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Asexual reproduction can be triggered by interspecific hybridization, but its emergence is supposedly rare, relying on exceptional combinations of suitable genomes. To examine how genomic and karyotype divergence between parental lineages affect the incidence of asexual gametogenesis, we experimentally hybridized fishes (Cobitidae) across a broad phylogenetic spectrum, assessed by whole exome data. Gametogenic pathways generally followed a continuum from sexual reproduction in hybrids between closely related evolutionary lineages to sterile or inviable crosses between distant lineages. However, most crosses resulted in a combination of sterile males and asexually reproducing females. Their gametes usually experienced problems in chromosome pairing, but females also produced a certain proportion of oocytes with premeiotically duplicated genomes, enabling their development into clonal eggs. Interspecific hybridization may thus commonly affect cell cycles in a specific way, allowing the formation of unreduced oocytes. The emergence of asexual gametogenesis appears tightly linked to hybrid sterility and constitutes an inherent part of the extended speciation continuum.

The structure of spined loaches diploid-poliploid complex of Cobitis genera representatives as well as Sabanjeewia aurata of the Eastern Ukraine river systems were investigated by allozyme analysis and cytometry. In total 39 samples and 1412 specimens from the upper left tributaries of the Middle Dnipro River, the Donets Basin, the coastal rivers of the Sea of Azov and the Lower Dnipro were studied. We identified the representatives of C. (superspecies taenia) (51.6 % of all researched specimens). C. melanoleuca (4.1 %), S. aurata (1.1 %), allodiploids C. (superspecies taenia) × C. melanoleuca (0.3 %) and two groups of polyploid hybrids (46.4 %). EET-group includes mainly C. elongatoides-2 taenia and C. elongatoides-taenia -tanaitica. EET-group (2.8 %) is represented only by C. elongatoides-2 tanaitica biotype. In the Lower Donets and the Lower Dnipro, there is a zone of introgressive hybridization between C. taenia and C. tanaitica. The structure of settlements differs accordingly to the river basins and has a tendency to decreasing of polyploids frequency respetivly to meridional direction. The analysis of loaches samples from the coastal rivers of the Sea of Azov collected in 1938 and samples from the Middle part of the Donets River in 1971 leads to the conclusion that polyploids in mentioned above regions appeared in 1960-1970s. The structure of diploid-polyploid settlements has an alternative character. More often, there is a predominance of diploids or polyploids. The reason of such bipolarity of settlements could be as reproductive displacement so a relatively strong tolerance of polyploids to anthropogenic climate change. [ABSTRACT FROM AUTHOR]

The structure of spined loaches diploid-poliploid complex of Cobitis genera representatives as well as Sabanjeewia aurata of the Eastern Ukraine river systems were investigated by allozyme analysis and cytometry. In total 39 samples and 1412 specimens from the upper left tributaries of the Dnieper River, the Donets Basin, the coastal rivers of the Azov Sea and the Lower Dnieper were studied. We identified the representatives of C. (superspecies taenia) (51,6% of all researched specimens). C melanoleuca (4,1%), S. aurata (1,1%), allodiploids C. (superspecies taenia) × C melanoleuca (0,3%) and two groups of polyploid hybrids (46,4%). EET-group includs mainly C. elongatoides – 2 taenia and C. elongatoides – taenia – tanaitica. EET-group (2,8%) is represented only by C. elongatoides – 2 tanaitica biotype. In the Lower Donets and the Lower Dnieper, there is a zone of introgressive hybridization between C. taenia and C. tanaitica. The structure of settlements differs accordingly to the river basins and has a tendency to decreasing of polyploids frequency respetivly to meridional direction. The analysis of loaches samples from the coastal rivers of the Azov Sea collected in 1938 and samples from the Middle part of the Donets River in 1971 leads to the conclusion that polyploids in mentioned above regions appeared in 1960-1970s. The structure of diploid-polyploid settlements has an alternative character. More often, there is a predominance of diploids or polyploids. The reason of such bipolarity of settlements could be as reproductive displacement so a relatively strong tolerance of polyploids to anthropogenic climate change.

To test the possibility of identifying the species and biotypes of spined loaches of the complex Cobitis elongatoides – taenia – tanaitica using body morphometric characteristics, we considered a pool of specimens from different river systems of Ukraine. The sample included three parental species and seven hybrid biotypes with various genome combinations, and the morphometry was based on 23 body parameters and 26 derivative indices. The variability was analyzed by standard and multivariate statistics. Neither any one measurement, nor their combination allowed identifying the specimens with 95-100% probability. Pooled, samples had no internal logic of morphological remoteness of hybrid biotypes and parental species in regards to their genetic similarity. Morphometry’s low resolution in case of pooled samples is linked to the specifics of body shape and significant geographic variability which partially evens out the between-group differences, while within samples the resolution was higher without reaching even 95% diagnostical certainty. All in all, the resolutions obtained for morphometric parameters are within results obtained in similar studies for other hybrid fishes.

The variability of morphological characters and coloration features used for identification of the species Cobitissaniae has been studied using the materials from the collection of the Zoological Museum of Lomonosov Moscow State University, which includes voucher samples with genetically confirmed species status, in order to clarify the dynamics of the diversity of spined loaches in Transcaucasia in the anthropogenic period. Significant variability of many characteristics at the intraspecific level has been revealed. Previously proposed taxonomic keys do not allow to identify correctly C. saniae and C. faridpaki, which are accepted in the status of cryptic allopatric species differentiated by the analysis of the mitochondrial genome. The characters are suggested that make it possible to differentiate C. saniae from C. taenia and C. melanoleuca, inhabiting the basin of the Caspian Sea, and from two species known from water bodies within the modern range of C. saniae: Khvalynskaya spined loach C. amphilekta, common in the basin of the Kyzylagach Bay in the 1930s, and a new species C. derzhavini described from the Kura River basin. [ABSTRACT FROM AUTHOR]

To test the possibility of identifying the species and biotypes of spined loaches of the complex Cobitis elongatoides-taenia-tanaitica using body morphometric characteristics, we considered a pool of specimens from different river systems of Ukraine. The sample included three parental species and seven hybrid biotypes with various genome combinations, and the morphometry was based on 23 body parameters and 26 derivative indices. The variability was analyzed by standard and multivariate statistics. Neither any one measurement, nor their combination allowed identifying the specimens with 95-100% probability. Pooled, samples had no internal logic of morphological remoteness of hybrid biotypes and parental species in regards to their genetic similarity. Morphometry's low resolution in case of pooled samples is linked to the specifics of body shape and significant geographic variability which partially evens out the between-group differences, while within samples the resolution was higher without reaching even 95% diagnostical certainty. All in all, the resolutions obtained for morphometric parameters are within results obtained in similar studies for other hybrid fishes. [ABSTRACT FROM AUTHOR]

The region of Balkans is often considered as an ichthyologic “hot spot”, with great number of species and high portion of endemics living in fresh waters in a relatively small area. The Adriatic watershed in Croatia and Herzegovina is inhabited by six spined loach species (genus Cobitis) whose extinction risk estimations were based solely on their extent of occurrence (and/or area of occupancy) and its fragmentation, and conservation proposals do not consider diversity below species level. In this investigation we employed molecular genetic methods to describe present genetic structure of the Adriatic spined loaches and reveal their demographic history. The divergence of the Adriatic lineages inside the genus Cobitis started in Miocene and lasted until Pleistocene epoch. Even though all the investigated species inhabit karstic rivers located in the same geographic area and that were subject of similar geological events, the results obtained reveal great differences in their genetic diversity and structure and point out the necessity of different conservation measures to ensure their future viability. High level of genetic polymorphism is characteristic for species located more to the south. Two species comprised of more than one population have completely different intraspecific structure; populations of C. illyrica are genetically distinct and represent separate evolutionary significant units, whereas intraspecific structure of C. narentana corresponds to metapopulational pattern. Without population genetic data, evolutionary significant units could be easily misidentified. Furthermore, the obtained results affirm that population genetic measurements are able to detect differences among closely located and related species and estimate extinction risk even more accurately than currently applied IUCN criteria. The investigation was published in PLoS ONE 10(7):e0131580. doi: 10.1371/journal.pone.0131580

Abstract: The family Cobitidae represents a characteristic element of the Eurasian ichthyofauna. Despite diverse features of sexual dimorphism, comparably few morphological characters have been utilized for taxonomic studies resulting in many unresolved puzzles. Here we present the phylogenetic relationships of Cobitidae as inferred from the mitochondrial cytochrome b gene and the nuclear gene RAG-1. Analyses of both markers show a group of eight nominal genera, which all occur in Europe and eastern, northern and western Asia, forming a monophyletic lineage (northern clade) while all other clades inhabit South and Southeast Asia (southern lineages). While all eight southern lineages correspond to genera as defined by morphological studies, only four lineages were reliably recovered within the northern clade, and of these only one (Sabanejewia) corresponds to a formerly considered genus. The genera Cobitis, Iksookimia and Niwaëlla were polyphyletic. A comparison of the two markers shows several incongruities within the northern clade and mitochondrial introgression at least in the genus Misgurnus. Mapping the characters of sexual dimorphism on our cladogram, we identified five character states that are diagnostic for certain lineages. Estimations of the divergence times dated the separation of the northern clade from the southern lineages to the middle Eocene (46 MYA) and the origin of “Cobitis”misgurnoides, the basal taxon of the northern clade, during early Oligocene (30–35 MYA). The geographic distribution of the major clades supports recently developed hypotheses about the river history of East Asia and further suggests that a range expansion of the northern clade in late Miocene (15 MYA) led to the colonisation of Europe by three already distinct genera. [Copyright &y& Elsevier]

Abstract: We estimated the phylogenetic relationships of all Ibero-African spined loaches of the genus Cobitis using the complete mitochondrial cytochrome b gene (1140bp). We analysed 93 individuals of seven cobitid species found in all the principal drainages of the Iberian Peninsula and North Africa. A molecular phylogeny was used to revise current systematics of the Ibero-African Cobitis species and to infer a biogeographical model for Cobitis in the Western Mediterranean area during the Cenozoic period. Phylogenetic analysis provided support for the monophyly of two mtDNA clades: Clade A or Italian Clade with the Italian species (C. bilineata, C. zanandreai), and Clade B or the Ibero-African Clade. The Ibero-African Clade included all species endemic for the Iberian Peninsula (C. vettonica, C. calderoni, and C. paludica) and North Africa (C. maroccana). The species C. paludica does not constitute a natural group, and could be divided into at least four monophyletic mtDNA lineages with moderate to high bootstrap values and posterior probability support. Phylogenetic relationships of the Ibero-African species were not resolved satisfactorily, but in all analyses C. calderoni from Northern Iberian Peninsula was basal. We have re-calibrated a molecular clock for the genus Cobitis (0.68% per million year by pairwise) using populations inhabiting both sides of the Gibraltar Strait. Application of this Cobitis mtDNA clock provides evidence that the Messinian salinity crisis played a primary role in the diversification of some Ibero-African cobitid species. The basal polytomies of the Ibero-African Clade might suggest that all mtDNA lineages diversified rapidly. [Copyright &y& Elsevier]