Hybrid sterility is a hallmark of speciation, but the underlying molecular mechanisms remain poorly understood. Here, we report that speciation may regularly proceed through a stage at which gene flow is completely interrupted, but hybrid sterility occurs only in male hybrids whereas female hybrids reproduce asexually. We analyzed gametogenic pathways in hybrids between the fish species Cobitis elongatoides and C. taenia, and revealed that male hybrids were sterile owing to extensive asynapsis and crossover reduction among heterospecific chromosomal pairs in their gametes, which was subsequently followed by apoptosis. We found that polyploidization allowed pairing between homologous chromosomes and therefore partially rescued the bivalent formation and crossover rates in triploid hybrid males. However, it was not sufficient to overcome sterility. In contrast, both diploid and triploid hybrid females exhibited premeiotic genome endoreplication, thereby ensuring proper bivalent formation between identical chromosomal copies. This endoreplication ultimately restored female fertility but it simultaneously resulted in the obligate production of clonal gametes, preventing any interspecific gene flow. In conclusion, we demonstrate that the emergence of asexuality can remedy hybrid sterility in a sex-specific manner and contributes to the speciation process.

Department of Biology and Ecology Faculty of Science University of Ostrava 710 00 Czech Republic

Department of Zoology Faculty of Biology and Biotechnology University of Warmia and Mazury in Olsztyn 10 719 Poland

Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses University of South Bohemia in České Budějovice Vodň any 389 25 Czech Republic

Institute of Zoology Academy of Science of Moldova Chisinau MD 2028 Republic of Moldova

Laboratory of Fish Genetics Institute of Animal Physiology and Genetics Czech Academy of Sciences Liběchov 277 21 Czech Republic

Museum of Natural History University of Wrocław 50 335 Poland

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Araya-Jaime C., Serrano É. A., de Andrade Silva D. M. Z., Yamashita M., Iwai T. et al. , 2015.  Surface-spreading technique of meiotic cells and immunodetection of synaptonemal complex proteins in teleostean fishes. Mol. Cytogenet. 8: 4 10.1186/s13039-015-0108-9 PubMed DOI PMC

Avise I. J., 2008.  Clonality : The genetics, Ecology, and Evolution of Sexual Abstinence in Vertebrate Animals: The Genetics, Ecology, and Evolution of Sexual Abstinence in Vertebrate Animals, Oxford University Press, Oxford: 10.1093/acprof:oso/9780195369670.001.0001 DOI

Balcova M., Faltusova B., Gergelits V., Bhattacharyya T., Mihola O. et al. , 2016.  Hybrid sterility locus on chromosome X controls meiotic recombination rate in mouse. PLoS Genet. 12: e1005906 10.1371/journal.pgen.1005906 PubMed DOI PMC

Bartoš O., Röslein J., Kotusz J., Pačes J., Pekárik L. et al. , 2019.  The legacy of sexual ancestors in phenotypic variability, gene expression and homoeolog regulation of asexual hybrids and polyploids. Mol. Biol. Evol. 36: 1902–1920. 10.1093/molbev/msz114 PubMed DOI PMC

Bateson W., 1909.  Heredity and variation in modern lights., pp. 85–101 in Darwin and Modern Science, Cambridge University Press, Cambridge.

Baudat F., and de Massy B., 2007.  Regulating double-stranded DNA break repair towards crossover or non-crossover during mammalian meiosis. Chromosome Res. Int. J. Mol. Supramol. Evol. Asp. Chromosome Biol. 15: 565–577. 10.1007/s10577-007-1140-3 PubMed DOI

Bernstein H., and Bernstein C., 2010.  Evolutionary origin of recombination during meiosis. Bioscience 60: 498–505. 10.1525/bio.2010.60.7.5 DOI

Bhattacharyya T., Gregorova S., Mihola O., Anger M., Sebestova J. et al. , 2013.  Mechanistic basis of infertility of mouse intersubspecific hybrids. Proc. Natl. Acad. Sci. USA 110: E468–E477. 10.1073/pnas.1219126110 PubMed DOI PMC

Blokhina Y. P., Nguyen A. D., Draper B. W., and Burgess S. M., 2018.  The telomere bouquet is a hub where meiotic double-strand breaks, synapsis, and stable homolog juxtaposition are coordinated in the zebrafish, Danio rerio. bioRxiv (Preprint posted September 27, 2018).10.1101/428086 PubMed DOI PMC

Bomblies K., Jones G., Franklin C., Zickler D., and Kleckner N., 2016.  The challenge of evolving stable polyploidy: could an increase in “crossover interference distance” play a central role? Chromosoma 125: 287–300. 10.1007/s00412-015-0571-4 PubMed DOI PMC

Bottani S., Zabet N. R., Wendel J. F., and Veitia R. A., 2018.  Gene expression dominance in allopolyploids: hypotheses and models. Trends Plant Sci. 23: 393–402. 10.1016/j.tplants.2018.01.002 PubMed DOI

Brown J. D., and O’Neill R. J., 2010.  Chromosomes, conflict, and epigenetics: chromosomal speciation revisited. Annu. Rev. Genomics Hum. Genet. 11: 291–316. 10.1146/annurev-genom-082509-141554 PubMed DOI

Callan H. G., 1986.  Lampbrush Chromosomes, Springer-Verlag, Berlin, Heidelberg: 10.1007/978-3-642-82792-1 DOI

Carman J. G., 1997.  Asynchronous expression of duplicate genes in angiosperms may cause apomixis, bispory, tetraspory, and polyembryony. Biol. J. Linn. Soc. Lond. 61: 51–94. 10.1111/j.1095-8312.1997.tb01778.x DOI

Choleva L., Janko K., Gelas K. D., Bohlen J., Šlechtová V. et al. , 2012.  Synthesis of clonality and polyploidy in vertebrate animals by hybridisation between two sexual species. Evolution 66: 2191–2203. 10.1111/j.1558-5646.2012.01589.x PubMed DOI

De Storme N., and Geelen D., 2013.  Sexual polyploidization in plants - cytological mechanisms and molecular regulation. New Phytol. 198: 670–684. 10.1111/nph.12184 PubMed DOI PMC

De Storme N., and Mason A., 2014.  Plant speciation through chromosome instability and ploidy change: cellular mechanisms, molecular factors and evolutionary relevance. Curr. Plant Biol. 1: 10–33. 10.1016/j.cpb.2014.09.002 DOI

Ernst A., 1918.  Bastardierung als Ursache der Apogamie im Pflanzenreich. Eine Hypothese zur experimentellen Vererbungs- und Abstammungslehre, Nabu Press, Charleston, SC: 10.5962/bhl.title.8212 DOI

Faria R., and Navarro A., 2010.  Chromosomal speciation revisited: rearranging theory with pieces of evidence. Trends Ecol. Evol. 25: 660–669. 10.1016/j.tree.2010.07.008 PubMed DOI

Gall J. G., Murphy C., Callan H. G., and Wu Z. A., 1991.  Lampbrush chromosomes. Methods Cell Biol. 36: 149–166. 10.1016/S0091-679X(08)60276-9 PubMed DOI

Graf J.-D., and M. Polls Pelaz, 1989 Evolutionary genetics of the Rana esculenta complex, pp. 289–302 in Evolution and Ecology of Unisexual Vertebrates, edited by R. M. Dawley and J. P. Bogart. New York State Museum, New York.

Grandont L., Jenczewski E., and Lloyd A., 2013.  Meiosis and its deviations in polyploid plants. Cytogenet. Genome Res. 140: 171–184. 10.1159/000351730 PubMed DOI

Gregorova S., Gergelits V., Chvatalova I., Bhattacharyya T., Valiskova B. et al. , 2018.  Modulation of Prdm9-controlled meiotic chromosome asynapsis overrides hybrid sterility in mice. Elife 7: e34282 10.7554/eLife.34282 PubMed DOI PMC

Griffiths S., Sharp R., Foote T. N., Bertin I., Wanous M. et al. , 2006.  Molecular characterization of Ph1 as a major chromosome pairing locus in polyploid wheat. Nature 439: 749–752. 10.1038/nature04434 PubMed DOI

Haldane J. B. S., 1922.  Sex ratio and unisexual sterility in hybrid animals. J. Genet. 12: 101–109. 10.1007/BF02983075 DOI

Hotz H., Mancino G., Bucciinnocenti S., Ragghianti M., Berger L. et al. , 1985.  Rana ridibunda varies geographically in inducing clonal gametogenesis in interspecies hybrids. J. Exp. Zool. 236: 199–210. 10.1002/jez.1402360210 DOI

Itono M., Morishima K., Fujimoto T., Bando E., Yamaha E. et al. , 2006.  Premeiotic endomitosis produces diploid eggs in the natural clone loach, Misgurnus anguillicaudatus (Teleostei: Cobitidae). J. Exp. Zool. 305A: 513–523. 10.1002/jez.a.283 PubMed DOI

Janko K., Bohlen J., Lamatsch D., Flajšhans M., Epplen J. T. et al. , 2007a The gynogenetic reproduction of diploid and triploid hybrid spined loaches (Cobitis: Teleostei), and their ability to establish successful clonal lineages—on the evolution of polyploidy in asexual vertebrates. Genetica 131: 185–194. 10.1007/s10709-006-9130-5 PubMed DOI

Janko K., Flajšhans M., Choleva L., Bohlen J., Lechtová V. Š. et al. , 2007b Diversity of European spined loaches (genus Cobitis L.): an update of the geographic distribution of the Cobitis taenia hybrid complex with a description of new molecular tools for species and hybrid determination. J. Fish Biol. 71: 387–408. 10.1111/j.1095-8649.2007.01663.x DOI

Janko K., Pačes J., Wilkinson-Herbots H., Costa R. J., Roslein J. et al. , 2018.  Hybrid asexuality as a primary postzygotic barrier between nascent species: on the interconnection between asexuality, hybridisation and speciation. Mol. Ecol. 27: 248–263. 10.1111/mec.14377 PubMed DOI PMC

Juchno D., and Boroń A., 2018.  Histological evidence that diploid hybrids of Cobitis taenia and C. elongatoides (Teleostei, Cobitidae) develop into fertile females and sterile males. Hydrobiologia 814: 147–159. 10.1007/s10750-018-3530-2 DOI

Juchno D., Jabłońska O., Boroń A., Kujawa R., Leska A. et al. , 2014.  Ploidy-dependent survival of progeny arising from crosses between natural allotriploid Cobitis females and diploid C. taenia males (Pisces, Cobitidae). Genetica 142: 351–359 [corrigenda: Genetica 143: 127 (2015)]. 10.1007/s10709-014-9779-0 PubMed DOI

Juchno D., Arai K., Boroń A., and Kujawa R., 2017.  Meiotic chromosome configurations in oocytes of Cobitis taenia and its polyploid hybrids. Ichthyol. Res. 64: 240–243. 10.1007/s10228-016-0556-1 DOI

Kearney M., Fujita M. K., and Ridenour J., 2009.  Lost sex in the reptiles: constraints and correlations, pp. 447–474 in Lost Sex: The Evolutionary Biology of Parthenogenesis. Springer-Verlag, Dordrecht, The Netherlands.

Kim I.-S., 2000.  Hybridisation experiment of diploid-triploid cobitid fishes, Cobitis sinensis-longicorpus complex (Pisces : Cobitidae). Folia Zool. (Brno) 49: 17–22.

Kochakpour N., and Moens P. B., 2008.  Sex-specific crossover patterns in Zebrafish (Danio rerio). Heredity 100: 489–495. 10.1038/sj.hdy.6801091 PubMed DOI

Kuroda M., Fujimoto T., Murakami M., Yamaha E., and Arai K., 2018.  Clonal reproduction assured by sister chromosome pairing in dojo loach, a teleost fish. Chromosome Res. 26: 243–253. 10.1007/s10577-018-9581-4 PubMed DOI

Kuroda M., Fujimoto T., Murakami M., Yamaha E., and Arai K., 2019.  Aberrant meiotic configurations cause sterility in clone-origin triploid and inter-group hybrid males of the dojo loach, Misgurnus anguillicaudatus. Cytogenet. Genome Res. 158: 46–54. 10.1159/000500303 PubMed DOI

Lampert K. P., Lamatsch D. K., Fischer P., Epplen J. T., Nanda I. et al. , 2007.  Automictic reproduction in interspecific hybrids of Poeciliid fish. Curr. Biol. 17: 1948–1953. 10.1016/j.cub.2007.09.064 PubMed DOI

Lenormand T., Engelstädter J., Johnston S. E., Wijnker E., and Haag C. R., 2016.  Evolutionary mysteries in meiosis. Philos. Trans. R. Soc. B Biol. Sci. 371: 20160001. 10.1098/rstb.2016.0001 PubMed DOI PMC

Li Y.-J., Gao Y.-C., Zhou H., Ma H.-Y., Li J.-Q. et al. , 2015.  Meiotic chromosome configurations in triploid progeny from reciprocal crosses between wild-type diploid and natural tetraploid loach Misgurnus anguillicaudatus in China. Genetica 143: 555–562. 10.1007/s10709-015-9853-2 PubMed DOI

Lukhtanov V. A., Dincă V., Friberg M., Šíchová J., Olofsson M. et al. , 2018.  Versatility of multivalent orientation, inverted meiosis, and rescued fitness in holocentric chromosomal hybrids. Proc. Natl. Acad. Sci. USA 115: E9610–E9619. 10.1073/pnas.1802610115 PubMed DOI PMC

Lutes A. A., Neaves W. B., Baumann D. P., Wiegraebe W., and Baumann P., 2010.  Sister chromosome pairing maintains heterozygosity in parthenogenetic lizards. Nature 464: 283–286. 10.1038/nature08818 PubMed DOI PMC

Macgregor H. C., and Uzzell T. M., 1964.  Gynogenesis in salamanders related to Ambystoma jeffersonianum. Science 143: 1043–1045. 10.1126/science.143.3610.1043 PubMed DOI

Macgregor H. C., and Varley J. M., 1983.  Working with Animal Chromosomes, John Wiley & Sons, New York.

Majtánová Z., Choleva L., Symonová R., Ráb P., Kotusz J. et al. , 2016.  Asexual Reproduction Does not apparently increase the rate of chromosomal evolution: karyotype stability in diploid and triploid clonal hybrid fish (Cobitis, Cypriniformes, Teleostei). PLoS One 11: e0146872 10.1371/journal.pone.0146872 PubMed DOI PMC

Mantovani B., and Scali V., 1992.  Hybridogenesis and androgenesis in the stick-insect Bacillus rossius-grandii benazzii (Insecta, Phasmatodea). Evolution 46: 783–796. 10.1111/j.1558-5646.1992.tb02084.x PubMed DOI

Moens P. B., 2006.  Zebrafish: chiasmata and interference. Genome 49: 205–208. 10.1139/g06-021 PubMed DOI

Morishima K., Yoshikawa H., and Arai K., 2008.  Meiotic hybridogenesis in triploid Misgurnus loach derived from a clonal lineage. Heredity 100: 581–586. 10.1038/hdy.2008.17 PubMed DOI

Morishima K., Yoshikawa H., and Arai K., 2012.  Diploid clone produces unreduced diploid gametes but tetraploid clone generates reduced diploid gametes in the Misgurnus loach. Biol. Reprod. 86: 33 10.1095/biolreprod.111.093302 PubMed DOI

Moritz C., Brown W. M., Densmore L. D., Wright J. W., Vyas D. et al. , 1989.  Genetic diversity and the dynamics of hybrid parthenogenesis in Cnemidophorus (Teiidae) and Heteronotia (Gekkonidae), pp. 87–112 in Evolution and Ecology of Unisexual Vertebrates, edited by Dawley R. M., Bogart J. P.. Albany: NY State Mus. Bull. 466.

Murphy R. W., Fu J., MacCulloch R. D., Darevsky I. S., and Kupriyanova L. A., 2000.  A fine line between sex and unisexuality: the phylogenetic constraints on parthenogenesis in lacertid lizards. Zool. J. Linn. Soc. 130: 527–549. 10.1111/j.1096-3642.2000.tb02200.x DOI

Park J.-Y., Kim I.-S., and Ko M.-H., 2011.  Characteristics of rare males in the cobitid unisexual complex, Cobitis hankugensis-Iksookimia longicorpa. Folia Zool. Praha 60: 290–294. 10.25225/fozo.v60.i4.a4.2011 DOI

Saitoh K., 1989.  Multiple sex-chromosome system in a loach fish. Cytogenet. Cell Genet. 52: 62–64. 10.1159/000132840 PubMed DOI

Saitoh K., Kim I. S., and Lee E. H., 2004.  Mitochondrial gene introgression between spined Loaches via hybridogenesis. Zool. Sci. 21: 795–798. 10.2108/zsj.21.795 PubMed DOI

Shimizu Y., Shibata N., and Yamashita M., 1997.  Spermiogenesis without preceding meiosis in the hybrid medaka between Oryzias latipes and O. curvinotus. J. Exp. Zool. 279: 102–112. 10.1002/(SICI)1097-010X(19970901)279:1<102::AID-JEZ10>3.0.CO;2-A DOI

Spangenberg V., Arakelyan M., Galoyan E., Matveevsky S., Petrosyan R. et al. , 2017.  Reticulate evolution of the rock lizards: meiotic chromosome dynamics and spermatogenesis in diploid and triploid males of the genus Darevskia. Genes (Basel) 8: 149 10.3390/genes8060149 PubMed DOI PMC

Stenberg P., and Saura A., 2009.  Cytology of asexual animals, pp. 63–74 in Lost Sex, edited by Schön I., Martens K., and Dijk P.. Springer, Netherlands: 10.1007/978-90-481-2770-2_4 DOI

Stenberg P., and Saura A., 2013.  Meiosis and its deviations in polyploid animals. Cytogenet. Genome Res. 140: 185–203. 10.1159/000351731 PubMed DOI

Torgasheva A. A., and Borodin P. M., 2016.  Cytological basis of sterility in male and female hybrids between sibling species of grey voles Microtus arvalis and M. levis. Sci. Rep. 6: 36564 10.1038/srep36564 PubMed DOI PMC

Tulchinsky A. Y., Johnson N. A., Watt W. B., and Porter A. H., 2014.  Hybrid incompatibility arises in a sequence-based bioenergetic model of transcription factor binding. Genetics 198: 1155–1166. 10.1534/genetics.114.168112 PubMed DOI PMC

Vasil’eva E. D., and Vasil’ev V. P., 1998.  Sibling species in genus Cobitis (Cobitidae). Cobitis rossomeridionalis sp. nova. J. Ichthyol. 38: 580–590.

Vasil’ev V. P., Akimova N. V., Emel’yanova N. G., Pavlov D. A., and Vasil’eva E. D., 2003.  Reproductive capacities in the polyploid males of spined loaches from the unisexual-bisexual complex, occurred in the Moscow River. Folia Biol. (Praha) 51: 67–73. PubMed

Vrijenhoek R. C., 1998.  Clonal organisms and the benefits of sex, pp. 151–172 in Advances in molecular ecology, edited by Carvalho G. R. IOS Press, Amsterdam.

Yoshikawa H., Morishima K., Kusuda S., Yamaha E., and Arai K., 2007.  Diploid sperm produced by artificially sex-reversed clone loaches. J. Exp. Zool. Part Ecol. Genet. Physiol. 307: 75–83. 10.1002/jez.a.337 PubMed DOI

Yoshikawa H., Morishima K., Fujimoto T., Saito T., Kobayashi T. et al. , 2009.  Chromosome doubling in early spermatogonia produces diploid spermatozoa in a natural clonal fish. Biol. Reprod. 80: 973–979. 10.1095/biolreprod.108.075150 PubMed DOI

Yoshikawa H., Xu D., Ino Y., Yoshino T., Hayashida T. et al. , 2018.  Hybrid sterility in fish caused by mitotic arrest of primordial germ cells. Genetics 209: 507–521. 10.1534/genetics.118.300777 PubMed DOI PMC

Zhang Q., Arai K., and Yamashita M., 1998.  Cytogenetic mechanisms for triploid and haploid eggs formation in the triploid loach, Misgurnus anguillicaudatus. J. Exp. Zool. 281: 608–619. 10.1002/(SICI)1097-010X(19980815)281:6<608::AID-JEZ9>3.0.CO;2-R DOI

Zickler D., 2006.  From early homologue recognition to synaptonemal complex formation. Chromosoma 115: 158–174. 10.1007/s00412-006-0048-6 PubMed DOI

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