1
|
Mezhzherin SV, Morozov-Leonov SY, Rostovska OV. Nuclear gene introgressions in hybrid populations of water frog Pelophylax esculentus complex: geographical analysis of the phenomenon and its interpretation. Genetica 2024; 152:31-42. [PMID: 38361120 DOI: 10.1007/s10709-024-00203-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 01/31/2024] [Indexed: 02/17/2024]
Abstract
Reproduction of water frog hybrids Pelophylax esculentus (Pelophylax ridibundus x Pelophylax lessonae) is associated with hemiclonal reproduction and backcrossing. The hemiclonal mode of reproduction occurs within P. esculentus allodiploids. In this case, the unrecombined genome of one parental species is transmitted to the offspring after premeiotic elimination of the chromosome set of the second parental species. Usually, the chromosome set of P. lessonae is eliminated, and the altered genome of P. ridibundus is passed on to the progeny. The hemiclonal inheritance within diploid Pelophylax esculentus hybrids may be accompanied by certain aberrations of premeiotic elimination. As a result, the formation of P. ridibundus specimens with introgressions of the P. lessonae genetic material, or the formation of recombinant hybrids occurs, depending on which of the parental species backcrossing takes place. The aim of our study is to describe the aberration of premeiotic elimination within the water frog P. esculentus complex detected by the nuclear gene Ldh-B inheritance, with an attempt to find out the causes of this phenomenon. It has been established that aberrations of premeiotic elimination are widespread, but only within populations of water frog from the river system of Upper Dnieper within Ukraine. The highest level of introgression takes place in the water frog populations within Kiev metropolis under conditions of expressed anthropogenization, while the maximum frequency of recombinants was detected within populations from the basin of Desna River, that has preserved native ecosystems. It was demonstrated that the frequency of premeiotic aberrations does not correlate with the intensity of interspecific water frog hybridization. Populations with introgressions are more common than populations with recombinants, however, within the latter, the frequency of recombination events is higher. The primary factor of gametogenesis aberrations, most likely, is the genetic characteristics of the local populations of parental species, since unambiguous explanations of this phenomenon based on the action of environmental stress (pollution of water systems) are not obvious.
Collapse
Affiliation(s)
- Sergey V Mezhzherin
- Department of Evolutionary Genetic and Fundamentals of Systematics, I.I. Schmalhausen Institute of Zoology, B. Khmel'nitskogo Str., Kiev-30, 01601, Ukraine
| | - Svyatoslav Yu Morozov-Leonov
- Department of Evolutionary Genetic and Fundamentals of Systematics, I.I. Schmalhausen Institute of Zoology, B. Khmel'nitskogo Str., Kiev-30, 01601, Ukraine.
| | - Olga V Rostovska
- Department of Evolutionary Genetic and Fundamentals of Systematics, I.I. Schmalhausen Institute of Zoology, B. Khmel'nitskogo Str., Kiev-30, 01601, Ukraine
| |
Collapse
|
2
|
Janko K, Mikulíček P, Hobza R, Schlupp I. Sperm-dependent asexual species and their role in ecology and evolution. Ecol Evol 2023; 13:e10522. [PMID: 37780083 PMCID: PMC10534198 DOI: 10.1002/ece3.10522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 08/16/2023] [Accepted: 08/24/2023] [Indexed: 10/03/2023] Open
Abstract
Sexual reproduction is the primary mode of reproduction in eukaryotes, but some organisms have evolved deviations from classical sex and switched to asexuality. These asexual lineages have sometimes been viewed as evolutionary dead ends, but recent research has revealed their importance in many areas of general biology. Our review explores the understudied, yet important mechanisms by which sperm-dependent asexuals that produce non-recombined gametes but rely on their fertilization, can have a significant impact on the evolution of coexisting sexual species and ecosystems. These impacts are concentrated around three major fields. Firstly, sperm-dependent asexuals can potentially impact the gene pool of coexisting sexual species by either restricting their population sizes or by providing bridges for interspecific gene flow whose type and consequences substantially differ from gene flow mechanisms expected under sexual reproduction. Secondly, they may impact on sexuals' diversification rates either directly, by serving as stepping-stones in speciation, or indirectly, by promoting the formation of pre- and postzygotic reproduction barriers among nascent species. Thirdly, they can potentially impact on spatial distribution of species, via direct or indirect (apparent) types of competition and Allee effects. For each such mechanism, we provide empirical examples of how natural sperm-dependent asexuals impact the evolution of their sexual counterparts. In particular, we highlight that these broad effects may last beyond the tenure of the individual asexual lineages causing them, which challenges the traditional perception that asexual lineages are short-lived evolutionary dead ends and minor sideshows. Our review also proposes new research directions to incorporate the aforementioned impacts of sperm-dependent asexuals. These research directions will ultimately enhance our understanding of the evolution of genomes and biological interactions in general.
Collapse
Affiliation(s)
- Karel Janko
- Laboratory of Non‐Mendelian Evolution, Institute of Animal Physiology and GeneticsAcademy of Sciences of the Czech RepublicLiběchovCzech Republic
- Department of Biology and Ecology, Faculty of ScienceUniversity of OstravaOstravaCzech Republic
| | - Peter Mikulíček
- Department of Zoology, Faculty of Natural SciencesComenius University in BratislavaBratislavaSlovakia
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of BiophysicsAcademy of Sciences of the Czech RepublicBrnoCzech Republic
| | - Ingo Schlupp
- Department of BiologyUniversity of OklahomaOklahomaNormanUSA
- Department of BiologyInternational Stock Center for Livebearing FishesOklahomaNormanUSA
| |
Collapse
|
3
|
Weigand H, Cross Lopez de Llergo J, Frantz AC. Genomic basis for an informed conservation management of
Pelophylax
water frogs in Luxembourg. Ecol Evol 2022; 12:e8810. [PMID: 35432923 PMCID: PMC9001158 DOI: 10.1002/ece3.8810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 03/14/2022] [Accepted: 03/24/2022] [Indexed: 11/17/2022] Open
Abstract
Genetic identification methods have become increasingly important for species that are difficult to identify in the field. A case in point is Pelophylax water frogs. While their morphological determination is highly complex, they include species protected under EU law and some that are classified as invasive. Additionally, genetic data can provide insights into their complex breeding systems, which may or may not involve the reproductive dependency of one species on another. Here, we generate baseline data for water frog monitoring in Luxembourg. We applied a countrywide sampling approach and used SNPs generated by ddRAD sequencing to identify individuals and infer the breeding systems present in the country. We found Pelophylax lessonae and P. kl. esculentus throughout Luxembourg, mostly living in syntopy. In general, a reproductive dependency of P. kl. esculentus on P. lessonae (L‐E system) was revealed. Besides this general system, we detected triploid P. kl. esculentus in six ponds. This indicates a modified L‐E system with reproductive dependency of the triploids on the diploid P. kl. esculentus. The invasive P. cf. bedriagae was detected in three ponds in southern Luxembourg, with evidence for hybridization with native water frogs. In addition to the ddRAD data, we tested a simple genetic method for future monitoring based on the MND1 marker. It showed in almost all cases, an identical species identification as the ddRAD data and was successfully applied to DNA extracts from mouth swabs. Combining this method with our baseline data will enable informed choices for the protection of native water frog species in Luxembourg.
Collapse
Affiliation(s)
- Hannah Weigand
- Musée National d'Histoire Naturelle de Luxembourg Luxembourg City Luxembourg
- Fondation faune‐flore Luxembourg City Luxembourg
| | | | - Alain C. Frantz
- Musée National d'Histoire Naturelle de Luxembourg Luxembourg City Luxembourg
| |
Collapse
|
4
|
Capture and return of sexual genomes by hybridogenetic frogs provide clonal genome enrichment in a sexual species. Sci Rep 2021; 11:1633. [PMID: 33452404 PMCID: PMC7810977 DOI: 10.1038/s41598-021-81240-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 01/04/2021] [Indexed: 01/29/2023] Open
Abstract
Hybridogenesis is a reproductive tool for sexual parasitism. Hybridogenetic hybrids use gametes from their sexual host for their own reproduction, but sexual species gain no benefit from such matings as their genome is later eliminated. Here, we examine the presence of sexual parasitism in water frogs through crossing experiments and genome-wide data. We specifically focus on the famous Central-European populations where Pelophylax esculentus males (hybrids of P. ridibundus and P. lessonae) live with P. ridibundus. We identified a system where the hybrids commonly produce two types of clonal gametes (hybrid amphispermy). The haploid lessonae genome is clonally inherited from generation to generation and assures the maintenance of hybrids through a process, in which lessonae sperm fertilize P. ridibundus eggs. The haploid ridibundus genome in hybrids received from P. ridibundus a generation ago, is perpetuated as clonal ridibundus sperm and used to fertilize P. ridibundus eggs, yielding female P. ridibundus progeny. These results imply animal reproduction in which hybridogenetic taxa are not only sexual parasites, but also participate in the formation of a sexual taxon in a remarkable way. This occurs through a process by which sexual gametes are being captured, converted to clones, and returned to sexual populations in one generation.
Collapse
|
5
|
Dubey S, Maddalena T, Bonny L, Jeffries DL, Dufresnes C. Population genomics of an exceptional hybridogenetic system of Pelophylax water frogs. BMC Evol Biol 2019; 19:164. [PMID: 31382876 PMCID: PMC6683362 DOI: 10.1186/s12862-019-1482-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 07/16/2019] [Indexed: 12/20/2022] Open
Abstract
Background Hybridogenesis can represent the first stage towards hybrid speciation where the hybrid taxon eventually weans off its parental species. In hybridogenetic water frogs, the hybrid Pelophylax kl. esculentus (genomes RL) usually eliminates one genome from its germline and relies on its parental species P. lessonae (genomes LL) or P. ridibundus (genomes RR) to perpetuate in so-called L-E and R-E systems. But not exclusively: some all-hybrid populations (E-E system) bypass the need for their parental species and fulfill their sexual cycle via triploid hybrid frogs. Genetic surveys are essential to understand the great diversity of these hybridogenetic dynamics and their evolution. Here we conducted such study using RAD-sequencing on Pelophylax from southern Switzerland (Ticino), a geographically-isolated region featuring different assemblages of parental P. lessonae and hybrid P. kl. esculentus. Results We found two types of hybridogenetic systems in Ticino: an L-E system in northern populations and a presumably all-hybrid E-E system in the closely-related southern populations, where P. lessonae was not detected. In the latter, we did not find evidence for triploid individuals from the population genomic data, but identified a few P. ridibundus (RR) as offspring from interhybrid crosses (LR × LR). Conclusions Assuming P. lessonae is truly absent from southern Ticino, the putative maintenance of all-hybrid populations without triploid individuals would require an unusual lability of genome elimination, namely that P. kl. esculentus from both sexes are capable of producing gametes with either L or R genomes. This could be achieved by the co-existence of L- and R- eliminating lineages or by “hybrid amphigamy”, i. e. males and females producing sperm and eggs among which both genomes are represented. These hypotheses imply that polyploidy is not the exclusive evolutionary pathway for hybrids to become reproductively independent, and challenge the classical view that hybridogenetic taxa are necessarily sexual parasites. Electronic supplementary material The online version of this article (10.1186/s12862-019-1482-4) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Sylvain Dubey
- Hintermann & Weber SA, Avenue des Alpes 25, 1820, Montreux, Switzerland.,Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland.,Agrosustain SA, c/o Agroscope, Route de Duillier 60, 1260, Nyon, Switzerland
| | | | - Laura Bonny
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland
| | - Daniel L Jeffries
- Department of Ecology and Evolution, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland
| | | |
Collapse
|
6
|
Morozov-Leonov SY. Hemiclone Diversity in the Hybrid Form Pelophylax esculentus-ridibundus (Amphibia, Ranidae) from the Prypyat, Dnestr, and Southern Boug River Basins. CYTOL GENET+ 2019. [DOI: 10.3103/s0095452719010092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
7
|
Unmack PJ, Adams M, Bylemans J, Hardy CM, Hammer MP, Georges A. Perspectives on the clonal persistence of presumed 'ghost' genomes in unisexual or allopolyploid taxa arising via hybridization. Sci Rep 2019; 9:4730. [PMID: 30894575 PMCID: PMC6426837 DOI: 10.1038/s41598-019-40865-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 02/20/2019] [Indexed: 01/19/2023] Open
Abstract
Although hybridization between non-sibling species rarely results in viable or fertile offspring, it occasionally produces self-perpetuating or sexually-parasitic lineages in which ancestral genomes are inherited clonally and thus may persist as ‘ghost species’ after ancestor extinction. Ghost species have been detected in animals and plants, for polyploid and diploid organisms, and across clonal, semi-clonal, and even sexual reproductive modes. Here we use a detailed investigation of the evolutionary and taxonomic status of a newly-discovered, putative ghost lineage (HX) in the fish genus Hypseleotris to provide perspectives on several important issues not previously explored by other studies on ghost species, but relevant to ongoing discussions about their detection, conservation, and artificial re-creation. Our comprehensive genetic (allozymes, mtDNA) and genomic (SNPs) datasets successfully identified a threatened sexual population of HX in one tiny portion of the extensive distribution displayed by two hemi-clonal HX-containing lineages. We also discuss what confidence should be placed on any assertion that an ancestral species is actually extinct, and how to assess whether any putative sexual ancestor represents a pure remnant, as shown here, or a naturally-occurring resurrection via the crossing of compatible clones or hemi-clones.
Collapse
Affiliation(s)
- P J Unmack
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia.
| | - M Adams
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia.,Department of Biological Sciences, University of Adelaide, Adelaide, SA, 5005, Australia
| | - J Bylemans
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia
| | - C M Hardy
- CSIRO Land and Water, GPO Box 1700, Canberra, ACT, 2601, Australia
| | - M P Hammer
- Museum & Art Gallery of the Northern Territory, Darwin, Northern Territory, 0810, Australia
| | - A Georges
- Institute for Applied Ecology, University of Canberra, Canberra, ACT, 2601, Australia
| |
Collapse
|
8
|
Morozov-Leonov SY. Hemiclone diversity in the hybrid form Pelophylax esculentus-ridibundus (Amphibia, Ranidae) from the Tisa river drainage. CYTOL GENET+ 2017. [DOI: 10.3103/s0095452717060093] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
9
|
Hoffmann A, Plötner J, Pruvost NBM, Christiansen DG, Röthlisberger S, Choleva L, Mikulíček P, Cogălniceanu D, Sas-Kovács I, Shabanov D, Morozov-Leonov S, Reyer HU. Genetic diversity and distribution patterns of diploid and polyploid hybrid water frog populations (Pelophylax esculentus complex) across Europe. Mol Ecol 2015; 24:4371-91. [PMID: 26308154 DOI: 10.1111/mec.13325] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 07/09/2015] [Accepted: 07/10/2015] [Indexed: 11/29/2022]
Abstract
Polyploidization is a rare yet sometimes successful way for animals to rapidly create geno- and phenotypes that may colonize new habitats and quickly adapt to environmental changes. In this study, we use water frogs of the Pelophylax esculentus complex, comprising two species (Pelophylax lessonae, genotype LL; Pelophylax ridibundus, RR) and various diploid (LR) and triploid (LLR, LRR) hybrid forms, summarized as P. esculentus, as a model for studying recent hybridization and polyploidization in the context of speciation. Specifically, we compared the geographic distribution and genetic diversity of diploid and triploid hybrids across Europe to understand their origin, maintenance and potential role in hybrid speciation. We found that different hybrid and parental genotypes are not evenly distributed across Europe. Rather, their genetic diversity is structured by latitude and longitude and the presence/absence of parental species but not of triploids. Highest genetic diversity was observed in central and eastern Europe, the lowest in the northwestern parts of Europe. This gradient can be explained by the decrease in genetic diversity during postglacial expansion from southeastern glacial refuge areas. Genealogical relationships calculated on the basis of microsatellite data clearly indicate that hybrids are of multiple origin and include a huge variety of parental genomes. Water frogs in mixed-ploidy populations without any parental species (i.e. all-hybrid populations) can be viewed as evolutionary units that may be on their way towards hybrid speciation. Maintenance of such all-hybrid populations requires a continuous exchange of genomes between diploids and triploids, but scenarios for alternative evolutionary trajectories are discussed.
Collapse
Affiliation(s)
- Alexandra Hoffmann
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Jörg Plötner
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, Berlin, 10115, Germany
| | - Nicolas B M Pruvost
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Ditte G Christiansen
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Sandra Röthlisberger
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Lukáš Choleva
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, AS CR, v.v.i., Rumburská 89, Liběchov, 277 21, Czech Republic.,Department of Biology and Ecology, Faculty of Science, University of Ostrava, Chittussiho 10, Ostrava, 710 00, Czech Republic
| | - Peter Mikulíček
- Department of Zoology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynska dolina B-1, Bratislava, SK-84215, Slovak Republic
| | - Dan Cogălniceanu
- Faculty of Natural Sciences and Agricultural Sciences, University Ovidius Constanţa, Al. Universităţii 1, corp B, Constanţa, Romania
| | - István Sas-Kovács
- Department of Biology, Faculty of Sciences, University of Oradea, Universitatii str. 1, Oradea, 410087, Romania
| | - Dmitry Shabanov
- Karazin Kharkiv National University, Svobody sq 4, Kharkiv, 62077, Ukraine
| | - Svyatoslav Morozov-Leonov
- Department of Evolutionary Genetic Basics of Systematics, Schmalhausen Institute of Zoology, B. Khmelnitskogo st., 15 Kyiv-30, Kyiv, MSP UA-01601, Ukraine
| | - Heinz-Ulrich Reyer
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| |
Collapse
|
10
|
Radojičić JM, Krizmanić I, Kasapidis P, Zouros E. Extensive mitochondrial heteroplasmy in hybrid water frog (Pelophylax spp.) populations from Southeast Europe. Ecol Evol 2015; 5:4529-41. [PMID: 26668720 PMCID: PMC4670067 DOI: 10.1002/ece3.1692] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 08/05/2015] [Accepted: 08/12/2015] [Indexed: 11/30/2022] Open
Abstract
Water frogs of the genus Pelophylax (previous Rana) species have been much studied in Europe for their outstanding reproductive mechanism in which sympatric hybridization between genetically distinct parental species produces diverse genetic forms of viable hybrid animals. The most common hybrid is P. esculentus that carries the genomes of both parental species, P. ridibundus and P. lessonae, but usually transfers the whole genome of only one parent to its offsprings (hybridogenesis). The evolutionary cost of transfer of the intact genome and hence the hemiclonal reproduction is the depletion of heterozygosity in the hybrid populations. Pelophylax esculentus presents an excellent example of the long‐term sustained hybridization and hemiclonal reproduction in which the effects of the low genetic diversity are balanced through the novel mutations and periodic recombinations. In this study, we analyzed the mitochondrial (mt) and microsatellites DNA variations in hybrid Pelophylax populations from southern parts of the Pannonian Basin and a north–south transect of the Balkan Peninsula, which are home for a variety of Pelophylax genetic lineages. The mtDNA haplotypes found in this study corresponded to P. ridibundus and P. epeiroticus of the Balkan – Anatolian lineage (ridibundus–bedriagae) and to P. lessonae and a divergent lessonae haplotype of the lessonae lineage. The mtDNA genomes showed considerable intraspecific variation and geographic differentiation. The Balkan wide distributed P. ridibundus was found in all studied populations and its nuclear genome, along with either the lessonae or the endemic epeiroticus genome, in all hybrids. An unexpected finding was that the hybrid populations were invariably heteroplasmic, that is, they contained the mtDNA of both parental species. We discussed the possibility that such extensive heteroplasmy is a result of hybridization and it comes from regular leakage of the paternal mtDNA from a sperm of one species that fertilizes eggs of another. In this case, the mechanisms that protect the egg from heterospecific fertilization and further from the presence of sperm mtDNA could become compromised due to their differences and divergence at both, mitochondrial and nuclear DNA. The heteroplasmy once retained in the fertilized egg could be transmitted by hybrid backcrossing to the progeny and maintained in a population over generations. The role of interspecies and heteroplasmic hybrid animals due to their genomic diversity and better fitness compare to the parental species might be of the special importance in adaptations to miscellaneous and isolated environments at the Balkan Peninsula.
Collapse
Affiliation(s)
- Jelena M Radojičić
- Hellenic Centre for Marine Research Institute of Marine Biology, Biotechnology and Aquaculture Heraklion Greece ; Department of Biology University of Crete Heraklion Greece
| | - Imre Krizmanić
- Faculty of Biology Institute of Zoology University of Belgrade Belgrade Serbia
| | - Panagiotis Kasapidis
- Hellenic Centre for Marine Research Institute of Marine Biology, Biotechnology and Aquaculture Heraklion Greece
| | | |
Collapse
|
11
|
Pruvost NBM, Mikulíček P, Choleva L, Reyer HU. Contrasting reproductive strategies of triploid hybrid males in vertebrate mating systems. J Evol Biol 2015; 28:189-204. [PMID: 25411907 DOI: 10.1111/jeb.12556] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 11/17/2014] [Indexed: 11/26/2022]
Abstract
The scarcity of parthenogenetic vertebrates is often attributed to their 'inferior' mode of clonal reproduction, which restricts them to self-reproduce their own genotype lineage and leaves little evolutionary potential with regard to speciation and evolution of sexual reproduction. Here, we show that for some taxa, such uniformity does not hold. Using hybridogenetic water frogs (Pelophylax esculentus) as a model system, we demonstrate that triploid hybrid males from two geographic regions exhibit very different reproductive modes. With an integrative data set combining field studies, crossing experiments, flow cytometry and microsatellite analyses, we found that triploid hybrids from Central Europe are rare, occur in male sex only and form diploid gametes of a single clonal lineage. In contrast, triploid hybrids from north-western Europe are widespread, occur in both sexes and produce recombined haploid gametes. These differences translate into contrasting reproductive roles between regions. In Central Europe, triploid hybrid males sexually parasitize diploid hybrids and just perpetuate their own genotype--which is the usual pattern in parthenogens. In north-western Europe, on the other hand, the triploid males are gamete donors for diploid hybrids, thereby stabilizing the mixed 2n-3n hybrid populations. By demonstrating these contrasting roles in male reproduction, we draw attention to a new significant evolutionary potential for animals with nonsexual reproduction, namely reproductive plasticity.
Collapse
Affiliation(s)
- N B M Pruvost
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | | | | | | |
Collapse
|
12
|
Mikulíček P, Kautman M, Kautman J, Pruvost NBM. Mode of hybridogenesis and habitat preferences influence population composition of water frogs (Pelophylax esculentus
complex, Anura: Ranidae) in a region of sympatric occurrence (western Slovakia). J ZOOL SYST EVOL RES 2014. [DOI: 10.1111/jzs.12083] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Peter Mikulíček
- Department of Zoology; Faculty of Natural Sciences; Comenius University; Bratislava Slovak Republic
| | - Matej Kautman
- Department of Biology and Wildlife Diseases; Faculty of Veterinary Hygiene and Ecology; University of Veterinary and Pharmaceutical Sciences; Brno Czech Republic
| | - Ján Kautman
- Slovak National Museum; Museum of Natural History; Bratislava Slovak Republic
| | - Nicolas B. M. Pruvost
- Institute of Evolutionary Biology and Environmental Studies; University of Zurich; Zurich Switzerland
| |
Collapse
|
13
|
Bove P, Milazzo P, Barbuti R. The role of deleterious mutations in the stability of hybridogenetic water frog complexes. BMC Evol Biol 2014; 14:107. [PMID: 24885008 PMCID: PMC4037432 DOI: 10.1186/1471-2148-14-107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/09/2014] [Indexed: 11/11/2022] Open
Abstract
Background Some species of water frogs originated from hybridization between different species. Such hybrid populations have a particular reproduction system called hybridogenesis. In this paper we consider the two species Pelophylax ridibundus and Pelophylax lessonae, and their hybrids Pelophylax esculentus. P. lessonae and P. esculentus form stable complexes (L-E complexes) in which P. esculentus are hemiclonal. In L-E complexes all the transmitted genomes by P. esculentus carry deleterious mutations which are lethal in homozygosity. Results We analyze, by means of an individual based computational model, L-E complexes. The results of simulations based on the model show that, by eliminating deleterious mutations, L-E complexes collapse. In addition, simulations show that particular female preferences can contribute to the diffusion of deleterious mutations among all P. esculentus frogs. Finally, simulations show how L-E complexes react to the introduction of translocated P. ridibundus. Conclusions The conclusions are the following: (i) deleterious mutations (combined with sexual preferences) strongly contribute to the stability of L-E complexes; (ii) female sexual choice can contribute to the diffusion of deleterious mutations; and (iii) the introduction of P. ridibundus can destabilize L-E complexes.
Collapse
Affiliation(s)
| | | | - Roberto Barbuti
- Dipartimento di Informatica, Università di Pisa, Largo B, Pontecorvo, 3, 56127 Pisa, Italy.
| |
Collapse
|
14
|
Leuenberger J, Gander A, Schmidt BR, Perrin N. Are invasive marsh frogs (Pelophylax ridibundus) replacing the native P. lessonae/P. esculentus hybridogenetic complex in Western Europe? Genetic evidence from a field study. CONSERV GENET 2014. [DOI: 10.1007/s10592-014-0585-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
15
|
Mikulíček P, Kautman M, Demovič B, Janko K. When a clonal genome finds its way back to a sexual species: evidence from ongoing but rare introgression in the hybridogenetic water frog complex. J Evol Biol 2014; 27:628-42. [PMID: 26227900 DOI: 10.1111/jeb.12332] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 12/02/2013] [Accepted: 01/06/2014] [Indexed: 11/28/2022]
Abstract
Besides several exceptions, asexual metazoans are usually viewed as ephemeral sinks for genomes, which become 'frozen' in clonal lineages after their emergence from ancestral sexual species. Here, we investigated whether and at what rate the asexuals are able to introgress their genomes back into the parental sexual population, thus more or less importantly affecting the gene pools of sexual species. We focused on hybridogenetic hybrids of western Palaearctic water frogs (Pelophylax esculentus), which originate through hybridization between P. ridibundus and P. lessonae, but transmit only clonal ridibundus genome into their gametes. Although usually mating with P. lessonae, P. esculentus may upon mating with P. ridibundus or another hybrid produce sexually reproducing P. ridibundus offspring with the introgressed ex-clonal genome. We compared the rate of nuclear amplified fragment length polymorphism (AFLP) and mitochondrial introgression in two types of populations, that is, those where P. ridibundus occurs in isolation and those where it lives with the hybridogens. Although significant differentiation (Φpt) between sexual and clonal ridibundus genomes suggested limited gene flow between sexuals and hybridogens, a non-negligible (~5%) proportion of P. ridibundus bore introgressed mtDNA and AFLP markers. Whereas transfer of mtDNA was exclusively unidirectional, introgression of nuclear markers was bidirectional. The proportion of introgressed P. ridibundus was highest in syntopic populations with P. esculentus, proving an ongoing and site-specific interspecific genetic transfer mediated by hybridogenetic hybrids. It turns out that asexual hybrids are not just a sink for genes of sexual species, but may significantly influence the genetic architecture of their sexual counterparts.
Collapse
Affiliation(s)
- P Mikulíček
- Department of Zoology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic
| | - M Kautman
- Department of Zoology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic.,Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
| | - B Demovič
- Department of Zoology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic.,State Nature Conservancy of the Slovak Republic, Administration of the Protected Landscape Area White Carpathians, Nemšová, Slovak Republic
| | - K Janko
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic, Liběchov, Czech Republic.,Life Science Research Centre, Department of Biology and Ecology, Faculty of Natural Sciences, University of Ostrava, Ostrava, Czech Republic
| |
Collapse
|
16
|
Luquet E, Vorburger C, Hervant F, Joly P, Kaufmann B, Schmeller DS, Léna JP, Grolet O, Konecny L, Plénet S. Invasiveness of an introduced species: the role of hybridization and ecological constraints. Biol Invasions 2011. [DOI: 10.1007/s10530-011-0010-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
17
|
Christiansen DG, Reyer HU. Effects of geographic distance, sea barriers and habitat on the genetic structure and diversity of all-hybrid water frog populations. Heredity (Edinb) 2010; 106:25-36. [PMID: 20372185 DOI: 10.1038/hdy.2010.37] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The history of population size and migration patterns leaves its mark in the genetics of populations. We investigate the genetic structure of the edible frog, Pelophylax esculentus in the Danish archipelago and adjacent countries. This frog is of particular interest because it is a hybrid that, in this area, forms all-hybrid populations of diploid (LR) and triploid (LLR and LRR) genomotypes with no (or very few) adults of the parental species (LL and RR). This study is the first to cover the entire geographic range of Danish, Swedish and German all-hybrid populations, documenting their extent and providing a broad picture of their diversity of neutral genetic markers and genomotype proportions. With 18 microsatellite markers, we found that genetic diversity declines northwards in agreement with the glacial refuge and central-marginal hypotheses; however, populations on small and medium-sized islands are no less diverse than those on large islands and continental peninsulas. Isolation by distance exists across the archipelago with limited influence of fragmentation by brackish seawater. The extremely low genetic diversity in all-hybrid populations, compared with adjacent populations, may be responsible for the maintenance of their special breeding system. We also show large variation among ponds in proportions of LLR, LR and LRR genomotypes, but little geographic pattern in their distribution. Instead, we found relationships between the genomotype proportions and some of 15 habitat parameters monitored. Body size differences among LLR, LR and LRR further suggest ecological differences.
Collapse
Affiliation(s)
- D G Christiansen
- Ecology, Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
| | | |
Collapse
|
18
|
Christiansen DG, Reyer HU. FROM CLONAL TO SEXUAL HYBRIDS: GENETIC RECOMBINATION VIA TRIPLOIDS IN ALL-HYBRID POPULATIONS OF WATER FROGS. Evolution 2009; 63:1754-68. [DOI: 10.1111/j.1558-5646.2009.00673.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
19
|
Holsbeek G, Jooris R. Potential impact of genome exclusion by alien species in the hybridogenetic water frogs (Pelophylax esculentus complex). Biol Invasions 2009. [DOI: 10.1007/s10530-009-9427-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
20
|
Hotz H, Guex GD, Beerli P, Semlitsch RD, Pruvost NBM. Hemiclone diversity in the hybridogenetic frog Rana esculenta outside the area of clone formation: the view from protein electrophoresis. J ZOOL SYST EVOL RES 2007. [DOI: 10.1111/j.1439-0469.2007.00430.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
21
|
Som C, Reyer HU. Hemiclonal reproduction slows down the speed of Muller's ratchet in the hybridogenetic frog Rana esculenta. J Evol Biol 2007; 20:650-60. [PMID: 17305831 DOI: 10.1111/j.1420-9101.2006.01243.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rare recombination in otherwise asexually reproducing organisms is known to beneficially influence the fitness in small populations. In most of the investigated organisms, asexual and rare sexual generations with recombination follow each other sequentially. Here we present a case where clonal reproduction and rare recombination occur simultaneously in the same population. The hybridogenetic water frog Rana esculenta (E), a hybrid between R. lessonae (L) and R. ridibunda (R) produces gametes that only contain the unaltered maternal R part of their genome. New generations of R. esculenta usually arise from E x L matings. Intraspecific E x E matings produce mostly inviable offspring, but in rare cases, female R. ridibunda arise from such matings which are capable of recombination. In the absence of conspecific males, these R females have to mate with E males, which results in further R females, or with L males, which produces new E lineages. This indirect mechanism reintroduces recombination into the otherwise clonally transmitted R genomes in R. esculenta populations. In this study, we show through Monte Carlo simulations that, in most cases, it is sufficient that only between 1 % and 10 % of mixed water frog populations consist of R females to prevent or significantly reduce the fixation and accumulation of deleterious mutations.
Collapse
Affiliation(s)
- C Som
- Institute of Zoology, University of Zurich, Zurich, Switzerland
| | | |
Collapse
|
22
|
Male mating speed promote hybridization in the Rana lessonae–Rana esculenta waterfrog system. Behav Ecol Sociobiol 2006. [DOI: 10.1007/s00265-005-0148-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
23
|
Schmeller DS, Seitz A, Crivelli A, Veith M. Crossing species' range borders: interspecies gene exchange mediated by hybridogenesis. Proc Biol Sci 2005; 272:1625-31. [PMID: 16048778 PMCID: PMC1559833 DOI: 10.1098/rspb.2005.3129] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The distribution of species is limited by their ability to adapt to local environments. For adaptation by selection, genetic variability is crucial. As founder effects reduce genetic variability, extension of species' range borders is usually slow due to the reduced probability of successful colonization. However, the range limit might be extended by incorporating locally adapted genes. In western Palaearctic waterfrogs, interspecies hybrids show hemiclonal gametogenesis, are fertile and reproductively mimic one parental species. Genetic analysis, using allozyme loci, shows that they mediate gene exchange between the two parental species. Selection analysis provides evidence for local adaptation of single locus genotypes. This suggests that hybridogenesis presents a process which increases the number of neoform parental genotypes, exposing these to selection, and thereby revealing locally adapted genotypes which are essential for species range expansion.
Collapse
Affiliation(s)
- Dirk S Schmeller
- Department of Population Biology, Institute of Zoology, Johannes Gutenberg-University, Saarstrasse 21, 55099 Mainz, Germany.
| | | | | | | |
Collapse
|
24
|
Ficetola GF, Bernardi FD. Interspecific Social Interactions and Breeding Success of the Frog Rana latastei: A Field Study. Ethology 2005. [DOI: 10.1111/j.1439-0310.2005.01089.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
25
|
REYER H, WÄLTI M, BÄTTIG I, ALTWEGG R, HELLRIEGEL B. Low proportions of reproducing hemiclonal females increase the stability of a sexual parasite–host system (
Rana esculenta
,
R. lessonae
). J Anim Ecol 2004. [DOI: 10.1111/j.0021-8790.2004.00881.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- H.‐U. REYER
- Zoological Institute, University of Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, Switzerland
| | - M.‐O. WÄLTI
- Zoological Institute, University of Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, Switzerland
| | - I. BÄTTIG
- Zoological Institute, University of Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, Switzerland
| | - R. ALTWEGG
- Zoological Institute, University of Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, Switzerland
| | - B. HELLRIEGEL
- Zoological Institute, University of Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, Switzerland
| |
Collapse
|
26
|
Abstract
European water frogs are characterized by anthropic introductions and Rana ridibunda may be considered as an invasive species. As such translocations may result in introgression of exotic genes in native populations, i.e. genetic pollution, we studied genetic characteristics (on 11 allozymic loci) of natural versus introduced water frogs. Our study contributed to (1) disclose 3 genetic markers allowing the identification of exotic frogs; (2) quantify the proportion of exotic frogs found in natural populations; and (3) suggest how genetic pollution may arise in these frogs.
Collapse
Affiliation(s)
- Alain Pagano
- Laboratoire d'écologie animale, Université d'Angers, Campus Belle Beille, 49045 Angers, France.
| | | | | | | |
Collapse
|
27
|
Guex GD, Hotz H, Semlitsch RD. Deleterious alleles and differential viability in progeny of natural hemiclonal frogs. Evolution 2002; 56:1036-44. [PMID: 12093017 DOI: 10.1111/j.0014-3820.2002.tb01414.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Abstract.-Spontaneous deleterious mutations are expected to accumulate through Muller's ratchet in clonally reproducing organisms and may lead to their extinction. We study deleterious mutations and their effects in a system of European frogs. Rana esculenta (RL), natural hybrids R. ridibunda (RR) X R. lessonae (LL), reproduce hemiclonally; both sexes exclude the L genome in the germ line and produce unrecombined R gametes; hybridity is restored each generation by matings of RL with coexisting LL. Different allozyme-defined hybrid hemiclones (R genome haplotypes) are thought to have originated independently from primary hybridizations RR x LL. Natural matings between two hybrids usually lead to inviable RR tadpoles. This inviability is thought to result from unmasked deleterious alleles on the clonally transmitted R genomes. Most simply it reflects homozygosity for recessive deleterious alleles at particular loci; alternatively (consistent with absence of RR adults in multiclonal populations) it may reflect hemiclone-specific sets of incompletely recessive deleterious mutations that cumulatively cause inviability when two such genomes are combined. If inviability results from the former, progeny of two hybrids of different hemiclones, whether allopatric or coexisting, should be viable, because it is improbable that their R genomes share recessive deleterious alleles at the same set of loci; if inviability results from the latter, progeny of hybrids of different hemiclones should be inviable, especially when hybrid lineages are old. We tested these hypotheses in artificial crosses, using frogs from three regions: hemiclonal hybrids outside R. ridibunda's range from northern Switzerland (two abundant coexisting allozyme-defined hemiclones; estimated lineage age < or = 5,000 generations) and from Sicily, Italy (one hemiclone; estimated age > or = 25,000 generations) and R. ridibunda from Poland. We generated RR progeny, which we reared under benign conditions in the laboratory, by crossing (1) two hybrids from the same region (H x H local); (2) two hybrids from different regions (H X H foreign); (3) hybrids and R. ridibunda (H X R); and (4) two R. ridibunda (R X R). Survival to metamorphosis was similar and high for R x R, H X H foreign, and H X R, whereas all tadpoles of H X H local died before metamorphosis. This supports the hypothesis that homozygosity for recessive deleterious mutations at particular loci causes inviability. Crosses within and between the two coexisting hemiclones from Switzerland were, however, equally inviable. This result may reflect episodic sexual recombination in RR progeny from exceptional successful interclonal hybrid X hybrid matings, followed by matings of such RR with LL. This process would both slow down or halt Muller's ratchet and disrupt genetic independence of coexisting hemiclones, so that the same remaining deleterious R alleles could exist in different allozyme-defined hemiclones. Whereas all data are consistent with the prediction of Muller's ratchet operating on clonally transmitted R genomes of natural hybrid lineages, they are insufficient to demonstrate such operation, because deleterious recessives that mutated after clone formation and those that preexisted in the R. ridibunda source populations that formed the hemiclonal lineages are not distinguished. The possibility of episodic sexual recombination must be carefully taken into account when studying Muller's ratchet in natural populations of this Rana system.
Collapse
Affiliation(s)
- Gaston-Denis Guex
- Zoologisches Museum and Zoologisches Institut, Universität Zürich, Switzerland.
| | | | | |
Collapse
|
28
|
Guex GD, Hotz H, Semlitsch RD. DELETERIOUS ALLELES AND DIFFERENTIAL VIABILITY IN PROGENY OF NATURAL HEMICLONAL FROGS. Evolution 2002. [DOI: 10.1554/0014-3820(2002)056[1036:daadvi]2.0.co;2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
29
|
Abstract
The hemiclonal waterfrog Rana esculenta (RL genotype), a bisexual hybrid between R. ridibunda (RR) and R. lessonae (LL), eliminates the L genome from its germline and clonally transmits the R genome (hybridogenesis). Matings between hybrids produce R. ridibunda offspring, but they generally die at an early larval stage. Mortality may be due to fixed recessive deleterious mutations in the clonally inherited R genomes that were either acquired through the advance of Muller's ratchet or else frozen in these genomes at hemiclone formation. From this hypothesis results a straightforward prediction: Matings between different hemiclones, that is, between R. esculenta possessing different R genomes of independent origin, should produce viable R. ridibunda offspring because it is unlikely that different clonal lineages have become fixed for the same mutations. I tested this prediction by comparing survival and larval performance of tadpoles from within- and between-population crossings using R. esculenta from Seseglio (Se) in southern, Alpnach (Al) in central, and Elliker Auen (El) in northern Switzerland, respectively. Se is isolated from the other populations by the Alps. Enzyme electrophoresis revealed that parents from Se belonged to a single hemiclone that was different from all hemiclones found north of the Alps. Parents from Al also belonged to one hemiclone, but parents from El belonged to three hemiclones, one of which was indistinguishable from the one in Al. Rana esculenta from Se produced inviable tadpoles when crossed with other hybrids of their own population, but when crossed with R. esculenta from Al and El, tadpoles successfully completed metamorphosis, supporting the hypothesis I tested. Within-population crosses from Al were also inviable, but some within-population crosses from El, where three hemiclones were present, produced viable offspring. Only part of the crosses between Al and El were viable, but there was no consistent relationship between hemiclone combination and tadpole survival. When backcrossed with the parental species R. ridibunda, hybrids from all source populations produced viable offspring. Performance of these tadpoles with a sexual and a clonal genome was comparable to that of normal, sexually produced R. ridibunda tadpoles. Thus, in the heterozygous state, the deleterious mutations on the clonal R genomes did not appear to reduce tadpole fitness.
Collapse
Affiliation(s)
- C Vorburger
- Institute of Zoology, University of Zürich, Switzerland.
| |
Collapse
|
30
|
|