome inversions fixed between species. Overall, our data conform to chromosomal speciation models in which rearrangements are proposed to serve as gene flow barriers. Contrary to other observations in Drosophila, the mitochondrial genome appears resilient to gene flow in the presence of nuclear exchange.
Collapse
Affiliation(s)
- Danielle K Herrig
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, IA, 52242
| | | | | | | |
Collapse
|
34
|
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
|
35
|
Martin SH, Dasmahapatra KK, Nadeau NJ, Salazar C, Walters JR, Simpson F, Blaxter M, Manica A, Mallet J, Jiggins CD. Genome-wide evidence for speciation with gene flow in Heliconius butterflies. Genome Res 2013; 23:1817-28. [PMID: 24045163 PMCID: PMC3814882 DOI: 10.1101/gr.159426.113] [Citation(s) in RCA: 439] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Most speciation events probably occur gradually, without complete and immediate reproductive isolation, but the full extent of gene flow between diverging species has rarely been characterized on a genome-wide scale. Documenting the extent and timing of admixture between diverging species can clarify the role of geographic isolation in speciation. Here we use new methodology to quantify admixture at different stages of divergence in Heliconius butterflies, based on whole-genome sequences of 31 individuals. Comparisons between sympatric and allopatric populations of H. melpomene, H. cydno, and H. timareta revealed a genome-wide trend of increased shared variation in sympatry, indicative of pervasive interspecific gene flow. Up to 40% of 100-kb genomic windows clustered by geography rather than by species, demonstrating that a very substantial fraction of the genome has been shared between sympatric species. Analyses of genetic variation shared over different time intervals suggested that admixture between these species has continued since early in speciation. Alleles shared between species during recent time intervals displayed higher levels of linkage disequilibrium than those shared over longer time intervals, suggesting that this admixture took place at multiple points during divergence and is probably ongoing. The signal of admixture was significantly reduced around loci controlling divergent wing patterns, as well as throughout the Z chromosome, consistent with strong selection for Müllerian mimicry and with known Z-linked hybrid incompatibility. Overall these results show that species divergence can occur in the face of persistent and genome-wide admixture over long periods of time.
Collapse
Affiliation(s)
- Simon H Martin
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Pereyra RT, Huenchuñir C, Johansson D, Forslund H, Kautsky L, Jonsson PR, Johannesson K. Parallel speciation or long-distance dispersal? Lessons from seaweeds (Fucus) in the Baltic Sea. J Evol Biol 2013; 26:1727-37. [PMID: 23859364 DOI: 10.1111/jeb.12170] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 03/04/2013] [Accepted: 03/28/2013] [Indexed: 11/30/2022]
Abstract
Parallel evolution has been invoked as a forceful mechanism of ecotype and species formation in many animal taxa. However, parallelism may be difficult to separate from recently monophyletically diverged species that are likely to show complex genetic relationships as a result of considerable shared ancestral variation and secondary hybridization in local areas. Thus, species' degrees of reproductive isolation, barriers to dispersal and, in particular, limited capacities for long-distance dispersal will affect demographical structures underlying mechanisms of divergent evolution. Here, we used nine microsatellite DNA markers to study intra- and interspecific genetic diversity of two recently diverged species of brown macroalgae, Fucus radicans (L. Bergström & L. Kautsky) and F. vesiculosus (Linnaeus), in the Baltic Sea. We further performed biophysical modelling to identify likely connectivity patterns influencing the species' genetic structures. For each species, we found intraspecific contrasting patterns of clonality incidence and population structure. In addition, strong genetic differentiation between the two species within each locality supported the existence of two distinct evolutionary lineages (FST = 0.15-0.41). However, overall genetic clustering analyses across both species' populations revealed that all populations from one region (Estonia) were more genetically similar to each other than to their own taxon from the other two regions (Sweden and Finland). Our data support a hypothesis of parallel speciation. Alternatively, Estonia may be the ancestral source of both species, but is presently isolated by oceanographic barriers to dispersal. Thus, a limited gene flow in combination with genetic drift could have shaped the seemingly parallel structure.
Collapse
Affiliation(s)
- R T Pereyra
- Department of Biological and Environmental Sciences - Tjärnö, University of Gothenburg, Strömstad, Sweden.
| | | | | | | | | | | | | |
Collapse
|
37
|
Coates BS, Johnson H, Kim KS, Hellmich RL, Abel CA, Mason C, Sappington TW. Frequency of hybridization between Ostrinia nubilalis E-and Z-pheromone races in regions of sympatry within the United States. Ecol Evol 2013; 3:2459-70. [PMID: 24567821 PMCID: PMC3930039 DOI: 10.1002/ece3.639] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 05/07/2013] [Accepted: 05/08/2013] [Indexed: 01/13/2023] Open
Abstract
Female European corn borer, Ostrinia nubilalis, produce and males respond to sex pheromone blends with either E- or Z-Δ11-tetradecenyl acetate as the major component. E- and Z-race populations are sympatric in the Eastern United States, Southeastern Canada, and the Mediterranean region of Europe. The E- and Z-pheromone races of O. nubilalis are models for incipient species formation, but hybridization frequencies within natural populations remain obscure due to lack of a high-throughput phenotyping method. Lassance et al. previously identified a pheromone gland-expressed fatty-acyl reductase gene (pgfar) that controls the ratio of Δ11-tetradecenyl acetate stereoisomers. We identified three single nucleotide polymorphism (SNP) markers within pgfar that are differentially fixed between E- and Z-race females, and that are ≥98.2% correlated with female pheromone ratios measured by gas chromatography. Genotypic data from locations in the United States demonstrated that pgfar-z alleles were fixed within historically allopatric Z-pheromone race populations in the Midwest, and that hybrid frequency ranged from 0.00 to 0.42 within 11 sympatric sites where the two races co-occur in the Eastern United States (mean hybridization frequency or heterozygosity (H O) = 0.226 ± 0.279). Estimates of hybridization between the E- and Z-races are important for understanding the dynamics involved in maintaining race integrity, and are consistent with previous estimates of low levels of genetic divergence between E- and Z-races and the presence of weak prezygotic mating barriers. This work describes the development of new single nucleotide polymorphism (SNP) markers within the pheromone gland expressed fatty acyl reductase (pgfar) gene of Ostrinia nubilalis. These SNPs were shown to segregate based upon female pheromone production, and thus provide the first description of an assay for genetic determination of O. nubilalis pheromone strain from field-collected samples. These assays were applied to estimate hybridization within field populations, and represent valuable tools for future population genetic studies of this species.
Collapse
Affiliation(s)
- Brad S Coates
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University Ames, Iowa, 50011 ; Department of Entomology, Iowa State University Ames, Iowa, 50011
| | - Holly Johnson
- Entomology and Wildlife Ecology, University of Delaware 531 S College Ave RM 250, Newark, Delaware, 19716-2160
| | - Kyung-Seok Kim
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University Ames, Iowa, 50011
| | - Richard L Hellmich
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University Ames, Iowa, 50011 ; Department of Entomology, Iowa State University Ames, Iowa, 50011
| | - Craig A Abel
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University Ames, Iowa, 50011
| | - Charles Mason
- Entomology and Wildlife Ecology, University of Delaware 531 S College Ave RM 250, Newark, Delaware, 19716-2160
| | - Thomas W Sappington
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University Ames, Iowa, 50011 ; Department of Entomology, Iowa State University Ames, Iowa, 50011
| |
Collapse
|
38
|
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
|
39
|
Wang Q, Abbott RJ, Yu QS, Lin K, Liu JQ. Pleistocene climate change and the origin of two desert plant species, Pugionium cornutum and Pugionium dolabratum (Brassicaceae), in northwest China. THE NEW PHYTOLOGIST 2013; 199:277-287. [PMID: 23550542 DOI: 10.1111/nph.12241] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 02/22/2013] [Indexed: 05/14/2023]
Abstract
Pleistocene climate change has had an important effect in shaping intraspecific genetic variation in many species; however, its role in driving speciation is less clear. We examined the possibility of a Pleistocene origin of the only two representatives of the genus Pugionium (Brassicaceae), Pugionium cornutum and Pugionium dolabratum, which occupy different desert habitats in northwest China. We surveyed sequence variation for internal transcribed spacer (ITS), three chloroplast (cp) DNA fragments, and eight low-copy nuclear genes among individuals sampled from 11 populations of each species across their geographic ranges. One ITS mutation distinguished the two species, whereas mutations in cpDNA and the eight low-copy nuclear gene sequences were not species-specific. Although interspecific divergence varied greatly among nuclear gene sequences, in each case divergence was estimated to have occurred within the Pleistocene when deserts expanded in northwest China. Our findings point to the importance of Pleistocene climate change, in this case an increase in aridity, as a cause of speciation in Pugionium as a result of divergence in different habitats that formed in association with the expansion of deserts in China.
Collapse
Affiliation(s)
- Qian Wang
- Key Laboratory for Bio-resources and Eco-environment, College of Life Science, Sichuan University, Chengdu, 6100065, China
| | - Richard J Abbott
- School of Biology, University of St Andrews, Mitchell Building, St Andrews, Fife, KY16 9TH, UK
| | - Qiu-Shi Yu
- State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating, Gansu Desert Control Research Institute, Lanzhou, 730000, Gansu, China
| | - Kao Lin
- Laboratory of Evolutionary Genomics, CAS-MPG Partner Institute for Computational Biology, Chinese Academy of Sciences, Shanghai, China
| | - Jian-Quan Liu
- Key Laboratory for Bio-resources and Eco-environment, College of Life Science, Sichuan University, Chengdu, 6100065, China
| |
Collapse
|
40
|
Zou XH, Yang Z, Doyle JJ, Ge S. Multilocus estimation of divergence times and ancestral effective population sizes of Oryza species and implications for the rapid diversification of the genus. THE NEW PHYTOLOGIST 2013; 198:1155-1164. [PMID: 23574344 DOI: 10.1111/nph.12230] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 02/08/2013] [Indexed: 06/02/2023]
Abstract
· Despite substantial investigations into Oryza phylogeny and evolution, reliable estimates of the divergence times and ancestral effective population sizes of major lineages in Oryza are challenging. · We sampled sequences of 106 single-copy nuclear genes from all six diploid genomes of Oryza to investigate the divergence times through extensive relaxed molecular clock analyses and estimated the ancestral effective population sizes using maximum likelihood and Bayesian methods. · We estimated that Oryza originated in the middle Miocene (c. 13-15 million years ago; Ma) and obtained an explicit time frame for two rapid diversifications in this genus. The first diversification involving the extant F-/G-genomes and possibly the extinct H-/J-/K-genomes occurred in the middle Miocene immediately after (within < 1 Myr) the origin of Oryza. The second giving rise to the A-/B-/C-genomes happened c. 5-6 Ma. We found that ancestral effective population sizes were much larger than those of extant species in Oryza. · We suggest that the climate fluctuations during the period from the middle Miocene to Pliocene may have contributed to the two rapid diversifications of Oryza species. Such information helps better understand the evolutionary history of Oryza and provides further insights into the pattern and mechanism of diversification in plants in general.
Collapse
Affiliation(s)
- Xin-Hui Zou
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Ziheng Yang
- Center for Computational and Evolutionary Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Jeff J Doyle
- Department of Plant Biology, Cornell University, 412 Mann Library Building, Ithaca, NY, 14853, USA
| | - Song Ge
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| |
Collapse
|
41
|
Abstract
Southern and eastern African populations that speak non-Bantu languages with click consonants are known to harbour some of the most ancient genetic lineages in humans, but their relationships are poorly understood. Here, we report data from 23 populations analysed at over half a million single-nucleotide polymorphisms, using a genome-wide array designed for studying human history. The southern African Khoisan fall into two genetic groups, loosely corresponding to the northwestern and southeastern Kalahari, which we show separated within the last 30,000 years. We find that all individuals derive at least a few percent of their genomes from admixture with non-Khoisan populations that began ∼1,200 years ago. In addition, the East African Hadza and Sandawe derive a fraction of their ancestry from admixture with a population related to the Khoisan, supporting the hypothesis of an ancient link between southern and eastern Africa. Hunter-gatherer populations in Africa preserve unique information about human history, but genetic sub-structures of these populations remain unclear. Using newly designed microarray and statistical methods, these authors analyse genetic compositions of southern African populations and reveal an ancient link between southern and eastern Africa.
Collapse
|
42
|
Brower AVZ. Introgression of wing pattern alleles and speciation via homoploid hybridization in Heliconius butterflies: a review of evidence from the genome. Proc Biol Sci 2012; 280:20122302. [PMID: 23235702 DOI: 10.1098/rspb.2012.2302] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The diverse Müllerian mimetic wing patterns of neotropical Heliconius (Nymphalidae) have been proposed to be not only aposematic signals to potential predators, but also intra- and interspecific recognition signals that allow the butterflies to maintain their specific identities, and which perhaps drive the process of speciation, as well. Adaptive features under differential selection that also serve as cues for assortative mating have been referred to as 'magic traits', which can drive ecological speciation. Such traits are expected to exhibit allelic differentiation between closely related species with ongoing gene flow, whereas unlinked neutral traits are expected to be homogenized to a greater degree by introgression. However, recent evidence suggests that interspecific hybridization among Heliconius butterflies may have resulted in adaptive introgression of these very same traits across species boundaries, and in the evolution of new species by homoploid hybrid speciation. The theory and data supporting various aspects of the apparent paradox of 'magic trait' introgression are reviewed, with emphasis on population genomic comparisons of Heliconius melpomene and its close relatives.
Collapse
Affiliation(s)
- Andrew V Z Brower
- Evolution and Ecology Group, Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132, USA.
| |
Collapse
|
43
|
Jenkins PA, Song YS, Brem RB. Genealogy-based methods for inference of historical recombination and gene flow and their application in Saccharomyces cerevisiae. PLoS One 2012; 7:e46947. [PMID: 23226196 PMCID: PMC3511476 DOI: 10.1371/journal.pone.0046947] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 09/10/2012] [Indexed: 11/17/2022] Open
Abstract
Genetic exchange between isolated populations, or introgression between species, serves as a key source of novel genetic material on which natural selection can act. While detecting historical gene flow from DNA sequence data is of much interest, many existing methods can be limited by requirements for deep population genomic sampling. In this paper, we develop a scalable genealogy-based method to detect candidate signatures of gene flow into a given population when the source of the alleles is unknown. Our method does not require sequenced samples from the source population, provided that the alleles have not reached fixation in the sampled recipient population. The method utilizes recent advances in algorithms for the efficient reconstruction of ancestral recombination graphs, which encode genealogical histories of DNA sequence data at each site, and is capable of detecting the signatures of gene flow whose footprints are of length up to single genes. Further, we employ a theoretical framework based on coalescent theory to test for statistical significance of certain recombination patterns consistent with gene flow from divergent sources. Implementing these methods for application to whole-genome sequences of environmental yeast isolates, we illustrate the power of our approach to highlight loci with unusual recombination histories. By developing innovative theory and methods to analyze signatures of gene flow from population sequence data, our work establishes a foundation for the continued study of introgression and its evolutionary relevance.
Collapse
Affiliation(s)
- Paul A. Jenkins
- Computer Science Division, University of California, Berkeley, California, United States of America
| | - Yun S. Song
- Computer Science Division, University of California, Berkeley, California, United States of America
- Department of Statistics, University of California, Berkeley, California, United States of America
| | - Rachel B. Brem
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| |
Collapse
|
44
|
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
|
45
|
Sankararaman S, Patterson N, Li H, Pääbo S, Reich D. The date of interbreeding between Neandertals and modern humans. PLoS Genet 2012; 8:e1002947. [PMID: 23055938 PMCID: PMC3464203 DOI: 10.1371/journal.pgen.1002947] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 07/27/2012] [Indexed: 12/26/2022] Open
Abstract
Comparisons of DNA sequences between Neandertals and present-day humans have shown that Neandertals share more genetic variants with non-Africans than with Africans. This could be due to interbreeding between Neandertals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. However, it could also be due to population structure that antedates the origin of Neandertal ancestors in Africa. We measure the extent of linkage disequilibrium (LD) in the genomes of present-day Europeans and find that the last gene flow from Neandertals (or their relatives) into Europeans likely occurred 37,000–86,000 years before the present (BP), and most likely 47,000–65,000 years ago. This supports the recent interbreeding hypothesis and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa. One of the key discoveries from the analysis of the Neandertal genome is that Neandertals share more genetic variants with non-Africans than with Africans. This observation is consistent with two hypotheses: interbreeding between Neandertals and modern humans after modern humans emerged out of Africa or population structure in the ancestors of Neandertals and modern humans. These hypotheses make different predictions about the date of last gene exchange between the ancestors of Neandertals and modern non-Africans. We estimate this date by measuring the extent of linkage disequilibrium (LD) in the genomes of present-day Europeans and find that the last gene flow from Neandertals into Europeans likely occurred 37,000–86,000 years before the present (BP), and most likely 47,000–65,000 years ago. This supports the recent interbreeding hypothesis and suggests that interbreeding occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa.
Collapse
Affiliation(s)
- Sriram Sankararaman
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- * E-mail: (SS); (SP); (DR)
| | - Nick Patterson
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Heng Li
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Svante Pääbo
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- * E-mail: (SS); (SP); (DR)
| | - David Reich
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- * E-mail: (SS); (SP); (DR)
| |
Collapse
|
46
|
Jacobsen F, Omland KE. Extensive introgressive hybridization within the northern oriole group (Genus Icterus) revealed by three-species isolation with migration analysis. Ecol Evol 2012; 2:2413-29. [PMID: 23145328 PMCID: PMC3492769 DOI: 10.1002/ece3.365] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 07/30/2012] [Accepted: 07/31/2012] [Indexed: 12/18/2022] Open
Abstract
Until recently, studies of divergence and gene flow among closely-related taxa were generally limited to pairs of sister taxa. However, organisms frequently exchange genes with other non-sister taxa. The “northern oriole” group within genus Icterus exemplifies this problem. This group involves the extensively studied hybrid zone between Baltimore oriole (Icterus galbula) and Bullock's oriole (I. bullockii), an alleged hybrid zone between I. bullockii and black-backed oriole (I. abeillei), and likely mtDNA introgression between I. galbula and I. abeillei. Here, we examine the divergence population genetics of the entire northern oriole group using a multipopulation Isolation-with-Migration (IM) model. In accordance with Haldane's rule, nuclear loci introgress extensively beyond the I. galbula–I. bullockii hybrid zone, while mtDNA does not. We found no evidence of introgression between I. bullockii and I. abeillei or between I. galbula and I. abeillei when all three species were analyzed together in a three-population model. However, traditional pairwise analysis suggested some nuclear introgression from I. abeillei into I. galbula, probably reflecting genetic contributions from I. bullockii unaccounted for in a two-population model. Thus, only by including all members of this group in the analysis was it possible to rigorously estimate the level of gene flow among these three closely related species.
Collapse
Affiliation(s)
- Frode Jacobsen
- Department of Biological Sciences, University of Maryland Baltimore County 1000 Hilltop Circle, Baltimore, MD, 21250, USA
| | | |
Collapse
|
47
|
Random roots and lineage sorting. Mol Phylogenet Evol 2012; 64:12-20. [DOI: 10.1016/j.ympev.2012.02.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 02/11/2012] [Accepted: 02/27/2012] [Indexed: 11/16/2022]
|
48
|
Pardo-Diaz C, Salazar C, Baxter SW, Merot C, Figueiredo-Ready W, Joron M, McMillan WO, Jiggins CD. Adaptive introgression across species boundaries in Heliconius butterflies. PLoS Genet 2012; 8:e1002752. [PMID: 22737081 PMCID: PMC3380824 DOI: 10.1371/journal.pgen.1002752] [Citation(s) in RCA: 254] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 04/19/2012] [Indexed: 11/19/2022] Open
Abstract
It is widely documented that hybridisation occurs between many closely related species, but the importance of introgression in adaptive evolution remains unclear, especially in animals. Here, we have examined the role of introgressive hybridisation in transferring adaptations between mimetic Heliconius butterflies, taking advantage of the recent identification of a gene regulating red wing patterns in this genus. By sequencing regions both linked and unlinked to the red colour locus, we found a region that displays an almost perfect genotype by phenotype association across four species, H. melpomene, H. cydno, H. timareta, and H. heurippa. This particular segment is located 70 kb downstream of the red colour specification gene optix, and coalescent analysis indicates repeated introgression of adaptive alleles from H. melpomene into the H. cydno species clade. Our analytical methods complement recent genome scale data for the same region and suggest adaptive introgression has a crucial role in generating adaptive wing colour diversity in this group of butterflies. Hybridisation occurs between many animal species, however its evolutionary relevance is still a matter of great debate. While some argue that hybridisation leads to maladaptive gene combinations, and therefore to an evolutionary dead end, others consider interspecific hybridisation as a process with great potential to fuel evolution. We examine this question by exploring the origins of red wing colouration, a trait under natural selection, in the adaptive radiation of closely related species of Heliconius butterflies. By sequencing genetic regions both linked and unlinked to the red wing pattern locus, we found experimental evidence supporting multiple hybridisation events that have mediated the acquisition of colour adaptations from H. melpomene to H. timareta. This introgression has allowed H. timareta to colonise new fitness peaks in the Müllerian mimicry landscape. In this way, our results support the idea that interspecific hybridisation in animals constitutes a source of genetic variation that promotes diversification.
Collapse
|
49
|
Banerjee P, Singh BN. Interspecific sexual isolation and phylogeny among different members of the Drosophila bipectinata species complex. Genetica 2012; 140:75-81. [PMID: 22638827 DOI: 10.1007/s10709-012-9659-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Accepted: 05/14/2012] [Indexed: 11/25/2022]
Abstract
The degree and pattern of sexual isolation among closely related species can be utilized for predicting the direction of evolution and deriving a phylogeny. The Drosophila bipectinata species complex is a group of four morphologically very similar species, belonging to the ananassae subgroup of the melanogaster species group. Sexual isolation among the members of this complex was studied by employing the male-choice technique. To test the difference between the homogamic and heterogamic matings, chi-square values were calculated under the assumption of random mating and the degree of sexual isolation was measured by estimating isolation index. To test the difference in proportions of heterogamic matings between reciprocal crosses, normal deviate (z) was calculated. The direction of evolution among these species has been discussed in the light of models proposed by different workers. Our results suggest that while D. bipectinata, Drosophila parabipectinata and Drosophila malerkotliana are closely related to each other, D. pseudoananassae is distantly related to these three species. The species pairs D. bipectinata and D. parabipectinata and D. parabipectinata and D. malerkotliana show asymmetrical sexual isolation. Based on this, it is suggested that D. bipectinata and D. malerkotliana share a common ancestor where as D. parabipectinata has been derived from D. bipectinata. Their phylogenetic relationship has been discussed in the light of phylogenies suggested by earlier workers.
Collapse
Affiliation(s)
- Parul Banerjee
- Genetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India
| | | |
Collapse
|
50
|
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
|