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Daniel L Hartl - One of the best experts on this subject based on the ideXlab platform.
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genetic dissection of hybrid incompatibilities between Drosophila simulans and d mauritiana ii mapping hybrid male sterility loci on the third chromosome
Genetics, 2003Co-Authors: Zhaobang Zeng, Daniel L Hartl, Jian Li, Cathy C. LaurieAbstract:Hybrid male sterility (HMS) is a rapidly evolving mechanism of reproductive isolation in Drosophila. Here we report a genetic analysis of HMS in third-chromosome segments of Drosophila mauritiana that were introgressed into a D. simulans background. Qualitative genetic mapping was used to localize 10 loci on 3R and a quantitative trait locus (QTL) procedure (multiple-interval mapping) was used to identify 19 loci on the entire chromosome. These genetic incompatibilities often show dominance and complex patterns of epistasis. Most of the HMS loci have relatively small effects and generally at least two or three of them are required to produce complete sterility. Only one small region of the third chromosome of D. mauritiana by itself causes a high level of infertility when introgressed into D. simulans. By comparison with previous studies of the X chromosome, we infer that HMS loci are only approximately 40% as dense on this autosome as they are on the X chromosome. These results are consistent with the gradual evolution of hybrid incompatibilities as a by-product of genetic divergence in allopatric populations.
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genetic dissection of hybrid incompatibilities between Drosophila simulans and d mauritiana i differential accumulation of hybrid male sterility effects on the x and autosomes
Genetics, 2003Co-Authors: Sining Chen, Daniel L Hartl, Cathy C. LaurieAbstract:The genetic basis of hybrid incompatibility in crosses between Drosophila mauritiana and D. simulans was investigated to gain insight into the evolutionary mechanisms of speciation. In this study, segments of the D. mauritiana third chromosome were introgressed into a D. simulans genetic background and tested as homozygotes for viability, male fertility, and female fertility. The entire third chromosome was covered with partially overlapping segments. Many segments were male sterile, while none were female sterile or lethal, confirming previous reports of the rapid evolution of hybrid male sterility (HMS). A statistical model was developed to quantify the HMS accumulation. In comparison with previous work on the X chromosome, we estimate that the X has approximately 2.5 times the density of HMS factors as the autosomes. We also estimate that the whole genome contains approximately 15 HMS "equivalents"-i.e., 15 times the minimum number of incompatibility factors necessary to cause complete sterility. Although some caveats for the quantitative estimate of a 2.5-fold density difference are described, this study supports the notion that the X chromosome plays a special role in the evolution of reproductive isolation. Possible mechanisms of a "large X" effect include selective fixation of new mutations that are recessive or partially recessive and the evolution of sex-ratio distortion systems.
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Sex-ratio segregation distortion associated with reproductive isolation in Drosophila.
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Daniel L Hartl, Cathy C. LaurieAbstract:Sex-ratio distortion is the most common form of non-Mendelian segregation observed in natural populations. It may occur even more frequently than direct observations suggest, because the dysgenic population consequences of a biased sex ratio are expected to result in the rapid evolution of suppressors, resulting in suppressed or “cryptic” segregation distortion. Here we report evidence for cryptic sex-ratio distortion that was discovered by introgressing segments of the genome of Drosophila mauritiana into the genome of Drosophila simulans. The autosomal suppressor of sex-ratio distortion, which is also associated with a reduction in hybrid male fertility, has been genetically localized to a region smaller than 80-kb pairs in chromosome 3.
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transposition of the mariner element from Drosophila mauritiana in zebrafish
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: James M Fadool, Daniel L Hartl, John E DowlingAbstract:With the increased popularity of zebrafish (Danio rerio) for mutagenesis studies, efficient methods for manipulation of its genome are needed. One approach is the use of a transposable element as a vector for gene transfer in this species. We report here the transformation of zebrafish and germ-line transmission of the mariner element from Drosophila mauritiana. The mariner element was selected because its transposition is independent of host-specific factors. One- to two-cell-stage zebrafish embryos were coinjected with a supercoiled plasmid carrying the nonautonomous mariner element peach and mRNA encoding the transposase. Surviving larvae were reared to adulthood, and the transmission of peach to the F1 generation was tested by PCR. Four of the 12 founders, following plasmid injections on 2 different days, transmitted the element to their progeny. Inheritance of the transgene from the F1 to the F2 generation showed a Mendelian pattern. No plasmid sequences were detected by PCR or Southern blot analysis, indicating transposition of peach rather than random integration of the plasmid DNA. These data provide evidence of transformation of a vertebrate with a transposable element and support the host-independent mechanism for transposition of the mariner element. We suggest this system could be used for insertional mutagenesis or for identifying active regions of the genome in the zebrafish.
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Germline transformation of Drosophila virilis with the transposable element mariner.
Genetics, 1996Co-Authors: Allan R. Lohe, Daniel L HartlAbstract:An important goal in molecular genetics has been to identify a transposable element that might serve as an efficient transformation vector in diverse species of insects. The transposable element mariner occurs naturally in a wide variety of insects. Although virtually all mariner elements are nonfunctional, the Mosl element isolated from Drosophila mauritiana is functional. Mosl was injected into the pole-cell region of embryos of D. virilis , which last shared a common ancestor with D. mauritiana 40 million years ago. Mosl PCR fragments were detected in several pools of DNA from progeny of injected animals, and backcross lines were established. Because G o lines were pooled, possibly only one transformation event was actually obtained, yielding a minimum frequency of 4%. Mosl segregated in a Mendelian fashion, demonstrating chromosomal integration. The copy number increased by spontaneous mobilization. In situ hybridization confirmed multiple polymorphic locations of Mosl. Integration results in a characteristic 2-bp TA duplication. One Mosl element integrated into a tandem array of 370-bp repeats. Some copies may have integrated into heterochromatin, as evidenced by their ability to support PCR amplification despite absence of a signal in Southern and in situ hybridizations.
Cathy C. Laurie - One of the best experts on this subject based on the ideXlab platform.
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genetic dissection of hybrid incompatibilities between Drosophila simulans and d mauritiana ii mapping hybrid male sterility loci on the third chromosome
Genetics, 2003Co-Authors: Zhaobang Zeng, Daniel L Hartl, Jian Li, Cathy C. LaurieAbstract:Hybrid male sterility (HMS) is a rapidly evolving mechanism of reproductive isolation in Drosophila. Here we report a genetic analysis of HMS in third-chromosome segments of Drosophila mauritiana that were introgressed into a D. simulans background. Qualitative genetic mapping was used to localize 10 loci on 3R and a quantitative trait locus (QTL) procedure (multiple-interval mapping) was used to identify 19 loci on the entire chromosome. These genetic incompatibilities often show dominance and complex patterns of epistasis. Most of the HMS loci have relatively small effects and generally at least two or three of them are required to produce complete sterility. Only one small region of the third chromosome of D. mauritiana by itself causes a high level of infertility when introgressed into D. simulans. By comparison with previous studies of the X chromosome, we infer that HMS loci are only approximately 40% as dense on this autosome as they are on the X chromosome. These results are consistent with the gradual evolution of hybrid incompatibilities as a by-product of genetic divergence in allopatric populations.
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genetic dissection of hybrid incompatibilities between Drosophila simulans and d mauritiana i differential accumulation of hybrid male sterility effects on the x and autosomes
Genetics, 2003Co-Authors: Sining Chen, Daniel L Hartl, Cathy C. LaurieAbstract:The genetic basis of hybrid incompatibility in crosses between Drosophila mauritiana and D. simulans was investigated to gain insight into the evolutionary mechanisms of speciation. In this study, segments of the D. mauritiana third chromosome were introgressed into a D. simulans genetic background and tested as homozygotes for viability, male fertility, and female fertility. The entire third chromosome was covered with partially overlapping segments. Many segments were male sterile, while none were female sterile or lethal, confirming previous reports of the rapid evolution of hybrid male sterility (HMS). A statistical model was developed to quantify the HMS accumulation. In comparison with previous work on the X chromosome, we estimate that the X has approximately 2.5 times the density of HMS factors as the autosomes. We also estimate that the whole genome contains approximately 15 HMS "equivalents"-i.e., 15 times the minimum number of incompatibility factors necessary to cause complete sterility. Although some caveats for the quantitative estimate of a 2.5-fold density difference are described, this study supports the notion that the X chromosome plays a special role in the evolution of reproductive isolation. Possible mechanisms of a "large X" effect include selective fixation of new mutations that are recessive or partially recessive and the evolution of sex-ratio distortion systems.
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Sex-ratio segregation distortion associated with reproductive isolation in Drosophila.
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Daniel L Hartl, Cathy C. LaurieAbstract:Sex-ratio distortion is the most common form of non-Mendelian segregation observed in natural populations. It may occur even more frequently than direct observations suggest, because the dysgenic population consequences of a biased sex ratio are expected to result in the rapid evolution of suppressors, resulting in suppressed or “cryptic” segregation distortion. Here we report evidence for cryptic sex-ratio distortion that was discovered by introgressing segments of the genome of Drosophila mauritiana into the genome of Drosophila simulans. The autosomal suppressor of sex-ratio distortion, which is also associated with a reduction in hybrid male fertility, has been genetically localized to a region smaller than 80-kb pairs in chromosome 3.
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quantitative genetic analysis of divergence in male secondary sexual traits between Drosophila simulans and Drosophila mauritiana
Evolution, 1997Co-Authors: John R True, Zhaobang Zeng, Lynn F Stam, Cathy C. LaurieAbstract:The sibling species Drosophila simulans and D. mauritiana differ significantly in a number of male secondary sexual traits, providing an ideal system for genetic analysis of interspecific morphological divergence. In the experiment reported here, F1 hybrids from a cross of two inbred lines were backcrossed in both directions and about 200 flies from each backcross were scored for several traits (bristle numbers and cuticle areas), as well as 18 markers distributed throughout the genome. Each trait was analyzed by composite interval mapping to identify quantitative trait loci (QTL) and estimate their effects. For each trait, from one to eight loci were detected, with more divergent traits showing evidence for greater numbers of QTL. Estimates of additive effects varied widely, with a range of 0.4 to 4.1 environmental standard deviation units and an average of 2.2 units. There was substantial evidence for nonadditive effects, since the magnitude of estimates often differed significantly between the two backcrosses. The sign of the estimated effect differed among QTL for bristle traits, but not for cuticle area traits, suggesting that these two types of trait may have undergone different types of selection. Finally, several similarities were found between different traits in the estimated positions of QTL, suggesting that pleiotropy and/or linkage of QTL may have been important in the evolution of these traits.
Christian Schlotterer - One of the best experts on this subject based on the ideXlab platform.
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Patterns of microsatellite variability in the Drosophila melanogaster complex.
Genetica, 2020Co-Authors: Bettina Harr, Christian SchlottererAbstract:Forty-seven microsatellite loci were amplified in Drosophila melanogaster, Drosophila simulans, Drosophila mauritiana and Drosophila sechellia. The two cosmopolitan species D. melanogaster and D. simulans were found to be the most variable ones, followed by D. mauritiana and D. sechellia. A model based clustering algorithm was applied to the population samples of D. melanogaster, D. simulans and D. sechellia. No evidence for population substructure was detected within species--most likely due to insufficient power. A Markov chain Monte Carlo method developed for demographic inference based on microsatellites provided unambiguous evidence for population contraction in D. melanogaster, D. simulans and D. sechellia, despite that the D. melanogaster and D. simulans population samples were of non-African origin and represented recently expanded populations.
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genetic architecture and functional characterization of genes underlying the rapid diversification of male external genitalia between Drosophila simulans and Drosophila mauritiana
Genetics, 2015Co-Authors: Kentaro M Tanaka, Christian Schlotterer, Corinna Hopfen, Matthew R Herbert, David L Stern, John P Masly, Alistair P Mcgregor, Maria D S NunesAbstract:Male sexual characters are often among the first traits to diverge between closely related species and identifying the genetic basis of such changes can contribute to our understanding of their evolutionary history. However, little is known about the genetic architecture or the specific genes underlying the evolution of male genitalia. The morphology of the claspers, posterior lobes, and anal plates exhibit striking differences between Drosophila mauritiana and D. simulans. Using QTL and introgression-based high-resolution mapping, we identified several small regions on chromosome arms 3L and 3R that contribute to differences in these traits. However, we found that the loci underlying the evolution of clasper differences between these two species are independent from those that contribute to posterior lobe and anal plate divergence. Furthermore, while most of the loci affect each trait in the same direction and act additively, we also found evidence for epistasis between loci for clasper bristle number. In addition, we conducted an RNAi screen in D. melanogaster to investigate if positional and expression candidate genes located on chromosome 3L, are also involved in genital development. We found that six of these genes, including components of Wnt signaling and male-specific lethal 3 (msl3), regulate the development of genital traits consistent with the effects of the introgressed regions where they are located and that thus represent promising candidate genes for the evolution these traits.
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low levels of transposable element activity in Drosophila mauritiana causes and consequences
bioRxiv, 2015Co-Authors: Robert Kofler, Christian SchlottererAbstract:Transposable elements (TEs) are major drivers of genomic and phenotypic evolution, yet many questions about their biology remain poorly understood. Here, we compare TE abundance between populations of the two sister species D. mauritiana und D. simulans and relate it to the more distantly related D. melanogaster. The low population frequency of most TE insertions in D. melanogaster and D. simulans has been a key feature of several models of TE evolution. In D. mauritiana, however, the majority of TE insertions are fixed (66%). We attribute this to a lower transposition activity of up to 47 TE families in D. mauritiana, rather than stronger purifying selection. Only three families, including the extensively studied Mariner, may have a higher activity in D. mauritiana. This remarkable difference in TE activity between two recently diverged Drosophila species (≈ 250,000 years), also supports the hypothesis that TE copy numbers in Drosophila may not reflect a stable equilibrium where the rate of TE gains equals the rate of TE losses by negative selection. We propose that the transposition rate heterogeneity results from the contrasting ecology of the two species: the extent of vertical extinction of TE families and horizontal acquisition of active TE copies may be very different between the colonizing D. simulans and the island endemic D. mauritiana. Our findings provide novel insights in the evolution of TEs in Drosophila and suggest that the ecology of the host species could be a major, yet underappreciated, factor governing the evolutionary dynamics of TEs.
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genome wide patterns of natural variation reveal strong selective sweeps and ongoing genomic conflict in Drosophila mauritiana
Genome Research, 2013Co-Authors: Ram Vinay Pandey, Robert Kofler, Christian SchlottererAbstract:Intragenomic conflict describes the phenomenon that within an organism some genetic elements (e.g., segregation distorters) increase their transmission at the expense of others (Werren 2011). Due to the preferential transmission, such elements spread in the population and can leave a characteristic trace of strongly reduced variability in the genome that resembles a selective sweep (Derome et al. 2004). Population genetic analyses of segregation distortion systems in Drosophila did not find a molecular signature similar to a classic selective sweep (Derome et al. 2004, 2008; Presgraves et al. 2009; Kingan et al. 2010; Bastide et al. 2011). The patterns of variability instead resembled partial selective sweeps, suggesting that the genetic element increased in frequency but did not reach fixation. This observation is consistent with the fact that elements of intragenomic conflict are frequently deleterious when homozygous (Wallace 1948; Curtsinger and Feldman 1980) or that suppressors of the intragenomic conflict have evolved (Hamilton 1967). In the Drosophila melanogaster complex, only a small number of genes involved in intragenomic conflict have been identified within natural populations (e.g., Sandler et al. 1959; Mercot et al. 1995). While this may suggest that intragenomic conflict is a relatively rare event, it needs to be considered that there is a strong ascertainment bias: The rapid spread of driver alleles is either prevented by a quick fixation of suppressor alleles, or, in case of sex chromosome–linked segregation distorters, populations with an advanced intragenomic conflict become extinct (Gershenson 1928; Hamilton 1967; Lyttle 1977). In both cases, past episodes of genomic conflict cannot be recognized in an intraspecific polymorphism analysis. Indeed, consistent with the idea that genomic conflict is a common phenomenon, detailed analysis of hybrids showed that “speciation” genes tend to be involved in intragenomic conflict, but their effect could be only detected in hybrids (Perez et al. 1993; Dermitzakis et al. 2000; Tao et al. 2001; Presgraves et al. 2003; Phadnis and Orr 2009; Tang and Presgraves 2009). Several genes involved in intragenomic conflict in Drosophila were discovered in the Drosophila simulans clade that consists of three recently diverged species, the cosmopolitan D. simulans and the island endemics Drosophila mauritiana and Drosophila sechellia. D. mauritiana was the first species for which a “speciation” gene could be characterized at the molecular level: In hybrid crosses with D. simulans, the Odysseus (OdsH) allele of D. mauritiana together with additional tightly linked factors causes hybrid male sterility in the F1 generation (Perez and Wu 1995; Ting et al. 1998) and has been later identified as a gene involved in genomic conflict (Bayes and Malik 2009). Another D. mauritiana gene, too much yin (tmy), causes both, hybrid male sterility and segregation distortion in crosses between D. mauritiana and D. simulans (Tao et al. 2001), whereas the heterochromatic hlx locus causes hybrid lethality between D. mauritiana and both of its sister species (Cattani and Presgraves 2009). Additional elements of intragenomic conflict have been identified between the more distantly related D. melanogaster and D. simulans, in which the interaction between the genes Hmr and Lhr contributes to hybrid male lethality in crosses between D. melanogaster and D. simulans (Brideau et al. 2006; Maheshwari and Barbash 2012). The D. simulans alleles of two nucleoporin genes, Nup962 and Nup160, cause recessive male lethality when crossed to a D. melanogaster X chromosome (Presgraves et al. 2003; Tang and Presgraves 2009), a phenomenon that has been also linked to genomic conflict (Presgraves 2007; Presgraves and Stephan 2007). While the NUP96 protein is highly conserved between D. simulans and D. mauritiana, the D. mauritiana allele of Nup96 has no hybrid-lethal effect, which suggests more complex genetic interactions leading to Nup96-dependent incompatibility (Barbash 2007). Despite the importance of D. mauritiana as a model for understanding the genetic basis of speciation, an annotated genome sequence is not yet available. Using de novo assembly, we generated a draft genome of D. mauritiana and estimated genome-wide polymorphism patterns from Pool-seq data. Our data show the impact of genes involved in genomic conflict on the evolution of the D. mauritiana lineage. Nucleoporin genes, implicated in hybrid incompatibilities that have evolved between D. simulans and D. melanogaster, are possible targets of recurrent positive selection due to ongoing genomic conflict (Presgraves and Stephan 2007). Unlike previous genome-wide polymorphism surveys of D. simulans and D. melanogaster (Begun et al. 2007; Langley et al. 2012), we find that in the D. mauritiana lineage, nucleoporins are among the genes showing the strongest evidence of recurrent adaptive evolution. Furthermore, the presence of a pair of meiotic drive genes and a “speciation” gene at the center of two valleys of strongly reduced variability suggests that these sweeps have been caused by genes involved in genomic conflict.
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multiple hybridization events between Drosophila simulans and Drosophila mauritiana are supported by mtdna introgression
Molecular Ecology, 2010Co-Authors: Maria D S Nunes, Pablo Orozcoter Wengel, Michaela Kreissl, Christian SchlottererAbstract:The study of speciation has advanced considerably in the last decades because of the increased application of molecular tools. In particular, the quantification of gene flow between recently diverged species could be addressed. Drosophila simulans and Drosophila mauritiana diverged, probably allopatrically, from a common ancestor approximately 250 000 years ago. However, these species share one mitochondrial DNA (mtDNA) haplotype indicative of a recent episode of introgression. To study the extent of gene flow between these species, we took advantage of a large sample of D. mauritiana and employed a range of different markers, i.e. nuclear and mitochondrial sequences, and microsatellites. This allowed us to detect two new mtDNA haplotypes (MAU3 and MAU4). These haplotypes diverged quite recently from haplotypes of the siII group present in cosmopolitan populations of D. simulans. The mean divergence time of the most diverged haplotype (MAU4) is approximately 127 000 years, which is more than 100 000 years before the assumed speciation time. Interestingly, we also found some evidence for gene flow at the nuclear level because an excess of putatively neutral loci shows significantly reduced differentiation between D. simulans and D. mauritiana. Our results suggest that these species are exchanging genes more frequently than previously thought.
Daven C Presgraves - One of the best experts on this subject based on the ideXlab platform.
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genome diversity and divergence in Drosophila mauritiana multiple signatures of faster x evolution
Genome Biology and Evolution, 2014Co-Authors: Daniel Garrigan, Sarah B Kingan, Anthony J Geneva, Jeffrey P Vedanayagam, Daven C PresgravesAbstract:Drosophila mauritiana is an Indian Ocean island endemic species that diverged from its two sister species, Drosophila simulans and Drosophila sechellia, approximately 240,000 years ago. Multiple forms of incomplete reproductive isolation have evolved among these species, including sexual, gametic, ecological, and intrinsic postzygotic barriers, with crosses among all three species conforming to Haldane’s rule: F1 hybrid males are sterile and F1 hybrid females are fertile. Extensive genetic resources and the fertility of hybrid females have made D. mauritiana, in particular, an important model for speciation genetics. Analyses between D. mauritiana and both of its siblings have shown that the X chromosome makes a disproportionate contribution to hybrid male sterility. But why the X plays a special role in the evolution of hybrid sterility in these, and other, species remains an unsolved problem. To complement functional genetic analyses, we have investigated the population genomics of D. mauritiana, giving special attention to differences between the X and the autosomes. We present a de novo genome assembly of D. mauritiana annotated with RNAseq data and a whole-genome analysis of polymorphism and divergence from ten individuals. Our analyses show that, relative to the autosomes, the X chromosome has reduced nucleotide diversity but elevated nucleotide divergence; an excess of recurrent adaptive evolution at its protein-coding genes; an excess of recent, strong selective sweeps; and a large excess of satellite DNA. Interestingly, one of two centimorgan-scale selective sweeps on the D. mauritiana X chromosome spans a region containing two sex-ratio meiotic drive elements and a high concentration of satellite DNA. Furthermore, genes with roles in reproduction and chromosome biology are enriched among genes that have histories of recurrent adaptive protein evolution. Together, these genome-wide analyses suggest that genetic conflict and frequent positive natural selection on the X chromosome have shaped the molecular evolutionary history of D. mauritiana, refining our understanding of the possible causes of the large X-effect in speciation.
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Cis‐ and trans‐acting genetic factors contribute to heterogeneity in the rate of crossing over between the Drosophila simulans clade species
Journal of Evolutionary Biology, 2012Co-Authors: M. V. Cattani, Sarah B Kingan, Daven C PresgravesAbstract:In the genus Drosophila, variation in recombination rates has been found within and between species. Genetic variation for both cis- and trans-acting factors has been shown to affect recombination rates within species, but little is known about the genetic factors that affect differences between species. Here, we estimate rates of crossing over for seven segments that tile across the euchromatic length of the X chromosome in the genetic backgrounds of three closely related Drosophila species. We first generated a set of Drosophila mauritiana lines each having two semidominant visible markers on the X chromosome and then introgressed these doubly marked segments into the genetic backgrounds of its sibling species, Drosophila simulans and Drosophila sechellia. Using these 21 lines (seven segments, three genetic backgrounds), we tested whether recombination rates within the doubly marked intervals differed depending on genetic background. We find significant heterogeneity among intervals and among species backgrounds. Our results suggest that a combination of both cis- and trans-acting factors have evolved among the three D. simulans clade species and interact to affect recombination rate.
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genetics and lineage specific evolution of a lethal hybrid incompatibility between Drosophila mauritiana and its sibling species
Genetics, 2009Co-Authors: Victoria M Cattani, Daven C PresgravesAbstract:The Dobzhansky–Muller model posits that intrinsic postzygotic reproductive isolation—the sterility or lethality of species hybrids—results from the evolution of incompatible epistatic interactions between species: favorable or neutral alleles that become fixed in the genetic background of one species can cause sterility or lethality in the genetic background of another species. The kind of hybrid incompatibility that evolves between two species, however, depends on the particular evolutionary history of the causative substitutions. An allele that is functionally derived in one species can be incompatible with an allele that is functionally derived in the other species (a derived-derived hybrid incompatibility). But an allele that is functionally derived in one species can also be incompatible with an allele that has retained the ancestral state in the other species (a derived-ancestral hybrid incompatibility). The relative abundance of such derived-derived vs. derived-ancestral hybrid incompatibilities is unknown. Here, we characterize the genetics and evolutionary history of a lethal hybrid incompatibility between Drosophila mauritiana and its two sibling species, D. sechellia and D. simulans. We show that a hybrid lethality factor(s) in the pericentric heterochromatin of the D. mauritiana X chromosome, hybrid lethal on the X (hlx), is incompatible with a factor(s) in the same small autosomal region from both D. sechellia and D. simulans, Suppressor of hlx [Su(hlx)]. By combining genetic and phylogenetic information, we infer that hlx-Su(hlx) hybrid lethality is likely caused by a derived-ancestral incompatibility, a hypothesis that can be tested directly when the genes are identified.
Maria D S Nunes - One of the best experts on this subject based on the ideXlab platform.
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genetic architecture and functional characterization of genes underlying the rapid diversification of male external genitalia between Drosophila simulans and Drosophila mauritiana
Genetics, 2015Co-Authors: Kentaro M Tanaka, Christian Schlotterer, Corinna Hopfen, Matthew R Herbert, David L Stern, John P Masly, Alistair P Mcgregor, Maria D S NunesAbstract:Male sexual characters are often among the first traits to diverge between closely related species and identifying the genetic basis of such changes can contribute to our understanding of their evolutionary history. However, little is known about the genetic architecture or the specific genes underlying the evolution of male genitalia. The morphology of the claspers, posterior lobes, and anal plates exhibit striking differences between Drosophila mauritiana and D. simulans. Using QTL and introgression-based high-resolution mapping, we identified several small regions on chromosome arms 3L and 3R that contribute to differences in these traits. However, we found that the loci underlying the evolution of clasper differences between these two species are independent from those that contribute to posterior lobe and anal plate divergence. Furthermore, while most of the loci affect each trait in the same direction and act additively, we also found evidence for epistasis between loci for clasper bristle number. In addition, we conducted an RNAi screen in D. melanogaster to investigate if positional and expression candidate genes located on chromosome 3L, are also involved in genital development. We found that six of these genes, including components of Wnt signaling and male-specific lethal 3 (msl3), regulate the development of genital traits consistent with the effects of the introgressed regions where they are located and that thus represent promising candidate genes for the evolution these traits.
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genetic and developmental analysis of differences in eye and face morphology between Drosophila simulans and Drosophila mauritiana
Evolution & Development, 2013Co-Authors: Maria D S Nunes, Corinna Hopfen, Saad Arif, Maarten Hilbrant, Isabel Almudi, Nico Posnien, Linta KuncheriaAbstract:Eye and head morphology vary considerably among insects and even between closely related species of Drosophila. Species of the D. melanogaster subgroup, and other Drosophila species, exhibit a negative correlation between eye size and face width (FW); for example, D. mauritiana generally has bigger eyes composed of larger ommatidia and conversely a narrower face than its sibling species. To better understand the evolution of eye and head morphology, we investigated the genetic and developmental basis of differences in eye size and FW between male D. mauritiana and D. simulans. QTL mapping of eye size and FW showed that the major loci responsible for the interspecific variation in these traits are localized to different genomic regions. Introgression of the largest effect QTL underlying the difference in eye size resulted in flies with larger eyes but no significant difference in FW. Moreover, introgression of a QTL region on the third chromosome that contributes to the FW difference between these species affected FW, but not eye size. We also observed that this difference in FW is detectable earlier in the development of the eye-antennal disc than the difference in the size of the retinal field. Our results suggest that different loci that act at different developmental stages underlie changes in eye size and FW. Therefore, while there is a negative correlation between these traits in Drosophila, we show genetically that they also have the potential to evolve independently and this may help to explain the evolution of these traits in other insects.
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multiple hybridization events between Drosophila simulans and Drosophila mauritiana are supported by mtdna introgression
Molecular Ecology, 2010Co-Authors: Maria D S Nunes, Pablo Orozcoter Wengel, Michaela Kreissl, Christian SchlottererAbstract:The study of speciation has advanced considerably in the last decades because of the increased application of molecular tools. In particular, the quantification of gene flow between recently diverged species could be addressed. Drosophila simulans and Drosophila mauritiana diverged, probably allopatrically, from a common ancestor approximately 250 000 years ago. However, these species share one mitochondrial DNA (mtDNA) haplotype indicative of a recent episode of introgression. To study the extent of gene flow between these species, we took advantage of a large sample of D. mauritiana and employed a range of different markers, i.e. nuclear and mitochondrial sequences, and microsatellites. This allowed us to detect two new mtDNA haplotypes (MAU3 and MAU4). These haplotypes diverged quite recently from haplotypes of the siII group present in cosmopolitan populations of D. simulans. The mean divergence time of the most diverged haplotype (MAU4) is approximately 127 000 years, which is more than 100 000 years before the assumed speciation time. Interestingly, we also found some evidence for gene flow at the nuclear level because an excess of putatively neutral loci shows significantly reduced differentiation between D. simulans and D. mauritiana. Our results suggest that these species are exchanging genes more frequently than previously thought.
