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Lasne C, Elkrewi M, Toups MA, Layana L, Macon A, Vicoso B. The Scorpionfly (Panorpa cognata) Genome Highlights Conserved and Derived Features of the Peculiar Dipteran X Chromosome. Mol Biol Evol 2023; 40:msad245. [PMID: 37988296 PMCID: PMC10715201 DOI: 10.1093/molbev/msad245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 10/05/2023] [Accepted: 11/07/2023] [Indexed: 11/23/2023] Open
Abstract
Many insects carry an ancient X chromosome-the Drosophila Muller element F-that likely predates their origin. Interestingly, the X has undergone turnover in multiple fly species (Diptera) after being conserved for more than 450 My. The long evolutionary distance between Diptera and other sequenced insect clades makes it difficult to infer what could have contributed to this sudden increase in rate of turnover. Here, we produce the first genome and transcriptome of a long overlooked sister-order to Diptera: Mecoptera. We compare the scorpionfly Panorpa cognata X-chromosome gene content, expression, and structure to that of several dipteran species as well as more distantly related insect orders (Orthoptera and Blattodea). We find high conservation of gene content between the mecopteran X and the dipteran Muller F element, as well as several shared biological features, such as the presence of dosage compensation and a low amount of genetic diversity, consistent with a low recombination rate. However, the 2 homologous X chromosomes differ strikingly in their size and number of genes they carry. Our results therefore support a common ancestry of the mecopteran and ancestral dipteran X chromosomes, and suggest that Muller element F shrank in size and gene content after the split of Diptera and Mecoptera, which may have contributed to its turnover in dipteran insects.
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Affiliation(s)
- Clementine Lasne
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Marwan Elkrewi
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Melissa A Toups
- Department of Life and Environmental Sciences, Bournemouth University, Poole, UK
| | - Lorena Layana
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Ariana Macon
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Beatriz Vicoso
- Institute of Science and Technology Austria, Klosterneuburg, Austria
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Freitas S, Parker DJ, Labédan M, Dumas Z, Schwander T. Evidence for cryptic sex in parthenogenetic stick insects of the genus Timema. Proc Biol Sci 2023; 290:20230404. [PMID: 37727092 PMCID: PMC10509586 DOI: 10.1098/rspb.2023.0404] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 08/23/2023] [Indexed: 09/21/2023] Open
Abstract
Obligately parthenogenetic species are expected to be short lived since the lack of sex and recombination should translate into a slower adaptation rate and increased accumulation of deleterious alleles. Some, however, are thought to have been reproducing without males for millions of years. It is not clear how these old parthenogens can escape the predicted long-term costs of parthenogenesis, but an obvious explanation is cryptic sex. In this study, we screen for signatures of cryptic sex in eight populations of four parthenogenetic species of Timema stick insects, some estimated to be older than 1 Myr. Low genotype diversity, homozygosity of individuals and high linkage disequilibrium (LD) unaffected by marker distances support exclusively parthenogenetic reproduction in six populations. However, in two populations (namely, of the species Timema douglasi and T. monikensis) we find strong evidence for cryptic sex, most likely mediated by rare males. These populations had comparatively high genotype diversities, lower LD, and a clear LD decay with genetic distance. Rare sex in species that are otherwise largely parthenogenetic could help explain the unusual success of parthenogenesis in the Timema genus and raises the question whether episodes of rare sex are in fact the simplest explanation for the persistence of many old parthenogens in nature.
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Affiliation(s)
- Susana Freitas
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Darren J. Parker
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- School of Natural Sciences, Bangor University, Bangor, UK
| | - Marjorie Labédan
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Zoé Dumas
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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Knyshov A, Gordon ERL, Masonick PK, Castillo S, Forero D, Hoey-Chamberlain R, Hwang WS, Johnson KP, Lemmon AR, Moriarty Lemmon E, Standring S, Zhang J, Weirauch C. Chromosome-Aware Phylogenomics of Assassin Bugs (Hemiptera: Reduvioidea) Elucidates Ancient Gene Conflict. Mol Biol Evol 2023; 40:msad168. [PMID: 37494292 PMCID: PMC10411492 DOI: 10.1093/molbev/msad168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 07/15/2023] [Accepted: 07/19/2023] [Indexed: 07/28/2023] Open
Abstract
Though the phylogenetic signal of loci on sex chromosomes can differ from those on autosomes, chromosomal-level genome assemblies for nonvertebrates are still relatively scarce and conservation of chromosomal gene content across deep phylogenetic scales has therefore remained largely unexplored. We here assemble a uniquely large and diverse set of samples (17 anchored hybrid enrichment, 24 RNA-seq, and 70 whole-genome sequencing samples of variable depth) for the medically important assassin bugs (Reduvioidea). We assess the performance of genes based on multiple features (e.g., nucleotide vs. amino acid, nuclear vs. mitochondrial, and autosomal vs. X chromosomal) and employ different methods (concatenation and coalescence analyses) to reconstruct the unresolved phylogeny of this diverse (∼7,000 spp.) and old (>180 Ma) group. Our results show that genes on the X chromosome are more likely to have discordant phylogenies than those on autosomes. We find that the X chromosome conflict is driven by high gene substitution rates that impact the accuracy of phylogenetic inference. However, gene tree clustering showed strong conflict even after discounting variable third codon positions. Alternative topologies were not particularly enriched for sex chromosome loci, but spread across the genome. We conclude that binning genes to autosomal or sex chromosomes may result in a more accurate picture of the complex evolutionary history of a clade.
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Affiliation(s)
- Alexander Knyshov
- Department of Entomology, University of California, Riverside, CA, USA
| | - Eric R L Gordon
- Ecology and Evolutionary Biology Department, University of Connecticut, Storrs, CT, USA
| | - Paul K Masonick
- Department of Entomology, University of California, Riverside, CA, USA
| | | | - Dimitri Forero
- Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Bogota, Colombia
| | | | - Wei Song Hwang
- Lee Kong Chian Natural History Museum, National University of Singapore, Queenstown, Singapore
| | - Kevin P Johnson
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL, USA
| | - Alan R Lemmon
- Department of Scientific Computing, Florida State University, Tallahassee, FL, USA
| | | | | | - Junxia Zhang
- Key Laboratory of Zoological Systematics and Application of Hebei Province, Institute of Life Science and Green Development, College of Life Sciences, Hebei University, Baoding, Hebei, China
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Ma W, Rovatsos M. Sex chromosome evolution: The remarkable diversity in the evolutionary rates and mechanisms. J Evol Biol 2022; 35:1581-1588. [DOI: 10.1111/jeb.14119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 10/21/2022] [Accepted: 10/24/2022] [Indexed: 12/03/2022]
Affiliation(s)
- Wen‐Juan Ma
- Department of Molecular Biosciences University of Kansas Lawrence Kansas USA
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