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Yarbrough E, Chandler C. Patterns of molecular evolution in a parthenogenic terrestrial isopod ( Trichoniscus pusillus). PeerJ 2024; 12:e17780. [PMID: 39071119 PMCID: PMC11276757 DOI: 10.7717/peerj.17780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 06/30/2024] [Indexed: 07/30/2024] Open
Abstract
The "paradox of sex" refers to the question of why sexual reproduction is maintained in the wild, despite how costly it is compared to asexual reproduction. Because of these costs, one might expect nature to select for asexual reproduction, yet sex seems to be continually selected for. Multiple hypotheses have been proposed to explain this incongruence, including the niche differentiation hypothesis, the Red Queen hypothesis, and accumulation of harmful mutations in asexual species due to inefficient purifying selection. This study focuses on the accumulation of mutations in two terrestrial isopods, Trichoniscus pusillus, which has sexual diploid and parthenogenic triploid forms, and Hyloniscus riparius, an obligately sexual relative. We surveyed sex ratios of both species in an upstate New York population and obtained RNA-seq data from wild-caught individuals of both species to examine within- and between-species patterns of molecular evolution in protein-coding genes. The sex ratio and RNA-seq data together provide strong evidence that this T. pusillus population is entirely asexual and triploid, while the H. riparius population is sexual and diploid. Although all the wild T. pusillus individuals used for sequencing shared identical genotypes at nearly all SNPs, supporting a clonal origin, heterozygosity and SNP density were much higher in T. pusillus than in the sexually reproducing H. riparius. This observation suggests this parthenogenic lineage may have arisen via mating between two divergent diploid lineages. Between-species sequence comparisons showed no evidence of ineffective purifying selection in the asexual T. pusillus lineage, as measured by the ratio of nonsynonymous to synonymous substitutions (dN/dS ratios). Likewise, there was no difference between T. pusillus and H. riparius in the ratios of nonsynonymous to synonymous SNPs overall (pN/pS). However, pN/pS ratios in T. pusillus were significantly higher when considering only SNPs that may have arisen via recent mutation after the transition to parthenogenesis. Thus, these recent SNPs are consistent with the hypothesis that purifying selection is less effective against new mutations in asexual lineages, but only over long time scales. This system provides a useful model for future studies on the evolutionary tradeoffs between sexual and asexual reproduction in nature.
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Affiliation(s)
- Emily Yarbrough
- Department of Biological Sciences, State University of New York at Oswego, Oswego, NY, United States of America
- Department of Biological Sciences, State University of New York at Binghamton, Binghamton, NY, United States of America
| | - Christopher Chandler
- Department of Biological Sciences, State University of New York at Oswego, Oswego, NY, United States of America
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2
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Nowell RW, Rodriguez F, Hecox-Lea BJ, Mark Welch DB, Arkhipova IR, Barraclough TG, Wilson CG. Bdelloid rotifers deploy horizontally acquired biosynthetic genes against a fungal pathogen. Nat Commun 2024; 15:5787. [PMID: 39025839 PMCID: PMC11258130 DOI: 10.1038/s41467-024-49919-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/18/2024] [Indexed: 07/20/2024] Open
Abstract
Coevolutionary antagonism generates relentless selection that can favour genetic exchange, including transfer of antibiotic synthesis and resistance genes among bacteria, and sexual recombination of disease resistance alleles in eukaryotes. We report an unusual link between biological conflict and DNA transfer in bdelloid rotifers, microscopic animals whose genomes show elevated levels of horizontal gene transfer from non-metazoan taxa. When rotifers were challenged with a fungal pathogen, horizontally acquired genes were over twice as likely to be upregulated as other genes - a stronger enrichment than observed for abiotic stressors. Among hundreds of upregulated genes, the most markedly overrepresented were clusters resembling bacterial polyketide and nonribosomal peptide synthetases that produce antibiotics. Upregulation of these clusters in a pathogen-resistant rotifer species was nearly ten times stronger than in a susceptible species. By acquiring, domesticating, and expressing non-metazoan biosynthetic pathways, bdelloids may have evolved to resist natural enemies using antimicrobial mechanisms absent from other animals.
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Affiliation(s)
- Reuben W Nowell
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
- Department of Life Sciences, Imperial College London; Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK
- Institute of Ecology and Evolution, University of Edinburgh; Ashworth Laboratories, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK
- Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Fernando Rodriguez
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, USA
| | - Bette J Hecox-Lea
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, USA
| | - David B Mark Welch
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, USA
| | - Irina R Arkhipova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA, USA
| | - Timothy G Barraclough
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
- Department of Life Sciences, Imperial College London; Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK
| | - Christopher G Wilson
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK.
- Department of Life Sciences, Imperial College London; Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
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3
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Morozov-Leonov SY. Reproduction and the Evolutionary Potential of the Hybrid Form Pelophylax Esculentus-Bidibundus (Amphibia, Ranidae) within the Drainages of Pripyat, Dniester, and Southern Bug Rivers. CYTOL GENET+ 2023. [DOI: 10.3103/s0095452723010085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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Population Genomic Analyses Suggest a Hybrid Origin, Cryptic Sexuality, and Decay of Genes Regulating Seed Development for the Putatively Strictly Asexual Kingdonia uniflora (Circaeasteraceae, Ranunculales). Int J Mol Sci 2023; 24:ijms24021451. [PMID: 36674965 PMCID: PMC9866071 DOI: 10.3390/ijms24021451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/20/2022] [Accepted: 12/28/2022] [Indexed: 01/15/2023] Open
Abstract
Asexual lineages are perceived to be short-lived on evolutionary timescales. Hence, reports for exceptional cases of putative 'ancient asexuals' usually raise questions about the persistence of such species. So far, there have been few studies to solve the mystery in plants. The monotypic Kingdonia dating to the early Eocene, contains only K. uniflora that has no known definitive evidence for sexual reproduction nor records for having congeneric sexual species, raising the possibility that the species has persisted under strict asexuality for a long period of time. Here, we analyze whole genome polymorphism and divergence in K. uniflora. Our results show that K. uniflora is characterized by high allelic heterozygosity and elevated πN/πS ratio, in line with theoretical expectations under asexual evolution. Allele frequency spectrum analysis reveals the origin of asexuality in K. uniflora occurred prior to lineage differentiation of the species. Although divergence within K. uniflora individuals exceeds that between populations, the topologies of the two haplotype trees, however, fail to match each other, indicating long-term asexuality is unlikely to account for the high allele divergence and K. uniflora may have a recent hybrid origin. Phi-test shows a statistical probability of recombination for the conflicting phylogenetic signals revealed by the split network, suggesting K. uniflora engages in undetected sexual reproduction. Detection of elevated genetic differentiation and premature stop codons (in some populations) in genes regulating seed development indicates mutational degradation of sexuality-specific genes in K. uniflora. This study unfolds the origin and persistence mechanism of a plant lineage that has been known to reproduce asexually and presents the genomic consequences of lack of sexuality.
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5
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Sofi IA, Rashid I, Lone JY, Tyagi S, Reshi ZA, Mir RR. Genetic diversity may help evolutionary rescue in a clonal endemic plant species of Western Himalaya. Sci Rep 2021; 11:19595. [PMID: 34599214 PMCID: PMC8486807 DOI: 10.1038/s41598-021-98648-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 08/25/2021] [Indexed: 02/08/2023] Open
Abstract
Habitat loss due to climate change may cause the extinction of the clonal species with a limited distribution range. Thus, determining the genetic diversity required for adaptability by these species in sensitive ecosystems can help infer the chances of their survival and spread in changing climate. We studied the genetic diversity and population structure of Sambucus wightiana-a clonal endemic plant species of the Himalayan region for understanding its possible survival chances in anticipated climate change. Eight polymorphic microsatellite markers were used to study the allelic/genetic diversity and population structure. In addition, ITS1-ITS4 Sanger sequencing was used for phylogeny and SNP detection. A total number of 73 alleles were scored for 37 genotypes at 17 loci for 8 SSRs markers. The population structural analysis using the SSR marker data led to identifying two sub-populations in our collection of 37 S. wightiana genotypes, with 11 genotypes having mixed ancestry. The ITS sequence data show a specific allele in higher frequency in a particular sub-population, indicating variation in different S. wightiana accessions at the sequence level. The genotypic data of SSR markers and trait data of 11 traits of S. wightiana, when analyzed together, revealed five significant Marker-Trait Associations (MTAs) through Single Marker Analysis (SMA) or regression analysis. Most of the SSR markers were found to be associated with more than one trait, indicating the usefulness of these markers for working out marker-trait associations. Moderate to high genetic diversity observed in the present study may provide insurance against climate change to S. wightiana and help its further spread.
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Affiliation(s)
- Irshad Ahmad Sofi
- grid.412997.00000 0001 2294 5433Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir 190006 India
| | - Irfan Rashid
- grid.412997.00000 0001 2294 5433Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir 190006 India
| | - Javaid Yousuf Lone
- grid.412997.00000 0001 2294 5433Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir 190006 India
| | - Sandhya Tyagi
- grid.418196.30000 0001 2172 0814Department of Plant Physiology, Indian Agricultural Research Institute, New Delhi, Delhi 110012 India
| | - Zafar A. Reshi
- grid.412997.00000 0001 2294 5433Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir 190006 India
| | - Reyazul Rouf Mir
- grid.444725.40000 0004 0500 6225Division of Genetics and Plant Breeding, Faculty of Agriculture, SKUAST-Kashmir, Wadura Campus, Sopore, Jammu and Kashmir 193201 India
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6
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Jaron KS, Bast J, Nowell RW, Ranallo-Benavidez TR, Robinson-Rechavi M, Schwander T. Genomic Features of Parthenogenetic Animals. J Hered 2021; 112:19-33. [PMID: 32985658 PMCID: PMC7953838 DOI: 10.1093/jhered/esaa031] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 08/17/2020] [Indexed: 12/21/2022] Open
Abstract
Evolution without sex is predicted to impact genomes in numerous ways. Case studies of individual parthenogenetic animals have reported peculiar genomic features that were suggested to be caused by their mode of reproduction, including high heterozygosity, a high abundance of horizontally acquired genes, a low transposable element load, or the presence of palindromes. We systematically characterized these genomic features in published genomes of 26 parthenogenetic animals representing at least 18 independent transitions to asexuality. Surprisingly, not a single feature was systematically replicated across a majority of these transitions, suggesting that previously reported patterns were lineage-specific rather than illustrating the general consequences of parthenogenesis. We found that only parthenogens of hybrid origin were characterized by high heterozygosity levels. Parthenogens that were not of hybrid origin appeared to be largely homozygous, independent of the cellular mechanism underlying parthenogenesis. Overall, despite the importance of recombination rate variation for the evolution of sexual animal genomes, the genome-wide absence of recombination does not appear to have had the dramatic effects which are expected from classical theoretical models. The reasons for this are probably a combination of lineage-specific patterns, the impact of the origin of parthenogenesis, and a survivorship bias of parthenogenetic lineages.
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Affiliation(s)
- Kamil S Jaron
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Jens Bast
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Reuben W Nowell
- Department of Life Sciences, Imperial College London, Ascot, Berkshire, UK
- Reuben W. Nowell is now at the Department of Zoology, University of Oxford, Oxford, UK
| | | | - Marc Robinson-Rechavi
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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Wachi N, Gau JJ, Fujie S, Fukano K, Maeto K. Genomic population structure of sympatric sexual and asexual populations in a parasitic wasp, Meteorus pulchricornis (Hymenoptera: Braconidae), inferred from six hundred single-nucleotide polymorphism loci. Mol Ecol 2021; 30:1612-1623. [PMID: 33634920 DOI: 10.1111/mec.15834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 01/22/2021] [Accepted: 02/04/2021] [Indexed: 11/28/2022]
Abstract
In spite of the two-fold reproductive advantage, asexual reproduction is not common in nature, probably due to the associated genetic deterioration or reduced genetic variation. To understand how genetic diversity is maintained in existing asexual populations, we investigated the genetic diversity and population structure of sympatric sexual and asexual populations of a parasitic wasp, Meteorus pulchricornis, using 614 genome-wide single nucleotide polymorphisms. The genetic structures of the apomictic asexual populations were distinct, showing considerable genetic differentiation among them. Most of the asexual populations were highly differentiated from the sympatric sexual population; some asexual individuals could not be distinguished from members of the sexual population. Furthermore, significantly fewer multilocus genotypes were identified in the asexual populations (1-7) compared to the sexual population (42), which is consistent with their apomictic nature. The observed patterns of fixed heterozygous sites suggest that most asexual populations had the same evolutionary origin and have long since evolved individually; the detected gene flow between the sexual population and a few asexual population may indicate independent origins of asexuality. The potential role of occasional males in apomictic wasps is also discussed.
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Affiliation(s)
- Nakatada Wachi
- Center for Strategic Research Project, Organization for Research Promotion, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Jin-Je Gau
- Graduate School of Agricultural Science, Kobe University, Nada, Kobe, Japan
| | - Shunpei Fujie
- Graduate School of Agricultural Science, Kobe University, Nada, Kobe, Japan.,Osaka Museum of Natural History, Higashisumiyoshi, Osaka, Japan
| | - Kenya Fukano
- Graduate School of Agricultural Science, Kobe University, Nada, Kobe, Japan
| | - Kaoru Maeto
- Graduate School of Agricultural Science, Kobe University, Nada, Kobe, Japan
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8
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Boyer L, Jabbour-Zahab R, Mosna M, Haag CR, Lenormand T. Not so clonal asexuals: Unraveling the secret sex life of Artemia parthenogenetica. Evol Lett 2021; 5:164-174. [PMID: 33868712 PMCID: PMC8045904 DOI: 10.1002/evl3.216] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 01/08/2021] [Accepted: 01/15/2021] [Indexed: 12/11/2022] Open
Abstract
The maintenance of sex is paradoxical as sexual species pay the “twofold cost of males” and should thus quickly be replaced by asexual mutants reproducing clonally. However, asexuals may not be strictly clonal and engage in “cryptic sex,” challenging this simple scenario. We study the cryptic sex life of the brine shrimp Artemia parthenogenetica, which has once been termed an “ancient asexual” and where no genetic differences have ever been observed between parents and offspring. This asexual species rarely produces males, which can hybridize with sexual females of closely related species and transmit asexuality to their offspring. Using such hybrids, we show that recombination occurs in asexual lineages, causing loss‐of‐heterozygosity and parent‐offspring differences. These differences cannot generally be observed in field‐sampled asexuals because once heterozygosity is lost, subsequent recombination leaves no footprint. Furthermore, using extensive paternity tests, we show that hybrid females can reproduce both sexually and asexually, and transmit asexuality to both sexually and asexually produced offspring in a dominant fashion. Finally, we show that, contrary to previous reports, field‐sampled asexual females also rarely reproduce sexually (rate ∼2‰). Overall, most previously known facts about Artemia asexuality turned out to be erroneous. More generally, our findings suggest that the evidence for strictly clonal reproduction of asexual species needs to be reconsidered, and that rare sex and consequences of nonclonal asexuality, such as gene flow within asexuals, need to be more widely taken into account in more realistic models for the maintenance of sex and the persistence of asexual lineages.
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Affiliation(s)
- Loreleï Boyer
- CEFE Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD Montpellier France
| | - Roula Jabbour-Zahab
- CEFE Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD Montpellier France
| | - Marta Mosna
- CEFE Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD Montpellier France
| | - Christoph R Haag
- CEFE Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD Montpellier France
| | - Thomas Lenormand
- CEFE Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD Montpellier France
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9
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Nowell RW, Wilson CG, Almeida P, Schiffer PH, Fontaneto D, Becks L, Rodriguez F, Arkhipova IR, Barraclough TG. Evolutionary dynamics of transposable elements in bdelloid rotifers. eLife 2021; 10:e63194. [PMID: 33543711 PMCID: PMC7943196 DOI: 10.7554/elife.63194] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 02/04/2021] [Indexed: 12/17/2022] Open
Abstract
Transposable elements (TEs) are selfish genomic parasites whose ability to spread autonomously is facilitated by sexual reproduction in their hosts. If hosts become obligately asexual, TE frequencies and dynamics are predicted to change dramatically, but the long-term outcome is unclear. Here, we test current theory using whole-genome sequence data from eight species of bdelloid rotifers, a class of invertebrates in which males are thus far unknown. Contrary to expectations, we find a variety of active TEs in bdelloid genomes, at an overall frequency within the range seen in sexual species. We find no evidence that TEs are spread by cryptic recombination or restrained by unusual DNA repair mechanisms. Instead, we find that that TE content evolves relatively slowly in bdelloids and that gene families involved in RNAi-mediated TE suppression have undergone significant expansion, which might mitigate the deleterious effects of active TEs and compensate for the consequences of long-term asexuality.
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Affiliation(s)
- Reuben W Nowell
- Department of Zoology, University of OxfordOxfordUnited Kingdom
- Department of Life Sciences, Imperial College London, Silwood Park CampusAscot, BerkshireUnited Kingdom
| | - Christopher G Wilson
- Department of Zoology, University of OxfordOxfordUnited Kingdom
- Department of Life Sciences, Imperial College London, Silwood Park CampusAscot, BerkshireUnited Kingdom
| | - Pedro Almeida
- Department of Life Sciences, Imperial College London, Silwood Park CampusAscot, BerkshireUnited Kingdom
- Division of Biosciences, University College LondonLondonUnited Kingdom
| | - Philipp H Schiffer
- Institute of Zoology, Section Developmental Biology, University of Cologne, KölnWormlabGermany
| | - Diego Fontaneto
- National Research Council of Italy, Water Research InstituteVerbania PallanzaItaly
| | - Lutz Becks
- Community Dynamics Group, Department of Evolutionary Ecology, Max Planck Institute for Evolutionary BiologyPlönGermany
- Aquatic Ecology and Evolution, University of KonstanzKonstanzGermany
| | - Fernando Rodriguez
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological LaboratoryWoods Hole, MAUnited States
| | - Irina R Arkhipova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological LaboratoryWoods Hole, MAUnited States
| | - Timothy G Barraclough
- Department of Zoology, University of OxfordOxfordUnited Kingdom
- Department of Life Sciences, Imperial College London, Silwood Park CampusAscot, BerkshireUnited Kingdom
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10
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Pachl P, Uusitalo M, Scheu S, Schaefer I, Maraun M. Repeated convergent evolution of parthenogenesis in Acariformes (Acari). Ecol Evol 2021; 11:321-337. [PMID: 33437432 PMCID: PMC7790623 DOI: 10.1002/ece3.7047] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 10/19/2020] [Accepted: 10/30/2020] [Indexed: 11/30/2022] Open
Abstract
The existence of old species-rich parthenogenetic taxa is a conundrum in evolutionary biology. Such taxa point to ancient parthenogenetic radiations resulting in morphologically distinct species. Ancient parthenogenetic taxa have been proposed to exist in bdelloid rotifers, darwinulid ostracods, and in several taxa of acariform mites (Acariformes, Acari), especially in oribatid mites (Oribatida, Acari). Here, we investigate the diversification of Acariformes and their ancestral mode of reproduction using 18S rRNA. Because parthenogenetic taxa tend to be more frequent in phylogenetically old taxa of Acariformes, we sequenced a wide range of members of this taxon, including early-derivative taxa of Prostigmata, Astigmata, Endeostigmata, and Oribatida. Ancestral character state reconstruction indicated that (a) Acariformes as well as Oribatida evolved from a sexual ancestor, (b) the primary mode of reproduction during evolution of Acariformes was sexual; however, species-rich parthenogenetic taxa radiated independently at least four times (in Brachychthonioidea (Oribatida), Enarthronota (Oribatida), and twice in Nothrina (Oribatida), (c) parthenogenesis additionally evolved frequently in species-poor taxa, for example, Tectocepheus, Oppiella, Rostrozetes, Limnozetes, and Atropacarus, and (d) sexual reproduction likely re-evolved at least three times from species-rich parthenogenetic clusters, in Crotonia (Nothrina), in Mesoplophora/Apoplophora (Mesoplophoridae, Enarthronota), and in Sphaerochthonius/Prototritia (Protoplophoridae, Enarthronota). We discuss possible reasons that favored the frequent diversification of parthenogenetic taxa including the continuous long-term availability of dead organic matter resources as well as generalist feeding of species as indicated by natural variations in stable isotope ratios.
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Affiliation(s)
- Patrick Pachl
- JFB Institute of Zoology and AnthropologyUniversity of GöttingenGöttingenGermany
| | - Matti Uusitalo
- Zoological MuseumCentre for Biodiversity of TurkuTurkuFinland
| | - Stefan Scheu
- JFB Institute of Zoology and AnthropologyUniversity of GöttingenGöttingenGermany
- Centre of Biodiversity and Sustainable Land UseUniversity of GöttingenGöttingenGermany
| | - Ina Schaefer
- JFB Institute of Zoology and AnthropologyUniversity of GöttingenGöttingenGermany
| | - Mark Maraun
- JFB Institute of Zoology and AnthropologyUniversity of GöttingenGöttingenGermany
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11
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Hojsgaard D, Schartl M. Skipping sex: A nonrecombinant genomic assemblage of complementary reproductive modules. Bioessays 2020; 43:e2000111. [PMID: 33169369 DOI: 10.1002/bies.202000111] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 09/26/2020] [Accepted: 09/29/2020] [Indexed: 02/03/2023]
Abstract
The unusual occurrence and developmental diversity of asexual eukaryotes remain a puzzle. De novo formation of a functioning asexual genome requires a unique assembly of sets of genes or gene states to disrupt cellular mechanisms of meiosis and gametogenesis, and to affect discrete components of sexuality and produce clonal or hemiclonal offspring. We highlight two usually overlooked but essential conditions to understand the molecular nature of clonal organisms, that is, a nonrecombinant genomic assemblage retaining modifiers of the sexual program, and a complementation between altered reproductive components. These subtle conditions are the basis for physiologically viable and genetically balanced transitions between generations. Genomic and developmental evidence from asexual animals and plants indicates the lack of complementation of molecular changes in the sexual reproductive program is likely the main cause of asexuals' rarity, and can provide an explanatory frame for the developmental diversity and lability of developmental patterns in some asexuals as well as for the discordant time to extinction estimations.
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Affiliation(s)
- Diego Hojsgaard
- Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), Albrecht-von-Haller Institute for Plant Sciences, University of Goettingen, Goettingen, Germany
| | - Manfred Schartl
- Department of Developmental Biochemistry, Biocenter, University of Wuerzburg, Wuerzburg, Germany.,The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
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12
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Spoelhof JP, Keeffe R, McDaniel SF. Does reproductive assurance explain the incidence of polyploidy in plants and animals? THE NEW PHYTOLOGIST 2020; 227:14-21. [PMID: 31883115 DOI: 10.1111/nph.16396] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Accepted: 12/17/2019] [Indexed: 06/10/2023]
Affiliation(s)
- Jonathan P Spoelhof
- Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611, USA
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Rachel Keeffe
- Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611, USA
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Stuart F McDaniel
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
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13
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Schiffer PH, Danchin EGJ, Burnell AM, Creevey CJ, Wong S, Dix I, O'Mahony G, Culleton BA, Rancurel C, Stier G, Martínez-Salazar EA, Marconi A, Trivedi U, Kroiher M, Thorne MAS, Schierenberg E, Wiehe T, Blaxter M. Signatures of the Evolution of Parthenogenesis and Cryptobiosis in the Genomes of Panagrolaimid Nematodes. iScience 2019; 21:587-602. [PMID: 31759330 PMCID: PMC6889759 DOI: 10.1016/j.isci.2019.10.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 07/17/2019] [Accepted: 10/21/2019] [Indexed: 12/12/2022] Open
Abstract
Most animal species reproduce sexually and fully parthenogenetic lineages are usually short lived in evolution. Still, parthenogenesis may be advantageous as it avoids the cost of sex and permits colonization by single individuals. Panagrolaimid nematodes have colonized environments ranging from arid deserts to Arctic and Antarctic biomes. Many are obligatory meiotic parthenogens, and most have cryptobiotic abilities, being able to survive repeated cycles of complete desiccation and freezing. To identify systems that may contribute to these striking abilities, we sequenced and compared the genomes and transcriptomes of parthenogenetic and outcrossing panagrolaimid species, including cryptobionts and non-cryptobionts. The parthenogens are triploids, most likely originating through hybridization. Adaptation to cryptobiosis shaped the genomes of panagrolaimid nematodes and is associated with the expansion of gene families and signatures of selection on genes involved in cryptobiosis. All panagrolaimids have acquired genes through horizontal gene transfer, some of which are likely to contribute to cryptobiosis.
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Affiliation(s)
- Philipp H Schiffer
- CLOE, Department for Biosciences, University College London, London, UK; Zoologisches Institut, Universität zu Köln, 50674 Köln, Germany; Institut für Genetik, Universität zu Köln, 50674 Köln, Germany.
| | | | - Ann M Burnell
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | | | - Simon Wong
- Irish Centre for High-End Computing, Tower Building, Trinity Technology & Enterprise Campus, Grand Canal Quay, Dublin D02 HP83, Ireland
| | - Ilona Dix
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Georgina O'Mahony
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Bridget A Culleton
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland; Megazyme, Bray Business Park, Bray, Co. Wicklow A98 YV29, Ireland
| | | | - Gary Stier
- Zoologisches Institut, Universität zu Köln, 50674 Köln, Germany
| | - Elizabeth A Martínez-Salazar
- Unidad Académica de Ciencias Biológicas, Laboratorio de Colecciones Biológicas y Sistemática Molecular, Universidad Autónoma de Zacatecas, Zacatecas, México
| | - Aleksandra Marconi
- Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Urmi Trivedi
- Edinburgh Genomics, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Michael Kroiher
- Zoologisches Institut, Universität zu Köln, 50674 Köln, Germany
| | - Michael A S Thorne
- British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
| | | | - Thomas Wiehe
- Institut für Genetik, Universität zu Köln, 50674 Köln, Germany
| | - Mark Blaxter
- Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh EH9 3FL, UK; Edinburgh Genomics, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
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Abstract
The origin and subsequent maintenance of sex and recombination are among the most elusive and controversial problems in evolutionary biology. Here, we propose a novel hypothesis, suggesting that sexual reproduction not only evolved to reduce the negative effects of the accumulation of deleterious mutations and processes associated with pathogen and/or parasite resistance but also to prevent invasion by transmissible selfish neoplastic cheater cells, henceforth referred to as transmissible cancer cells. Sexual reproduction permits systematic change of the multicellular organism's genotype and hence an enhanced detection of transmissible cancer cells by immune system. Given the omnipresence of oncogenic processes in multicellular organisms, together with the fact that transmissible cancer cells can have dramatic effects on their host fitness, our scenario suggests that the benefits of sex and concomitant recombination will be large and permanent, explaining why sexual reproduction is, despite its costs, the dominant mode of reproduction among eukaryotes.
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Leung C, Breton S, Angers B. A trait-based ecology to assess the acclimation of a sperm-dependent clonal fish compared to its sexual host. PeerJ 2018; 6:e5896. [PMID: 30405974 PMCID: PMC6216994 DOI: 10.7717/peerj.5896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 10/09/2018] [Indexed: 11/20/2022] Open
Abstract
Background Survival in temporally or spatially changing environments is a prerequisite for the perpetuation of a given species. In addition to genetic variation, the role of epigenetic processes is crucial in the persistence of organisms. For instance, mechanisms such as developmental flexibility enable the adjustment of the phenotype of a given individual to changing conditions throughout its development. However, the extent of factors other than genetic variability, like epigenetic processes, in the production of alternative phenotype and the consequences in realized ecological niches is still unclear. Methods In this study, we compared the extent of realized niches between asexual and sexual individuals from different environments. We used a trait-based ecology approach exploiting trophic and locomotive structures to infer the environment that each biotype actually used. More specifically, we compared the morphology of the all-female clonal and sperm-dependent fish Chrosomus eos-neogaeus to that of their sexual host species C. eos in common garden and natural conditions. Results Transfer from natural to controlled conditions resulted in a similar shift in measured morphology for clonal and sexual individuals suggesting comparable level of flexibility in both kinds of organisms. However, clonal, but not sexual, individuals displayed a consistent phenotype when reared in uniform conditions indicating that in absence of genetic variation, one phenotype corresponds to one niche. This contrasted with results from natural conditions where clones were morphologically as variable as sexual individuals within a sampled site. In addition, similar phenotypic changes for both clonal and sexual individuals were observed among the majority of sampled sites, indicating that they responded similarly to the same environments. Discussion Our results indicated that clones can efficiently use different niches and may evolve in a range of environmental conditions comparable to that of a sexual species, thus underlying the importance of factors other than genetic variability, like epigenetic processes, for coping with environmental heterogeneity.
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Affiliation(s)
- Christelle Leung
- Department of Biological Sciences, Université de Montréal, Montréal, QC, Canada
| | - Sophie Breton
- Department of Biological Sciences, Université de Montréal, Montréal, QC, Canada
| | - Bernard Angers
- Department of Biological Sciences, Université de Montréal, Montréal, QC, Canada
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16
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Denton RD, Morales AE, Gibbs HL. Genome-specific histories of divergence and introgression between an allopolyploid unisexual salamander lineage and two ancestral sexual species. Evolution 2018; 72:1689-1700. [PMID: 29926914 DOI: 10.1111/evo.13528] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 06/07/2018] [Accepted: 06/14/2018] [Indexed: 02/06/2023]
Abstract
Quantifying introgression between sexual species and polyploid lineages traditionally thought to be asexual is an important step in understanding what drives the longevity of putatively asexual groups. Here, we capitalize on three recent innovations-ultraconserved element (UCE) sequencing, bioinformatic techniques for identifying genome-specific variation in polyploids, and model-based methods for evaluating historical gene flow-to measure the extent and tempo of introgression over the evolutionary history of an allopolyploid lineage of all-female salamanders and two ancestral sexual species. Our analyses support a scenario in which the genomes sampled in unisexual salamanders last shared a common ancestor with genomes in their parental species ∼3.4 million years ago, followed by a period of divergence between homologous genomes. Recently, secondary introgression has occurred at different times with each sexual species during the last 500,000 years. Sustained introgression of sexual genomes into the unisexual lineage is the defining characteristic of their reproductive mode, but this study provides the first evidence that unisexual genomes have undergone long periods of divergence without introgression. Unlike other sperm-dependent taxa in which introgression is rare, the alternating periods of divergence and introgression between unisexual salamanders and their sexual relatives could explain why these salamanders are among the oldest described unisexual animals.
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Affiliation(s)
- Robert D Denton
- Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, Ohio 43210
- Ohio Biodiversity Conservation Partnership, Columbus, Ohio 43210
- Current Address: Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269
| | - Ariadna E Morales
- Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, Ohio 43210
| | - H Lisle Gibbs
- Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, Ohio 43210
- Ohio Biodiversity Conservation Partnership, Columbus, Ohio 43210
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17
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Lherminier P. [Informative predation: Towards a new species concept]. C R Biol 2018; 341:209-218. [PMID: 29606595 DOI: 10.1016/j.crvi.2018.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Revised: 02/27/2018] [Accepted: 02/27/2018] [Indexed: 10/17/2022]
Abstract
We distinguish two types of predations: the predation of matter-energy equals the food chain, and the informative predation is the capture of the information brought by the sexual partners. The cell or parent consumes energy and matter to grow, multiply and produce offspring. A fixed amount of resources is divided by the number of organisms, so individual growth and numerical multiplication are limited by depletion resources of the environment. Inversely, fertilization does not destroy information, but instead produces news. The information is multiplied by the number of partners and children, since each fertilization gives rise to a new genome following a combinatorial process that continues without exhaustion. The egg does not swallow the sperm to feed, but exchange good food for quality information. With the discovery of sex, that is, 1.5 Ga ago, life added soft predation to hard predation, i.e. information production within each species to matter-energy flow between species. Replicative and informative structures are subject to two competing biological constraints: replicative fidelity promotes proliferation, but limits adaptive evolution. On the contrary, the offspring of a couple obviously cannot be a copy of both partners, they are a new production, a re-production. Sexual recombination allows the exponential enrichment of the genetic diversity, thus promoting indefinite adaptive and evolutionary capacities. Evolutionary history illustrates this: the bacteria proliferate but have remained at the first purely nutritive stage in which most of the sensory functions, mobility, defense, and feeding have experienced almost no significant novelty in three billion years. Another world appeared with the sexual management of information. Sexual reproduction actually combines two functions: multiplicative by "vertical transfer" and informative by "horizontal transfer". This distinction is very common: polypus - medusa alternations, parasite multiplication cycles, the lytochal and deuterotochal parthenogenesis of aphids, and the innumerable para- and pseudo-sexual strategies of plants opportunistically combine the two modes of asexual replication and sexual combination. However, for the majority of animals and multicellular plants that produce many gametes, numerical proliferation by descendants and informative diversity by sexuality are mutually implicated, for example in the seed. The true discovery of eukaryotes may not be the "true nucleus", as their name implies, but an orderly informative function. The field of recombinations circumscribes a class of partners genetically compatible with each other, each simultaneously prey and predator of the DNA of the other. The mythical Maxwell demon capable of tracing entropy by sorting molecules according to their state does exist: each mate is the other's Maxwell's demon. While a sexless bacterium is simply divided into two cells, two sexual parents work together to produce a single offspring a time. Added to this are the burdens involved in meiosis and crossing-over, cellular diploidy, and mating. Sex produces an information gain that is paid for by a cost of energy-material, and this barter must be fair to survive. The domains of sexual intercourse are very diverse: uniparental reproduction, alternation of asexual proliferation and sexual information, self-fertilization, endogamy, exogamy, panmixis, diffuse or structured polymorphism, fertile or sterile hybridization, horizontal transfers. Each species is a recombination field between two domains, cloning and hybridization. Multiplicative descent and informative fertilization are organically distinct, but selectively associated: the information produced by the parents' sexuality favors the predation of matter-energy and therefore the proliferation of offspring, and this proliferation in turn favors the sexed producers of information. The equation specific to each species is: enough energy to proliferate, enough information to diversify. Alternatively, two other reproductive modes obtain or transmit less information at lower cost: not enough recombinations=repetitive clonal proliferation, and too many recombinations=disordered hybridization. But these marginal modes have poor prospects, as the model of the species is successfully attractive. Better discriminate to better inform. In bacteria, the exchanged and incorporated DNA segments are directly identified by the parity of the complementary strands, which determines simultaneously the similarity, the offspring, and the pairing. In eukaryotes, on the contrary, somatic growth and germinal information are segregated. During speciation, adaptive information is compacted, delocalized, codified and published to inform the species about its own state: the prezygotic relationship governs viable mating. Under the effect of sexual selection, the runaway and the reinforcement of the characters related to courtship testifies to their identifying function, which explains the paradox of the singularity and luxuriance of the sexual hypertrophies. The speciation discretizes a balanced recombination field and validates the informative relations. The species is without degree. Mates of a species recognize each other quickly and well because the logic of coding disengages from the ecological game of adaptations. The system of mate recognition has a function of cohesion and its regularity allows the adaptations of the less regular being, it is neither elitist nor normative, it is subjected neither to a level of aptitudes, nor to sexual performances, but permissive; it protects the variability and polymorphism. Two mutually irreducible relationships triggered the debate between the taxonomists who support the phyletic definition of the species by the descendance, and the proponents of the definition by interfertility. Such a taxonomic disagreement is not insurmountable, but the issue is deeper than taxonomic concepts, because these concepts relate to two different modes of evolution. According to the phyletic model, each species is a lineage passively isolated by external circumstances; on the contrary, in the sexual model each species is actively produced by an internal process of adjustment between replicative costs and informative gains. Each species develops a solution of the equation that matches material-energy expenditures with informative gains. A species concept based on a lasting relationship between these two quantities or on the limits of certain values or their equilibrium is therefore legitimate. It is this equilibrium that all couples resolve, without our formulation being as clearly as biology desires and as physics demands. Energy expenditures and informative gains in sexuality are almost impossible to measure, yet observation and experience allow an approximate ranking of the energy/information ratio. For example, endogamy is more economical, but less diversifying than exogamy, polymorphism increases information, the reinforcement of sexual isolation limits the rate of unproductive fertilization, between neighboring species hybridization allows certain genetic contributions, etc. A closed species evolves naturally towards another just as closed. On the contrary, the artificial transfer of DNA opens the species. The natural boundaries that isolate the species are easily trespassed as energy costs and constraints of sexual recognition are easily controlled; and the perspectives of manipulations are visible, whereas natural selection never anticipates and thus works blindly. Informative, artificially directed predation stimulates the evolution of species.
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18
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Toman J, Flegr J. General environmental heterogeneity as the explanation of sexuality? Comparative study shows that ancient asexual taxa are associated with both biotically and abiotically homogeneous environments. Ecol Evol 2018; 8:973-991. [PMID: 29375771 PMCID: PMC5773305 DOI: 10.1002/ece3.3716] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 11/13/2017] [Accepted: 11/20/2017] [Indexed: 11/22/2022] Open
Abstract
Ecological theories of sexual reproduction assume that sexuality is advantageous in certain conditions, for example, in biotically or abiotically more heterogeneous environments. Such theories thus could be tested by comparative studies. However, the published results of these studies are rather unconvincing. Here, we present the results of a new comparative study based exclusively on the ancient asexual clades. The association with biotically or abiotically homogeneous environments in these asexual clades was compared with the same association in their sister, or closely related, sexual clades. Using the conservative definition of ancient asexuals (i.e., age >1 million years), we found eight pairs of taxa of sexual and asexual species, six differing in the heterogeneity of their inhabited environment on the basis of available data. The difference between the environmental type associated with the sexual and asexual species was then compared in an exact binomial test. The results showed that the majority of ancient asexual clades tend to be associated with biotically, abiotically, or both biotically and abiotically more homogeneous environments than their sexual controls. In the exploratory part of the study, we found that the ancient asexuals often have durable resting stages, enabling life in subjectively homogeneous environments, live in the absence of intense biotic interactions, and are very often sedentary, inhabiting benthos, and soil. The consequences of these findings for the ecological theories of sexual reproduction are discussed.
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Affiliation(s)
- Jan Toman
- Faculty of ScienceLaboratory of Evolutionary BiologyDepartment of Philosophy and History of SciencesCharles UniversityPragueCzech Republic
| | - Jaroslav Flegr
- Faculty of ScienceLaboratory of Evolutionary BiologyDepartment of Philosophy and History of SciencesCharles UniversityPragueCzech Republic
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19
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Fradin H, Kiontke K, Zegar C, Gutwein M, Lucas J, Kovtun M, Corcoran DL, Baugh LR, Fitch DHA, Piano F, Gunsalus KC. Genome Architecture and Evolution of a Unichromosomal Asexual Nematode. Curr Biol 2017; 27:2928-2939.e6. [PMID: 28943090 PMCID: PMC5659720 DOI: 10.1016/j.cub.2017.08.038] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 10/24/2022]
Abstract
Asexual reproduction in animals, though rare, is the main or exclusive mode of reproduction in some long-lived lineages. The longevity of asexual clades may be correlated with the maintenance of heterozygosity by mechanisms that rearrange genomes and reduce recombination. Asexual species thus provide an opportunity to gain insight into the relationship between molecular changes, genome architecture, and cellular processes. Here we report the genome sequence of the parthenogenetic nematode Diploscapter pachys with only one chromosome pair. We show that this unichromosomal architecture is shared by a long-lived clade of asexual nematodes closely related to the genetic model organism Caenorhabditis elegans. Analysis of the genome assembly reveals that the unitary chromosome arose through fusion of six ancestral chromosomes, with extensive rearrangement among neighboring regions. Typical nematode telomeres and telomeric protection-encoding genes are lacking. Most regions show significant heterozygosity; homozygosity is largely concentrated to one region and attributed to gene conversion. Cell-biological and molecular evidence is consistent with the absence of key features of meiosis I, including synapsis and recombination. We propose that D. pachys preserves heterozygosity and produces diploid embryos without fertilization through a truncated meiosis. As a prelude to functional studies, we demonstrate that D. pachys is amenable to experimental manipulation by RNA interference.
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Affiliation(s)
- Hélène Fradin
- Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Karin Kiontke
- Department of Biology, New York University, New York, NY 10003, USA
| | - Charles Zegar
- Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Michelle Gutwein
- Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Jessica Lucas
- Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Mikhail Kovtun
- Duke Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - David L Corcoran
- Duke Center for Genomic and Computational Biology, Duke University, Durham, NC 27708, USA
| | - L Ryan Baugh
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - David H A Fitch
- Department of Biology, New York University, New York, NY 10003, USA.
| | - Fabio Piano
- Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Kristin C Gunsalus
- Department of Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA; Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
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20
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Abstract
Most animals have male and female sexes, implying that sex is ancient and beneficial; yet some have survived for millions of years without sex. The genome of the parthenogenetic nematode Diploscapter pachys gives clues as to how 'ancient asexual' animals can exist.
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Affiliation(s)
- Erich M Schwarz
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
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21
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Wickell DA, Windham MD, Wang X, Macdonald SJ, Beck JB. Can asexuality confer a short-term advantage? Investigating apparent biogeographic success in the apomictic triploid fern Myriopteris gracilis. AMERICAN JOURNAL OF BOTANY 2017; 104:1254-1265. [PMID: 28814405 PMCID: PMC6013364 DOI: 10.3732/ajb.1700126] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Accepted: 07/03/2017] [Indexed: 05/16/2023]
Abstract
PREMISE OF THE STUDY Although asexual taxa are generally seen as evolutionary dead ends, asexuality appears to provide a short-term benefit in some taxa, including a wider geographic distribution compared to sexual relatives. However, this may be an illusion created by multiple, morphologically cryptic, asexual lineages, each occupying a relatively small area. In this study we investigate the role of multiple lineages in the biogeography of Myriopteris gracilis Fée (Pteridaceae), a North American apomictic triploid fern species with a particularly large range. METHODS Range-wide asexuality was assessed by counting spores/sporangium in 606 Myriopteris gracilis specimens from across the species range, and lineage structure was assessed with both plastid DNA sequence and Genotyping By Sequencing (GBS) SNP datasets. KEY RESULTS Spore counting of >600 specimens identified no sexual populations, establishing that Myriopteris gracilis is exclusively asexual. The plastid data estimated the crown age of M. gracilis at ca. 2.5 mya and identified two lineages, each largely confined to the eastern or western portions of the range. These groups were further subdivided by the GBS data, revealing at least seven asexual lineages of varying geographic distributions, each occupying a relatively small portion of the total range of M. gracilis. CONCLUSIONS Although maintained exclusively through asexual reproduction, the broad distribution of Myriopteris gracilis is a compilation of numerous, independently formed asexual lineages. Since no single asexual lineage occupies the full extent of the species distribution, recurrent lineage formation should be considered when evaluating the short-term benefit of asexuality in this taxon and others.
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Affiliation(s)
- David A. Wickell
- Department of Biological Science, Wichita State University, Wichita, Kansas 67260 USA
| | - Michael D. Windham
- Department of Biological Science, Duke University, Durham, North Carolina 27708 USA
| | - Xiaofei Wang
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045 USA
| | - Stuart J. Macdonald
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045 USA
| | - James B. Beck
- Department of Biological Science, Wichita State University, Wichita, Kansas 67260 USA
- Botanical Research Institute of Texas, Fort Worth, Texas 76107 USA
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22
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Burke NW, Bonduriansky R. Sexual Conflict, Facultative Asexuality, and the True Paradox of Sex. Trends Ecol Evol 2017; 32:646-652. [PMID: 28651895 DOI: 10.1016/j.tree.2017.06.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 05/31/2017] [Accepted: 06/04/2017] [Indexed: 11/19/2022]
Abstract
Theory suggests that occasional or conditional sex involving facultative switching between sexual and asexual reproduction is the optimal reproductive strategy. Therefore, the true 'paradox of sex' is the prevalence of obligate sex. This points to the existence of powerful, general impediments to the invasion of obligately sexual populations by facultative mutants, and recent studies raise the intriguing possibility that a key impediment could be sexual conflict. Using Bateman gradients we show that facultative asexuality can amplify sexual conflict over mating, generating strong selection for both female resistance and male coercion. We hypothesize that invasions are most likely to succeed when mutants have negative Bateman gradients, can avoid mating, and achieve high fecundity through asexual reproduction - a combination unlikely to occur in natural populations.
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Affiliation(s)
- Nathan W Burke
- Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales Sydney, Sydney, Australia.
| | - Russell Bonduriansky
- Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales Sydney, Sydney, Australia
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23
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Hybridization and polyploidy enable genomic plasticity without sex in the most devastating plant-parasitic nematodes. PLoS Genet 2017; 13:e1006777. [PMID: 28594822 PMCID: PMC5465968 DOI: 10.1371/journal.pgen.1006777] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 04/24/2017] [Indexed: 11/19/2022] Open
Abstract
Root-knot nematodes (genus Meloidogyne) exhibit a diversity of reproductive modes ranging from obligatory sexual to fully asexual reproduction. Intriguingly, the most widespread and devastating species to global agriculture are those that reproduce asexually, without meiosis. To disentangle this surprising parasitic success despite the absence of sex and genetic exchanges, we have sequenced and assembled the genomes of three obligatory ameiotic and asexual Meloidogyne. We have compared them to those of relatives able to perform meiosis and sexual reproduction. We show that the genomes of ameiotic asexual Meloidogyne are large, polyploid and made of duplicated regions with a high within-species average nucleotide divergence of ~8%. Phylogenomic analysis of the genes present in these duplicated regions suggests that they originated from multiple hybridization events and are thus homoeologs. We found that up to 22% of homoeologous gene pairs were under positive selection and these genes covered a wide spectrum of predicted functional categories. To biologically assess functional divergence, we compared expression patterns of homoeologous gene pairs across developmental life stages using an RNAseq approach in the most economically important asexually-reproducing nematode. We showed that >60% of homoeologous gene pairs display diverged expression patterns. These results suggest a substantial functional impact of the genome structure. Contrasting with high within-species nuclear genome divergence, mitochondrial genome divergence between the three ameiotic asexuals was very low, signifying that these putative hybrids share a recent common maternal ancestor. Transposable elements (TE) cover a ~1.7 times higher proportion of the genomes of the ameiotic asexual Meloidogyne compared to the sexual relative and might also participate in their plasticity. The intriguing parasitic success of asexually-reproducing Meloidogyne species could be partly explained by their TE-rich composite genomes, resulting from allopolyploidization events, and promoting plasticity and functional divergence between gene copies in the absence of sex and meiosis.
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Ho EKH, Agrawal AF. Aging asexual lineages and the evolutionary maintenance of sex. Evolution 2017; 71:1865-1875. [PMID: 28444897 DOI: 10.1111/evo.13260] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/13/2017] [Accepted: 04/17/2017] [Indexed: 12/24/2022]
Abstract
Finite populations of asexual and highly selfing species suffer from a reduced efficacy of selection. Such populations are thought to decline in fitness over time due to accumulating slightly deleterious mutations or failing to adapt to changing conditions. These within-population processes that lead nonrecombining species to extinction may help maintain sex and outcrossing through species level selection. Although inefficient selection is proposed to elevate extinction rates over time, previous models of species selection for sex assumed constant diversification rates. For sex to persist, classic models require that asexual species diversify at rates lower than sexual species; the validity of this requirement is questionable, both conceptually and empirically. We extend past models by allowing asexual lineages to decline in diversification rates as they age, that is nonrecombining lineages "senesce" in diversification rates. At equilibrium, senescing diversification rates maintain sex even when asexual lineages, at young ages, diversify faster than their sexual progenitors. In such cases, the age distribution of asexual lineages contains a peak at intermediate values rather than showing the exponential decline predicted by the classic model. Coexistence requires only that the average rate of diversification in asexuals be lower than that of sexuals.
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Affiliation(s)
- Eddie K H Ho
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
| | - Aneil F Agrawal
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
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Dodd RS, Douhovnikoff V. Adjusting to Global Change through Clonal Growth and Epigenetic Variation. Front Ecol Evol 2016. [DOI: 10.3389/fevo.2016.00086] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Ali S, Soubeyrand S, Gladieux P, Giraud T, Leconte M, Gautier A, Mboup M, Chen W, de Vallavieille-Pope C, Enjalbert J. cloncase: Estimation of sex frequency and effective population size by clonemate resampling in partially clonal organisms. Mol Ecol Resour 2016; 16:845-61. [DOI: 10.1111/1755-0998.12511] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 01/29/2016] [Accepted: 02/02/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Sajid Ali
- UMR1290, BIOGER; INRA-AgroParisTech; BP01 78850 Thiverval-Grignon France
- Institute of Biotechnology and Genetic Engineering; the University of Agriculture, Peshawar; 25000 Peshawar Pakistan
| | - Samuel Soubeyrand
- UR546 Biostatistics and Spatial Processes; INRA; 84914 Avignon France
| | - Pierre Gladieux
- Ecologie Systématique Evolution; CNRS; Univ. Paris-Sud; AgroParisTech; Université Paris-Saclay; 91400 Orsay France
- UMR385 Biologie et Génétique des Interactions Plante-Parasite; CIRAD; INRA; F-34398 Montpellier France
| | - Tatiana Giraud
- Ecologie Systématique Evolution; CNRS; Univ. Paris-Sud; AgroParisTech; Université Paris-Saclay; 91400 Orsay France
| | - Marc Leconte
- UMR1290, BIOGER; INRA-AgroParisTech; BP01 78850 Thiverval-Grignon France
| | - Angélique Gautier
- UMR1290, BIOGER; INRA-AgroParisTech; BP01 78850 Thiverval-Grignon France
| | - Mamadou Mboup
- DuPont de Nemours (France) SAS Crop Protection - European Research & Development Center; 24, rue du Moulin 68740 Nambsheim France
| | - Wanquan Chen
- State Key Laboratory for Biology of Plant Diseases and Insect Pests; Institute of Plant Protection; Chinese Academy of Agricultural Sciences; No. 2 Yuanmingyuan West Road Beijing 100193 China
| | | | - Jérôme Enjalbert
- Ecologie Systématique Evolution; CNRS; Univ. Paris-Sud; AgroParisTech; Université Paris-Saclay; 91400 Orsay France
- GQE - Le Moulon; INRA; Univ. Paris-Sud; CNRS; AgroParisTech; Université Paris-Saclay; F-91190 Gif-sur-Yvette France
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Bromham L, Hua X, Cardillo M. Detecting Macroevolutionary Self-Destruction from Phylogenies. Syst Biol 2015; 65:109-27. [PMID: 26454872 DOI: 10.1093/sysbio/syv062] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 08/18/2015] [Indexed: 12/14/2022] Open
Abstract
Phylogenetic analyses have lent support to the concept of lineage selection: that biological lineages can have heritable traits that influence their capacity to persist and diversify, and thereby affect their representation in biodiversity. While many discussions have focused on "positive" lineage selection, where stably heritable properties of lineages enhance their diversification rate, there are also intriguing examples that seem to represent "negative" lineage selection, where traits reduce the likelihood that a lineage will persist or speciate. In this article, we test whether a particular pattern of negative lineage selection is detectable from the distributions of the trait on a phylogeny. "Self-destructive" traits are those that arise often but then disappear again because they confer either a raised extinction rate or they are prone to a high rate of trait loss. For such a trait, the reconstructed origins will tend to be dispersed across the tips of the phylogeny, rather than defining large clades of related lineages that all share the trait. We examine the utility of four possible measures of "tippiness" as potential indicators of macroevolutionary self-destruction, applying them to phylogenies on which trait evolution has been simulated under different combinations of parameters for speciation, extinction, trait gain, and trait loss. We use an efficient simulation approach that starts with the required number of tips with and without the trait and uses a model to work "backwards" to construct different possible trees that result in that set of tips. We then apply these methods to a number of case studies: salt tolerance in grasses, color polymorphism in birds of prey, and selfing in nightshades. We find that the relative age of species, measured from tip length, can indicate a reduced speciation rate but does not identify traits that increase the extinction rate or the trait loss rate. We show that it is possible to detect cases of macroevolutionary self-destruction by considering the number of tips with the trait that arise from each inferred origin, and the degree to which the trait is scattered across the phylogeny. These metrics, and the methods we present, may be useful for testing macroevolutionary hypotheses from phylogenetic patterns.
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Affiliation(s)
- Lindell Bromham
- Centre for Macroevolution and Macroecology, Division of Ecology, Evolution and Genetics, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Xia Hua
- Centre for Macroevolution and Macroecology, Division of Ecology, Evolution and Genetics, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Marcel Cardillo
- Centre for Macroevolution and Macroecology, Division of Ecology, Evolution and Genetics, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
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Montelongo T, Gómez-Zurita J. Nonrandom Patterns of Genetic Admixture Expose the Complex Historical Hybrid Origin of Unisexual Leaf Beetle Species in the GenusCalligrapha. Am Nat 2015; 185:113-34. [DOI: 10.1086/678408] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Becks L, Alavi Y. Using Microevolution to Explain the Macroevolutionary Observations for the Evolution of Sex. INTERDISCIPLINARY EVOLUTION RESEARCH 2015. [DOI: 10.1007/978-3-319-15045-1_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Lively CM, Morran LT. The ecology of sexual reproduction. J Evol Biol 2014; 27:1292-303. [PMID: 24617324 PMCID: PMC4077903 DOI: 10.1111/jeb.12354] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 01/28/2014] [Accepted: 01/29/2014] [Indexed: 11/28/2022]
Abstract
Sexual reproduction is widely regarded as one of the major unexplained phenomena in biology. Nonetheless, while a general answer may remain elusive, considerable progress has been made in the last few decades. Here, we first review the genesis of, and support for, the major ecological hypotheses for biparental sexual reproduction. We then focus on the idea that host-parasite coevolution can favour cross-fertilization over uniparental forms of reproduction, as this hypothesis currently has the most support from natural populations. We also review the results from experimental evolution studies, which tend to show that exposure to novel environments can select for higher levels of sexual reproduction, but that sex decreases in frequency after populations become adapted to the previously novel conditions. In contrast, experimental coevolution studies suggest that host-parasite interactions can lead to the long-term persistence of sex. Taken together, the evidence from natural populations and from laboratory experiments point to antagonistic coevolution as a potent and possibly ubiquitous force of selection favouring cross-fertilization and recombination.
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Affiliation(s)
- C M Lively
- Department of Biology, Indiana University, Bloomington, IN, USA
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31
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Paczesniak D, Jokela J, Larkin K, Neiman M. Discordance between nuclear and mitochondrial genomes in sexual and asexual lineages of the freshwater snail Potamopyrgus antipodarum. Mol Ecol 2013; 22:4695-710. [PMID: 23957656 DOI: 10.1111/mec.12422] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 05/29/2013] [Accepted: 06/05/2013] [Indexed: 11/30/2022]
Abstract
The presence and extent of mitonuclear discordance in coexisting sexual and asexual lineages provides insight into 1) how and when asexual lineages emerged, and 2) the spatial and temporal scales at which the ecological and evolutionary processes influencing the evolution of sexual and asexual reproduction occur. Here, we used nuclear single-nucleotide polymorphism (SNP) markers and a mitochondrial gene to characterize phylogeographic structure and the extent of mitonuclear discordance in Potamopyrgus antipodarum. This New Zealand freshwater snail is often used to study the evolution and maintenance of sex because obligately sexual and obligately asexual individuals often coexist. While our data indicate that sexual and asexual P. antipodarum sampled from the same lake population are often genetically similar, suggesting recent origin of these asexuals from sympatric sexual P. antipodarum, we also found significantly more population structure in sexuals vs. asexuals. This latter result suggests that some asexual lineages originated in other lakes and/or in the relatively distant past. When comparing mitochondrial and nuclear population genetic structure, we discovered that one mitochondrial haplotype ('1A') was rare in sexuals, but common and widespread in asexuals. Haplotype 1A frequency and nuclear genetic diversity were not associated, suggesting that the commonness of this haplotype cannot be attributed entirely to genetic drift and pointing instead to a role for selection.
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Affiliation(s)
- Dorota Paczesniak
- Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600, Dübendorf, Switzerland; Department of Environmental Systems Science, ETH-Zürich, Universitätstrasse 16, 8092, Zürich, Switzerland
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32
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Wilson CG, Sherman PW. Spatial and temporal escape from fungal parasitism in natural communities of anciently asexual bdelloid rotifers. Proc Biol Sci 2013; 280:20131255. [PMID: 23825214 DOI: 10.1098/rspb.2013.1255] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sexual reproduction is costly, but it is nearly ubiquitous among plants and animals, whereas obligately asexual taxa are rare and almost always short-lived. The Red Queen hypothesis proposes that sex overcomes its costs by enabling organisms to keep pace with coevolving parasites and pathogens. If so, the few cases of stable long-term asexuality ought to be found in groups whose coevolutionary interactions with parasites are unusually weak. In theory, antagonistic coevolution will be attenuated if hosts disperse among patches within a metapopulation separately from parasites and more rapidly. We examined whether these conditions are met in natural communities of bdelloid rotifers, one of the longest-lived asexual lineages. At any life stage, these microscopic invertebrates can tolerate the complete desiccation of their ephemeral freshwater habitats, surviving as dormant propagules that are readily carried by the wind. In our field experiments, desiccation and wind transport enabled bdelloids to disperse independently of multiple fungal parasites, in both time and space. Surveys of bdelloid communities in unmanipulated moss patches confirmed that fungal parasitism was negatively correlated with extended drought and increasing height (exposure to wind). Bdelloid ecology therefore matches a key condition of models in which asexuals persist through spatio-temporal decoupling from coevolving enemies.
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Affiliation(s)
- Christopher G Wilson
- Division of Ecology and Evolution, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK.
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de Vienne DM, Giraud T, Gouyon PH. Lineage Selection and the Maintenance of Sex. PLoS One 2013; 8:e66906. [PMID: 23825582 PMCID: PMC3688966 DOI: 10.1371/journal.pone.0066906] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 05/12/2013] [Indexed: 02/04/2023] Open
Abstract
Sex predominates in eukaryotes, despite its short-term disadvantage when compared to asexuality. Myriad models have suggested that short-term advantages of sex may be sufficient to counterbalance its twofold costs. However, despite decades of experimental work seeking such evidence, no evolutionary mechanism has yet achieved broad recognition as explanation for the maintenance of sex. We explore here, through lineage-selection models, the conditions favouring the maintenance of sex. In the first model, we allowed the rate of transition to asexuality to evolve, to determine whether lineage selection favoured species with the strongest constraints preventing the loss of sex. In the second model, we simulated more explicitly the mechanisms underlying the higher extinction rates of asexual lineages than of their sexual counterparts. We linked extinction rates to the ecological and/or genetic features of lineages, thereby providing a formalisation of the only figure included in Darwin's "The origin of species". Our results reinforce the view that the long-term advantages of sex and lineage selection may provide the most satisfactory explanations for the maintenance of sex in eukaryotes, which is still poorly recognized, and provide figures and a simulation website for training and educational purposes. Short-term benefits may play a role, but it is also essential to take into account the selection of lineages for a thorough understanding of the maintenance of sex.
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Affiliation(s)
- Damien M. de Vienne
- Bionformatics and Genomics Programme, Center for Genomic Regulation (CRG), Barcelona, Spain
- Bionformatics and Genomics Programme, University Pompeu Fabra (UPF), Barcelona, Spain
| | - Tatiana Giraud
- Ecologie, Systématique et Evolution, CNRS UMR 8079, Orsay, France
- Ecologie, Systématique et Evolution, Université Paris-Sud, Orsay, France
| | - Pierre-Henri Gouyon
- Département Systématique et Evolution, Origine, Structure, Evolution de la Biodiversité, UMR 7205 CNRS-MNHN, Muséum National d'Histoire Naturelle, Paris, France
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Elzinga JA, Jokela J, Shama LNS. Large variation in mitochondrial DNA of sexual and parthenogenetic Dahlica triquetrella (Lepidoptera: Psychidae) shows multiple origins of parthenogenesis. BMC Evol Biol 2013; 13:90. [PMID: 23622052 PMCID: PMC3655047 DOI: 10.1186/1471-2148-13-90] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 04/02/2013] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Obligate parthenogenesis is relatively rare in animals. Still, in some groups it is quite common and has evolved and persisted multiple times. These groups may provide important clues to help solve the 'paradox of sex'. Several species in the Psychidae (Lepidoptera) have obligate parthenogenesis. Dahlica triquetrella is one of those species where multiple transitions to parthenogenesis are postulated based on intensive cytological and behavioural studies. This has led to the hypothesis that multiple transitions from sexuals to diploid parthenogens occurred during and after the last glacial period, followed by transitions from parthenogenetic diploids to parthenogenetic tetraploids. Our study is the first to test these hypotheses using a molecular phylogeny based on mtDNA from multiple sexual and parthenogenetic populations from a wide geographic range. RESULTS Parthenogenetic (and sexual) D. triquetrella are not monophyletic, and considerable sequence variation is present suggesting multiple transitions to parthenogenesis. However, we could not establish ancestral sexual haplotypes from our dataset. Our data suggest that some parthenogenetic clades have evolved, indicating origins of parthenogenesis before the last glacial period. CONCLUSIONS Multiple transitions to parthenogenesis have taken place in Dahlica triquetrella, confirming previous hypotheses. The number of different parthenogenetic clades, haplotypes and their apparent evolutionary age, clearly show that parthenogenesis has been a very successful reproductive strategy in this species over a long period.
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Affiliation(s)
- Jelmer A Elzinga
- Department of Environmental and Biological Sciences, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland
| | - Jukka Jokela
- EAWAG, Swiss Federal Institute of Aquatic Science and Technology, and ETH-Zürich, Institute of Integrative Biology, Ueberlandstrasse 133, 8600, Dübendorf, Switzerland
| | - Lisa NS Shama
- EAWAG, Swiss Federal Institute of Aquatic Science and Technology, and ETH-Zürich, Institute of Integrative Biology, Ueberlandstrasse 133, 8600, Dübendorf, Switzerland
- Current address: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Wadden Sea Station Sylt, Hafenstraße 43, D-25992, List/Sylt, Germany
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Forbes AA, Rice LA, Stewart NB, Yee WL, Neiman M. Niche differentiation and colonization of a novel environment by an asexual parasitic wasp. J Evol Biol 2013; 26:1330-40. [PMID: 23517017 DOI: 10.1111/jeb.12135] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 01/17/2013] [Accepted: 01/19/2013] [Indexed: 12/23/2022]
Abstract
How do asexual taxa become adapted to a diversity of environments, and how do they persist despite changing environmental conditions? These questions are linked by their mutual focus on the relationship between genetic variation, which is often limited in asexuals, and the ability to respond to environmental variation. Asexual taxa originating from a single ancestor present a unique opportunity to assess rates of phenotypic and genetic change when access to new genetic variation is limited to mutation. Diachasma muliebre is an asexual Hymenopteran wasp that is geographically and genetically isolated from all sexual relatives. D. muliebre attack larvae of the western cherry fruit fly (Rhagoletis indifferens), which in turn feed inside bitter cherry fruit (Prunus emarginata) in August and September. R. indifferens has recently colonized a new host plant with an earlier fruiting phenology (June/July), domesticated sweet cherries (P. avium), and D. muliebre has followed its host into this temporally earlier niche. We tested three hypotheses: 1) that all D. muliebre lineages originate from a single asexual ancestor; 2) that different D. muliebre lineages (as defined by unique mtDNA haplotypes) have differentiated on their ancestral host in an important life-history trait, eclosion timing; and 3) that early-eclosing lineages have preferentially colonized the new sweet cherry niche. We find that mitochondrial COI and microsatellite data provide strong support for a single ancestral origin for all lineages. Furthermore, COI sequencing revealed five mitochondrial haplotypes among D. muliebre, and individual wasps possessing one distinctive mitochondrial haplotype (haplotype II) eclosed as reproductive adults significantly earlier than wasps with all other haplotypes. In addition, this early-eclosing lineage of D. muliebre is one of two lineages that have colonized the P. avium habitat, consistent with the preferential colonization hypothesis. These data suggest that D. muliebre has evolved adaptive phenotypic variation despite limited genetic variation, and that this variation has subsequently allowed an expansion of some wasps into a novel habitat. The D. muliebre system may allow for in-depth study of adaptation and long-term persistence of asexual taxa.
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Affiliation(s)
- A A Forbes
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA.
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Elzinga JA, Chevasco V, Mappes J, Grapputo A. Low parasitism rates in parthenogenetic bagworm moths do not support the parasitoid hypothesis for sex. J Evol Biol 2012; 25:2547-58. [PMID: 23106981 DOI: 10.1111/jeb.12000] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/27/2012] [Accepted: 08/28/2012] [Indexed: 11/30/2022]
Abstract
The parasite hypothesis for sex is one of the many theories that have been suggested to solve the mystery of the widespread occurrence of sex despite its high short-term costs. It suggests that sexual lineages have an evolutionary advantage over parthenogens because they can frequently generate new genotypes that are temporarily less prone to coevolving parasites. In this study, we looked for further supporting evidence for the parasite hypothesis of sex in an attempt to understand the coexistence of sexual and parthenogenetic bagworm moths (Naryciinae). The bagworm moths and their parasitoids form one of the few natural host-parasite systems where sexual and parthenogenetic hosts are apparently not separated by ecological or geographical barriers. Furthermore, in support of the parasite hypothesis for sex, parthenogenetic presence is negatively correlated with parasitism rate. We specifically tested, by identifying the reproductive mode of the parasitized individuals, whether parasitoids preferentially attack the parthenogens in sites with both sexual and parthenogenetic forms, as predicted by the parasite hypothesis. We collected hosts from sites with different frequencies of parthenogenetic and sexual moths. A DNA barcoding approach was used to determine the reproductive mode of the parasitized hosts. Furthermore, we investigated whether differences in host and parasitoid phenology could provide an alternative explanation for the variation in parasitism rates between parthenogens and sexuals. Our results contradict the prediction of the parasite hypothesis because parthenogenetic bagworm moths were less parasitized than sexuals in sympatric sites. Our findings can be explained by differences in phenology between the parthenogenetic and sexual moths rather than genetic incompatibility between parthenogenetic hosts and parasitoids. The stable coexistence of sexual and parthenogenetic Naryciinae despite the many apparent costs of sex in this system remains a mystery. Our work adds to the list of studies were the assumptions of the parasite hypothesis for sex are not all met.
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Affiliation(s)
- J A Elzinga
- Department of Biological and Environmental Science, Centre of Excellence in Biological Interactions, University of Jyväskylä, Jyväskylä, Finland.
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Dynamic formation of asexual diploid and polyploid lineages: multilocus analysis of Cobitis reveals the mechanisms maintaining the diversity of clones. PLoS One 2012; 7:e45384. [PMID: 23028977 PMCID: PMC3447977 DOI: 10.1371/journal.pone.0045384] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 08/16/2012] [Indexed: 11/19/2022] Open
Abstract
Given the hybrid genomic constitutions and increased ploidy of many asexual animals, the identification of processes governing the origin and maintenance of clonal diversity provides useful information about the evolutionary consequences of interspecific hybridization, asexuality and polyploidy. In order to understand the processes driving observed diversity of biotypes and clones in the Cobitis taenia hybrid complex, we performed fine-scale genetic analysis of Central European hybrid zone between two sexual species using microsatellite genotyping and mtDNA sequencing. We found that the hybrid zone is populated by an assemblage of clonally (gynogenetically) reproducing di-, tri- and tetraploid hybrid lineages and that successful clones, which are able of spatial expansion, recruit from two ploidy levels, i.e. diploid and triploid. We further compared the distribution of observed estimates of clonal ages to theoretical distributions simulated under various assumptions and showed that new clones are most likely continuously recruited from ancestral populations. This suggests that the clonal diversity is maintained by dynamic equilibrium between origination and extinction of clonal lineages. On the other hand, an interclonal selection is implied by nonrandom spatial distribution of individual clones with respect to the coexisting sexual species. Importantly, there was no evidence for sexually reproducing hybrids or clonally reproducing non-hybrid forms. Together with previous successful laboratory synthesis of clonal Cobitis hybrids, our data thus provide the most compelling evidence that 1) the origin of asexuality is causally linked to interspecific hybridization; 2) successful establishment of clones is not restricted to one specific ploidy level and 3) the initiation of clonality and polyploidy may be dynamic and continuous in asexual complexes.
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Cryptic species in putative ancient asexual darwinulids (Crustacea, Ostracoda). PLoS One 2012; 7:e39844. [PMID: 22802945 PMCID: PMC3389007 DOI: 10.1371/journal.pone.0039844] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/01/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Fully asexually reproducing taxa lack outcrossing. Hence, the classic Biological Species Concept cannot be applied. METHODOLOGY/PRINCIPAL FINDINGS We used DNA sequences from the mitochondrial COI gene and the nuclear ITS2 region to check species boundaries according to the evolutionary genetic (EG) species concept in five morphospecies in the putative ancient asexual ostracod genera, Penthesilenula and Darwinula, from different continents. We applied two methods for detecting cryptic species, namely the K/θ method and the General Mixed Yule Coalescent model (GMYC). We could confirm the existence of species in all five darwinulid morphospecies and additional cryptic diversity in three morphospecies, namely in Penthesilenula brasiliensis, Darwinula stevensoni and in P. aotearoa. The number of cryptic species within one morphospecies varied between seven (P. brasiliensis), five to six (D. stevensoni) and two (P. aotearoa), respectively, depending on the method used. Cryptic species mainly followed continental distributions. We also found evidence for coexistence at the local scale for Brazilian cryptic species of P. brasiliensis and P. aotearoa. Our ITS2 data confirmed that species exist in darwinulids but detected far less EG species, namely two to three cryptic species in P. brasiliensis and no cryptic species at all in the other darwinulid morphospecies. CONCLUSIONS/SIGNIFICANCE Our results clearly demonstrate that both species and cryptic diversity can be recognized in putative ancient asexual ostracods using the EG species concept, and that COI data are more suitable than ITS2 for this purpose. The discovery of up to eight cryptic species within a single morphospecies will significantly increase estimates of biodiversity in this asexual ostracod group. Which factors, other than long-term geographic isolation, are important for speciation processes in these ancient asexuals remains to be investigated.
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Meirmans S, Meirmans PG, Kirkendall LR. The costs of sex: facing real-world complexities. QUARTERLY REVIEW OF BIOLOGY 2012; 87:19-40. [PMID: 22518931 DOI: 10.1086/663945] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Understanding the maintenance of sexual reproduction constitutes a difficult problem for evolutionary biologists because of the immediate costs that sex seems to incur. Typically, general benefits to sex and recombination are investigated that might outweigh these costs. However, several factors can strongly influence the complex balance between costs and benefits of sex; these include constraints on the evolution of asexuality, ecological differentiation, and certain lif-history traits. We review these factors and their empirical support for the first time in a unified framework and find that they can reduce the costs of sex, circumvent them, or make them inapplicable. These factors can even tip the scales to a net benefit for sex. The reviewed factors affect species and species groups differently, and we conclude consequently that understanding the maintenance of sex could turn out to be more species-specific than commonly assumed. Interestingly, our study suggests that, in some species, no general benefits to sex and recombination might be needed to understand the maintenance of sex, as in our case study of dandelions.
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Affiliation(s)
- Stephanie Meirmans
- Centre for the Study of the Sciences and the Humanities and Department of Biology, University of Bergen 5020 Bergen, Norway.
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40
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Castonguay E, Angers B. The key role of epigenetics in the persistence of asexual lineages. GENETICS RESEARCH INTERNATIONAL 2012; 2012:534289. [PMID: 22567390 PMCID: PMC3335536 DOI: 10.1155/2012/534289] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 10/14/2011] [Accepted: 10/24/2011] [Indexed: 11/24/2022]
Abstract
Asexual organisms, often perceived as evolutionary dead ends, can be long-lived and geographically widespread. We propose that epigenetic mechanisms could play a crucial role in the evolutionary persistence of these lineages. Genetically identical organisms could rely on phenotypic plasticity to face environmental variation. Epigenetic modifications could be the molecular mechanism enabling such phenotypic plasticity; they can be influenced by the environment and act at shorter timescales than mutation. Recent work on the asexual vertebrate Chrosomus eos-neogaeus (Pisces: Cyprinidae) provides broad insights into the contribution of epigenetics in genetically identical individuals. We discuss the extension of these results to other asexual organisms, in particular those resulting from interspecific hybridizations. We finally develop on the evolutionary relevance of epigenetic variation in the context of heritability.
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Affiliation(s)
- Emilie Castonguay
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
| | - Bernard Angers
- Département de Sciences Biologiques, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, QC, Canada H3C 3J7
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41
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The Evolution of Inbred Social Systems in Spiders and Other Organisms. ADVANCES IN THE STUDY OF BEHAVIOR 2012. [DOI: 10.1016/b978-0-12-394288-3.00003-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Abstract
One hope of trying to understand why sex is so powerful and prevalent a mode of reproduction relies on the rare examples of animals that persist long-term without having sex. Now, several species of stick insects join that illustrious circle.
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WILSON CHRISTOPHERG. Desiccation-tolerance in bdelloid rotifers facilitates spatiotemporal escape from multiple species of parasitic fungi. Biol J Linn Soc Lond 2011. [DOI: 10.1111/j.1095-8312.2011.01737.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Beck JB, Windham MD, Pryer KM. Do asexual polyploid lineages lead short evolutionary lives? A case study from the fern genus Astrolepis. Evolution 2011; 65:3217-29. [PMID: 22023587 DOI: 10.1111/j.1558-5646.2011.01362.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A life-history transition to asexuality is typically viewed as leading to a heightened extinction risk, and a number of studies have evaluated this claim by examining the relative ages of asexual versus closely related sexual lineages. Surprisingly, a rigorous assessment of the age of an asexual plant lineage has never been published, although asexuality is extraordinarily common among plants. Here, we estimate the ages of sexual diploids and asexual polyploids in the fern genus Astrolepis using a well-supported plastid phylogeny and a relaxed-clock dating approach. The 50 asexual polyploid samples we included were conservatively estimated to comprise 19 distinct lineages, including a variety of auto- and allopolyploid genomic combinations. All were either the same age or younger than the crown group comprising their maternal sexual-diploid parents based simply on their phylogenetic position. Node ages estimated with the relaxed-clock approach indicated that the average maximum age of asexual lineages was 0.4 My, and individual lineages were on average 7 to 47 times younger than the crown- and total-ages of their sexual parents. Although the confounding association between asexuality and polyploidy precludes definite conclusions regarding the effect of asexuality, our results suggest that asexuality limits evolutionary potential in Astrolepis.
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Affiliation(s)
- James B Beck
- Department of Biology, Duke University, Durham, North Carolina 27708, USA.
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Janko K, Drozd P, Eisner J. Do clones degenerate over time? Explaining the genetic variability of asexuals through population genetic models. Biol Direct 2011; 6:17. [PMID: 21371316 PMCID: PMC3064643 DOI: 10.1186/1745-6150-6-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 03/03/2011] [Indexed: 11/25/2022] Open
Abstract
Background Quest for understanding the nature of mechanisms governing the life span of clonal organisms lasts for several decades. Phylogenetic evidence for recent origins of most clones is usually interpreted as proof that clones suffer from gradual age-dependent fitness decay (e.g. Muller's ratchet). However, we have shown that a neutral drift can also qualitatively explain the observed distribution of clonal ages. This finding was followed by several attempts to distinguish the effects of neutral and non-neutral processes. Most recently, Neiman et al. 2009 (Ann N Y Acad Sci.:1168:185-200.) reviewed the distribution of asexual lineage ages estimated from a diverse array of taxa and concluded that neutral processes alone may not explain the observed data. Moreover, the authors inferred that similar types of mechanisms determine maximum asexual lineage ages in all asexual taxa. In this paper we review recent methods for distinguishing the effects of neutral and non-neutral processes and point at methodological problems related with them. Results and Discussion We found that contemporary analyses based on phylogenetic data are inadequate to provide any clear-cut answer about the nature and generality of processes affecting evolution of clones. As an alternative approach, we demonstrate that sequence variability in asexual populations is suitable to detect age-dependent selection against clonal lineages. We found that asexual taxa with relatively old clonal lineages are characterised by progressively stronger deviations from neutrality. Conclusions Our results demonstrate that some type of age-dependent selection against clones is generally operational in asexual animals, which cover a wide taxonomic range spanning from flatworms to vertebrates. However, we also found a notable difference between the data distribution predicted by available models of sequence evolution and those observed in empirical data. These findings point at the possibility that processes affecting clonal evolution differ from those described in recent studies, suggesting that theoretical models of asexual populations must evolve to address this problem in detail. Reviewers This article was reviewed by Isa Schön (nominated by John Logsdon), Arcady Mushegian and Timothy G. Barraclough (nominated by Laurence Hurst).
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Affiliation(s)
- Karel Janko
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Liběchov, Czech Republic.
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Unisexual reproduction among vertebrates. Trends Genet 2011; 27:81-8. [DOI: 10.1016/j.tig.2010.12.002] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 12/06/2010] [Accepted: 12/08/2010] [Indexed: 11/19/2022]
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Nelson AE, Neiman M. Persistent Copulation in Asexual Female Potamopyrgus antipodarum: Evidence for Male Control with Size-Based Preferences. INTERNATIONAL JOURNAL OF EVOLUTIONARY BIOLOGY 2011; 2011:439046. [PMID: 21716737 PMCID: PMC3119465 DOI: 10.4061/2011/439046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 01/12/2011] [Accepted: 02/03/2011] [Indexed: 01/18/2023]
Abstract
Transitions from sexual to asexual reproduction provide a useful context for investigating the evolutionary loss of nonfunctional traits. It is often assumed that useless behaviors or structures will degrade, but this process is poorly understood. Potamopyrgus antipodarum is an ancestrally sexual New Zealand freshwater snail characterized by numerous independent transitions to asexual all-female lineages. The availability of multiple independently-derived asexual lineages of various time since derivation from sexual ancestors means that the P. antipodarum system is well-suited for the study of trait loss related to mating behavior and copulation. Here, we asked whether mating behavior in asexual female P. antipodarum degrades with increasing asexual lineage age. While copulation frequency did not differ in females from old versus young asexual lineages, post hoc analyses indicated that it was instead positively associated with mean lineage female size. We observed that female P. antipodarum take a passive physical role in copulatory interactions, indicating that female behavior may not be a useful variable for detection of sex-related vestigialization in this system. Instead, males seem to be in proximate control of copulation frequencies, meaning that male mating behavior may be a primary determinant of the expression of mating behavior in asexual female P. antipodarum.
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Affiliation(s)
- Amanda E Nelson
- Department of Biology, University of Iowa, 143 Biology Building, Iowa City, IA 52242-1324, USA
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Abstract
Under the Red Queen hypothesis, host-parasite coevolution selects against common host genotypes. Although this mechanism might underlie the persistence of sexual reproduction, it might also maintain high clonal diversity. Alternatively, clonal diversity might be maintained by multiple origins of parthenogens from conspecific sexuals, a feature in many animal groups. Herein, we addressed the maintenance of overall genetic diversity by coevolving parasites, as predicted by the Red Queen hypothesis. We specifically examined the contribution of parasites to host clonal diversity and the frequency of sexually reproducing individuals in natural stream populations of Potamopyrgus antipodarum snails. We also tested the alternative hypothesis that clonal diversity is maintained by the input of clones by mutation from sympatric sexuals. Clonal diversity and the frequency of sexual individuals were both positively related to infection frequency. Surprisingly, although clones are derived by mutation from sexual snails, parasites explained more of the genotypic variation among parthenogenetic subpopulations. Our findings thus highlight the importance of parasites as drivers of clonal diversity, as well as sex.
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Affiliation(s)
- Kayla C King
- Department of Biology, Indiana University, Bloomington, Indiana 47401-3700, USA.
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Abstract
No evidence of sexual reproduction has been detected in many eukaryotes, but this "negative evidence" of obligatory asexuality is still met with widespread skepticism. This is partly because obligatory asexual reproduction is deleterious in the long run and partly because it is logically possible that there are undetected sexual individuals. I point out that this skepticism stems from failure to think statistically, and the absence of sexual individuals in a sufficiently large sample can be very convincing evidence of obligatory asexuality. A survey of rotifer workers showed that approximately 458 515 bdelloid rotifers have been examined without finding any males or hermaphrodites; applying the Poisson distribution to these data shows that the upper 95% confidence interval of the number of sexual individuals is less than 8.1 x 10(-6). In darwinulid ostracods, a smaller sample puts the estimate at less than 1.75 x 10(-4) sexual individuals. If there were undetected sexual individuals at these low levels, the frequency of outcrossing must be even lower; so that sex will be ineffective and easily lost. Furthermore, recently published evidence shows that these ancient asexuals are not "scandalous" but merely the tail end of the age distribution of asexual lineages.
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Affiliation(s)
- C William Birky
- Department of Ecology and Evolutionary Biology, Biological Sciences West, The University of Arizona, Tucson, AZ 85721, USA.
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