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Loaches of Cobitis - fish with high potential for hybridization and subsequent polyploidization. How to determine the “potential for hybridization"? Does it exist?

Alicja Boron1* and Dorota Juchno1
  • 1 University of Warmia and Mazury in Olsztyn, Department of Zoology, Poland

Loaches Cobitidae include 262 species divided into 28 genera. Genus Cobitis is composed of 95 species of which 31 are distributed in European inland waters. Some of these species as the spined loach C. taenia Linnaeus, 1758, the Danubian loach C. elongatoides Bacescu & Maier, 1969 and the Don spined loach C. tanaitica Bacescu & Maier, 1969 through hybridization followed by premeiotic genome duplication produced polyploids. Long-term comparative cytogenetic studies of Cobitis taxa from 28 Polish populations revealed that 21 of them were diploid-tetraploid, containing not numerous C. taenia individuals and Cobitis hybrids as triploid females (3n=73-75) and tetraploids (4n=97-99) of both sexes. In the next population, apart from the listed taxa, there were also a few diploid C. taenia x C. elongatoides hybrids, while the other one and five were only C. elongatoides and C. taenia populations, respectively. So, the processes of hybridization and subsequent polyploidization completed successfully ensuring dominance of polyploid hybrids. Although C. taenia in exclusively populations is very numerous however, such populations are few (Juchno et al. 2014; Boroń et al. 2015). Which loaches properties make them hybridize and their hybrids not only survive but also reproduce? There are excellent studies about hybridizations as important steps leading to animal polyploidy, and processes of clonality and polyploidy in vertebrate animals originated by hybridization between two sexual species, about relations of polyploidy and hybridization, and their evolutionary consequences (among others: Choleva et al. 2012; Janko et al. 2012, 2017; Bartoš et al. 2019). Hybridization can speed adaptive evolution, furthermore the are frequently noted data on the association between hybridization and adaptive radiation, range expansion and invasion (among others: Mitchell et al. 2019). However, many intrinsic, determined by well-established genetic differences between species (e.g. reproductive barriers to fertilization and embryo development) and/or extrinsic isolating barriers prevent interspecific hybridization. At the same time there are fish taxa, among which the hybrids and polyploids are relatively frequent (Leggatt and Iwama 2003). How to determine the “potential for hybridization"? Does it exist? We summarized some features of hybridizing taxa which seem to be important in such determination, related to: a) phylogeny and genetics (evolutionary processes, postglacial distribution, polyploid origin, lack of determinate sex chromosomes, karyotype, DNA structure and content), b) biology (the ability to adapt to changing environmental conditions, reproductive mode, type of gamete formation, reproductive success, survival of offspring, lifespan, age of sexual maturity, preferred temperature range of water during spawning, spawning time, length and type of spawning, the ability to create hybrids from related species), c) environmental factors (type of water reservoir, catchment area, flood risk) and d) currently very important human activities (climate change, global warming, floods, water pollution, etc.) which can induce hybridization, apart other affecting the existence of extrinsic isolating barriers mediated by the action of environmental factors. In this study, the above mentioned data of Cobitis taxa and on some other natural hybrids and polyploids among loaches (Misgurnus) and cyprinids (e.g. Squalius, Carassius) are analyzed and compared to test the hypothesis that it is possible to indicate which properties of these taxa create their potential for hybridization leading to living and reproducing hybrids with an evolutionary future. Indication of the hybridization potential may allow, among others prediction of hybridization processes in the context of their impact on biological diversity or those among native and non-native fish species as a result of human activities.

Acknowledgements

This work was partially supported by grant no. 2011/03/B/NZ8/02982 of the National Science Center (NCN) and by project no. 12.610.006-300 of the Warmia and Mazury University in Olsztyn.

References

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Keywords: biology of species, Cobitis, hybridization, Polyploidy, reproducing barriers

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

Presentation Type: Oral

Topic: EVOLUTION AND ECOLOGY OF FISH WITH ASEXUAL REPRODUCTION, HYBRID COMPLEXES AND POLYPLOIDY, WITH SPECIAL FOCUS ON LOACHES (COBITOIDEI)

Citation: Boron A and Juchno D (2019). Loaches of Cobitis - fish with high potential for hybridization and subsequent polyploidization. How to determine the “potential for hybridization"? Does it exist?. Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00029

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Received: 26 May 2019; Published Online: 14 Aug 2019.

* Correspondence: Prof. Alicja Boron, University of Warmia and Mazury in Olsztyn, Department of Zoology, Olsztyn, Poland, alibo@uwm.edu.pl