Phylogeography of a freshwater sculpin, Cottus nozawae, from the northeastern part of Honshu Island, Japan |
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Authors: | Ryota Yokoyama Akira Goto |
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Institution: | (1) Laboratory of Breeding Science, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minatocho, Hakodate 041-8611, Japan (e-mail: yokoryo@fish.hokudai.ac.jp), JP |
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Abstract: | The fluvial sculpin, Cottus
nozawae, is a coldwater-adapted fish distributed in Hokkaido Island and the northeastern part of Honshu Island (Tohoku District),
Japan. Mitochondrial DNA (mtDNA) control region sequencing was used to investigate the geographic distribution of genetic
variation and phylogeography of C. nozawae. Most populations possessed unique haplotypes, few being shared across river systems. Phylogenetic analysis of the sequences
of the mtDNA control region and adjacent regions of C. nozawae revealed three distinct phylogenetic groups that differed by 3.05% to 3.11%, corresponding to distinct geographic regions,
Hokkaido Island, northern Tohoku District, and Yamagata Prefecture (southwestern Tohoku District), respectively. The divergence
times of three groups were estimated to be about 1.5 million years ago by applying a general rate for mtDNA, suggesting that
the divergence among them might have occurred in the early Pleistocene. Divergence among the haplotypes within the group from
the northern Tohoku District was also high (1.84%), no haplotypes being shared by local populations in different river systems
in this region. Local populations from a single river system in this region comprise a distinct lineage that differed from
other river systems. Such genetically divergent population structures among the different regions and river systems are considered
to have resulted mainly from long-term isolation and restricted gene flow among river systems, probably promoted by the fluvial
benthic life history and low dispersal ability of this species.
Received: April 12, 2001 / Revised: December 1, 2001 / Accepted: December 19, 2001 |
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Keywords: | Freshwater cottoid Mitochondrial DNA Control region sequences Genetic variation |
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