Abstract
Two species Lefua echigonia and Lefua sp. 2 of the eight-barbel loach inhabit the Tokai region of Honshu, Japan. We determined sequences of the mitochondrial D-loop region to elucidate intraspecific phylogenetic relationships and variation in these two species. Lefua sp. 2 represented high intraspecific genetic similarity and complicated haplotype network, but three assemblages were recognized, including specimens mainly from Yahagi, Toyo, and Tenryu River systems, respectively, and named Groups 1 to 3. Divergence of Group 1 from the others was marginally supported, but Group 2 was paraphyletic to Group 3, suggesting the existence of two populations, i.e. Yahagi River population and Toyo-Tenryu River population. Lefua echigonia also represented high intraspecific genetic similarity, and two assemblages with slight genetic differentiation were discernible, including specimens from Shizuoka and southeastern Aichi prefectures and those from northwestern Aichi, Gifu, and Mie prefectures, respectively, and named Groups A and B. Star-like relationships of haplotypes suggested the dispersal origin located in eastern Aichi prefecture. The two species are threatened to extinction and thus we proposed evolutionary significant units for conservation.
Highlights
Eight-barbel loaches belonging to the genus Lefua (Balitoridae, Cypriniformes) are primary freshwater fish less than 10 cm in total length
The loach had been identified as Lefua sp. on morphological and ecological grounds as above, our phylogenetic study by mitochondrial DNA and nuclear DNA sequencing showed that the loach in the Tokai region comprised a monophyletic group and was more closely related to L. echigonia than to Lefua sp
We demonstrated that L. echigonia comprised genetically seven intraspecific populations (Hokuriku, Tohoku, Yamagata, North-Kanto, South-Kanto, Kinki, and Tokai) and Lefua sp. 1 comprised two intraspecific populations (Kii-Shikoku and Sanyo) [7] [15]
Summary
Eight-barbel loaches belonging to the genus Lefua (Balitoridae, Cypriniformes) are primary freshwater fish less than 10 cm in total length. Than L. echigonia [3] [4], and on ecological traits with habitats of relatively fast-flowing mountain streams with gravelly beds of Lefua sp. Is waiting for a formal scientific description This species is distributed in western Japan including Kinki, Hokuriku, and Chugoku districts in Honshu and in Shikoku. Their distributions are disjunct, both species occur in relatively fast-flowing mountain streams with gravelly beds and generally have more slender bodies for adapting to fastflowing streams than L. echigonia. 1 comprised two intraspecific populations (Kii-Shikoku and Sanyo) [7] [15] These populations occur in regions that are geographically well separated by mountain ranges and highlands [1] [16]. Elucidation of cryptic ESUs is crucial for the protection of this unique loach
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