Zoological Studies

Vol. 45 No. 2, 2006

Phylogeographic Structure of Lenok (Brachymystax lenok Pallas) (Salmoninae, Salmonidae) Populations in Water Systems of Eastern China, Inferred from Mitochondrial DNA Sequences

Ying-Zhe Xia1,2, Yi-Yu Chen3, and Yan Sheng1,*

1School of Environment and Natural Resource, Renmin University of China, Beijing 100872, China
2Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
3Chinese Academy of Sciences, Beijing 100864, China

Ying-Zhe Xia, Yi-Yu Chen, and Yan Sheng (2006) Salmonid fishes represent a model system for addressing a wide range of biogeographic, evolutionary, and conservation questions. Studies on the genetic structure and phylogeographic pattern of Brachymystax lenok Pallas (Salmoninae, Salmonidae) populations are important for addressing the systematics, evolution, and effective conservation of the species. Partial sequences of the mitochondrial control region (835 bp) and cytochrome (cyt) b (1069 bp) were obtained by PCR amplification from 71 B. lenok individuals from 7 populations in the river systems of northern China. Analysis of molecular variance indicated that a high proportion of the total genetic variance was distributed among regions, supporting strong geographic structuring of mtDNA polymorphism. Phylogenetic analysis was conducted using Neighbor-joining (NJ), maximum likelihood (ML), and Bayesian approaches, based on the combined control region and cyt b sequences. Seventeen haplotypes were assigned to 3 clades that were related to geographic regions. No shared haplotypes were found among regions. The pattern of phylogenetic discontinuity, which is associated with spatial separation, is a result of both historical (long-term, zoogeographic barriers to gene flow) and contemporary (limited dispersal and gene flow capabilities) components. Based on our results, together with geological age data, we inferred that after entering the Amur River drainage, lenoks spread southwardly along inland drainages and hypothesize the dispersal route of the species in the water systems of eastern China. We further propose that each of the 3 evolutionarily distinct groups of lenok populations should be protected in order to avoid the loss of biodiversity. It is highly recommended that management efforts focus on riverine conservation, and avoid translocations among populations of different regions.

Key words: Phylogeography, Mitochondrial DNA, Control region, Cytochrome b, Brachymystax lenok.

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