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HODDA M. Phylum Nematoda: trends in species descriptions, the documentation of diversity, systematics, and the species concept. Zootaxa 2022; 5114:290-317. [DOI: 10.11646/zootaxa.5114.1.2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Indexed: 11/04/2022]
Abstract
This paper summarizes the trends in nematode species description and systematics emerging from a comparison of the latest comprehensive classification and census of Phylum Nematoda (Hodda 2022a, b) with earlier classifications (listed in Hodda 2007). It also offers some general observations on trends in nematode systematics emerging from the review of the voluminous literature used to produce the classification. The trends in nematodes can be compared with developments in the systematics of other organisms to shed light on many of the general issues confronting systematists now and into the future.
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Suetsugu K. Gynomonoecy in a mycoheterotrophic orchid Eulophia zollingeri with autonomous selfing hermaphroditic flowers and putatively outcrossing female flowers. PeerJ 2020; 8:e10272. [PMID: 33194432 PMCID: PMC7597633 DOI: 10.7717/peerj.10272] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/08/2020] [Indexed: 11/20/2022] Open
Abstract
Most orchid species exhibit an extreme case of hermaphroditism, owing to the fusion of male and female organs into a gynostemium. Exceptions to this rule have only been reported from the subtribes Catasetinae and Satyriinae. Here, I report an additional orchidaceous example whose flowers are not always hermaphroditic. In several Japanese populations of Eulophia zollingeri (Rchb.f.) J.J.Sm, a widespread Asian and Oceanian orchid, some flowers possess both the anther (i.e., anther cap and pollinaria) and stigma, whereas others possess only the stigma. Therefore, pollination experiments, an investigation of floral morphology and observations of floral visitors were conducted to understand the reproductive biology of E. zollingeri in Miyazaki Prefecture, Japan. It was confirmed that E. zollingeri studied here possesses a gynomonoecious reproductive system, a sexual system in which a single plant has both female flowers and hermaphroditic flowers. In addition, hermaphroditic flowers often possess an effective self-pollination system while female flowers could avoid autogamy but suffered from severe pollinator limitation, due to a lack of agamospermy and low insect-mediated pollination. The present study represents the first documented example of gynomonoecy within Orchidaceae. Gynomonoecy in E. zollingeri may be maintained by the tradeoff in reproductive traits between female flowers (with low fruit set but potential outcrossing benefits) and hermaphroditic flowers (with high fruit set but inbreeding depression in selfed offspring). This mixed mating is probably important in mycoheterotrophic E. zollingeri because it occurs in shaded forest understorey with a paucity of pollinators.
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Affiliation(s)
- Kenji Suetsugu
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan
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Abstract
In diverse parasite taxa, from scale insects to root-knot nematodes, asexual lineages have exceptionally large host ranges, larger than those of their sexual relatives. Phylogenetic comparative studies of parasite taxa indicate that increases in host range and geographic range increase the probability of establishment of asexual lineages. At first pass, this convergence of traits appears counter-intuitive: intimate, antagonistic association with an enormous range of host taxa correlates with asexual reproduction, which should limit genetic variation within populations. Why would narrow host ranges favor sexual parasites and large host ranges favor asexual parasites? To take on this problem I link theory on ecological specialization to the two predominant hypotheses for the evolution of sex. I argue that both hypotheses predict a positive association between host range and the probability of invasion of asexual parasites, mediated either by variation in population size or in the strength of antagonistic coevolution. I also review hypotheses on colonization and the evolution of niche breadth in asexual lineages. I emphasize parasite taxa, with their diversity of reproductive modes and ecological strategies, as valuable assets in the hunt for solutions to the classic problems of the evolution of sex and geographic parthenogenesis.
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Affiliation(s)
- Amanda K Gibson
- Wissenschaftskolleg zu Berlin, Berlin, Germany.,Department of Biology, University of Virginia, Charlottesville, VA, USA
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Khan S, Zhao X, Hou Y, Yuan C, Li Y, Luo X, Liu J, Feng X. Analysis of genome-wide SNPs based on 2b-RAD sequencing of pooled samples reveals signature of selection in different populations of Haemonchus contortus. J Biosci 2019; 44:97. [PMID: 31502575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The parasitic nematode Haemonchus contortus is one of the world's most important parasites of small ruminants that causes significant economic losses to the livestock sector. The population structure and selection in its various strains are poorly understood. No study so far compared its different populations using genome-wide data. Here, we focused on different geographic populations of H. contours from China (Tibet, TB; Hubei, HB; Inner Mongolia, IM; Sichuan, SC), UK and Australia (AS), using genome-wide population-genomic approaches, to explore genetic diversity, population structure and selection. We first performed next-generation high-throughput 2b RAD pool sequencing using Illumina technology, and identified single-nucleotide polymorphisms (SNPs) in all the strains. We identified 75,187 SNPs for TB, 82,271 for HB, 82,420 for IM, 79,803 for SC, 83,504 for AS and 78,747 for UK strain. The SNPs revealed low-nucleotide diversity (pi= 0.0092-0.0133) within each strain, and a significant differentiation level (average Fst = 0.34264) among them. Chinese populations TB and SC, along with the UK strain, were more divergent populations. Chinese populations IM and HB showed affinities to the Australian strain. We then analysed signature of selection and detected 44 (UK) and 03 (AS) private selective sweeps containing 49 and 05 genes, respectively. Finally, we performed the functional annotation of selective sweeps and proposed biological significance to signature of selection. Our data suggest that 2b-RAD pool sequencing can be used to assess the signature of selection in H. contortus.
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Affiliation(s)
- Sawar Khan
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Key Laboratory of Animal Parasitology, Ministry of Agriculture of China, Shanghai 200241, People's Republic of China
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Khan S, Zhao X, Hou Y, Yuan C, Li Y, Luo X, Liu J, Feng X. Analysis of genome-wide SNPs based on 2b-RAD sequencing of pooled samples reveals signature of selection in different populations of Haemonchus contortus. J Biosci 2019. [DOI: 10.1007/s12038-019-9917-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Maraun M, Caruso T, Hense J, Lehmitz R, Mumladze L, Murvanidze M, Nae I, Schulz J, Seniczak A, Scheu S. Parthenogenetic vs. sexual reproduction in oribatid mite communities. Ecol Evol 2019; 9:7324-7332. [PMID: 31380053 PMCID: PMC6662391 DOI: 10.1002/ece3.5303] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 05/09/2019] [Accepted: 05/10/2019] [Indexed: 11/26/2022] Open
Abstract
The dominance of sex in Metazoa is enigmatic. Sexual species allocate resources to the production of males, while potentially facing negative effects such as the loss of well-adapted genotypes due to recombination, and exposure to diseases and predators during mating. Two major hypotheses have been put forward to explain the advantages of parthenogenetic versus sexual reproduction in animals, that is, the Red Queen hypothesis and the Tangled Bank/Structured Resource Theory of Sex. The Red Queen hypothesis assumes that antagonistic predator-prey/ parasite-host interactions favor sex. The Structured Resource Theory of Sex predicts sexual reproduction to be favored if resources are in short supply and aggregated in space. In soil, a remarkable number of invertebrates reproduce by parthenogenesis, and this pattern is most pronounced in oribatid mites (Oribatida, Acari). Oribatid mites are abundant in virtually any soil across very different habitats, and include many sexual and parthenogenetic (thelytokous) species. Thereby, they represent an ideal model group to investigate the role of sexual versus parthenogenetic reproduction across different ecosystems and habitats. Here, we compiled data on oribatid mite communities from different ecosystems and habitats across biomes, including tropical rainforests, temperate forests, grasslands, arable fields, salt marshes, bogs, caves, and deadwood. Based on the compiled dataset, we analyzed if the percentage of parthenogenetic species and the percentage of individuals of parthenogenetic species are related to total oribatid mite density, species number, and other potential driving factors of the reproductive mode including altitude and latitude. We then interpret the results in support of either the Red Queen hypothesis or the Structured Resource Theory of Sex. Overall, the data showed that low density of oribatid mites due to harsh environmental conditions is associated with high frequency of parthenogenesis supporting predictions of the Structured Resource Theory of Sex rather than the Red Queen hypothesis.
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Affiliation(s)
- Mark Maraun
- JFB Institute of Zoology and AnthropologyGeorg August University GöttingenGöttingenGermany
| | - Tancredi Caruso
- School of Biological Sciences and Institute for Global Food SecurityQueen's University of BelfastBelfastNorthern Ireland
| | - Jonathan Hense
- Fachdidaktik Biologie, Nees‐InstitutRheinische Friedrich‐Wilhelms Universität BonnBonnGermany
| | | | - Levan Mumladze
- Institute of Ecology and Institute of ZoologyIlia State UniversityTbilisiGeorgia
| | - Maka Murvanidze
- Institute of Entomology of AgriculturalUniversity of GeorgiaTbilisiGeorgia
| | - Ioana Nae
- Emil Racovita Institute of Speleology of Romanian AcademyBucharestRomania
| | - Julia Schulz
- JFB Institute of Zoology and AnthropologyGeorg August University GöttingenGöttingenGermany
| | - Anna Seniczak
- RealfagbyggetUniversity Museum of Bergen, University of BergenBergenNorway
| | - Stefan Scheu
- JFB Institute of Zoology and AnthropologyGeorg August University GöttingenGöttingenGermany
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GIBSON AMANDAK, MORRAN LEVIT. A Model for Evolutionary Ecology of Disease: The Case for Caenorhabditis Nematodes and Their Natural Parasites. J Nematol 2018. [DOI: 10.21307/jofnem-2017-083] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Gibson AK, Morran LT. A Model for Evolutionary Ecology of Disease: The Case for Caenorhabditis Nematodes and Their Natural Parasites. J Nematol 2017; 49:357-372. [PMID: 29353923 PMCID: PMC5770282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Indexed: 06/07/2023] Open
Abstract
Many of the outstanding questions in disease ecology and evolution call for combining observation of natural host-parasite populations with experimental dissection of interactions in the field and the laboratory. The "rewilding" of model systems holds great promise for this endeavor. Here, we highlight the potential for development of the nematode Caenorhabditis elegans and its close relatives as a model for the study of disease ecology and evolution. This powerful laboratory model was disassociated from its natural habitat in the 1960s. Today, studies are uncovering that lost natural history, with several natural parasites described since 2008. Studies of these natural Caenorhabditis-parasite interactions can reap the benefits of the vast array of experimental and genetic tools developed for this laboratory model. In this review, we introduce the natural parasites of C. elegans characterized thus far and discuss resources available to study them, including experimental (co)evolution, cryopreservation, behavioral assays, and genomic tools. Throughout, we present avenues of research that are interesting and feasible to address with caenorhabditid nematodes and their natural parasites, ranging from the maintenance of outcrossing to the community dynamics of host-associated microbes. In combining natural relevance with the experimental power of a laboratory supermodel, these fledgling host-parasite systems can take on fundamental questions in evolutionary ecology of disease.
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Affiliation(s)
| | - Levi T Morran
- Department of Biology, Emory University, Atlanta, GA 30322
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Castillo DM, Gibson AK, Moyle LC. Assortative mating and self-fertilization differ in their contributions to reinforcement, cascade speciation, and diversification. Curr Zool 2016; 62:169-181. [PMID: 29491904 PMCID: PMC5804227 DOI: 10.1093/cz/zow004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 01/07/2016] [Indexed: 11/14/2022] Open
Abstract
Cascade speciation and reinforcement can evolve rapidly when traits are pleiotropic and act as both signal/cue in nonrandom mating. Here, we examine the contribution of two key traits-assortative mating and self-fertilization-to reinforcement and (by extension) cascade speciation. First, using a population genetic model of reinforcement we find that both assortative mating and self-fertilization can make independent contributions to increased reproductive isolation, consistent with reinforcement. Self-fertilization primarily evolves due to its 2-fold transmission advantage when inbreeding depression (d) is lower (d < 0.45) but evolves as a function of the cost of hybridization under higher inbreeding depression (0.45 < d < 0.48). When both traits can evolve simultaneously, increased self-fertilization often prohibits the evolution of assortative mating. We infer that, under specific conditions, mating system transitions are more likely to lead to increased reproductive isolation and initiate cascade speciation, than assortative mating. Based on the results of our simulations, we hypothesized that transitions to self-fertilization could contribute to clade-wide diversification if reinforcement or cascade speciation is common. We tested this hypothesis with comparative data from two different groups. Consistent with our hypothesis, there was a trend towards uniparental reproduction being associated with increased diversification rate in the Nematode phylum. For the plant genus Mimulus, however, self-fertilization was associated with reduced diversification. Reinforcement driving speciation via transitions to self-fertilization might be short lived or unsustainable across macroevolutionary scales in some systems (some plants), but not others (such as nematodes), potentially due to differences in susceptibility to inbreeding depression and/or the ability to transition between reproductive modes.
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Affiliation(s)
- Dean M. Castillo
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
| | - Amanda K. Gibson
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
| | - Leonie C. Moyle
- Department of Biology, 1001 East Third Street, Indiana University, Bloomington, IN 47405, USA
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Shimada D. Checklist of the subfamily Adoncholaiminae Gerlach and Riemann, 1974 (Nematoda: Oncholaimida: Oncholaimidae) of the world: genera, species, distribution, and reference list for taxonomists and ecologists. Biodivers Data J 2016; 4:e6577. [PMID: 26929708 PMCID: PMC4759407 DOI: 10.3897/bdj.4.e6577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 01/18/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Adoncholaiminae is one of the seven subfamilies in the free-living aquatic nematode family Oncholaimidae. Nematodes in Adoncholaiminae are found from various water environment of the world. However, a checklist of all Adoncholaiminae species including full literature, especially information of experimental (not taxonomic) works, has not been updated for more than 40 years. NEW INFORMATION A revised checklist of the subfamily Adoncholaiminae of the world is provided. It contains 31 valid and 13 invalid species names in four genera with synonyms, collection records, and full literature from 1860's to 2015 for each species. A literature survey of total 477 previous papers was conducted in this work, and 362 of them are newly added to checklist.
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Affiliation(s)
- Daisuke Shimada
- Department of Biology, Keio University, 4-1-1, Hiyoshi, Yokohama, 223-8521, Japan
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