Contribution of recombination and selection to molecular evolution of Citrus tristeza virus

The genetic variation of Citrus tristeza virus (CTV) was analysed by comparing the predominant sequence variants in seven genomic regions (p33, p65, p61, p18, p13, p20 and p23) of 18 pathogenically distinct isolates from seven different countries. Analyses of the selective constraints acting on each codon suggest that most regions were under purifying selection. Phylogenetic analysis shows diverse patterns of molecular evolution for different genomic regions. A first clade composed of isolates that are genetically close to the reference mild isolates T385 or T30 was inferred from all genomic regions. A second clade, mostly comprising virulent isolates, was defined from regions p33, p65, p13 and p23. For regions p65, p61, p18, p13 and p23, a third clade that mostly included South American isolates could not be related to any reference genotype. Phylogenetic relationships among isolates did not reflect their geographical origin, suggesting significant gene flow between geographically distant areas. Incongruent phylogenetic trees for different genomic regions suggested recombination events, an extreme that was supported by several recombination-detecting methods. A phylogenetic network incorporating the effect of recombination showed an explosive radiation pattern for the evolution of some isolates and also grouped isolates by virulence. Taken together, the above results suggest that negative selection, gene flow, sequence recombination and virulence may be important factors driving CTV evolution.

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Constructing Phylogenetic Networks Based on the Isomorphism of Datasets

BioMed Research International ◽

10.1155/2016/4236858 ◽

2016 ◽

Vol 2016 ◽

pp. 1-7

Author(s):

Juan Wang ◽

Zhibin Zhang ◽

Yanjuan Li

Keyword(s):

Molecular Evolution ◽

Phylogenetic Trees ◽

Phylogenetic Network ◽

Phylogenetic Networks ◽

The Relationship

Constructing rooted phylogenetic networks from rooted phylogenetic trees has become an important problem in molecular evolution. So far, many methods have been presented in this area, in which most efficient methods are based on the incompatible graph, such as the CASS, the LNETWORK,and the BIMLR. This paper will research the commonness of the methods based on the incompatible graph, the relationship between incompatible graph and the phylogenetic network, and the topologies of incompatible graphs. We can find out all the simplest datasets for a topologyGand construct a network for every dataset. For any one datasetC, we can compute a network from the network representing the simplest dataset which is isomorphic toC. This process will save more time for the algorithms when constructing networks.

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Phylogenetic Trees and Networks Can Serve as Powerful and Complementary Approaches for Analysis of Genomic Data

Systematic Biology ◽

10.1093/sysbio/syz056 ◽

2019 ◽

Vol 69 (3) ◽

pp. 593-601 ◽

Cited By ~ 9

Author(s):

Christopher Blair ◽

Cécile Ané

Keyword(s):

Gene Flow ◽

Phylogenetic Trees ◽

Evolutionary History ◽

Incomplete Lineage Sorting ◽

Gene Tree ◽

Phylogenetic Network ◽

Genomic Data ◽

Point Of View ◽

Phylogenetic Networks ◽

Lineage Sorting

Abstract Genomic data have had a profound impact on nearly every biological discipline. In systematics and phylogenetics, the thousands of loci that are now being sequenced can be analyzed under the multispecies coalescent model (MSC) to explicitly account for gene tree discordance due to incomplete lineage sorting (ILS). However, the MSC assumes no gene flow post divergence, calling for additional methods that can accommodate this limitation. Explicit phylogenetic network methods have emerged, which can simultaneously account for ILS and gene flow by representing evolutionary history as a directed acyclic graph. In this point of view, we highlight some of the strengths and limitations of phylogenetic networks and argue that tree-based inference should not be blindly abandoned in favor of networks simply because they represent more parameter rich models. Attention should be given to model selection of reticulation complexity, and the most robust conclusions regarding evolutionary history are likely obtained when combining tree- and network-based inference.

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Chloroplast Genomes for Five Skeletonema Species: Comparative and Phylogenetic Analysis

Frontiers in Plant Science ◽

10.3389/fpls.2021.774617 ◽

2021 ◽

Vol 12 ◽

Author(s):

Shuya Liu ◽

Qing Xu ◽

Kuiyan Liu ◽

Yongfang Zhao ◽

Nansheng Chen

Keyword(s):

Molecular Evolution ◽

Critical Role ◽

Nuclear Genome ◽

Sequence Divergence ◽

Purifying Selection ◽

Species Selection ◽

Chloroplast Genomes ◽

High Sequence Divergence ◽

High Conservation ◽

Genomic Regions

Skeletonema species are cosmopolitan coastal diatoms that exhibit important roles in ecological system. The chloroplast genomes (cpDNAs) have been proven to be important in the study of molecular evolution and genetic diversity. However, cpDNA of only a single Skeletonema species (S. pseudocostatum) has been constructed, hindering in-depth investigation on Skeletonema species. In this study, complete cpDNAs of five Skeletonema species were constructed with cpDNAs of four species S. marinoi, S. tropicum, S. costatum, and S. grevillea constructed for the first time. These cpDNAs had similar sizes and same numbers of genes. These cpDNAs were highly syntenic with no substantial expansions, contractions, or inversions. Interestingly, two copies of petF, which encodes ferredoxin with critical role in iron dependency, were found in all five Skeletonema species, with one copy in the cpDNA and another copy in the nuclear genome of each species. Selection analysis revealed that all PCGs of cpDNAs were undergoing purifying selection. Despite the high conservation of these cpDNAs, nine genomic regions with high sequence divergence were identified, which illustrated substantial variations that could be used as markers for phylogenetic inference and for tracking Skeletonema species in the field. Additionally, the numbers of simple sequence repeats varied among different cpDNAs, which were useful for detecting genetic polymorphisms. The divergence times estimated using PCGs of cpDNAs revealed that most of these species were established within ∼33 Mya, consistent with that estimated using mtDNAs. Overall, the current study deepened our understanding about the molecular evolution of Skeletonema cpDNAs.

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Population genetics of Aedes albopictus (Diptera: Culicidae) in its native range in Lao People’s Democratic Republic

Parasites & Vectors ◽

10.1186/s13071-019-3740-0 ◽

2019 ◽

Vol 12 (1) ◽

Author(s):

Maysa Tiemi Motoki ◽

Dina Madera Fonseca ◽

Elliott Frederic Miot ◽

Bruna Demari-Silva ◽

Phoutmany Thammavong ◽

...

Keyword(s):

Population Structure ◽

Gene Flow ◽

Aedes Albopictus ◽

Isolation By Distance ◽

Genetic Locus ◽

Lao Pdr ◽

Phylogenetic Network ◽

Population Expansion ◽

Recent Population Expansion ◽

The Usa

Abstract Background The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. Methods We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. Results We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. Conclusions Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.

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Impact of male trait exaggeration on sex-biased gene expression and genome architecture in a water strider

BMC Biology ◽

10.1186/s12915-021-01021-4 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

William Toubiana ◽

David Armisén ◽

Corentin Dechaud ◽

Roberto Arbore ◽

Abderrahman Khila

Keyword(s):

Gene Expression ◽

Sexual Selection ◽

Enrichment Analysis ◽

Purifying Selection ◽

Genome Architecture ◽

Water Strider ◽

Secondary Sexual Traits ◽

Genomic Regions ◽

Small Clusters ◽

Secondary Sexual

Abstract Background Exaggerated secondary sexual traits are widespread in nature and often evolve under strong directional sexual selection. Although heavily studied from both theoretical and empirical viewpoints, we have little understanding of how sexual selection influences sex-biased gene regulation during the development of exaggerated secondary sexual phenotypes, and how these changes are reflected in genomic architecture. This is primarily due to the limited availability of representative genomes and associated tissue and sex transcriptomes to study the development of these traits. Here we present the genome and developmental transcriptomes, focused on the legs, of the water strider Microvelia longipes, a species where males exhibit strikingly long third legs compared to females, which they use as weapons. Results We generated a high-quality genome assembly with 90% of the sequence captured in 13 scaffolds. The most exaggerated legs in males were particularly enriched in both sex-biased and leg-biased genes, indicating a specific signature of gene expression in association with trait exaggeration. We also found that male-biased genes showed patterns of fast evolution compared to non-biased and female-biased genes, indicative of directional or relaxed purifying selection. By contrast to male-biased genes, female-biased genes that are expressed in the third legs, but not the other legs, are over-represented in the X chromosome compared to the autosomes. An enrichment analysis for sex-biased genes along the chromosomes revealed also that they arrange in large genomic regions or in small clusters of two to four consecutive genes. The number and expression of these enriched regions were often associated with the exaggerated legs of males, suggesting a pattern of common regulation through genomic proximity in association with trait exaggeration. Conclusion Our findings indicate how directional sexual selection may drive sex-biased gene expression and genome architecture along the path to trait exaggeration and sexual dimorphism.

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Allele frequency divergence reveals ubiquitous influence of positive selection in Drosophila

10.1101/2021.03.15.435474 ◽

2021 ◽

Author(s):

Jason Bertram

Keyword(s):

Allele Frequency ◽

Evolutionary Biology ◽

Polymorphic Locus ◽

Purifying Selection ◽

Allele Frequencies ◽

Intermediate Allele ◽

Genome Wide ◽

Signature Of Selection ◽

Basic Objective ◽

Genomic Regions

Resolving the role of natural selection is a basic objective of evolutionary biology. It is generally difficult to detect the influence of selection because ubiquitous non-selective stochastic change in allele frequencies (genetic drift) degrades evidence of selection. As a result, selection scans typically only identify genomic regions that have undergone episodes of intense selection. Yet it seems likely such episodes are the exception; the norm is more likely to involve subtle, concurrent selective changes at a large number of loci. We develop a new theoretical approach that uncovers a previously undocumented genome-wide signature of selection in the collective divergence of allele frequencies over time. Applying our approach to temporally-resolved allele frequency measurements from laboratory and wild Drosophila populations, we quantify the selective contribution to allele frequency divergence and find that selection has substantial effects on much of the genome. We further quantify the magnitude of the total selection coefficient (a measure of the combined effects of direct and linked selection) at a typical polymorphic locus, and find this to be large (of order 1%) even though most mutations are not directly under selection. We find that selective allele frequency divergence is substantial at intermediate allele frequencies, which we argue is most parsimoniously explained by positive --- not purifying --- selection. Thus, in these populations most mutations are far from evolving neutrally in the short term (tens of generations), including mutations with neutral fitness effects, and the result cannot be explained simply as a purging of deleterious mutations.

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Mitochondrial DNAs provide insight into trypanosome phylogeny and molecular evolution

10.21203/rs.3.rs-27858/v1 ◽

2020 ◽

Author(s):

Christopher Kay ◽

Tom A Williams ◽

Wendy Gibson

Keyword(s):

Molecular Evolution ◽

Trypanosoma Brucei ◽

Rna Editing ◽

Phylogenetic Trees ◽

Nucleotide Composition ◽

Sub Saharan Africa ◽

African Trypanosomes ◽

Animal Pathogens ◽

Recent Emergence ◽

The Impact

Abstract Background: Trypanosomes are single-celled eukaryotic parasites characterised by the unique biology of their mitochondrial DNA (mtDNA). African livestock trypanosomes impose a major burden on agriculture across sub-Saharan Africa, but are poorly understood compared to those that cause sleeping sickness and Chagas disease in humans. Here we explore the potential of trypanosome mtDNA to study the evolutionary history of trypanosomes and the molecular evolution of their mtDNAs.Results: We used long-read sequencing to completely assemble mtDNAs from four previously uncharacterized African trypanosomes, and leveraged these assemblies to scaffold and assemble a further 103 trypanosome mtDNAs from published short-read data. While synteny was largely conserved, there were repeated, independent losses of Complex I genes. Comparison of edited and non-edited genes revealed the impact of RNA editing on nucleotide composition, with non-edited genes approaching the limits of GC loss. African tsetse-transmitted trypanosomes showed high levels of RNA editing compared to other trypanosomes. Whole mtDNA coding regions were used to construct time-resolved phylogenetic trees, revealing deep divergence events among isolates of the pathogens Trypanosoma brucei and T. congolense .Conclusions: Our mtDNA data represents a new resource for experimental and evolutionary analyses of trypanosome phylogeny, molecular evolution and function. Molecular clock analyses yielded a timescale for trypanosome evolution congruent with major biogeographical events in Africa and revealed the recent emergence of Trypanosoma brucei gambiense and T. equiperdum , major human and animal pathogens.

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Multiple incursion pathways for Helicoverpa armigera in Brazil show its genetic diversity spreading in a connected world

10.1101/762229 ◽

2019 ◽

Cited By ~ 1

Author(s):

Jonas A. Arnemann ◽

Stephen H. Roxburgh ◽

Tom Walsh ◽

Jerson V.C. Guedes ◽

Karl H.J. Gordon ◽

...

Keyword(s):

Spatial Distribution ◽

Gene Flow ◽

South America ◽

New World ◽

Flow Patterns ◽

South American ◽

Southern Brazil ◽

American Continent ◽

Central Brazil ◽

South American Continent

AbstractThe Old World cotton bollworm Helicoverpa armigera was first detected in Brazil with subsequent reports from Paraguay, Argentina, Bolivia, and Uruguay. This pattern suggests that the H. armigera spread across the South American continent following incursions into northern/central Brazil, however, this hypothesis has not been tested. Here we compare northern and central Brazilian H. armigera mtDNA COI haplotypes with those from southern Brazil, Uruguay, Argentina, and Paraguay. We infer spatial genetic and gene flow patterns of this dispersive pest in the agricultural landscape of South America. We show that the spatial distribution of H. armigera mtDNA haplotypes and its inferred gene flow patterns in the southwestern region of South America exhibited signatures inconsistent with a single incursion hypothesis. Simulations on spatial distribution patterns show that the detection of rare and/or the absence of dominant mtDNA haplotypes in southern H. armigera populations are inconsistent with genetic signatures observed in northern and central Brazil. Incursions of H. armigera into the New World are therefore likely to have involved independent events in northern/central Brazil, and southern Brazil/Uruguay-Argentina-Paraguay. This study demonstrates the significant biosecurity challenges facing the South American continent, and highlights alternate pathways for introductions of alien species into the New World.

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Craniometric data support a mosaic model of demic and cultural Neolithic diffusion to outlying regions of Europe

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2010.2678 ◽

2011 ◽

Vol 278 (1720) ◽

pp. 2874-2880 ◽

Cited By ~ 35

Author(s):

Noreen von Cramon-Taubadel ◽

Ron Pinhasi

Keyword(s):

Gene Flow ◽

Cultural Transmission ◽

Complete Replacement ◽

Cultural Elements ◽

Near Eastern ◽

Farming Communities ◽

Geographical Regions ◽

Significant Gene ◽

Transition To Agriculture ◽

Outlying Regions

The extent to which the transition to agriculture in Europe was the result of biological (demic) diffusion from the Near East or the adoption of farming practices by indigenous hunter–gatherers is subject to continuing debate. Thus far, archaeological study and the analysis of modern and ancient European DNA have yielded inconclusive results regarding these hypotheses. Here we test these ideas using an extensive craniometric dataset representing 30 hunter–gatherer and farming populations. Pairwise population craniometric distance was compared with temporally controlled geographical models representing evolutionary hypotheses of biological and cultural transmission. The results show that, following the physical dispersal of Near Eastern/Anatolian farmers into central Europe, two biological lineages were established with limited gene flow between them. Farming communities spread across Europe, while hunter–gatherer communities located in outlying geographical regions adopted some cultural elements from the farmers. Therefore, the transition to farming in Europe did not involve the complete replacement of indigenous hunter–gatherer populations despite significant gene flow from the Southwest Asia. This study suggests that a mosaic process of dispersal of farmers and their ideas was operating in outlying regions of Europe, thereby reconciling previously conflicting results obtained from genetic and archaeological studies.

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