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Hybridization of Caucasian barbels of the genus Barbus s. str.

Boris A. Levin1* and Gandlin A. Alexander1
  • 1 Institute of Biology of Inland Waters, Russian Academy of Sciences, Russia

The genus Barbus s. str. is an evolutionary tetraploid lineage that comprises > 30 species distributed in Europe and West Asia. Compared to the barbels from Western and Central Europe, the taxonomy, phylogeny, and evolutionary history of Caucasian barbels are under investigated. Caucasus is a large mountain system located between the Black and Caspian seas which is considered as one of the world’s biodiversity ‘hotspots’ under conservation. All Caucasian Barbus (five-six species) were considered to be allopatrically distributed in the region. Recently the sympatric co-occurrence of B. kubanicus and B. tauricus was detected (Levin et al., 2019) in the Kuban River, Northern Caucasus, where from only B. kubanicus was previously reported. The B. tauricus was recorded in two rivers, the Abin and Neberdjai. Both are left tributaries of lower Kuban. The aim of the study was to test whether sympatrically occurring Barbus spp. do hybridize or coexist without hybridization. Materials and Methods DNA samples (n=75) were collected during 2015-2019 in the Kuban River basin and from the rivers discharging to the eastern part of Black Sea from 28 localities. Marker of mtDNA, a cytochrome b (cytb, 993 bp) and marker of nDNA, a second intron of beta actin gene (Act-2, 447 bp) were analyzed. Additional cytb sequences (n=12) from other rivers of Black Sea were added from the GenBank for analysis. The phylogenetic tree was built using both BI and ML approaches using GTR+G+I model. Haplotype networks were built with help of PopART 1.7 using median joining algorithm. Heterozygotes of individual sequences of Act-2 were identified by double peaks in chromatograms. All polymorphic sites were carefully inspected to ensure consistent identification of such positions. The sequences were aligned using Muscle 3.8.31. Alleles (haplotypes) of the Act-2 were inferred using Phase version 2.1 with 1 000 burn-in steps and 1 000 iterations. Some individuals carried alleles of different size due to insertion/deletions polymorphism, as were evident from offset chromatogram peaks. Results Recently discovered Kuban population of B. tauricus is not similar to geographically closest conspecific populations from the eastern coast of the Black Sea or from Crimean Peninsula according to cytb sequences. It is genetically closer to populations from southern coast in Turkey. This supports the hypothesis of different waves of migration and dispersal of fish fauna during freshwater phases of the Black Sea (Ryan et al., 2003; Kotlik et al., 2004; Turan et al., 2018; Levin et al., 2019). Hence, we consider Kuban population of B. tauricus as relic. Six individuals of B. tauricus in Kuban basin were heterozygous in Act-2 sequences having one allele specific to B. kubanicus. In addition, four individuals of B. tauricus were homozygous in Act-2 sequences however possessed mtDNA from B. kubanicus that provides an evidence of mitochondrial introgression. Turan et al. (2018) reported that some individuals of B. kubanicus have mtDNA of B. tauricus in the Kuban basin based on cytochrome oxidase I subunit sequences. They considered this as an trace of ancient hybridization. According to our data, it might be not ancient but ongoing hybridization in zone of sympatric co-occurrence of two barbel species. Major conclusions Our study provides an evidence on hybridization between Caucasian barbels. Hybridization between B. kubanicus and B. tauricus was detected in their sympatric co-occurrence in the Lower Kuban basin. It resulted from secondary contact of two Caucasian species, one of which has colonized the Kuban River during one of the freshwater phases of the Black Sea.

Acknowledgements

The study was supported by Russian Foundation for Basic Research (grant no. 19-04-00719). We are very grateful to all persons, which shared field operations as well as to Evgeniy Simonov for his bioinformatician help.

References

References Kotlik, P., Bogutskaya, N. G., & Ekmekci, F. G. (2004). Circum Black Sea phylogeography of Barbus freshwater fishes: divergence in the Pontic glacial refugium. Molecular Ecology, 13, 87-95. Levin B.A., Gandlin A.A., Simonov E.S., Levina M.A., Barmintseva A.E., Japoshvili B., Mugue N.S., Mumladze L., Mustafayev N.J., Pashkov A.N. Roubenyan H.R., Shapovalov M.I., Doadrio I. (2019). Phylogeny, phylogeography and hybridization of Caucasian barbels of the genus Barbus (Actinopterygii, Cyprinidae). Molecular Phylogenetics and Evolution, 135, 31-44. Ryan, W. B., Major, C. O., Lericolais, G., & Goldstein, S. L. (2003). Catastrophic flooding of the Black Sea. Annual Review of Earth and Planetary Sciences, 31(1), 525-554. Turan, D., Kaya, C., Geiger, M., Freyhof, J. (2018). Barbus anatolicus, a new barbel from the Kızılırmak and Yeşilırmak River drainages in northern Anatolia (Teleostei: Cyprinidae). Zootaxa, 4461(4), 539-557.

Keywords: Caucasus, Cyprinids, hybridization, Barbus, Introgression

Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.

Presentation Type: Poster

Topic: TAXONOMY, PHYLOGENY AND ZOOGEOGRAPHY

Citation: Levin BA and Alexander GA (2019). Hybridization of Caucasian barbels of the genus Barbus s. str.. Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00124

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Received: 30 May 2019; Published Online: 14 Aug 2019.

* Correspondence: Dr. Boris A Levin, Institute of Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia, borislyovin@mail.ru