Obligate parthenogenesis evolved in reptiles convergently several times, mainly through interspecific hybridization. The obligate parthenogenetic complexes typically include both diploid and triploid lineages. Offspring of parthenogenetic hybrids are genetic copies of their mother; however, the cellular mechanism enabling the production of unreduced cells is largely unknown. Here, we show that oocytes go through meiosis in three widespread, or even strongly invasive, obligate parthenogenetic complexes of geckos, namely in diploid and triploid Lepidodactylus lugubris, and triploid Hemiphyllodactylus typus and Heteronotia binoei. In all four lineages, the majority of oocytes enter the pachytene at the original ploidy level, but their chromosomes cannot pair properly and instead form univalents, bivalents and multivalents. Unreduced eggs with clonally inherited genomes are formed from germ cells that had undergone premeiotic endoreplication, in which appropriate segregation is ensured by the formation of bivalents made from copies of identical chromosomes. We conclude that the induction of premeiotic endoreplication in reptiles was independently co-opted at least four times as an essential component of parthenogenetic reproduction and that this mechanism enables the emergence of fertile polyploid lineages within parthenogenetic complexes.

• Klíčová slova
• Asexuality, Endoreplication, Geckos, Meiosis, Obligatory parthenogenesis, Reptiles,
• MeSH
• diploidie MeSH
• endoreduplikace MeSH
• ještěři * genetika   MeSH
• partenogeneze genetika   MeSH
• triploidie MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Among vertebrates, obligate parthenogenesis occurs exclusively in squamate reptiles. Premeiotic endoreplication in a small subset of developing oocytes has been documented as the mechanism of production of unreduced eggs in minutely explored obligate parthenogenetic lineages, namely in teiids and geckos. The situation in the lacertid genus Darevskia has been discussed for decades. Certain observations suggested that the ploidy level is restored during egg formation through a fusion of egg and polar body nuclei in Darevskia unisexualis and D. armeniaca. In this study, we re-evaluated the fusion hypothesis by studying diplotene chromosomes in adult females of sexual species D. raddei nairensis and obligate parthenogens D. armeniaca, D. dahli and D. unisexualis. We revealed 19 bivalents in the sexual species and 38 bivalents in the diploid obligate parthenogens, which uncovers premeiotic endoreplication as the mechanism of the production of non-reduced eggs in parthenogenetic females. The earlier contradicting reports can likely be attributed to the difficulty in identifying mispairing of chromosomes in pachytene, and the fact that in parthenogenetic reptiles relying on premeiotic endoreplication only a small subset of developing oocytes undergo genome doubling and overcome the pachytene checkpoint. This study highlights co-option of premeiotic endoreplication for escape from sexual reproduction in all independent hybrid origins of obligate parthenogenesis in vertebrates studied to date.

• Klíčová slova
• Lacertidae, asexuality, meiosis, obligatory parthenogenesis, reptiles, vertebrates,
• MeSH
• ještěři * fyziologie   genetika   MeSH
• meióza MeSH
• partenogeneze * MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Although reproductive assurance has been suggested to be one of the most important factors shaping the differential distributional patterns between sexuals and asexuals (geographic parthenogenesis), it has only rarely been studied in natural populations of vascular plants with autonomous apomixis. Moreover, there are almost no data concerning the putative relationship between the level of apomictic versus sexual plant reproduction on one hand, and reproductive assurance on the other. We assessed the level of sexual versus apomictic reproduction in diploid and triploid plants of Hieracium alpinum across its distributional range using flow cytometric analyses of seeds, and compared the level of potential and realized seed set, i.e. reproductive assurance, between the two cytotypes under field and greenhouse conditions. Flow cytometric screening of embryos and endosperms of more than 4,100 seeds showed that diploids produced solely diploid progeny sexually, while triploids produced triploid progeny by obligate apomixis. Potential fruit set was much the same in diploids and triploids from the field and the greenhouse experiment. While in the pollination-limited environment in the greenhouse apomictic triploids had considerably higher realized fruit set than sexual diploids, there was no significant difference between cytotypes under natural conditions. In addition, sexuals varied to a significantly larger extent in realized fruit set than asexuals under both natural and greenhouse conditions. Our results indicate that triploid plants reproduce by obligate apomixis, assuring more stable and predictable fruit reproduction when compared to sexual diploids. This advantage could provide apomictic triploids with a superior colonisation ability, mirrored in a strong geographic parthenogenesis pattern observed in this species.

• Klíčová slova
• FCSS, Apomixis, breeding system, flow cytometry, fruit set, geographic parthenogenesis, polyploidy, reproductive assurance, unreduced gametes,
• MeSH
• apomixie * MeSH
• Asteraceae genetika   fyziologie   MeSH
• diploidie MeSH
• endosperm fyziologie   MeSH
• ovoce růst a vývoj   MeSH
• průtoková cytometrie MeSH
• rozmnožování MeSH
• semena rostlinná růst a vývoj   MeSH
• triploidie * MeSH
• Publikační typ
• časopisecké články MeSH

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.

• Klíčová slova
• Cobitis, clonality, endoreplication, gynogenesis, hybridization, meiosis, polyploidy, speciation,
• MeSH
• biologická evoluce MeSH
• chromozomy MeSH
• hybridní buňky cytologie   fyziologie   MeSH
• infertilita genetika   MeSH
• meióza * MeSH
• partenogeneze * MeSH
• ryby genetika   fyziologie   MeSH
• vznik druhů (genetika) * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Recent studies of the distribution and diversity of freshwater zooplankton have indicated that the previously understudied Eastern Palearctic region is an important biogeographic hotspot. Here, we explored the lineage diversity and reproductive modes of the Daphnia pulex species group across China. Members of this group are often keystone species of standing water bodies and are frequently used as a model system for ecological, evolutionary and, more recently, genomic studies. We found members of the D. pulex group in seven of seventy-six Chinese water bodies examined. We analyzed their phylogenetic position using mitochondrial markers, and explored the genetic structure of six populations using microsatellite markers. Mitochondrial DNA analysis suggested the presence of two distinct species complexes in China: the D. pulex complex that has a global distribution, and an apparently endemic Eastern Palearctic D. mitsukuri complex. Microsatellite analyses of six populations suggested that three of these reproduced by cyclical parthenogenesis, as evidenced by high clonal diversity and the absence of deviations from the Hardy-Weinberg equilibrium. In contrast, three other populations showed remarkably low diversity of multilocus genotypes. This suggests an obligate parthenogenetic reproductive mode, which was confirmed in one of the populations by comparison of genotypes of Daphnia adults and dormant embryos. All presumably obligate parthenogenetic clones were heterozygous at the majority of microsatellite loci, suggesting their hybrid origin. This was further supported by analyses of a small GTPase nuclear gene (rab4), as two alleles within single individuals belonged to different clades. Interestingly, one putatively obligate parthenogenetic clone carried three distinct alleles suggesting higher ploidy and potential gene flow between the D. pulicaria and D. mitsukuri complexes. Our data show that the expansion of the D. pulex complex in the Eastern Palearctic was associated with widespread hybridization.

• Klíčová slova
• Eastern Palearctic, Heterozygosity, Microsatellites, Mitochondrial DNA, Obligate parthenogenesis, Rab4,
• MeSH
• analýza hlavních komponent MeSH
• Daphnia klasifikace   genetika   MeSH
• fylogeneze * MeSH
• genetická variace * MeSH
• haplotypy MeSH
• jezera * MeSH
• mikrosatelitní repetice genetika   MeSH
• mitochondriální DNA genetika   MeSH
• mitochondriální geny MeSH
• pravděpodobnostní funkce MeSH
• rozmnožování genetika   MeSH
• zeměpis MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Čína MeSH
• Názvy látek
• mitochondriální DNA MeSH

In natural, permanently frozen habitats, some organisms may be preserved for hundreds to tens of thousands of years. For example, stems of Antarctic moss were successfully regrown from an over millennium-old sample covered by ice for about 400 years1. Likewise, whole campion plants were regenerated from seed tissue preserved in relict 32,000-year-old permafrost2, and nematodes were revived from the permafrost of two localities in northeastern Siberia, with source sediments dated over 30,000 years BP3. Bdelloid rotifers, microscopic multicellular animals, are known for their ability to survive extremely low temperatures4. Previous reports suggest survival after six to ten years when frozen between -20° to 0°C4-6. Here, we report the survival of an obligate parthenogenetic bdelloid rotifer, recovered from northeastern Siberian permafrost radiocarbon-dated to ∼24,000 years BP. This constitutes the longest reported case of rotifer survival in a frozen state. We confirmed the finding by identifying rotifer actin gene sequences in a metagenome obtained from the same sample. By morphological and molecular markers, the discovered rotifer belongs to the genus Adineta, and aligns with a contemporary Adineta vaga isolate collected in Belgium. Experiments demonstrated that the ancient rotifer withstands slow cooling and freezing (∼1°C min-1) for at least seven days. We also show that a clonal culture can continuously reproduce in the laboratory by parthenogenesis.

• MeSH
• metagenom MeSH
• partenogeneze MeSH
• permafrost * MeSH
• vířníci klasifikace   genetika   růst a vývoj   izolace a purifikace   MeSH
• zmrazování * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• dopisy MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geografické názvy
• Sibiř MeSH

Rubus subgen. Rubus includes common European species with highly complicated taxonomy, ongoing hybridisation and facultative apomixis. Out of approximately 750 species recognised in Europe, only 3 diploid sexual species are known, along with numerous apomictic brambles that are highly connected to polyploidy. One exception of a tetraploid taxon is R. ser. Glandulosi, which is known for prevalent sexuality. This taxon highly hybridises with tetraploid members of R. ser. Discolores and leads to the origin of many hybridogenous populations and individuals. In this study, we verify reproduction modes in different diploid, triploid and tetraploid species of subgen. Rubus, with focus on taxa putatively involved in such hybridisation by applying flow cytometric seed screen analysis. We found 100 % sexuality of diploid species, whereas triploid species had obligate unreduced embryo sac development. In contrast, tetraploid plants had varying degrees of sexuality. Additionally, we discovered that R. bifrons has the ability to undergo a reproduction mode switch as a reaction to environmental conditions. These results provide insight into reproductive modes of European brambles and shed light on their reticulate evolution and speciation.

• MeSH
• apomixie MeSH
• délka genomu MeSH
• diploidie MeSH
• druhová specificita MeSH
• endosperm embryologie   genetika   fyziologie   MeSH
• partenogeneze MeSH
• polyploidie * MeSH
• průtoková cytometrie MeSH
• Rosaceae embryologie   genetika   fyziologie   MeSH
• rozmnožování MeSH
• semena rostlinná embryologie   genetika   fyziologie   MeSH
• tetraploidie MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Bdelloid rotifers are a group of microscopic invertebrates known for their obligate parthenogenesis and exceptional resistance to extreme environments. Their diversity and distributions are poorly studied in Asia, especially in China. In order to better understand the species distribution and diversity of bdelloid rotifers in China, a scientific surveys of habitats was conducted with 61 samples (both terrestrial and aquatic habitats) from 11 provinces and regions of China, ranging from tropics to subtropics with a specific focus on poorly sampled areas (Oriental) during September 2017 to October 2018. A total of 59 morphospecies (including subspecies) were found, of which, thirty-nine morphospecies (including one genus) are new records for China, almost doubling the number of previous records. Four rare morphospecies (Adineta cf. acuticornis Haigh, A. beysunae Örstan, Habrotrocha ligula loxoglotta De Koning and H. serpens Donner) are depicted and redescribed, and an updated checklist of Chinese bdelloids with their location and ecological information is presented. This study provides new data from a large region of China, enriching the knowledge of bdelloid biodiversity, and their global biogeography.

• Klíčová slova
• Oriental region, bdelloids, biogeography, morphospecies, taxonomy,
• Publikační typ
• časopisecké články MeSH

The Hieracium and Pilosella (Lactuceae, Asteraceae) genera of closely related hawkweeds contain species with two different modes of gametophytic apomixis (asexual seed formation). Both genera contain polyploid species, and in wild populations, sexual and apomictic species co-exist. Apomixis is known to co-exist with sexuality in apomictic Pilosella individuals, however, apomictic Hieracium have been regarded as obligate apomicts. Here, a developmental analysis of apomixis within 16 Hieracium species revealed meiosis and megaspore tetrad formation in 1 to 7% of ovules, for the first time indicating residual sexuality in this genus. Molecular markers linked to the two independent, dominant loci LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP) controlling apomixis in Pilosella piloselloides subsp. praealta were screened across 20 phenotyped Hieracium individuals from natural populations, and 65 phenotyped Pilosella individuals from natural and experimental cross populations, to examine their conservation, inheritance and association with reproductive modes. All of the tested LOA and LOP-linked markers were absent in the 20 Hieracium samples irrespective of their reproductive mode. Within Pilosella, LOA and LOP-linked markers were essentially absent within the sexual plants, although they were not conserved in all apomictic individuals. Both loci appeared to be inherited independently, and evidence for additional genetic factors influencing quantitative expression of LOA and LOP was obtained. Collectively, these data suggest independent evolution of apomixis in Hieracium and Pilosella and are discussed with respect to current knowledge of the evolution of apomixis.

• MeSH
• apomixie genetika   MeSH
• Asteraceae genetika   MeSH
• biologická evoluce * MeSH
• DNA chloroplastová genetika   MeSH
• DNA rostlinná genetika   MeSH
• genetické lokusy * MeSH
• genetické markery MeSH
• haplotypy MeSH
• konzervovaná sekvence MeSH
• molekulární sekvence - údaje MeSH
• populační genetika MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné geny * MeSH
• semena rostlinná genetika   MeSH
• typy dědičnosti MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA chloroplastová MeSH
• DNA rostlinná MeSH
• genetické markery MeSH

The water fleas of the Daphnia pulex complex play a key role in freshwater ecosystems throughout the northern hemisphere. Despite the fact that they have been the subject of study for numerous biological disciplines, their phylogeny and species delimitation remain controversial. We used DNA sequence variation of the mitochondrial ND5 gene to reconstruct the phylogenetic relationships of D. pulicaria Forbes, a widespread member of this complex from North America and Europe. Populations from the two continents respectively split into two evolutionary lineages, Eastern Nearctic and European, which each belong to another main clade within the D. pulex complex (the pulicaria and tenebrosa groups, respectively). Unexpectedly, melanin and carotenoid pigmented D. pulicaria populations from European high-mountain lakes were not allied with the transparent populations inhabiting the same lakes and the lowland ponds and reservoirs throughout Europe, but were included with the samples from Canada and Greenland in the Eastern Nearctic lineage. Until now populations belonging to this lineage were known only from Canada and North Atlantic islands, but not from mainland Europe. Independent data from microsatellite markers supported the genetic distinctiveness of the sympatric carotenoid pigmented and transparent populations and suggested that they may have undergone transition to obligate parthenogenesis, possibly as a consequence of past introgressive hybridization. Two different taxa are therefore confused under the name D. pulicaria in Europe. The close phylogenetic relationships of European populations with those from Canada and Greenland suggest that the Nearctic lineage is of recent origin in Europe via intercontinental dispersal from the North America. It has evolved melanin and carotenoid pigmentation as adaptations against the UV light stress, which enable it to share habitat occupied by the transparent European species. The Nearctic D. pulicaria thus provides a new model for studying successful intercontinental invasion. In general, our study demonstrates that a considerable part of the diversity among widespread taxa of cladoceran crustaceans has been overlooked in morphological taxonomies.

• MeSH
• Daphnia klasifikace   genetika   MeSH
• fylogeneze * MeSH
• genotyp MeSH
• mikrosatelitní repetice genetika   MeSH
• mitochondriální DNA genetika   MeSH
• molekulární evoluce MeSH
• molekulární sekvence - údaje MeSH
• sekvenční analýza DNA MeSH
• zeměpis MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH
• Názvy látek
• mitochondriální DNA MeSH