Morphologies and population genetic structures of the eight-barbel loach of the genus Lefua on southern Sakhalin
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Morphologies and population genetic structures of the eight‑barbel loach of the genus Lefua on southern Sakhalin Yoshiyasu Machida1 · Minoru Kanaiwa2 · Sergey V. Shedko3 · Hajime Matsubara4 · Hirozumi Kobayashi5 · Ixchel F. Mandagi5,6 · Akira Ooyagi7 · Kazunori Yamahira5 Received: 7 December 2019 / Revised: 5 August 2020 / Accepted: 6 September 2020 © The Ichthyological Society of Japan 2020
Abstract Coldwater, primary freshwater, fish such as the eight-barbel loach, Lefua nikkonis, are thought to have colonised Hokkaido from the continental Far East via Sakhalin Island during the Late Pleistocene. Lefua populations have been reported on southern Sakhalin, but detailed morphological and population structure analyses have not yet been completed. This information is important for reconstructing the colonisation history of L. nikkonis to Hokkaido. In this study, morphological analysis revealed that L. nikkonis and two continental congeners, Lefua pleskei and Lefua costata, are distinguishable from each other, and Lefua collected from southern Sakhalin is morphologically more similar to L. nikkonis. Random forest analysis, a machine learning classification method, classified all Sakhalin individuals as L. nikkonis. Haplotype analysis of mitochondrial DNA sequences revealed that all but one Sakhalin haplotype are shared with L. nikkonis and none is shared with the two continental congeners, which supports the hypothesis that Sakhalin Lefua are L. nikkonis. However, none of the Sakhalin haplotypes was distributed on northern Hokkaido. This discontinuous distribution of haplotypes across Sakhalin and Hokkaido suggests that the Sakhalin Lefua populations are not native. Some of the Sakhalin haplotypes were found only on Hokkaido’s Ishikari River system or the Tokachi River system, suggesting that they originated from these regions. Because previous field surveys reported wild Lefua only from northwestern Sakhalin, we concluded that native Lefua on southern Sakhalin may have gone extinct after they colonised Hokkaido in the Middle Pleistocene. Keywords Random forest analysis · MtDNA · Siberian primary freshwater fish · Alien species Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10228-020-00783-1) contains supplementary material, which is available to authorized users. * Yoshiyasu Machida [email protected] 1
Bihoro Museum, Bihoro, Hokkaido 092‑0002, Japan
2
Mie University Graduate School, Faculty of Bioresources, Tsu, Mie 514‑8507, Japan
3
Federal Scientific Center of the East Asia Terrestrial Biodiversity FEB RAS, Vladivostok 690022, Russia
4
Faculty of Biological Science and Technology, Institute of Science and Engineering, Kanazawa University, Noto Center for Fisheries Science and Technology, Kanazawa University, Noto, Ishikawa 927‑0552, Japan
5
Tropical Biosphere Research Center, University of the Ryukyus, Okinawa 903‑0213, Japan
6
Faculty of Fisheries and Marine Science, Sam Ratulangi University, Manado 95115, Indonesia
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