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Waheed A, Shen L, Nkurikiyimfura O, Fang H, Wang Y, Andersson B, Zhan J, Yang L. Evaluating the contribution of historical and contemporary temperature to the oospore production of self-fertile Phytophthora infestans. Evol Appl 2024; 17:e13643. [PMID: 38293269 PMCID: PMC10824702 DOI: 10.1111/eva.13643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/27/2023] [Accepted: 01/03/2024] [Indexed: 02/01/2024] Open
Abstract
Reproductive systems play an important role in the ecological function of species, but little is known about how climate change, such as global warming, may affect the reproductive systems of microbes. In this study, 116 Phytophthora infestans isolates sampled from five different altitudes along a mountain were evaluated under five temperature regimes to determine the effects of historical and experimental temperature on the reproductive system of the pathogen. Both altitude, a proxy for historical pathogen adaptation to temperature, and temperature used in the experiment affected the sexual reproduction of the pathogen, with experimental temperature, that is, contemporary temperature, playing a role several times more important than historical temperature. Furthermore, the potential of sexual reproduction, measured by the number of oospores quantified, increased with the temperature breadth (i.e., difference between the highest and lowest temperature at which sexual reproduction takes place) of the pathogen and reached the maximum at the experimental temperature of 21°C, which is higher than the annual average temperature in many potato-producing areas. The results suggest that rising air temperature associated with global warming may increase the potential of sexual reproduction in P. infestans. Given the importance of sexuality in pathogenicity and ecological adaptation of pathogens, these results suggest that global warming may increase the threat of P. infestans to agricultural production and other ecological services and highlight that new epidemiological strategies may need to be implemented for future food security and ecological resilience.
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Affiliation(s)
- Abdul Waheed
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of OceanographyMinjiang UniversityFuzhouChina
| | - Lin‐Lin Shen
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of OceanographyMinjiang UniversityFuzhouChina
| | | | - Han‐Mei Fang
- Institute of Plant PathologyFujian Agriculture and Forestry UniversityFuzhouChina
| | - Yan‐Ping Wang
- College of Chemistry and Life SciencesChengdu Normal UniversityChengduChina
| | - Björn Andersson
- Department of Forest Mycology and Plant PathologySwedish University of Agricultural SciencesUppsalaSweden
| | - Jiasui Zhan
- Department of Forest Mycology and Plant PathologySwedish University of Agricultural SciencesUppsalaSweden
| | - Li‐Na Yang
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, Fuzhou Institute of OceanographyMinjiang UniversityFuzhouChina
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2
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Archetti M. Soft selection reduces loss of heterozygosity in asexual reproduction. J Evol Biol 2023; 36:1313-1327. [PMID: 37584223 DOI: 10.1111/jeb.14209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 06/27/2023] [Accepted: 07/19/2023] [Indexed: 08/17/2023]
Abstract
The adaptive value of sexual reproduction is still debated in evolutionary theory. It has been proposed that the advantage of sexual reproduction over asexual reproduction is to promote genetic diversity, to prevent the accumulation of harmful mutations or to preserve heterozygosity. Since these hypothetical advantages depend on the type of asexual reproduction, understanding how selection affects the taxonomic distribution of each type could help us discriminate between existing hypotheses. Here, I argue that soft selection, competition among embryos or offspring in selection arenas prior to the hard selection of the adult phase, reduces loss of heterozygosity in certain types of asexual reproduction. Since loss of heterozygosity leads to the unmasking of recessive deleterious mutations in the progeny of asexual individuals, soft selection facilitates the evolution of these types of asexual reproduction. Using a population genetics model, I calculate how loss of heterozygosity affects fitness for different types of apomixis and automixis, and I show that soft selection significantly reduces loss of heterozygosity, hence increases fitness, in apomixis with suppression of the first meiotic division and in automixis with central fusion, the most common types of asexual reproduction. Therefore, if sexual reproduction evolved to preserve heterozygosity, soft selection should be associated with these types of asexual reproduction. I discuss the evidence for this prediction and how this and other observations on the distribution of different types of asexual reproduction in nature is consistent with the heterozygosity hypothesis.
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Affiliation(s)
- Marco Archetti
- Department of Biology, W210 MSC, Pennsylvania State University, University Park, Pennsylvania, USA
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3
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Winter M, Harms K, Johnsen PJ, Buckling A, Vos M. Testing for the fitness benefits of natural transformation during community-embedded evolution. Microbiology (Reading) 2023; 169:001375. [PMID: 37526972 PMCID: PMC10482379 DOI: 10.1099/mic.0.001375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 07/18/2023] [Indexed: 08/02/2023]
Abstract
Natural transformation is a process where bacteria actively take up DNA from the environment and recombine it into their genome or reconvert it into extra-chromosomal genetic elements. The evolutionary benefits of transformation are still under debate. One main explanation is that foreign allele and gene uptake facilitates natural selection by increasing genetic variation, analogous to meiotic sex. However, previous experimental evolution studies comparing fitness gains of evolved transforming- and isogenic non-transforming strains have yielded mixed support for the 'sex hypothesis.' Previous studies testing the sex hypothesis for natural transformation have largely ignored species interactions, which theory predicts provide conditions favourable to sex. To test for the adaptive benefits of bacterial transformation, the naturally transformable wild-type Acinetobacter baylyi and a transformation-deficient ∆comA mutant were evolved for 5 weeks. To provide strong and potentially fluctuating selection, A. baylyi was embedded in a community of five other bacterial species. DNA from a pool of different Acinetobacter strains was provided as a substrate for transformation. No effect of transformation ability on the fitness of evolved populations was found, with fitness increasing non-significantly in most treatments. Populations showed fitness improvement in their respective environments, with no apparent costs of adaptation to competing species. Despite the absence of fitness effects of transformation, wild-type populations evolved variable transformation frequencies that were slightly greater than their ancestor which potentially could be caused by genetic drift.
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Affiliation(s)
- Macaulay Winter
- European Centre for Environment and Human Health, University of Exeter Medical School, Environment and Sustainability Institute, Penryn Campus, TR10 9FE, UK
| | - Klaus Harms
- Microbial Pharmacology and Population Biology Research Group, Department of Pharmacy, Faculty of Health Sciences, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Pål Jarle Johnsen
- Microbial Pharmacology and Population Biology Research Group, Department of Pharmacy, Faculty of Health Sciences, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Angus Buckling
- Department of Biosciences, University of Exeter, Penryn Campus, TR10 9FE, UK
| | - Michiel Vos
- European Centre for Environment and Human Health, University of Exeter Medical School, Environment and Sustainability Institute, Penryn Campus, TR10 9FE, UK
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4
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Papach A, Beaurepaire A, Yañez O, Huwiler M, Williams GR, Neumann P. Multiple mating by both sexes in an invasive insect species, Aethina tumida (Coleoptera: Nitidulidae). Insect Sci 2023; 30:517-529. [PMID: 36097706 DOI: 10.1111/1744-7917.13112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 07/11/2022] [Accepted: 08/18/2022] [Indexed: 06/15/2023]
Abstract
Multiple mating by both sexes is common among sexually reproducing animals. Small hive beetles (SHB), Aethina tumida, are parasites of bee nests endemic to sub-Saharan Africa and have become a widespread invasive species. Despite the considerable economic damages they can cause, their basic biology remains poorly understood. Here we show that male and female small hive beetles can mate multiple times, suggesting that costs for mating are low in this species. In an invasive A. tumida population in the United States, a combination of laboratory experiments for males and paternity analysis with eight polymorphic DNA microsatellite markers for field-caught females were used to estimate the number of mating by both sexes. The data show that females and males can mate multiple times-females mated with up to eight males, whereas males mated with at least seven females. The results also showed that A. tumida displayed a skewed paternity, although this was not consistent among the tested females. Thus, first or last male advantage seem to be unlikely in A. tumida. Our observations that individuals of both sexes of A. tumida can mate multiple times opens new research avenues for examining drivers of multiple mating and determining the role it may play in promoting biological invasions.
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Affiliation(s)
- Anna Papach
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Agroscope, Swiss Bee Research Centre, Bern, Switzerland
| | - Alexis Beaurepaire
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Agroscope, Swiss Bee Research Centre, Bern, Switzerland
| | - Orlando Yañez
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Agroscope, Swiss Bee Research Centre, Bern, Switzerland
| | - Meret Huwiler
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Geoffrey R Williams
- Department of Entomology & Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Peter Neumann
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Agroscope, Swiss Bee Research Centre, Bern, Switzerland
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5
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Abstract
DNA methylation is an ancient epigenetic pathway found across eukaryotes. Nevertheless, the targets of DNA methylation within genomes evolve extremely rapidly. Arthropods display many such examples. The mealybug Planococcus citri has evolved methylation at promoter sequences, associated with gene silencing just as in mammals. In this issue of Molecular Ecology, Bain et al. (2021), thoroughly characterise mealybug methylation, exploring its potential functions in gene expression and the spectacular sexual dimorphism that is a characteristic of this species. Their results provide new insights into the complex relationship between DNA methylation and gene expression and highlight how rapidly different methylation systems can evolve.
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Affiliation(s)
- Peter Sarkies
- Department of Biochemistry, University of Oxford, Oxford, UK.,Institute of Clinical Sciences, Imperial College London, London, UK
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6
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Adhikari K, Son JH, Rensink AH, Jaweria J, Bopp D, Beukeboom LW, Meisel RP. Temperature-dependent effects of house fly proto-Y chromosomes on gene expression could be responsible for fitness differences that maintain polygenic sex determination. Mol Ecol 2021; 30:5704-5720. [PMID: 34449942 DOI: 10.1111/mec.16148] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 08/20/2021] [Indexed: 12/21/2022]
Abstract
Sex determination, the developmental process by which sexually dimorphic phenotypes are established, evolves fast. Evolutionary turnover in a sex determination pathway may occur via selection on alleles that are genetically linked to a new master sex determining locus on a newly formed proto-sex chromosome. Species with polygenic sex determination, in which master regulatory genes are found on multiple different proto-sex chromosomes, are informative models to study the evolution of sex determination and sex chromosomes. House flies are such a model system, with male determining loci possible on all six chromosomes and a female-determiner on one of the chromosomes as well. The two most common male-determining proto-Y chromosomes form latitudinal clines on multiple continents, suggesting that temperature variation is an important selection pressure responsible for maintaining polygenic sex determination in this species. Temperature-dependent fitness effects could be manifested through temperature-dependent gene expression differences across proto-Y chromosome genotypes. These gene expression differences may be the result of cis regulatory variants that affect the expression of genes on the proto-sex chromosomes, or trans effects of the proto-Y chromosomes on genes elswhere in the genome. We used RNA-seq to identify genes whose expression depends on proto-Y chromosome genotype and temperature in adult male house flies. We found no evidence for ecologically meaningful temperature-dependent expression differences of sex determining genes between male genotypes, but we were probably not sampling an appropriate developmental time-point to identify such effects. In contrast, we identified many other genes whose expression depends on the interaction between proto-Y chromosome genotype and temperature, including genes that encode proteins involved in reproduction, metabolism, lifespan, stress response, and immunity. Notably, genes with genotype-by-temperature interactions on expression were not enriched on the proto-sex chromosomes. Moreover, there was no evidence that temperature-dependent expression is driven by chromosome-wide cis-regulatory divergence between the proto-Y and proto-X alleles. Therefore, if temperature-dependent gene expression is responsible for differences in phenotypes and fitness of proto-Y genotypes across house fly populations, these effects are driven by a small number of temperature-dependent alleles on the proto-Y chromosomes that may have trans effects on the expression of genes on other chromosomes.
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Affiliation(s)
- Kiran Adhikari
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Jae Hak Son
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Anna H Rensink
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Jaweria Jaweria
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Daniel Bopp
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Leo W Beukeboom
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Richard P Meisel
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
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7
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Kozlowski DKL, Hassanaly‐Goulamhoussen R, Da Rocha M, Koutsovoulos GD, Bailly‐Bechet M, Danchin EGJ. Movements of transposable elements contribute to the genomic plasticity and species diversification in an asexually reproducing nematode pest. Evol Appl 2021; 14:1844-1866. [PMID: 34295368 PMCID: PMC8288018 DOI: 10.1111/eva.13246] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 12/14/2022] Open
Abstract
Despite reproducing without sexual recombination, Meloidogyne incognita is an adaptive and versatile phytoparasitic nematode. This species displays a global distribution, can parasitize a large range of plants, and can overcome plant resistance in a few generations. The mechanisms underlying this adaptability remain poorly known. At the whole-genome level, only a few single nucleotide variations have been observed across different geographical isolates with distinct ranges of compatible hosts. Exploring other factors possibly involved in genomic plasticity is thus important. Transposable elements (TEs), by their repetitive nature and mobility, can passively and actively impact the genome dynamics. This is particularly expected in polyploid hybrid genomes such as the one of M. incognita. Here, we have annotated the TE content of M. incognita, analyzed the statistical properties of this TE landscape, and used whole-genome pool-seq data to estimate the mobility of these TEs across twelve geographical isolates, presenting variations in ranges of compatible host plants. DNA transposons are more abundant than retrotransposons, and the high similarity of TE copies to their consensus sequences suggests they have been at least recently active. We have identified loci in the genome where the frequencies of presence of a TE showed substantial variations across the different isolates. Overall, variations in TE frequencies across isolates followed their phylogenetic divergence, suggesting TEs participate in the species diversification. Compared with the M. incognita reference genome, we detected isolate and lineage-specific de novo insertion of some TEs, including within genic regions or in the upstream regulatory regions. We validated by PCR the insertion of some of these TEs inside genic regions, confirming TE movements have possible functional impacts. Overall, we show DNA transposons can drive genomic plasticity in M. incognita and their role in genome evolution of other parthenogenetic animal deserves further investigation.
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8
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Meirmans PG. Niche divergence contributes to geographical parthenogenesis in two dandelion taxa. J Evol Biol 2021; 34:1071-1086. [PMID: 33955626 PMCID: PMC8362108 DOI: 10.1111/jeb.13794] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 03/29/2021] [Accepted: 04/25/2021] [Indexed: 12/11/2022]
Abstract
Many sexual-asexual complexes show a distinct pattern where the asexuals have larger and more northerly ranges than closely related sexuals. A prime candidate to explain this so-called "geographical parthenogenesis" is ecological niche divergence between the sexuals and asexuals. Modern niche modelling techniques allow testing niche divergence by directly comparing the niches of sexuals and asexuals. In this study, I use such techniques to perform range-wide tests of whether nine bioclimatic variables, including annual mean temperature and annual precipitation, contribute to geographical parthenogenesis in two dandelion taxa: Taraxacum section Ruderalia and Taraxacum section Erythrosperma, which are both comprised of sexual diploids and asexual triploids. For both sections, I found evidence of niche divergence, though the exact nature of this divergence was different for the two sections. In section Ruderalia, the sexuals preferred warmer and wetter conditions, whereas in section Erythrosperma, the sexuals preferred dryer conditions. Using Species Distribution Modelling, consistent differences between the sexuals and asexuals were found when looking at the niche determinants: the variables that are most important for modelling the distribution. Furthermore, and in contrast with theoretical expectations that predict that the sexuals should have a wider niche, in section Erythrosperma the asexuals were found to have a wider niche than the sexuals. In conclusion, differences in niche optima, niche determinants, and niche width all contribute to the pattern of geographical parthenogenesis of these two dandelion taxa. However, the results also indicate that the exact causation of geographical parthenogenesis is not uniform across taxa.
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Affiliation(s)
- Patrick G Meirmans
- Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Amsterdam, The Netherlands
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9
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Brandeis M. Were eukaryotes made by sex?: Sex might have been vital for merging endosymbiont and host genomes giving rise to eukaryotes. Bioessays 2021; 43:e2000256. [PMID: 33860546 DOI: 10.1002/bies.202000256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 03/16/2021] [Accepted: 03/17/2021] [Indexed: 11/10/2022]
Abstract
I hypothesize that the appearance of sex facilitated the merging of the endosymbiont and host genomes during early eukaryote evolution. Eukaryotes were formed by symbiosis between a bacterium that entered an archaeon, eventually giving rise to mitochondria. This entry was followed by the gradual transfer of most bacterial endosymbiont genes into the archaeal host genome. I argue that the merging of the mitochondrial genes into the host genome was vital for the evolution of genuine eukaryotes. At the time this process commenced it was unprecedented and required a novel mechanism. I suggest that this mechanism was meiotic sex, and that its appearance might have been THE crucial step that enabled the evolution of proper eukaryotes from early endosymbiont containing proto-eukaryotes. Sex might continue to be essential today for keeping genome insertions in check. Also see the video abstract here: https://youtu.be/aVMvWMpomac.
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Affiliation(s)
- Michael Brandeis
- The Department of Genetics, The Hebrew University of Jerusalem, Jerusalem, Israel
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10
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Einfeldt AL, Kess T, Messmer A, Duffy S, Wringe BF, Fisher J, den Heyer C, Bradbury IR, Ruzzante DE, Bentzen P. Chromosome level reference of Atlantic halibut Hippoglossus hippoglossus provides insight into the evolution of sexual determination systems. Mol Ecol Resour 2021; 21:1686-1696. [PMID: 33655659 DOI: 10.1111/1755-0998.13369] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 02/24/2021] [Indexed: 12/22/2022]
Abstract
Changes in the genetic mechanisms that control sexual determination have occurred independently across the tree of life, and with exceptional frequency in teleost fishes. To investigate the genomic changes underlying the evolution of sexual determination, we sequenced a chromosome-level genome, multitissue transcriptomes, and reduced representation population data for the Atlantic halibut (Hippoglossus hippoglossus), which has an XY/XX sex determination mechanism and has recently diverged (0.9-3.8 Ma) from the Pacific halibut (Hippoglossus stenolepis), which has a ZZ/ZW system. We used frequency and coverage-based population approaches to identify a putative sex-determining factor, GSDF. We characterized regions with elevated heterozygosity and linkage disequilibrium indicating suppression of recombination across a nascent sex chromosome. We detected testis-specific expression of GSDF, the sequence of which is highly conserved across flatfishes. Based on evidence from genome-wide association, coverage, linkage disequilibrium, testis and brain transcriptomes, and sequence conservation with other flatfishes, we propose a mechanism for the recent evolution of an XY sex-determination mechanism in Atlantic halibut. Changes to the ancestral sex-determining gene DMRT1 in regulating the downstream gene GSDF probably coincided with GSDF, or a proximal regulatory element of it, becoming the primary sex-determining factor. Our results suggest changes to a small number of elements can have drastic repercussions for the genomic substrate available to sex-specific evolutionary forces, providing insight into how certain elements repeatedly evolve to control sex across taxa. Our chromosome-level assembly, multitissue transcriptomes, and population genomic data provide a valuable resource and understanding of the evolution of sexual systems in fishes.
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Affiliation(s)
| | - Tony Kess
- Fisheries and Oceans Canada, Dartmouth, NS, Canada
| | | | - Steven Duffy
- Fisheries and Oceans Canada, St. John's, NL, Canada
| | | | - Jonathan Fisher
- Fisheries and Marine Institute of Memorial University, St. John's, NL, Canada
| | | | | | | | - Paul Bentzen
- Biology Department, Dalhousie University, Halifax, NS, Canada
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11
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Liegeois M, Sartori M, Schwander T. Extremely Widespread Parthenogenesis and a Trade-Off Between Alternative Forms of Reproduction in Mayflies (Ephemeroptera). J Hered 2021; 112:45-57. [PMID: 32918457 PMCID: PMC7953839 DOI: 10.1093/jhered/esaa027] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/28/2020] [Indexed: 11/14/2022] Open
Abstract
Studying alternative forms of reproduction in natural populations is of fundamental importance for understanding the costs and benefits of sex. Mayflies are one of the few animal groups where sexual reproduction co-occurs with different types of parthenogenesis, providing ideal conditions for identifying benefits of sex in natural populations. Here, we establish a catalog of all known mayfly species capable of reproducing by parthenogenesis, as well as species unable to do so. Overall, 1.8% of the described species reproduce parthenogenetically, which is an order of magnitude higher than reported in other animal groups. This frequency even reaches 47.8% if estimates are based on the number of studied rather than described mayfly species, as reproductive modes have thus far been studied in only 17 out of 42 families. We find that sex is a more successful strategy than parthenogenesis (associated with a higher hatching success of eggs), with a trade-off between the hatching success of parthenogenetic and sexual eggs. This means that improving the capacity for parthenogenesis may come at a cost for sexual reproduction. Such a trade-off can help explain why facultative parthenogenesis is extremely rare among animals despite its potential to combine the benefits of sexual and parthenogenetic reproduction. We argue that parthenogenesis is frequently selected in mayflies in spite of this probable trade-off because their typically low dispersal ability and short and fragile adult life may frequently generate situations of mate limitation in females. Mayflies are currently clearly underappreciated for understanding the benefits of sex under natural conditions.
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Affiliation(s)
- Maud Liegeois
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Cantonal Museum of Zoology, Palais de Rumine, Place de la Riponne, Lausanne, Switzerland
| | - Michel Sartori
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Cantonal Museum of Zoology, Palais de Rumine, Place de la Riponne, Lausanne, Switzerland
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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13
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Abstract
Organisms across the tree of life have complex life cycles that include both sexual and asexual reproduction or that are obligately asexual. These organisms include ecologically dominant species that structure many terrestrial and marine ecosystems, as well as many pathogens, pests, and invasive species. We must consider both the evolution and maintenance of these various reproductive modes and how these modes shape the genetic diversity, adaptive evolution, and ability to persist in the species that exhibit them. Thus, having a common framework is a key aspect of understanding the biodiversity that shapes our planet. In the 2019 AGA President's Symposium, Sex and Asex: The genetics of complex life cycles, researchers investigating a wide range of taxonomic models and using a variety of modes of investigation coalesced around a common theme-understanding not only how such complex life cycles may evolve, but how they are shaped by the evolutionary and ecological forces around them. In this introduction to the Special Issue from the symposium, we give an overview of some of the key ideas and areas of investigation (a common clonal lexicon, we might say) and introduce the breadth of work submitted by symposium participants.
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Affiliation(s)
- Maria E Orive
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045
| | - Stacy A Krueger-Hadfield
- Department of Biology, University of Alabama, Birmingham, 1300 University Blvd., Birmingham, AL 35294
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14
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Rushworth CA, Brandvain Y, Mitchell‐Olds T. Identifying the fitness consequences of sex in complex natural environments. Evol Lett 2020; 4:516-529. [PMID: 33312687 PMCID: PMC7719549 DOI: 10.1002/evl3.194] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/14/2020] [Accepted: 08/24/2020] [Indexed: 02/06/2023] Open
Abstract
In the natural world, sex prevails, despite its costs. Although much effort has been dedicated to identifying the intrinsic costs of sex (e.g., the cost of males), few studies have identified the ecological fitness consequences of sex. Furthermore, correlated biological traits that differ between sexuals and asexuals may alter these costs, or even render the typical costs of sex irrelevant. We conducted a large-scale, multisite, reciprocal transplant using multiple sexual and asexual genotypes of a native North American wildflower to show that sexual genotypes have reduced lifetime fitness, despite lower herbivory. We separated the effects of sex from those of hybridity, finding that overwinter survival is elevated in asexuals regardless of hybridity, but herbivores target hybrid asexuals more than nonhybrid asexual or sexual genotypes. Survival is lowest in homozygous sexual lineages, implicating inbreeding depression as a cost of sex. Our results show that the consequences of sex are shaped not just by sex itself, but by complex natural environments, correlated traits, and the identity and availability of mates.
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Affiliation(s)
- Catherine A. Rushworth
- Department of Evolution and EcologyUniversity of California, DavisDavisCalifornia95616
- University and Jepson HerbariaUniversity of California, BerkeleyBerkeleyCalifornia94720
- Department of Plant and Microbial BiologyUniversity of MinnesotaSt. PaulMinnesota55108
- Department of BiologyDuke UniversityDurhamNorth Carolina27708
| | - Yaniv Brandvain
- Department of Plant and Microbial BiologyUniversity of MinnesotaSt. PaulMinnesota55108
| | - Tom Mitchell‐Olds
- Department of BiologyDuke UniversityDurhamNorth Carolina27708
- Center for Genomic and Computational BiologyDuke UniversityDurhamNorth Carolina27708
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15
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Becheler R, Guillemin M, Stoeckel S, Mauger S, Saunier A, Brante A, Destombe C, Valero M. After a catastrophe, a little bit of sex is better than nothing: Genetic consequences of a major earthquake on asexual and sexual populations. Evol Appl 2020; 13:2086-2100. [PMID: 32908606 PMCID: PMC7463374 DOI: 10.1111/eva.12967] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/04/2020] [Accepted: 03/05/2020] [Indexed: 11/27/2022] Open
Abstract
Catastrophic events can have profound effects on the demography of a population and consequently on genetic diversity. The dynamics of postcatastrophic recovery and the role of sexual versus asexual reproduction in buffering the effects of massive perturbations remain poorly understood, in part because the opportunity to document genetic diversity before and after such events is rare. Six natural (purely sexual) and seven cultivated (mainly clonal due to farming practices) populations of the red alga Agarophyton chilense were surveyed along the Chilean coast before, in the days after and 2 years after the 8.8 magnitude earthquake in 2010. The genetic diversity of sexual populations appeared sensitive to this massive perturbation, notably through the loss of rare alleles immediately after the earthquake. By 2012, the levels of diversity returned to those observed before the catastrophe, probably due to migration. In contrast, enhanced rates of clonality in cultivated populations conferred a surprising ability to buffer the instantaneous loss of diversity. After the earthquake, farmers increased the already high rate of clonality to maintain the few surviving beds, but most of them collapsed rapidly. Contrasting fates between sexual and clonal populations suggest that betting on strict clonality to sustain production is risky, probably because this extreme strategy hampered adaptation to the brutal environmental perturbation induced by the catastrophe.
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Affiliation(s)
- Ronan Becheler
- Centro de Conservación MarinaDepartamento de EcologíaFacultad de Ciencias BiológicasPontificia Universidad Católica de ChileCasillaChile
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
| | - Marie‐Laure Guillemin
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
- Instituto de Ciencias Ambientales y EvolutivasFacultad de CienciasUniversidad Austral de ChileValdiviaChile
| | - Solenn Stoeckel
- UMR1349 Institute for Genetics, Environment and Plant ProtectionINRALe RheuFrance
| | - Stéphane Mauger
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
| | - Alice Saunier
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
- Instituto de Ciencias Ambientales y EvolutivasFacultad de CienciasUniversidad Austral de ChileValdiviaChile
| | - Antonio Brante
- Departamento de EcologíaFacultad de CienciasUniversidad Católica de la Santísima Concepción (UCSC)ConcepciónChile
- Centro de Investigación en Biodiversidad y Ambientes Sustentables (CIBAS)UCSCConcepciónChile
| | - Christophe Destombe
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
| | - Myriam Valero
- UMI 3614Evolutionary Biology and Ecology of AlgaeCNRSSorbonne UniversitéUniversidad Austral de ChilePontificia Universidad Católica de ChileRoscoffFrance
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16
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Jalinsky J, Logsdon JM, Neiman M. Male phenotypes in a female framework: Evidence for degeneration in sperm produced by male snails from asexual lineages. J Evol Biol 2020; 33:1050-1059. [PMID: 32304112 DOI: 10.1111/jeb.13632] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 03/21/2020] [Accepted: 04/02/2020] [Indexed: 01/14/2023]
Abstract
How changes in selective regimes affect trait evolution is an important open biological question. We take advantage of naturally occurring and repeated transitions from sexual to asexual reproduction in a New Zealand freshwater snail species, Potamopyrgus antipodarum, to address how evolution in an asexual context-including the potential for relaxed selection on male-specific traits-influences sperm morphology. The occasional production of male offspring by the otherwise all-female asexual P. antipodarum lineages affords a unique and powerful opportunity to assess the fate of sperm traits in a context where males are exceedingly rare. These comparisons revealed that the sperm produced by 'asexual' males are markedly distinct from sexual counterparts. We also found that the asexual male sperm harboured markedly higher phenotypic variation and was much more likely to be morphologically abnormal. Together, these data suggest that transitions to asexual reproduction might be irreversible, at least in part because male function is likely to be compromised. These results are also consistent with a scenario where relaxed selection and/or mutation accumulation in the absence of sex translates into rapid trait degeneration.
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Affiliation(s)
- Joseph Jalinsky
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - John M Logsdon
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Maurine Neiman
- Department of Biology, University of Iowa, Iowa City, IA, USA
- Department of Gender, Women's, and Sexuality Studies, University of Iowa, Iowa City, IA, USA
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17
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Cutter AD. Reproductive transitions in plants and animals: selfing syndrome, sexual selection and speciation. New Phytol 2019; 224:1080-1094. [PMID: 31336389 DOI: 10.1111/nph.16075] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/17/2019] [Indexed: 05/23/2023]
Abstract
The evolution of predominant self-fertilisation frequently coincides with the evolution of a collection of phenotypes that comprise the 'selfing syndrome', in both plants and animals. Genomic features also display a selfing syndrome. Selfing syndrome traits often involve changes to male and female reproductive characters that were subject to sexual selection and sexual conflict in the obligatorily outcrossing ancestor, including the gametic phase for both plants and animals. Rapid evolution of reproductive traits, due to both relaxed selection and directional selection under the new status of predominant selfing, lays the genetic groundwork for reproductive isolation. Consequently, shifts in sexual selection pressures coupled to transitions to selfing provide a powerful paradigm for investigating the speciation process. Plant and animal studies, however, emphasise distinct selective forces influencing reproductive-mode transitions: genetic transmission advantage to selfing or reproductive assurance outweighing the costs of inbreeding depression vs the costs of males and meiosis. Here, I synthesise links between sexual selection, evolution of selfing and speciation, with particular focus on identifying commonalities and differences between plant and animal systems and pointing to areas warranting further synergy.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
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18
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Bast J, Jaron KS, Schuseil D, Roze D, Schwander T. Asexual reproduction reduces transposable element load in experimental yeast populations. eLife 2019; 8:48548. [PMID: 31486772 PMCID: PMC6783261 DOI: 10.7554/elife.48548] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 09/04/2019] [Indexed: 01/04/2023] Open
Abstract
Theory predicts that sexual reproduction can either facilitate or restrain transposable element (TE) accumulation by providing TEs with a means of spreading to all individuals in a population, versus facilitating TE load reduction via purifying selection. By quantifying genomic TE loads over time in experimental sexual and asexual Saccharomyces cerevisiae populations, we provide direct evidence that TE loads decrease rapidly under asexual reproduction. We show, using simulations, that this reduction may occur via evolution of TE activity, most likely via increased excision rates. Thus, sex is a major driver of genomic TE loads and at the root of the success of TEs. The genetic information of most living organisms contains parasitic invaders known as transposable elements. These genetic sequences multiply by copying and pasting themselves through the genome, but this process can disrupt the activity of important genes and put the organism at risk. How transposable elements proliferate in a population depends on the way organisms reproduce. If they simply clone themselves asexually, the selfish elements cannot spread between the different clones. If the organisms mate together their respective transposable elements get mixed, which helps the sequences to spread more easily and to potentially become more virulent. However, sexual reproduction also comes with mechanisms that keep transposable elements in check. Bast, Jaron et al. took advantage of the fact that yeasts can reproduce with or without mating to explore whether sexual or asexual organisms are better at controlling the spread of transposable elements. The number of copies of transposable elements in the genomes of yeast grown sexually or asexually was assessed. The results showed that sexual populations kept constant numbers of selfish elements, while asexual organisms lost these genomic parasites over time. Simulations then revealed that this difference emerged because a defense gene that helps to delete transposable elements was spreading more quickly in the asexual group. The work by Bast, Jaron et al. therefore suggests that sex is responsible for the evolutionary success of transposable elements, while asexual populations can discard these sequences over time. Sex therefore helps genetic parasites, somewhat similar to sexually transmitted diseases, to spread between individuals and remain virulent.
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Affiliation(s)
- Jens Bast
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Kamil S Jaron
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Donovan Schuseil
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Denis Roze
- UMI3614 Evolutionary Biology and Ecology of Alga, Centre National de la Recherche Scientifique (CNRS), Roscoff, France.,Station Biologique de Roscoff, Sorbonne Université, Roscoff, France
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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19
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Moore JS, Benestan L. Let's talk about sex: A rigorous statistical framework to assign the sex of individuals from reduced-representation sequencing data. Mol Ecol Resour 2019; 18:191-193. [PMID: 29575750 DOI: 10.1111/1755-0998.12761] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 01/22/2018] [Accepted: 01/24/2018] [Indexed: 12/19/2022]
Abstract
Molecular markers have been used to identify the sex of sampled individuals for several decades, but the time-consuming development phase prevented their application in many systems. Recently, a growing number of papers have applied reduced-representation sequencing (RRS) protocols to the identification of sex-specific markers without the use of test crosses or prior genomic information. While such an approach has great advantages in terms of versatility and ease of use, the "shotgun sequencing" nature of RRS data sets leads to a high amount of missing data, which results in statistical challenges to the confident assignment of sex to individuals. In this issue of Molecular Ecology Resources, Stovall et al. (Molecular Ecology Resources, 18, 2018) provide a statistical framework to answer two questions: (1) how many individuals of one sex only must possess a genotype for this locus to be considered significantly sex-specific? and (2) How many sex-specific loci must an individual of unknown sex possess (in a given data set) to be confidently assigned a sex? The statistical pipeline introduced, and applied to samples of New Zealand fur seal (Arctocephalus forsteri) to identify 90 sex-specific loci, should be broadly applicable to a large number of species and constitutes a nice addition to the molecular ecology toolkit in the genomics era.
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Affiliation(s)
- Jean-Sébastien Moore
- Institut de Biologie Intégrative et des Systèmes, Département de Biologie, Université Laval, Québec, QC, Canada
| | - Laura Benestan
- Institut de Biologie Intégrative et des Systèmes, Département de Biologie, Université Laval, Québec, QC, Canada
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20
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Abstract
The cumulative reproductive cost of multi-locus selection has been considered to be a potentially limiting factor on the rate of adaptive evolution. In this paper, we show that Haldane's arguments for the accumulation of reproductive costs over multiple loci are valid only for a clonally reproducing population of asexual genotypes. We show that a sexually reproducing population avoids this accumulation of costs. Thus, sex removes a perceived reproductive constraint on the rate of adaptive evolution. The significance of our results is twofold. First, the results demonstrate that adaptation based on multiple genes-such as selection acting on the standing genetic variation-does not entail a huge reproductive cost as suggested by Haldane, provided of course that the population is reproducing sexually. Second, this reduction in the cost of natural selection provides a simple biological explanation for the advantage of sex. Specifically, Haldane's calculations illustrate the evolutionary disadvantage of asexuality; sexual reproduction frees the population from this disadvantage.
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Affiliation(s)
- Donal A Hickey
- Department of Biology, Concordia University, 7141 Sherbrooke West, Montreal, QC H4B 1R6, Canada
| | - G Brian Golding
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada
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21
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Morgan-Richards M, Langton-Myers SS, Trewick SA. Loss and gain of sexual reproduction in the same stick insect. Mol Ecol 2019; 28:3929-3941. [PMID: 31386772 PMCID: PMC6852293 DOI: 10.1111/mec.15203] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 06/17/2019] [Accepted: 07/30/2019] [Indexed: 01/10/2023]
Abstract
The outcome of competition between different reproductive strategies within a single species can be used to infer selective advantage of the winning strategy. Where multiple populations have independently lost or gained sexual reproduction it is possible to investigate whether the advantage is contingent on local conditions. In the New Zealand stick insect Clitarchus hookeri, three populations are distinguished by recent change in reproductive strategy and we determine their likely origins. One parthenogenetic population has established in the United Kingdom and we provide evidence that sexual reproduction has been lost in this population. We identify the sexual population from which the parthenogenetic population was derived, but show that the UK females have a post‐mating barrier to fertilisation. We also demonstrate that two sexual populations have recently arisen in New Zealand within the natural range of the mtDNA lineage that otherwise characterizes parthenogenesis in this species. We infer independent origins of males at these two locations using microsatellite genotypes. In one population, a mixture of local and nonlocal alleles suggested males were the result of invasion. Males in another population were most probably the result of loss of an X chromosome that produced a male phenotype in situ. Two successful switches in reproductive strategy suggest local competitive advantage for outcrossing over parthenogenetic reproduction. Clitarchus hookeri provides remarkable evidence of repeated and rapid changes in reproductive strategy, with competitive outcomes dependent on local conditions.
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Affiliation(s)
| | | | - Steven A Trewick
- Wildlife & Ecology, Massey University, Palmerston North, New Zealand
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22
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Decaestecker E, Bulteel L. Parasites opt for the best of both worlds. eLife 2019; 8:49615. [PMID: 31368888 PMCID: PMC6675540 DOI: 10.7554/elife.49615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 07/30/2019] [Indexed: 11/27/2022] Open
Abstract
The fungal parasite Podosphaera plantaginis employs both sexual and asexual reproduction to increase its chances of infecting the plant Plantago lanceolata.
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Affiliation(s)
- Ellen Decaestecker
- Department of Biology, Katholieke Universiteit Leuven Kulak, Kortrijk, Belgium
| | - Lore Bulteel
- Department of Biology, Katholieke Universiteit Leuven Kulak, Kortrijk, Belgium
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23
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Laine AL, Barrès B, Numminen E, Siren JP. Variable opportunities for outcrossing result in hotspots of novel genetic variation in a pathogen metapopulation. eLife 2019; 8:47091. [PMID: 31210640 PMCID: PMC6667214 DOI: 10.7554/elife.47091] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 06/18/2019] [Indexed: 11/17/2022] Open
Abstract
Many pathogens possess the capacity for sex through outcrossing, despite being able to reproduce also asexually and/or via selfing. Given that sex is assumed to come at a cost, these mixed reproductive strategies typical of pathogens have remained puzzling. While the ecological and evolutionary benefits of outcrossing are theoretically well-supported, support for such benefits in pathogen populations are still scarce. Here, we analyze the epidemiology and genetic structure of natural populations of an obligate fungal pathogen, Podosphaera plantaginis. We find that the opportunities for outcrossing vary spatially. Populations supporting high levels of coinfection –a prerequisite of sex – result in hotspots of novel genetic diversity. Pathogen populations supporting coinfection also have a higher probability of surviving winter. Jointly our results show that outcrossing has direct epidemiological consequences as well as a major impact on pathogen population genetic diversity, thereby providing evidence of ecological and evolutionary benefits of outcrossing in pathogens. The existence of sex – broadly defined as the coming together of genes from different individuals – is one of the big evolutionary puzzles. Reproduction allows an organism to pass on its genes to future generations. However, while asexual and self-fertilizing individuals transmit all of their genes to their offspring, individuals that reproduce through sex transmit only half of their genome. This is considered the cost of sex. Many pathogens reproduce through sex, despite often also being able to reproduce asexually or by self-fertilization. Typically a pre-requisite of sex in pathogens is for at least two different strains to infect the same host. Aside from this limitation, little is known about when, where and why pathogens have sex. It has been tricky to study due to the microscopic size of pathogens and the difficulties of identifying different sexes. Moreover, sexual reproduction may be triggered by environmental cues that are difficult to mimic under controlled experimental conditions. Are there any benefits associated with pathogen sex? To find out, Laine et al. analyzed data collected over the course of four years from thousands of populations of a powdery mildew fungus that infected plants across the Åland islands. This revealed that the opportunities for pathogen sex vary in different locations. Areas where multiple strains of the fungus commonly infect the same plants result in hotspots of new genetic diversity. These mixed populations are also more likely to survive winter. This demonstrates the potential for pathogen sexual reproduction to provide an ecological benefit. Identifying areas and populations where pathogens have sex can help to identify when and where new strains are most likely to emerge. In the future, studies that use similar methods to Laine et al. could help to predict where infections and diseases are highly likely to arise.
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Affiliation(s)
- Anna-Liisa Laine
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland.,Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse, Switzerland
| | - Benoit Barrès
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland
| | - Elina Numminen
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland
| | - Jukka P Siren
- Research Centre for Ecological Change, Organismal and Evolutionary Biology, University of Helsinki, Helsinki, Finland.,Helsinki Institute for Information Technology, Department of Computer Science, Aalto University, Espoo, Finland
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24
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Wang S, Veller C, Sun F, Ruiz-Herrera A, Shang Y, Liu H, Zickler D, Chen Z, Kleckner N, Zhang L. Per-Nucleus Crossover Covariation and Implications for Evolution. Cell 2019; 177:326-338.e16. [PMID: 30879787 PMCID: PMC6472931 DOI: 10.1016/j.cell.2019.02.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 12/17/2018] [Accepted: 02/13/2019] [Indexed: 12/25/2022]
Abstract
Crossing over is a nearly universal feature of sexual reproduction. Here, analysis of crossover numbers on a per-chromosome and per-nucleus basis reveals a fundamental, evolutionarily conserved feature of meiosis: within individual nuclei, crossover frequencies covary across different chromosomes. This effect results from per-nucleus covariation of chromosome axis lengths. Crossovers can promote evolutionary adaptation. However, the benefit of creating favorable new allelic combinations must outweigh the cost of disrupting existing favorable combinations. Covariation concomitantly increases the frequencies of gametes with especially high, or especially low, numbers of crossovers, and thus might concomitantly enhance the benefits of crossing over while reducing its costs. A four-locus population genetic model suggests that such an effect can pertain in situations where the environment fluctuates: hyper-crossover gametes are advantageous when the environment changes while hypo-crossover gametes are advantageous in periods of environmental stasis. These findings reveal a new feature of the basic meiotic program and suggest a possible adaptive advantage.
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Affiliation(s)
- Shunxin Wang
- Center for Reproductive Medicine, Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China.
| | - Carl Veller
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA; Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA
| | - Fei Sun
- School of Medicine, Institute of Reproductive Medicine, Nantong University, Nantong, Jiangsu, China
| | - Aurora Ruiz-Herrera
- Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina (IBB), Universitat Autònoma de Barcelona (UAB), Barcelona, Spain; Departament de Biologia Cellular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
| | - Yongliang Shang
- Center for Reproductive Medicine, Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China
| | - Hongbin Liu
- Center for Reproductive Medicine, Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China
| | - Denise Zickler
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette Cedex 91198, France
| | - Zijiang Chen
- Center for Reproductive Medicine, Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China
| | - Nancy Kleckner
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
| | - Liangran Zhang
- Center for Reproductive Medicine, Shandong University, National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Key Laboratory of Reproductive Endocrinology of Ministry of Education, Jinan, Shandong 250001, China; Advanced Medical Research Institute, Shandong University, Jinan, Shandong 250014, China; State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China.
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25
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Abstract
When trying to find a mate, one might think about using a dating app. Imagine that someone else has installed the same app and tries to access the same potential mates that you have chosen, and that this someone uses false facts about himself/herself to increase the chance of dating someone before you or anyone else with honest status information does. Sounds familiar? It actually is, and in no way is such comportment restricted to human courtship behaviour. Alternative reproductive tactics (ARTs) are widespread in the animal kingdom. In this issue of Molecular Ecology, Cardoso, Gonçalves, Goesmann, Canário, and Oliveira () investigate plastic ARTs of the peacock blenny (Salaria pavo), in which males occur in three morphs: nestholders, sneakers and transitionals between the two former. They apply transcriptome sequencing to answer the question how brain gene expression contributes to sex role-specific behaviour and to intersex phenotypes.
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Affiliation(s)
- Astrid Böhne
- Zoological Institute, University of Basel, Basel, Switzerland
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26
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Abstract
Bacterial gene transfer agents (GTAs) are small virus-like particles that package DNA fragments and inject them into cells. They are encoded by gene clusters resembling defective prophages, with genes for capsid head and tail components. These gene clusters are usually assumed to be maintained by selection for the benefits of GTA-mediated recombination, but this has never been tested. We rigorously examined the potential benefits of GTA-mediated recombination, considering separately transmission of GTA-encoding genes and recombination of all chromosomal genes. In principle GTA genes could be directly maintained if GTA particles spread them to GTA- cells often enough to compensate for the loss of GTA-producing cells. However, careful bookkeeping showed that losses inevitably exceed gains for two reasons. First, cells must lyse to release particles to the environment. Second, GTA genes are not preferentially replicated before DNA is packaged. A simulation model was then used to search for conditions where recombination of chromosomal genes makes GTA+ populations fitter than GTA- populations. Although the model showed that both synergistic epistasis and some modes of regulation could generate fitness benefits large enough to overcome the cost of lysis, these benefits neither allowed GTA+ cells to invade GTA- populations, nor allowed GTA+ populations to resist invasion by GTA- cells. Importantly, the benefits depended on highly improbable assumptions about the efficiencies of GTA production and recombination. Thus, the selective benefits that maintain GTA gene clusters over many millions of years must arise from consequences other than transfer of GTA genes or recombination of chromosomal genes.
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Affiliation(s)
- Rosemary J Redfield
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Shannon M Soucy
- Department of Biological Sciences, Dartmouth College, Hanover, NH, United States
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27
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Tibayrenc M, Ayala F. Hybridization in Trypanosoma congolense does not challenge the predominant clonal evolution model. A comment on Tihon et al., 2017, Mol. Ecol. Mol Ecol 2018; 27:3421-3424. [PMID: 30146716 DOI: 10.1111/mec.14714] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 04/17/2018] [Accepted: 04/19/2018] [Indexed: 11/28/2022]
Abstract
Tihon et al. have just published in Mol. Ecol. a fine genomic study on Trypanosoma congolense, agent of Animal African Trypanosomiasis. They present very convincing evidence that T. congolense underwent several hybridization events between distinct genetic lines in Zambia. They claim that their data challenge our predominant clonal evolution model (PCE) of micropathogens. We point out the main tenets of our model and show that Tihon et al.'s claim is based on a misinterpretation of the PCE model. Actually, their data strongly support PCE in T. congolense at a microevolutionary level.
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Affiliation(s)
- Michel Tibayrenc
- Maladies Infectieuses et Vecteurs Ecologie, Génétique, Evolution et Contrôle, MIVEGEC (IRD 224-CNRS 5290-UM1-UM2), Institut de recherché pour le développement, Montpellier, France
| | - Francisco Ayala
- Department of Ecology and Evolutionary Biology, University of California at Irvine, Irvine, California
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28
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Micheletti SJ, Narum SR. Utility of pooled sequencing for association mapping in nonmodel organisms. Mol Ecol Resour 2018; 18:825-837. [PMID: 29633534 DOI: 10.1111/1755-0998.12784] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 03/14/2018] [Accepted: 03/15/2018] [Indexed: 11/30/2022]
Abstract
High-density genome-wide sequencing increases the likelihood of discovering genes of major effect and genomic structural variation in organisms. While there is an increasing availability of reference genomes across broad taxa, the greatest limitation to whole-genome sequencing of multiple individuals continues to be the costs associated with sequencing. To alleviate excessive costs, pooling multiple individuals with similar phenotypes and sequencing the homogenized DNA (Pool-Seq) can achieve high genome coverage, but at the loss of individual genotypes. Although Pool-Seq has been an effective method for association mapping in model organisms, it has not been frequently utilized in natural populations. To extend bioinformatic tools for rapid implementation of Pool-Seq data in nonmodel organisms, we developed a pipeline called PoolParty and illustrate its effectiveness in genetic association mapping. Alignment expectations based on five pooled Chinook salmon (Oncorhynchus tshawytscha) libraries showed that approximately 48% genome coverage per library could be achieved with reasonable sequencing effort. We additionally examined male and female O. tshawytscha libraries to illustrate how Pool-Seq techniques can successfully map known genes associated with functional differences among sexes such as growth hormone 2. Finally, we compared pools of individuals of different spawning ages for each sex to discover novel genes involved with age at maturity in O. tshawytscha such as opsin4 and transmembrane protein19. While not appropriate for every system, Pool-Seq data processed by the PoolParty pipeline is a practical method for identifying genes of major effect in nonmodel organisms when high genome coverage is necessary and cost is a limiting factor.
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Affiliation(s)
- Steven J Micheletti
- Columbia River Inter-Tribal Fish Commission, Hagerman Fish Culture Experiment Station, Hagerman, Idaho
| | - Shawn R Narum
- Columbia River Inter-Tribal Fish Commission, Hagerman Fish Culture Experiment Station, Hagerman, Idaho
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29
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Abstract
Why is sex ubiquitous when asexual reproduction is much less costly? Sex disrupts coadapted gene complexes; it also causes costs associated with mate finding and the production of males who do not themselves bear offspring. Theory predicts parasites select for host sex, because genetically variable offspring can escape infection from parasites adapted to infect the previous generations. We examine this using a facultative sexual crustacean, Daphnia magna, and its sterilizing bacterial parasite, Pasteuria ramosa. We obtained sexually and asexually produced offspring from wild-caught hosts and exposed them to contemporary parasites or parasites isolated from the same population one year later. We found rapid parasite adaptation to replicate within asexual but not sexual offspring. Moreover, sexually produced offspring were twice as resistant to infection as asexuals when exposed to parasites that had coevolved alongside their parents (i.e. the year two parasite). This fulfils the requirement that the benefits of sex must be both large and rapid for sex to be favoured by selection.
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Affiliation(s)
- Stuart K J R Auld
- Division of Biological and Environmental Sciences, University of Stirling, Room 3B164, Cottrell Building, Stirling, Stirlingshire FK9 4LA, UK
| | - Shona K Tinkler
- Division of Biological and Environmental Sciences, University of Stirling, Room 3B164, Cottrell Building, Stirling, Stirlingshire FK9 4LA, UK
| | - Matthew C Tinsley
- Division of Biological and Environmental Sciences, University of Stirling, Room 3B164, Cottrell Building, Stirling, Stirlingshire FK9 4LA, UK
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30
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Pesce D, Lehman N, de Visser JAGM. Sex in a test tube: testing the benefits of in vitro recombination. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0529. [PMID: 27619693 DOI: 10.1098/rstb.2015.0529] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2016] [Indexed: 01/06/2023] Open
Abstract
The origin and evolution of sex, and the associated role of recombination, present a major problem in biology. Sex typically involves recombination of closely related DNA or RNA sequences, which is fundamentally a random process that creates but also breaks up beneficial allele combinations. Directed evolution experiments, which combine in vitro mutation and recombination protocols with in vitro or in vivo selection, have proved to be an effective approach for improving functionality of nucleic acids and enzymes. As this approach allows extreme control over evolutionary conditions and parameters, it also facilitates the detection of small or position-specific recombination benefits and benefits associated with recombination between highly divergent genotypes. Yet, in vitro approaches have been largely exploratory and motivated by obtaining improved end products rather than testing hypotheses of recombination benefits. Here, we review the various experimental systems and approaches used by in vitro studies of recombination, discuss what they say about the evolutionary role of recombination, and sketch their potential for addressing extant questions about the evolutionary role of sex and recombination, in particular on complex fitness landscapes. We also review recent insights into the role of 'extracellular recombination' during the origin of life.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.
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Affiliation(s)
- Diego Pesce
- Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands
| | - Niles Lehman
- Department of Chemistry, Portland State University, Portland, OR 97207, USA
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31
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Abstract
Several species of asexuals appear to have existed for millions of years. This is despite the prevalent view that natural selection is weakened without gene exchange, which should cause these organisms to rapidly go extinct. In theory, one can identify evolutionary long-lived asexuals from their allelic sequence divergence, also known as the 'Meselson effect', which leads to elevated within-individual diversity. Yet evidence that this phenomenon exists is mixed. Furthermore, several confounding factors can lead to similar outcomes, including the formation of asexual species by hybridization. Disentangling these factors has proved to be tricky, but Ament-Velásquez et al. (2016) have provided an elegant solution in this issue of Molecular Ecology. They studied transcriptomes and mitochondrial DNA from the Lineus genus of nemertean worms, which contains both sexual and asexual types, to first show that the asexual L. pseudolactus is a hybrid between a sexual and an asexual species. After isolating out diversity arising from this hybridization, they find subsequent evidence for the Meselson effect. This study sets a new standard for differentiating between the complex causes and consequences of asexuality.
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Affiliation(s)
- Matthew Hartfield
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada M5S 3B2.,Bioinformatics Research Centre, University of Aarhus, 8000C, Aarhus, Denmark
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32
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Levitis DA, Zimmerman K, Pringle A. Is meiosis a fundamental cause of inviability among sexual and asexual plants and animals? Proc Biol Sci 2017; 284:20170939. [PMID: 28768890 PMCID: PMC5563809 DOI: 10.1098/rspb.2017.0939] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 06/23/2017] [Indexed: 11/12/2022] Open
Abstract
Differences in viability between asexually and sexually generated offspring strongly influence the selective advantage and therefore the prevalence of sexual reproduction (sex). However, no general principle predicts when sexual offspring will be more viable than asexual offspring. We hypothesize that when any kind of reproduction is based on a more complex cellular process, it will encompass more potential failure points, and therefore lower offspring viability. Asexual reproduction (asex) can be simpler than sex, when offspring are generated using only mitosis. However, when asex includes meiosis and meiotic restitution, gamete production is more complex than in sex. We test our hypothesis by comparing the viability of asexual and closely related sexual offspring across a wide range of plants and animals, and demonstrate that meiotic asex does result in lower viability than sex; without meiosis, asex is mechanistically simple and provides higher viability than sex. This phylogenetically robust pattern is supported in 42 of 44 comparisons drawn from diverse plants and animals, and is not explained by the other variables included in our model. Other mechanisms may impact viability, such as effects of reproductive mode on heterozygosity and subsequent viability, but we propose the complexity of cellular processes of reproduction, particularly meiosis, as a fundamental cause of early developmental failure and mortality. Meiosis, the leading cause of inviability in humans, emerges as a likely explanation of offspring inviability among diverse eukaryotes.
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Affiliation(s)
- Daniel A Levitis
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Biology, Bates College, Lewiston, ME 04240, USA
| | - Kolea Zimmerman
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
- Ginkgo Bioworks, 25-27 Drydock Avenue 8th Floor, Boston, MA 02210, USA
| | - Anne Pringle
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
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33
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Abstract
This study examines the dynamics of a competition and a host-parasite model in which the interactions are determined by quantitative characters. Both models are extensions of one-dimensional difference equations that can exhibit complicated dynamics. Compared to these basic models, the phenotypic variability given by the quantitative characters reduces the size of the density fluctuations in asexual populations. With sexual reproduction, which is described by modeling the genetics of the quantitative character explicitly with many haploid loci that determine the character additively, this reduction in fitness variance is magnified. Moreover, quantitative genetics can induce simple dynamics. For example, the sexual population can have a two-cycle when the asexual system is chaotic. This paper discusses the consequences for the evolution of sex. The higher mean growth rate implied by the lower fitness variance in sexual populations is an advantage that can overcome a twofold intrinsic growth rate of asexuals. The advantage is bigger when the asexual population contains only a subset of the phenotypes present in the sexual population, which conforms with the tangled bank theory for the evolution of sex and shows that tangled bank effects also occur in host-parasite systems. The results suggest that explicitly describing the genetics of a quantitative character leads to more flexible models than the usual assumption of normal character distributions, and therefore to a better understanding of the character's impact on population dynamics.
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Affiliation(s)
- Michael Doebeli
- Zoology Institute, University of Basel, Rheinsprung 9, CH-4051, Basel, Switzerland
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34
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Bell G. THE ECOLOGY AND GENETICS OF FITNESS IN CHLAMYDOMONAS. IV. THE PROPERTIES OF MIXTURES OF GENOTYPES OF THE SAME SPECIES. Evolution 2017; 45:1036-1046. [PMID: 28564047 DOI: 10.1111/j.1558-5646.1991.tb04368.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/1990] [Accepted: 11/29/1990] [Indexed: 11/29/2022]
Abstract
The properties of mixtures of genotypes of Chlamydomonas reinhardtii were investigated by growing them in monoculture and in all possible pairwise combinations in chemically defined axenic medium. Two sets of genotypes produced by crossing wild-type isolates were cultured in each of two physical environments. Mixtures were consistently more productive and less variable over environments than were their constituent monocultures. The average performance of a genotype in mixture was tightly correlated with its performance in monoculture. Reisolation of spores from mixtures at the end of growth showed that the mixtures became dominated by the component with the greater performance in monoculture, so that the properties of mixtures were attributable to replacement rather than to complementation. These results differ from those of similar trials using a range of different species of Chlamydomonas, where genetic interactions were found to be important. They are discussed in relation to theories of diversity and diversification, and related to the agronomic use of crop mixtures.
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Affiliation(s)
- Graham Bell
- Department of Biology, McGill University, Montreal, Quebec, H3A 1B1, CANADA
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35
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Normark BB. PHYLOGENY AND EVOLUTION OF PARTHENOGENETIC WEEVILS OF THE ARAMIGUS TESSELLATUS SPECIES COMPLEX (COLEOPTERA: CURCULIONIDAE: NAUPACTINI): EVIDENCE FROM MITOCHONDRIAL DNA SEQUENCES. Evolution 2017; 50:734-745. [PMID: 28568943 DOI: 10.1111/j.1558-5646.1996.tb03883.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/1994] [Accepted: 05/03/1995] [Indexed: 11/30/2022]
Abstract
Molecular-phylogenetic studies of parthenogenetic animals have been a valuable recent addition to the literature on the evolutionary biology of sex. By illuminating the origins and ages of parthenogenetic lineages, such studies can help to define the temporal scale at which selection acts against parthenogenetic lineages, as well as provide an essential framework for further study. Although parthenogenetic weevils have played an important role in cytogenetic and protein-electrophoretic studies of parthenogenesis, they have not previously been subjects of DNA-based molecular-phylogenetic study. A mitochondrial DNA study of Aramigus tessellatus, a species complex of weevils native to South America, indentified 12 distinct (1-9% divergent) maternal lineages, of which 2 represent sexual populations, while at least 9 represent parthenogenetic lineages. These lineages partially correspond to lineages previously recognized by morphological differences. Phylogenetic analysis found 14 most parsimonious trees, according to which parthenogenesis appears to have arisen 3-7 times. There is a monophyletic group of lineages (the "brown clade"), having up to 4.5% sequence divergence within it, which may be primitively parthenogenetic and over 2 million years old.
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Affiliation(s)
- Benjamin B Normark
- Section of Ecology and Systematics, Cornell University, Ithaca, New York, 14853
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36
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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37
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Abstract
Over four decades ago, John Maynard Smith showed that a mutation causing asexual reproduction should rapidly spread in a dioecious sexual population. His reasoning was that the per‐capita birth rate of an asexual population would exceed that of a sexual population, because asexual females do not invest in sons. Hence, there is a cost of sexual reproduction that Maynard Smith called the “cost of males.” Assuming all else is otherwise equal among sexual and asexual females, the cost is expected to be two‐fold in outcrossing populations with separate sexes and equal sex ratios. Maynard Smith's model led to one of the most interesting questions in evolutionary biology: why is there sex? There are, however, no direct estimates of the proposed cost of sex. Here, we measured the increase in frequency of asexual snails in natural, mixed population of sexual and asexual snails in large outdoor mesocosms. We then extended Maynard Smith's model to predict the change in frequency of asexuals for any cost of sex and for any initial frequency of asexuals. Consistent with the “all‐else equal” assumption, we found that the increase in frequency of asexual snails closely matched that predicted under a two‐fold cost.
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Affiliation(s)
- Amanda K Gibson
- Department of Biology, Indiana University; 1001 E 3 Street; Bloomington, IN 47405, USA.,Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Lynda F Delph
- Department of Biology, Indiana University; 1001 E 3 Street; Bloomington, IN 47405, USA
| | - Curtis M Lively
- Department of Biology, Indiana University; 1001 E 3 Street; Bloomington, IN 47405, USA
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38
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Pinello JF, Lai AL, Millet JK, Cassidy-Hanley D, Freed JH, Clark TG. Structure-Function Studies Link Class II Viral Fusogens with the Ancestral Gamete Fusion Protein HAP2. Curr Biol 2017; 27:651-60. [PMID: 28238660 DOI: 10.1016/j.cub.2017.01.049] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 12/31/2016] [Accepted: 01/24/2017] [Indexed: 11/24/2022]
Abstract
The conserved transmembrane protein, HAP2/GCS1, has been linked to fertility in a wide range of taxa and is hypothesized to be an ancient gamete fusogen. Using template-based structural homology modeling, we now show that the ectodomain of HAP2 orthologs from Tetrahymena thermophila and other species adopt a protein fold remarkably similar to the dengue virus E glycoprotein and related class II viral fusogens. To test the functional significance of this predicted structure, we developed a flow-cytometry-based assay that measures cytosolic exchange across the conjugation junction to rapidly probe the effects of HAP2 mutations in the Tetrahymena system. Using this assay, alterations to a region in and around a predicted "fusion loop" in T. thermophila HAP2 were found to abrogate membrane pore formation in mating cells. Consistent with this, a synthetic peptide corresponding to the HAP2 fusion loop was found to interact directly with model membranes in a variety of biophysical assays. These results raise interesting questions regarding the evolutionary relationships of class II membrane fusogens and harken back to a long-held argument that eukaryotic sex arose as the byproduct of selection for the horizontal transfer of a "selfish" genetic element from cell to cell via membrane fusion.
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39
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Luijckx P, Ho EK, Gasim M, Chen S, Stanic A, Yanchus C, Kim YS, Agrawal AF. Higher rates of sex evolve during adaptation to more complex environments. Proc Natl Acad Sci U S A 2017; 114:534-9. [PMID: 28053226 DOI: 10.1073/pnas.1604072114] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A leading hypothesis for the evolutionary maintenance of sexual reproduction proposes that sex is advantageous because it facilitates adaptation. Changes in the environment stimulate adaptation but not all changes are equivalent; a change may occur along one or multiple environmental dimensions. In two evolution experiments with the facultatively sexual rotifer Brachionus calyciflorus, we test how environmental complexity affects the evolution of sex by adapting replicate populations to various environments that differ from the original along one, two, or three environmental dimensions. Three different estimates of fitness (growth, lifetime reproduction, and population density) confirmed that populations adapted to their new environment. Growth measures revealed an intriguing cost of complex adaptations: populations that adapted to more complex environments lost greater amounts of fitness in the original environment. Furthermore, both experiments showed that B. calyciflorus became more sexual when adapting to a greater number of environmental dimensions. Common garden experiments confirmed that observed changes in sex were heritable. As environments in nature are inherently complex these findings help explain why sex is maintained in natural populations.
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40
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Romiguier J, Fournier A, Yek SH, Keller L. Convergent evolution of social hybridogenesis in Messor harvester ants. Mol Ecol 2016; 26:1108-1117. [PMID: 27813203 DOI: 10.1111/mec.13899] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 09/26/2016] [Accepted: 10/12/2016] [Indexed: 12/14/2022]
Abstract
Sexual reproduction generally requires no more than two partners. Here, we show convergent evolution of social hybridogenesis, a reproductive system requiring three reproductive partners in harvester ants. In this unorthodox reproductive system, two distinct genetic lineages live in sympatry and queens have to mate with males of their own lineage to produce queens along with males of the alternative lineage to produce workers. Using a large transcriptomic data set of nine species, we show that social hybridogenesis evolved at least three times independently in the genus Messor. Moreover, a study of 13 populations of Messor barbarus revealed that this mode of reproduction is fixed in the whole range of this ecologically dominant species. Finally, we show that workers can produce males carrying genes of the two genetic lineages, raising the possibility of rare gene flow between lineages contributing to the long-term maintenance of pairs of interdependent lineages. These results emphasize the evolutionary importance of social hybridogenesis, a major transition possibly linked to the peculiar ecology of harvester ants.
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Affiliation(s)
- Jonathan Romiguier
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
| | - Axel Fournier
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
| | - Sze Huei Yek
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
| | - Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, 1015, Lausanne, Switzerland
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41
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Abstract
Theory predicts that sexual reproduction is difficult to maintain if asexuality is an option, yet sex is very common. To understand why, it is important to pay attention to repeatably occurring conditions that favour transitions to, or persistence of, asexuality. Geographic parthenogenesis is a term that has been applied to describe a large variety of patterns where sexual and related asexual forms differ in their geographic distribution. Often asexuality is stated to occur in a habitat that is, in some sense, marginal, but the interpretation differs across studies: parthenogens might not only predominate near the margin of the sexuals' distribution, but might also extend far beyond the sexual range; they may be disproportionately found in newly colonizable areas (e.g. areas previously glaciated), or in habitats where abiotic selection pressures are relatively stronger than biotic ones (e.g. cold, dry). Here, we review the various patterns proposed in the literature, the hypotheses put forward to explain them, and the assumptions they rely on. Surprisingly, few mathematical models consider geographic parthenogenesis as their focal question, but all models for the evolution of sex could be evaluated in this framework if the (often ecological) causal factors vary predictably with geography. We also recommend broadening the taxa studied beyond the traditional favourites.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.
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Affiliation(s)
- Anaïs Tilquin
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland Centre of Excellence in Biological Interactions, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Hanna Kokko
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland Centre of Excellence in Biological Interactions, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
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42
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Abstract
We review the phenomenon of condition-dependent sex-where individuals' condition affects the likelihood that they will reproduce sexually rather than asexually. In recent years, condition-dependent sex has been studied both theoretically and empirically. Empirical results in microbes, fungi and plants support the theoretical prediction that negative condition-dependent sex, in which individuals in poor condition are more likely to reproduce sexually, can be evolutionarily advantageous under a wide range of settings. Here, we review the evidence for condition-dependent sex and its potential implications for the long-term survival and adaptability of populations. We conclude by asking why condition-dependent sex is not more commonly observed, and by considering generalizations of condition-dependent sex that might apply even for obligate sexuals.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.
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Affiliation(s)
- Yoav Ram
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Lilach Hadany
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 6997801, Israel
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43
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Abstract
Facultative sex combines sexual and asexual reproduction in the same individual (or clone) and allows for a large diversity of life-history patterns regarding the timing, frequency and intensity of sexual episodes. In addition, other life-history traits such as a diapause stage may become linked to sex. Here, we develop a matrix modelling framework for addressing the cost of sex in facultative sexuals, in constant, periodic and stochastically fluctuating environments. The model is parametrized using life-history data from Brachionus calyciflorus, a facultative sexual rotifer in which sex and diapause are linked. Sexual propensity was an important driver of costs in constant environments, in which high costs (always > onefold, and sometimes > twofold) indicated that asexuals should outcompete facultative sexuals. By contrast, stochastic environments with high temporal autocorrelation favoured facultative sex over obligate asex, in particular, if the penalty to fecundity in 'bad' environments was large. In such environments, obligate asexuals were constrained by their life cycle length (i.e. time from birth to last reproductive adult age class), which determined an upper limit to the number of consecutive bad periods they could tolerate. Nevertheless, when facultative asexuals with different sexual propensities competed simultaneously against each other and asex, the lowest sex propensity was the most successful in stochastic environments with positive autocorrelation. Our results suggest that a highly specific mechanism (i.e. diapause linked to sex) can alone stabilize facultative sex in these animals, and protect it from invasion of both asexual and pure sexual strategies.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.
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Affiliation(s)
- Claus-Peter Stelzer
- Research Institute for Limnology, University of Innsbruck, 5310 Mondsee, Austria
| | - Jussi Lehtonen
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia
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44
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Gibson AK, Xu JY, Lively CM. Within-population covariation between sexual reproduction and susceptibility to local parasites. Evolution 2016; 70:2049-60. [PMID: 27402345 DOI: 10.1111/evo.13001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 06/08/2016] [Accepted: 06/16/2016] [Indexed: 01/30/2023]
Abstract
Evolutionary biology has yet to reconcile the ubiquity of sex with its costs relative to asexual reproduction. Here, we test the hypothesis that coevolving parasites maintain sex in their hosts. Specifically, we examined the distributions of sexual reproduction and susceptibility to local parasites within a single population of freshwater snails (Potamopyrgus antipodarum). Susceptibility to local trematode parasites (Microphallus sp.) is a relative measure of the strength of coevolutionary selection in this system. Thus, if coevolving parasites maintain sex, sexual snails should be common where susceptibility is high. We tested this prediction in a mixed population of sexual and asexual snails by measuring the susceptibility of snails from multiple sites in a lake. Consistent with the prediction, the frequency of sexual snails was tightly and positively correlated with susceptibility to local parasites. Strikingly, in just two years, asexual females increased in frequency at sites where susceptibility declined. We also found that the frequency of sexual females covaries more strongly with susceptibility than with the prevalence of Microphallus infection in the field. In linking susceptibility to the frequency of sexual hosts, our results directly implicate spatial variation in coevolutionary selection in driving the geographic mosaic of sex.
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Affiliation(s)
- Amanda K Gibson
- Department of Biology, Indiana University, Bloomington, Indiana, 47405.
| | - Julie Y Xu
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| | - Curtis M Lively
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
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Lavanchy G, Strehler M, Llanos Roman MN, Lessard-Therrien M, Humbert JY, Dumas Z, Jalvingh K, Ghali K, Fontcuberta García-Cuenca A, Zijlstra B, Arlettaz R, Schwander T. Habitat heterogeneity favors asexual reproduction in natural populations of grassthrips. Evolution 2016; 70:1780-90. [PMID: 27346066 PMCID: PMC5129508 DOI: 10.1111/evo.12990] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 05/23/2016] [Accepted: 06/05/2016] [Indexed: 01/23/2023]
Abstract
Explaining the overwhelming success of sex among eukaryotes is difficult given the obvious costs of sex relative to asexuality. Different studies have shown that sex can provide benefits in spatially heterogeneous environments under specific conditions, but whether spatial heterogeneity commonly contributes to the maintenance of sex in natural populations remains unknown. We experimentally manipulated habitat heterogeneity for sexual and asexual thrips lineages in natural populations and under seminatural mesocosm conditions by varying the number of hostplants available to these herbivorous insects. Asexual lineages rapidly replaced the sexual ones, independently of the level of habitat heterogeneity in mesocosms. In natural populations, the success of sexual thrips decreased with increasing habitat heterogeneity, with sexual thrips apparently only persisting in certain types of hostplant communities. Our results illustrate how genetic diversity-based mechanisms can favor asexuality instead of sex when sexual lineages co-occur with genetically variable asexual lineages.
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Affiliation(s)
- Guillaume Lavanchy
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland.
| | - Marie Strehler
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland
| | - Maria Noemi Llanos Roman
- Graduate School-Doctoral program in Biomedical Sciences, National University of Trujillo, Trujillo, Peru
| | - Malie Lessard-Therrien
- Institute of Ecology and Evolution, University of Bern, Baltzerstrasse, Bern, Switzerland
| | - Jean-Yves Humbert
- Institute of Ecology and Evolution, University of Bern, Baltzerstrasse, Bern, Switzerland
| | - Zoé Dumas
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland
| | - Kirsten Jalvingh
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland
| | - Karim Ghali
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland
| | | | - Bart Zijlstra
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland
| | - Raphaël Arlettaz
- Institute of Ecology and Evolution, University of Bern, Baltzerstrasse, Bern, Switzerland
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Biophore, Lausanne, Switzerland
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Whitlock AO, Peck KM, Azevedo RB, Burch CL. An Evolving Genetic Architecture Interacts with Hill-Robertson Interference to Determine the Benefit of Sex. Genetics 2016; 203:923-36. [PMID: 27098911 DOI: 10.1534/genetics.116.186916] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Accepted: 04/06/2016] [Indexed: 02/05/2023] Open
Abstract
Sex is ubiquitous in the natural world, but the nature of its benefits remains controversial. Previous studies have suggested that a major advantage of sex is its ability to eliminate interference between selection on linked mutations, a phenomenon known as Hill-Robertson interference. However, those studies may have missed both important advantages and important disadvantages of sexual reproduction because they did not allow the distributions of mutational effects and interactions (i.e., the genetic architecture) to evolve. Here we investigate how Hill-Robertson interference interacts with an evolving genetic architecture to affect the evolutionary origin and maintenance of sex by simulating evolution in populations of artificial gene networks. We observed a long-term advantage of sex-equilibrium mean fitness of sexual populations exceeded that of asexual populations-that did not depend on population size. We also observed a short-term advantage of sex-sexual modifier mutations readily invaded asexual populations-that increased with population size, as was observed in previous studies. We show that the long- and short-term advantages of sex were both determined by differences between sexual and asexual populations in the evolutionary dynamics of two properties of the genetic architecture: the deleterious mutation rate ([Formula: see text]) and recombination load ([Formula: see text]). These differences resulted from a combination of selection to minimize [Formula: see text] which is experienced only by sexuals, and Hill-Robertson interference experienced primarily by asexuals. In contrast to the previous studies, in which Hill-Robertson interference had only a direct impact on the fitness advantages of sex, the impact of Hill-Robertson interference in our simulations was mediated additionally by an indirect impact on the efficiency with which selection acted to reduce [Formula: see text].
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Herron MD. Origins of multicellular complexity: Volvox and the volvocine algae. Mol Ecol 2016; 25:1213-23. [PMID: 26822195 DOI: 10.1111/mec.13551] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 12/21/2015] [Accepted: 12/26/2015] [Indexed: 11/28/2022]
Abstract
The collection of evolutionary transformations known as the 'major transitions' or 'transitions in individuality' resulted in changes in the units of evolution and in the hierarchical structure of cellular life. Volvox and related algae have become an important model system for the major transition from unicellular to multicellular life, which touches on several fundamental questions in evolutionary biology. The Third International Volvox Conference was held at the University of Cambridge in August 2015 to discuss recent advances in the biology and evolution of this group of algae. Here, I highlight the benefits of integrating phylogenetic comparative methods and experimental evolution with detailed studies of developmental genetics in a model system with substantial genetic and genomic resources. I summarize recent research on Volvox and its relatives and comment on its implications for the genomic changes underlying major evolutionary transitions, evolution and development of complex traits, evolution of sex and sexes, evolution of cellular differentiation and the biophysics of motility. Finally, I outline challenges and suggest future directions for research into the biology and evolution of the volvocine algae.
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Affiliation(s)
- Matthew D Herron
- Division of Biological Sciences, University of Montana, 32 Campus Dr., Missoula, MT, 59812, USA
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48
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Abstract
Transposable elements (TEs) and other repetitive DNA can accumulate in the absence of recombination, a process contributing to the degeneration of Y-chromosomes and other nonrecombining genome portions. A similar accumulation of repetitive DNA is expected for asexually reproducing species, given their entire genome is effectively nonrecombining. We tested this expectation by comparing the whole-genome TE loads of five asexual arthropod lineages and their sexual relatives, including asexual and sexual lineages of crustaceans (Daphnia water fleas), insects (Leptopilina wasps), and mites (Oribatida). Surprisingly, there was no evidence for increased TE load in genomes of asexual as compared to sexual lineages, neither for all classes of repetitive elements combined nor for specific TE families. Our study therefore suggests that nonrecombining genomes do not accumulate TEs like nonrecombining genomic regions of sexual lineages. Even if a slight but undetected increase of TEs were caused by asexual reproduction, it appears to be negligible compared to variance between species caused by processes unrelated to reproductive mode. It remains to be determined if molecular mechanisms underlying genome regulation in asexuals hamper TE activity. Alternatively, the differences in TE dynamics between nonrecombining genomes in asexual lineages versus nonrecombining genome portions in sexual species might stem from selection for benign TEs in asexual lineages because of the lack of genetic conflict between TEs and their hosts and/or because asexual lineages may only arise from sexual ancestors with particularly low TE loads.
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Affiliation(s)
- Jens Bast
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Ina Schaefer
- J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Goettingen, Goettingen, Germany
| | - Tanja Schwander
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Mark Maraun
- J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Goettingen, Goettingen, Germany
| | - Stefan Scheu
- J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Goettingen, Goettingen, Germany
| | - Ken Kraaijeveld
- Department of Ecological Science, VU University Amsterdam, Amsterdam, The Netherlands Leiden Genome Technology Center, Department of Human genetics, Leiden University Medical Center, Leiden, The Netherlands
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Abstract
The high prevalence of sexual reproduction is considered a paradox mainly for two reasons. First, asexuals should enjoy various growth benefits because they seemingly rid themselves of the many inefficiencies of sexual reproduction-the so-called costs of sex. Second, there seems to be no lack of asexual origins because losses of sexual reproduction have been described in almost every larger eukaryotic taxon. Current attempts to resolve this paradox concentrate on a few hypotheses that provide universal benefits that would compensate for these costs and give sexual reproduction a net advantage. However, are new asexual lineages really those powerful invaders that could quickly displace their sexual ancestors? Research on the costs of sex indicates that sex is often stabilized by highly lineage-specific mechanisms. Two main categories can be distinguished. First are beneficial traits that evolved within a particular species and became tightly associated with sex (e.g., a mating system that involves sexual selection, or a sexual diapausing stage that allows survival through harsh periods). If such traits are absent in asexuals, simple growth efficiency considerations will not capture the fitness benefits gained by skipping sexual reproduction. Second, lineage-specific factors might prevent asexuals from reaching their full potential (e.g., dependence on fertilization in sperm-dependent parthenogens). Such observations suggest that the costs of sex are highly variable and often lower than theoretical considerations suggest. This has implications for the magnitude of universal benefits required to resolve the paradox of sex.
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50
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Young BW, Dean MD. To be, or not to be, related: how female guppies bias sperm usage. Mol Ecol 2015; 24:4039-41. [PMID: 26255978 DOI: 10.1111/mec.13272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 06/11/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Brent W Young
- Molecular and Computational Biology, University of Southern California, 1050 Childs Way, Los Angeles, 90089, CA, USA
| | - Matthew D Dean
- Molecular and Computational Biology, University of Southern California, 1050 Childs Way, Los Angeles, 90089, CA, USA
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