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Crowley LM, Roy HE, Brown PM. The genome sequence of the ten-spot ladybird, Adalia decempunctata (Linnaeus, 1758). Wellcome Open Res 2024; 9:106. [PMID: 38966305 PMCID: PMC11222777 DOI: 10.12688/wellcomeopenres.21008.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2024] [Indexed: 07/06/2024] Open
Abstract
We present a genome assembly from an individual male Adalia decempunctata (the ten-spot ladybird; Arthropoda; Insecta; Coleoptera; Coccinellidae). The genome sequence is 489.4 megabases in span. Most of the assembly is scaffolded into 12 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 19.68 kilobases in length.
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Affiliation(s)
| | - Helen E. Roy
- UK Centre for Ecology & Hydrology, Crowmarsh Gifford, England, UK
| | | | | | | | - Wellcome Sanger Institute Tree of Life Management, Samples and Laboratory team
- University of Oxford, Oxford, England, UK
- UK Centre for Ecology & Hydrology, Crowmarsh Gifford, England, UK
- Anglia Ruskin University, Cambridge, England, UK
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2
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Yao YL, Ma XY, Wang TY, Yan JY, Chen NF, Hong JS, Liu BQ, Xu ZQ, Zhang N, Lv C, Sun X, Luan JB. A bacteriocyte symbiont determines whitefly sex ratio by regulating mitochondrial function. Cell Rep 2023; 42:112102. [PMID: 36774548 DOI: 10.1016/j.celrep.2023.112102] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 11/28/2022] [Accepted: 01/26/2023] [Indexed: 02/13/2023] Open
Abstract
Nutritional symbionts influence host reproduction, but the underlying molecular mechanisms are largely unclear. We previously found that the bacteriocyte symbiont Hamiltonella impacts the sex ratio of the whitefly Bemisia tabaci. Hamiltonella synthesizes folate by cooperation with the whitefly. Folate deficiency by Hamiltonella elimination or whitefly gene silencing distorted whitefly sex ratio, and folate supplementation restored the sex ratio. Hamiltonella deficiency or gene silencing altered histone H3 lysine 9 trimethylation (H3K9me3) level, which was restored by folate supplementation. Genome-wide chromatin immunoprecipitation-seq analysis of H3K9me3 indicated mitochondrial dysfunction in symbiont-deficient whiteflies. Hamiltonella deficiency compromised mitochondrial quality of whitefly ovaries. Repressing ovary mitochondrial function led to distorted whitefly sex ratio. These findings indicate that the symbiont-derived folate regulates host histone methylation modifications, which thereby impacts ovary mitochondrial function, and finally determines host sex ratio. Our study suggests that a nutritional symbiont can regulate animal reproduction in a way that differs from reproductive manipulators.
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Affiliation(s)
- Ya-Lin Yao
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Xin-Yu Ma
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Tian-Yu Wang
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Jin-Yang Yan
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Nai-Fei Chen
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Ji-Sheng Hong
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Bing-Qi Liu
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Zi-Qi Xu
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Nuo Zhang
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Chao Lv
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Xiang Sun
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China
| | - Jun-Bo Luan
- Liaoning Key Laboratory of Economic and Applied Entomology, College of Plant Protection, Shenyang Agricultural University, Shenyang 110866, China.
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3
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Wang T, Li TC, Miao YH, Wu LN, Chen YQ, Huang DW, Xiao JH. The gender-specific impact of starvation on mitotypes diversity in adults of Drosophila melanogaster. Open Biol 2022; 12:220108. [PMID: 36167086 PMCID: PMC9514890 DOI: 10.1098/rsob.220108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In animals, starvation can increase the level of reactive oxygen species (ROS) in some tissues. Mitochondrial DNA (mtDNA) is more vulnerable to being attacked by ROS due to the lack of histone protection, leading to oxidative damage. However, whether starvation is associated with the genetic diversity of mtDNA remains unclear. Here, by using adult individuals of Drosophila melanogaster under three different feeding treatments (starvation, with the provision of only water, and normal feeding), based on the high-throughput sequencing results of the PCR amplicons of the partial sequences of the mitochondrial gene cytochrome c oxidase subunit I (mt-cox1), no significant difference in the mean number of mitochondrial haplotypes and the mean genetic distance of haplotypes within individuals were identified between the three treatment groups. Coupled with the low proportion of heterogeneous mt-cox1 sequences within each individual, it suggested that starvation had a limited impact on mitotype genetic diversity and mitochondrial function. Nevertheless, starvation could significantly increase the sequence number of haplotypes containing specific mutations, and for males with higher levels of mitochondrial heteroplasmy than females in the normal feeding group, starvation could further increase their mitochondrial heteroplasmy.
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Affiliation(s)
- Tao Wang
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
| | - Tian-Chu Li
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
| | - Yun-Heng Miao
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
| | - Luo-Nan Wu
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
| | - Yu-Qiao Chen
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
| | - Da-Wei Huang
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
| | - Jin-Hua Xiao
- College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China
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4
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Abstract
Microorganisms that reside within or transmit through arthropod reproductive tissues have profound impacts on host reproduction, health and evolution. In this Review, we discuss select principles of the biology of microorganisms in arthropod reproductive tissues, including bacteria, viruses, protists and fungi. We review models of specific symbionts, routes of transmission, and the physiological and evolutionary outcomes for both hosts and microorganisms. We also identify areas in need of continuing research, to answer the fundamental questions that remain in fields within and beyond arthropod-microorganism associations. New opportunities for research in this area will drive a broader understanding of major concepts as well as the biodiversity, mechanisms and translational applications of microorganisms that interact with host reproductive tissues.
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5
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Lambert SM, Streicher JW, Fisher‐Reid MC, Méndez de la Cruz FR, Martínez‐Méndez N, García-Vázquez UO, Nieto Montes de Oca A, Wiens JJ. Inferring introgression using RADseq and
D
FOIL
: Power and pitfalls revealed in a case study of spiny lizards (
Sceloporus
). Mol Ecol Resour 2019; 19:818-837. [DOI: 10.1111/1755-0998.12972] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 10/26/2018] [Indexed: 02/03/2023]
Affiliation(s)
- Shea M. Lambert
- Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona
| | - Jeffrey W. Streicher
- Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona
- Department of Life Sciences The Natural History Museum London UK
| | - M. Caitlin Fisher‐Reid
- Department of Biological Sciences Bridgewater State University Bridgewater Massachusetts
| | - Fausto R. Méndez de la Cruz
- Laboratorio de Herpetología, Instituto de Biología Universidad Nacional Autónoma de México Mexico City Mexico
| | - Norberto Martínez‐Méndez
- Laboratorio de Bioconservación y Manejo, Departamento de Zoología Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional Mexico City Mexico
| | - Uri Omar García-Vázquez
- Unidad Multidisciplinaria de Investigación, Facultad de Estudios Superiores Zaragoza Universidad Nacional Autónoma de México Mexico City Mexico
| | - Adrián Nieto Montes de Oca
- Departamento de Biología Evolutiva, Facultad de Ciencias Universidad Nacional Autónoma de México Mexico City Mexico
| | - John J. Wiens
- Department of Ecology and Evolutionary Biology University of Arizona Tucson Arizona
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6
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Palenko MV, Andrianov BV, Romanov DA, Zakharov IA. Geographical Ecocline Polymorphism of the Distribution of Mitochondrial Haplotypes of Adalia bipunctata Linnaeus, 1758 (Coleoptera: Coccinellidae) of Norway. RUSS J GENET+ 2018. [DOI: 10.1134/s1022795418040117] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Complex Coding and Regulatory Polymorphisms in a Restriction Factor Determine the Susceptibility of Drosophila to Viral Infection. Genetics 2017. [PMID: 28630113 PMCID: PMC5560813 DOI: 10.1534/genetics.117.201970] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
It is common to find that major-effect genes are an important cause of variation in susceptibility to infection. Here we have characterized natural variation in a gene called pastrel that explains over half of the genetic variance in susceptibility to the Drosophila C virus (DCV) in populations of Drosophila melanogaster We found extensive allelic heterogeneity, with a sample of seven alleles of pastrel from around the world conferring four phenotypically distinct levels of resistance. By modifying candidate SNPs in transgenic flies, we show that the largest effect is caused by an amino acid polymorphism that arose when an ancestral threonine was mutated to alanine, greatly increasing resistance to DCV. Overexpression of the ancestral, susceptible allele provides strong protection against DCV; indicating that this mutation acted to improve an existing restriction factor. The pastrel locus also contains complex structural variation and cis-regulatory polymorphisms altering gene expression. We find that higher expression of pastrel is associated with increased survival after DCV infection. To understand why this variation is maintained in populations, we investigated genetic variation surrounding the amino acid variant that is causing flies to be resistant. We found no evidence of natural selection causing either recent changes in allele frequency or geographical variation in frequency, suggesting that this is an old polymorphism that has been maintained at a stable frequency. Overall, our data demonstrate how complex genetic variation at a single locus can control susceptibility to a virulent natural pathogen.
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8
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Scriven JJ, Whitehorn PR, Goulson D, Tinsley MC. Niche partitioning in a sympatric cryptic species complex. Ecol Evol 2016; 6:1328-39. [PMID: 26848386 PMCID: PMC4730923 DOI: 10.1002/ece3.1965] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 12/21/2015] [Accepted: 12/23/2015] [Indexed: 11/24/2022] Open
Abstract
Competition theory states that multiple species should not be able to occupy the same niche indefinitely. Morphologically, similar species are expected to be ecologically alike and exhibit little niche differentiation, which makes it difficult to explain the co‐occurrence of cryptic species. Here, we investigated interspecific niche differentiation within a complex of cryptic bumblebee species that co‐occur extensively in the United Kingdom. We compared the interspecific variation along different niche dimensions, to determine how they partition a niche to avoid competitive exclusion. We studied the species B. cryptarum, B. lucorum, and B. magnus at a single location in the northwest of Scotland throughout the flight season. Using mitochondrial DNA for species identification, we investigated differences in phenology, response to weather variables and forage use. We also estimated niche region and niche overlap between different castes of the three species. Our results show varying levels of niche partitioning between the bumblebee species along three niche dimensions. The species had contrasting phenologies: The phenology of B. magnus was delayed relative to the other two species, while B. cryptarum had a relatively extended phenology, with workers and males more common than B. lucorum early and late in the season. We found divergent thermal specialisation: In contrast to B. cryptarum and B. magnus, B. lucorum worker activity was skewed toward warmer, sunnier conditions, leading to interspecific temporal variation. Furthermore, the three species differentially exploited the available forage plants: In particular, unlike the other two species, B. magnus fed predominantly on species of heather. The results suggest that ecological divergence in different niche dimensions and spatio‐temporal heterogeneity in the environment may contribute to the persistence of cryptic species in sympatry. Furthermore, our study suggests that cryptic species provide distinct and unique ecosystem services, demonstrating that morphological similarity does not necessarily equate to ecological equivalence.
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Affiliation(s)
- Jessica J Scriven
- Biological and Environmental Sciences School of Natural Sciences University of Stirling Stirling FK9 4LA UK
| | - Penelope R Whitehorn
- Biological and Environmental Sciences School of Natural Sciences University of Stirling Stirling FK9 4LA UK
| | - Dave Goulson
- School of Life Sciences University of Sussex Falmer Brighton BN1 9QG UK
| | - Matthew C Tinsley
- Biological and Environmental Sciences School of Natural Sciences University of Stirling Stirling FK9 4LA UK
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9
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Cao C, Magwire MM, Bayer F, Jiggins FM. A Polymorphism in the Processing Body Component Ge-1 Controls Resistance to a Naturally Occurring Rhabdovirus in Drosophila. PLoS Pathog 2016; 12:e1005387. [PMID: 26799957 PMCID: PMC4723093 DOI: 10.1371/journal.ppat.1005387] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 12/17/2015] [Indexed: 12/30/2022] Open
Abstract
Hosts encounter an ever-changing array of pathogens, so there is continual selection for novel ways to resist infection. A powerful way to understand how hosts evolve resistance is to identify the genes that cause variation in susceptibility to infection. Using high-resolution genetic mapping we have identified a naturally occurring polymorphism in a gene called Ge-1 that makes Drosophila melanogaster highly resistant to its natural pathogen Drosophila melanogaster sigma virus (DMelSV). By modifying the sequence of the gene in transgenic flies, we identified a 26 amino acid deletion in the serine-rich linker region of Ge-1 that is causing the resistance. Knocking down the expression of the susceptible allele leads to a decrease in viral titre in infected flies, indicating that Ge-1 is an existing restriction factor whose antiviral effects have been increased by the deletion. Ge-1 plays a central role in RNA degradation and the formation of processing bodies (P bodies). A key effector in antiviral immunity, the RNAi induced silencing complex (RISC), localises to P bodies, but we found that Ge-1-based resistance is not dependent on the small interfering RNA (siRNA) pathway. However, we found that Decapping protein 1 (DCP1) protects flies against sigma virus. This protein interacts with Ge-1 and commits mRNA for degradation by removing the 5’ cap, suggesting that resistance may rely on this RNA degradation pathway. The serine-rich linker domain of Ge-1 has experienced strong selection during the evolution of Drosophila, suggesting that this gene may be under long-term selection by viruses. These findings demonstrate that studying naturally occurring polymorphisms that increase resistance to infections enables us to identify novel forms of antiviral defence, and support a pattern of major effect polymorphisms controlling resistance to viruses in Drosophila. Hosts and their pathogens are engaged in a never-ending arms race, and hosts must continually evolve new defences to protect themselves from infection. In the fruit fly Drosophila melanogaster we show that virus resistance can evolve through a single mutation. In flies that are highly resistant to a naturally occurring virus called sigma virus we identified a deletion in the protein-coding region of a gene called Ge-1. We experimentally confirmed that this was the cause of resistance by deleting this region in transgenic flies. Furthermore, we show that even the susceptible allele of Ge-1 helps protect flies against the virus, suggesting that this mutation has made an existing antiviral defence more effective. Ge-1 plays a central role in RNA degradation in regions of the cytoplasm called P bodies, and our results suggest that this pathway has been recruited during evolution to protect D. melanogaster against sigma virus. The protein domain that contains the deletion has experienced strong selection during its evolution, suggesting that it may be involved in an ongoing arms race with viruses.
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Affiliation(s)
- Chuan Cao
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
| | - Michael M. Magwire
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Florian Bayer
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Francis M. Jiggins
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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10
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Morphological and molecular characterization of a sexually reproducing colony of the booklouse Liposcelis bostrychophila (Psocodea: Liposcelididae) found in Arizona. Sci Rep 2015; 5:10429. [PMID: 26013922 PMCID: PMC4444836 DOI: 10.1038/srep10429] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 04/14/2015] [Indexed: 01/06/2023] Open
Abstract
The booklouse, Liposcelis bostrychophila, is a worldwide pest of stored products. For decades, only thelytokous parthenogenetic reproduction was documented in L. bostrychophila. Male L. bostrychophila were first found in Hawaii in 2002. In 2009, a sexual strain was found in Arizona. We examined the morphology of both males and females of the Arizona strain and compared the Arizona sexual strain with the Hawaii sexual strain and the parthenogenetic strains of L. bostrychophila. The sexual and parthenogenetic strains show some differences in eye morphology. To examine the relationship between sexual and asexual lineages, we sequenced the mitochondrial 12S and 16S ribosomal RNA genes of males and females from the Arizona strain. Phylogenetic analyses of L. bostrychophila individuals revealed that: 1) the sexually reproducing colony found in Arizona contains two closely related mitochondrial DNA haplotypes--one present in only females and the other in both males and females; and 2) the Arizona sexual strain was most closely related to a parthenogenetic strain in Illinois. We detected Rickettsia in all of the parthenogenetic individuals we checked but not in any Arizona sexual individuals. Further evidence is required to establish whether the presence of Rickettsia is linked to asexual reproduction in Liposcelis.
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11
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Abstract
In virtually all multicellular eukaryotes, mitochondria are transmitted exclusively through one parent, usually the mother. In this short review, we discuss some of the major consequences of uniparental transmission of mitochondria, including deleterious effects in males and selection for increased transmission through females. Many of these consequences, particularly sex ratio distortion, have well-studied parallels in other maternally transmitted genetic elements, such as bacterial endosymbionts of arthropods. We also discuss the consequences of linkage between mitochondria and other maternally transmitted genetic elements, including the role of cytonuclear incompatibilities in maintaining polymorphism. Finally, as a case study, we discuss a recently discovered maternally transmitted sex ratio distortion in an insect that is associated with extraordinarily divergent mitochondria.
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12
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Kazancıoğlu E, Arnqvist G. The maintenance of mitochondrial genetic variation by negative frequency-dependent selection. Ecol Lett 2013; 17:22-7. [PMID: 24134428 DOI: 10.1111/ele.12195] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 07/05/2013] [Accepted: 09/15/2013] [Indexed: 11/30/2022]
Abstract
Mitochondrial genes generally show high levels of standing genetic variation, which is puzzling given the accumulating evidence for phenotypic effects of mitochondrial genetic variation. Negative frequency-dependent selection, where the relative fitness of a genotype is inversely related to its frequency in a population, provides a potent and potentially general process that can maintain mitochondrial polymorphism. We assessed the change in mitochondrial haplotype frequencies over 10 generations of experimental evolution in 180 seed beetle populations in the laboratory, where haplotypes competed for propagation to subsequent generations. We found that haplotypes consistently increased in frequency when they were initially rare and decreased in frequency when initially common. Our results have important implications for the use of mtDNA haplotype frequency data to infer population level processes and they revive the general hypothesis that negative frequency-dependent selection, presumably caused by habitat heterogeneity, may commonly promote polymorphism in ecologically relevant life history genes.
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Affiliation(s)
- Erem Kazancıoğlu
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyv. 18 D, SE-752 36, Uppsala, Sweden
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13
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Elnagdy S, Majerus MEN, Gardener M, Lawson Handley LJ. The direct effects of male killer infection on fitness of ladybird hosts (Coleoptera: Coccinellidae). J Evol Biol 2013; 26:1816-25. [PMID: 23869568 DOI: 10.1111/jeb.12186] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 04/08/2013] [Accepted: 04/10/2013] [Indexed: 11/30/2022]
Abstract
Male killing bacteria are common in insects and are thought to persist in host populations primarily by indirect fitness benefits to infected females, whereas direct fitness effects are generally assumed to be neutral or deleterious. Here, we estimated the effect of male killer infection on direct fitness (number of eggs laid, as a measure of fecundity, together with survival) and other life-history traits (development time and body size) in seven ladybird host/male killer combinations. Effects of male killers on fecundity ranged, as expected, from costly to neutral; however, we found evidence of reduced development time and increased survival and body size in infected strains. Greater body size in Spiroplasma-infected Harmonia axyridis corresponded to greater ovariole number and therefore higher potential fecundity. To our knowledge, this is the first report of direct benefits of male killer infection after explicitly controlling for indirect fitness effects. Neutral or deleterious fitness effects of male killer infection should not therefore be automatically assumed.
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Affiliation(s)
- S Elnagdy
- Department of Genetics, University of Cambridge, Cambridge, UK
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14
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Population genomics of the Wolbachia endosymbiont in Drosophila melanogaster. PLoS Genet 2012; 8:e1003129. [PMID: 23284297 PMCID: PMC3527207 DOI: 10.1371/journal.pgen.1003129] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 10/02/2012] [Indexed: 11/23/2022] Open
Abstract
Wolbachia are maternally inherited symbiotic bacteria, commonly found in arthropods, which are able to manipulate the reproduction of their host in order to maximise their transmission. The evolutionary history of endosymbionts like Wolbachia can be revealed by integrating information on infection status in natural populations with patterns of sequence variation in Wolbachia and host mitochondrial genomes. Here we use whole-genome resequencing data from 290 lines of Drosophila melanogaster from North America, Europe, and Africa to predict Wolbachia infection status, estimate relative cytoplasmic genome copy number, and reconstruct Wolbachia and mitochondrial genome sequences. Overall, 63% of Drosophila strains were predicted to be infected with Wolbachia by our in silico analysis pipeline, which shows 99% concordance with infection status determined by diagnostic PCR. Complete Wolbachia and mitochondrial genomes show congruent phylogenies, consistent with strict vertical transmission through the maternal cytoplasm and imperfect transmission of Wolbachia. Bayesian phylogenetic analysis reveals that the most recent common ancestor of all Wolbachia and mitochondrial genomes in D. melanogaster dates to around 8,000 years ago. We find evidence for a recent global replacement of ancestral Wolbachia and mtDNA lineages, but our data suggest that the derived wMel lineage arose several thousand years ago, not in the 20th century as previously proposed. Our data also provide evidence that this global replacement event is incomplete and is likely to be one of several similar incomplete replacement events that have occurred since the out-of-Africa migration that allowed D. melanogaster to colonize worldwide habitats. This study provides a complete genomic analysis of the evolutionary mode and temporal dynamics of the D. melanogaster–Wolbachia symbiosis, as well as important resources for further analyses of the impact of Wolbachia on host biology. Host–microbe interactions play important roles in the physiology, development, and ecology of many organisms. Studying how hosts and their microbial symbionts evolve together over time is crucial for understanding the impact that microbes have on host biology. With the advent of high-throughput sequencing technologies, it is now possible to obtain complete genomic information for hosts and their associated microbes. Here we use whole-genome sequences from ∼300 strains of the fruitfly Drosophila melanogaster to reveal the evolutionary history of this model species and its intracellular bacterial symbiont Wolbachia. The major findings of this study are that Wolbachia in D. melanogaster is inherited strictly through the egg with no evidence of horizontal transfer from other species, that the genealogies of Wolbachia and mitochondrial genomes are virtually the same, and that both Wolbachia and mitochondrial genomes show evidence for a recent incomplete global replacement event, which has left remnant lineages in North America, Europe, and Africa. We also use the fact that Wolbachia and mitochondrial genomes have the same genealogy to estimate the rate of molecular evolution for Wolbachia, which allows us to put dates on key events in the history of this important host–microbe model system.
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15
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Kvie KS, Hogner S, Aarvik L, Lifjeld JT, Johnsen A. Deep sympatric mtDNA divergence in the autumnal moth (Epirrita autumnata). Ecol Evol 2012; 3:126-44. [PMID: 23404314 PMCID: PMC3568849 DOI: 10.1002/ece3.434] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 10/29/2012] [Accepted: 11/01/2012] [Indexed: 02/01/2023] Open
Abstract
Deep sympatric intraspecific divergence in mtDNA may reflect cryptic species or formerly distinct lineages in the process of remerging. Preliminary results from DNA barcoding of Scandinavian butterflies and moths showed high intraspecific sequence variation in the autumnal moth, Epirrita autumnata. In this study, specimens from different localities in Norway and some samples from Finland and Scotland, with two congeneric species as outgroups, were sequenced with mitochondrial and nuclear markers to resolve the discrepancy found between mtDNA divergence and present species-level taxonomy. We found five COI sub-clades within the E. autumnata complex, most of which were sympatric and with little geographic structure. Nuclear markers (ITS2 and Wingless) showed little variation and gave no indications that E. autumnata comprises more than one species. The samples were screened with primers for Wolbachia outer surface gene (wsp) and 12% of the samples tested positive. Two Wolbachia strains were associated with different mtDNA sub-clades within E. autumnata, which may indicate indirect selection/selective sweeps on haplotypes. Our results demonstrate that deep mtDNA divergences are not synonymous with cryptic speciation and this has important implications for the use of mtDNA in species delimitation, like in DNA barcoding.
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Affiliation(s)
- Kjersti S Kvie
- Natural History Museum, University of Oslo P.O. Box 1172, Blindern, N-0318, Oslo, Norway ; Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science P.O. Box 8146 Dep, N-0033, Oslo, Norway
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16
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Sonnleitner ST, Simeoni J, Lang S, Dobler G, Speck S, Zelger R, Schennach H, Lass-Flörl C, Walder G. Spotted fever group--Rickettsiae in the Tyrols: evidence by seroepidemiology and PCR. Zoonoses Public Health 2012; 60:284-90. [PMID: 22883690 DOI: 10.1111/j.1863-2378.2012.01534.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aim of our study was to assess the occurrence of Rickettsia in the inner-alpine valleys of the Eastern Alps and to determine the amount of seroreaction among the local human population. Ticks were investigated by PCR and the percentage of seropositives was determined among local blood donors by an in-house immunofluorescence assay. The local cut-off titre for screening of IgG was set at 1 : 128 with a well-characterised low-risk collective according to WHO-guidelines. Positive sera were confirmed by independent re-testing. Rickettsia is present in ticks north and south of the continental divide. Of 259 ticks investigated, 12.4% are positive for Rickettsia. Of over 1200 blood donors tested so far, 7.7% bear IgG at a titre of 1 : 128 or higher against R. helvetica. R. helvetica is present in the study area, causes immunoreaction among local residents and is associated with anamnestic erythema. Furthermore, screening with a second Spotted Fever Group Rickettsia indicates that significant parts of the Tyrolean population are exposed to a Rickettsia other than R. helvetica.
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Affiliation(s)
- S T Sonnleitner
- Department of Hygiene, Medical Microbiology and Social Medicine, Innsbruck Medical University, Innsbruck, Austria.
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Shaikevich EV, Ivshina EV, Zakharov IA. Polymorphism of mitochondrial DNA and distribution of cytoplasmic symbionts in the populations of two-spot ladybird beetle Adalia bipunctata. RUSS J GENET+ 2012. [DOI: 10.1134/s1022795412040102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Frankham R. How closely does genetic diversity in finite populations conform to predictions of neutral theory? Large deficits in regions of low recombination. Heredity (Edinb) 2012; 108:167-78. [PMID: 21878983 PMCID: PMC3282390 DOI: 10.1038/hdy.2011.66] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Revised: 06/21/2011] [Accepted: 06/27/2011] [Indexed: 11/09/2022] Open
Abstract
Levels of genetic diversity in finite populations are crucial in conservation and evolutionary biology. Genetic diversity is required for populations to evolve and its loss is related to inbreeding in random mating populations, and thus to reduced population fitness and increased extinction risk. Neutral theory is widely used to predict levels of genetic diversity. I review levels of genetic diversity in finite populations in relation to predictions of neutral theory. Positive associations between genetic diversity and population size, as predicted by neutral theory, are observed for microsatellites, allozymes, quantitative genetic variation and usually for mitochondrial DNA (mtDNA). However, there are frequently significant deviations from neutral theory owing to indirect selection at linked loci caused by balancing selection, selective sweeps and background selection. Substantially lower genetic diversity than predicted under neutrality was found for chromosomes with low recombination rates and high linkage disequilibrium (compared with 'normally' recombining chromosomes within species and adjusted for different copy numbers and mutation rates), including W (median 100% lower) and Y (89% lower) chromosomes, dot fourth chromosomes in Drosophila (94% lower) and mtDNA (67% lower). Further, microsatellite genetic and allelic diversity were lost at 12 and 33% faster rates than expected in populations adapting to captivity, owing to widespread selective sweeps. Overall, neither neutral theory nor most versions of the genetic draft hypothesis are compatible with all empirical results.
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Affiliation(s)
- R Frankham
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia.
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19
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Magwire MM, Bayer F, Webster CL, Cao C, Jiggins FM. Successive increases in the resistance of Drosophila to viral infection through a transposon insertion followed by a Duplication. PLoS Genet 2011; 7:e1002337. [PMID: 22028673 PMCID: PMC3197678 DOI: 10.1371/journal.pgen.1002337] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 08/22/2011] [Indexed: 11/30/2022] Open
Abstract
To understand the molecular basis of how hosts evolve resistance to their parasites, we have investigated the genes that cause variation in the susceptibility of Drosophila melanogaster to viral infection. Using a host-specific pathogen of D. melanogaster called the sigma virus (Rhabdoviridae), we mapped a major-effect polymorphism to a region containing two paralogous genes called CHKov1 and CHKov2. In a panel of inbred fly lines, we found that a transposable element insertion in the protein coding sequence of CHKov1 is associated with increased resistance to infection. Previous research has shown that this insertion results in a truncated messenger RNA that encodes a far shorter protein than the susceptible allele. This resistant allele has rapidly increased in frequency under directional selection and is now the commonest form of the gene in natural populations. Using genetic mapping and site-specific recombination, we identified a third genotype with considerably greater resistance that is currently rare in the wild. In these flies there have been two duplications, resulting in three copies of both the truncated allele of CHKov1 and CHKov2 (one of which is also truncated). Remarkably, the truncated allele of CHKov1 has previously been found to confer resistance to organophosphate insecticides. As estimates of the age of this allele predate the use of insecticides, it is likely that this allele initially functioned as a defence against viruses and fortuitously "pre-adapted" flies to insecticides. These results demonstrate that strong selection by parasites for increased host resistance can result in major genetic changes and rapid shifts in allele frequencies; and, contrary to the prevailing view that resistance to pathogens can be a costly trait to evolve, the pleiotropic effects of these changes can have unexpected benefits.
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Affiliation(s)
- Michael M Magwire
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom.
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20
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Elnagdy S, Majerus MEN, Handley LJL. The value of an egg: resource reallocation in ladybirds (Coleoptera: Coccinellidae) infected with male-killing bacteria. J Evol Biol 2011; 24:2164-72. [PMID: 21745250 DOI: 10.1111/j.1420-9101.2011.02346.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Male-killing bacteria are thought to persist in host populations by vertical transmission and conferring direct and/or indirect fitness benefits to their hosts. Here, we test the role of indirect fitness benefits accrued from resource reallocation in species that engage in sibling egg cannibalism. We found that a single-egg meal significantly increased larval survival in 12 ladybird species, but the value of an egg (to survival) differed substantially between species. Next, we tested the impact of three male-killing bacteria on larval survival in one ladybird species, Adalia bipunctata. Spiroplasma reduced larval survival, whereas Wolbachia and Rickettsia had no effect. However, Spiroplasma-infected larvae showed the greatest response to a single-egg meal. The indirect fitness benefit obtained from a single egg is thus so large that even male-killing bacteria with direct fitness costs can persist in host populations. This study supports the hypothesis that fitness compensation via resource reallocation can explain male-killing bacteria persistence.
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Affiliation(s)
- S Elnagdy
- Department of Genetics, University of Cambridge, Cambridge, UK
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21
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Dyer KA, Burke C, Jaenike J. Wolbachia-mediated persistence of mtDNA from a potentially extinct species. Mol Ecol 2011; 20:2805-17. [PMID: 21595768 DOI: 10.1111/j.1365-294x.2011.05128.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Drosophila quinaria is polymorphic for infection with Wolbachia, a maternally transmitted endosymbiont. Wolbachia-infected individuals carry mtDNA that is only distantly related to the mtDNA of uninfected individuals, and the clade encompassing all mtDNA haplotypes within D. quinaria also includes the mtDNA of several other species of Drosophila. Nuclear gene variation reveals no difference between the Wolbachia-infected and uninfected individuals of D. quinaria, indicating that they all belong to the same interbreeding biological species. We suggest that the Wolbachia and the mtDNA with which it is associated were derived via interspecific hybridization and introgression. The sequences in the Wolbachia and the associated mtDNA are ≥6% divergent from those of any known Drosophila species. Thus, in spite of nearly complete species sampling, the sequences from which these mitochondria were derived remain unknown, raising the possibility that the donor species is extinct. The association between Wolbachia infection and mtDNA type within D. quinaria suggests that Wolbachia may be required for the continued persistence of the mtDNA from an otherwise extinct Drosophila species. We hypothesize that pathogen-protective effects conferred by Wolbachia operate in a negative frequency-dependent manner, thus bringing about a stable polymorphism for Wolbachia infection.
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Affiliation(s)
- Kelly A Dyer
- Department of Genetics, University of Georgia, Athens, GA 30602, USA.
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22
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GUEGUEN GWÉNAELLE, VAVRE FABRICE, GNANKINE OLIVIER, PETERSCHMITT MICHEL, CHARIF DELPHINE, CHIEL ELAD, GOTTLIEB YUVAL, GHANIM MURAD, ZCHORI-FEIN EINAT, FLEURY FRÉDÉRIC. Endosymbiont metacommunities, mtDNA diversity and the evolution of the Bemisia tabaci (Hemiptera: Aleyrodidae) species complex. Mol Ecol 2010; 19:4365-76. [DOI: 10.1111/j.1365-294x.2010.04775.x] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Abstract
Insect heritable symbionts have proven to be ubiquitous, based on molecular screening of various insect lineages. Recently, molecular and experimental approaches have yielded an immensely richer understanding of their diverse biological roles, resulting in a burgeoning research literature. Increasingly, commonalities and intermediates are being discovered between categories of symbionts once considered distinct: obligate mutualists that provision nutrients, facultative mutualists that provide protection against enemies or stress, and symbionts such as Wolbachia that manipulate reproductive systems. Among the most far-reaching impacts of widespread heritable symbiosis is that it may promote speciation by increasing reproductive and ecological isolation of host populations, and it effectively provides a means for transfer of genetic information among host lineages. In addition, insect symbionts provide some of the extremes of cellular genomes, including the smallest and the fastest evolving, raising new questions about the limits of evolution of life.
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Affiliation(s)
- Nancy A Moran
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA.
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Weinert LA, Werren JH, Aebi A, Stone GN, Jiggins FM. Evolution and diversity of Rickettsia bacteria. BMC Biol 2009; 7:6. [PMID: 19187530 PMCID: PMC2662801 DOI: 10.1186/1741-7007-7-6] [Citation(s) in RCA: 254] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 02/02/2009] [Indexed: 02/04/2023] Open
Abstract
Background Rickettsia are intracellular symbionts of eukaryotes that are best known for infecting and causing serious diseases in humans and other mammals. All known vertebrate-associated Rickettsia are vectored by arthropods as part of their life-cycle, and many other Rickettsia are found exclusively in arthropods with no known secondary host. However, little is known about the biology of these latter strains. Here, we have identified 20 new strains of Rickettsia from arthropods, and constructed a multi-gene phylogeny of the entire genus which includes these new strains. Results We show that Rickettsia are primarily arthropod-associated bacteria, and identify several novel groups within the genus. Rickettsia do not co-speciate with their hosts but host shifts most often occur between related arthropods. Rickettsia have evolved adaptations including transmission through vertebrates and killing males in some arthropod hosts. We uncovered one case of horizontal gene transfer among Rickettsia, where a strain is a chimera from two distantly related groups, but multi-gene analysis indicates that different parts of the genome tend to share the same phylogeny. Conclusion Approximately 150 million years ago, Rickettsia split into two main clades, one of which primarily infects arthropods, and the other infects a diverse range of protists, other eukaryotes and arthropods. There was then a rapid radiation about 50 million years ago, which coincided with the evolution of life history adaptations in a few branches of the phylogeny. Even though Rickettsia are thought to be primarily transmitted vertically, host associations are short lived with frequent switching to new host lineages. Recombination throughout the genus is generally uncommon, although there is evidence of horizontal gene transfer. A better understanding of the evolution of Rickettsia will help in the future to elucidate the mechanisms of pathogenicity, transmission and virulence.
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Affiliation(s)
- Lucy A Weinert
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, EH9 3JT, UK.
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Effective population size and tests of neutrality at cytoplasmic genes inArabidopsis. Genet Res (Camb) 2008; 90:119-28. [DOI: 10.1017/s0016672307008920] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SummaryCytoplasmic genomes typically lack recombination, implying that genetic hitch-hiking could be a predominant force structuring nucleotide polymorphism in the chloroplast and mitochondria. We test this hypothesis by analysing nucleotide polymorphism data at 28 loci across the chloroplast and mitochondria of the outcrossing plantArabidopsis lyrata, and compare patterns with multiple nuclear loci, and the highly selfingArabidopsis thaliana. The maximum likelihood estimate of the ratio of effective population size at cytoplasmic relative to nuclear genes inA. lyratadoes not depart from the neutral expectation of 0·5. Similarly, the ratio of effective size inA. thalianais close to unity, the neutral expectation for a highly selfing species. The results are thus consistent with neutral organelle polymorphism in these species or with comparable effects of hitch-hiking in both cytoplasmic and nuclear genes, in contrast to the results of recent studies on gynodioecious taxa. The four-gamete test and composite likelihood estimation provide evidence for very low levels of recombination in the organelles ofA. lyrata, although permutation tests do not suggest that adjacent polymorphic sites are more closely linked than more distant sites across the two genomes, suggesting that mutation hotspots or very low rates of gene conversion could explain the data.
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Weinert LA, Tinsley MC, Temperley M, Jiggins FM. Are we underestimating the diversity and incidence of insect bacterial symbionts? A case study in ladybird beetles. Biol Lett 2008; 3:678-81. [PMID: 17878145 PMCID: PMC2111056 DOI: 10.1098/rsbl.2007.0373] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Vertically transmitted bacterial symbionts are common in arthropods. However, estimates of their incidence and diversity are based on studies that test for a single bacterial genus and often only include small samples of each host species. Focussing on ladybird beetles, we collected large samples from 21 species and tested them for four different bacterial symbionts. Over half the species were infected, and there were often multiple symbionts in the same population. In most cases, more females than males were infected, suggesting that the symbionts may be sex ratio distorters. Many of these infections would have been missed in previous studies as they only infect a small proportion of the population. Furthermore, 11 out of the 17 symbionts discovered by us were either in the genus Rickettsia or Spiroplasma, which are rarely sampled. Our results suggest that the true incidence and diversity of bacterial symbionts in insects may be far greater than previously thought.
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Affiliation(s)
- Lucy A Weinert
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, UK.
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Tinsley MC, Majerus ME. Small steps or giant leaps for male-killers? Phylogenetic constraints to male-killer host shifts. BMC Evol Biol 2007; 7:238. [PMID: 18047670 PMCID: PMC2222251 DOI: 10.1186/1471-2148-7-238] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Accepted: 11/29/2007] [Indexed: 11/17/2022] Open
Abstract
Background Arthropods are infected by a wide diversity of maternally transmitted microbes. Some of these manipulate host reproduction to facilitate population invasion and persistence. Such parasites transmit vertically on an ecological timescale, but rare horizontal transmission events have permitted colonisation of new species. Here we report the first systematic investigation into the influence of the phylogenetic distance between arthropod species on the potential for reproductive parasite interspecific transfer. Results We employed a well characterised reproductive parasite, a coccinellid beetle male-killer, and artificially injected the bacterium into a series of novel species. Genetic distances between native and novel hosts were ascertained by sequencing sections of the 16S and 12S mitochondrial rDNA genes. The bacterium colonised host tissues and transmitted vertically in all cases tested. However, whilst transmission efficiency was perfect within the native genus, this was reduced following some transfers of greater phylogenetic distance. The bacterium's ability to distort offspring sex ratios in novel hosts was negatively correlated with the genetic distance of transfers. Male-killing occurred with full penetrance following within-genus transfers; but whilst sex ratio distortion generally occurred, it was incomplete in more distantly related species. Conclusion This study indicates that the natural interspecific transmission of reproductive parasites might be constrained by their ability to tolerate the physiology or genetics of novel hosts. Our data suggest that horizontal transfers are more likely between closely related species. Successful bacterial transfer across large phylogenetic distances may require rapid adaptive evolution in the new species. This finding has applied relevance regarding selection of suitable bacteria to manipulate insect pest and vector populations by symbiont gene-drive systems.
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Affiliation(s)
- Matthew C Tinsley
- School of Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK.
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28
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Abstract
Male-killing bacteria are maternally inherited endosymbionts that selectively kill male offspring of their arthropod hosts. Using both analytical techniques and computer simulations, we studied the impact of these bacteria on the population genetics of their hosts. In particular, we derived and corroborated formulas for the fixation probability of mutant alleles, mean times to fixation and fixation or extinction, and heterozygosity for varying male-killer prevalence. Our results demonstrate that infections with male-killing bacteria impede the spread of beneficial alleles, facilitate the spread of deleterious alleles, and reduce genetic variation. The reason for this lies in the strongly reduced fitness of infected females combined with no or very limited gene flow from infected females to uninfected individuals. These two properties of male-killer-infected populations reduce the population size relevant for the initial emergence and spread of mutations. In contrast, use of Wright's equation relating sex ratio to effective population size produces misleading predictions. We discuss the relationship to the similar effect of background selection, the impact of other sex-ratio-distorting endosymbionts, and how our results affect the interpretation of empirical data on genetic variation in male-killer-infected populations.
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Affiliation(s)
- Jan Engelstädter
- Department of Biology, University College London, London NW1 2HE, United Kingdom.
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