Abstract
The phylogeography of Schizothorax waltoni, an endemic and endangered tetraploid schizothoracine fish in the Yarlung Tsangpo River (YLTR) on southern margin of Qinghai-Tibet Plateau (QTP), was investigated using two mitochondrial DNA regions and eleven microsatellite loci. Analyses of concatenated sequences of cytochrome b (1141 bp) and the control region (712 bp) revealed high haplotype diversity and moderate nucleotide diversity. High genetic diversity was observed based on microsatellite variation. Both mtDNA and microsatellite analyses revealed significant genetic differentiation between the eastern population (Mainling) and the other four populations to the west, and non-significant genetic differentiation amongst the three central populations in the west. Significant genetic differentiation was observed between the western population (Shigatse) and the three central populations based on microsatellite analyses alone. Bayesian skyline plot analyses showed that S. waltoni experienced a pronounced population expansion 0.05 to 0.10 Ma. Hierarchical structure analyses of microsatellite data indicated that S. waltoni could be split into three groups (western, central and eastern YLTR). The results indicate that three management units should be considered for S. waltoni. Our findings highlight the need for the conservation and effective management of S. waltoni, which is a key member of the endemic and highly threatened fishes of the QTP.
Highlights
Fishes are the most abundant group of vertebrates, and nearly half of their number are found in freshwater systems that constitute < 0.01% of the earth’s water[1]
cytochrome b gene (Cyt b) and control region (CR) sequences from each sample were concatenated into one sequence of 1853 bp (5′-Cyt b + CR-3′) for phylogenetic analysis, to give a total of 37 mitochondrial DNA (mtDNA) haplotypes in the concatenated data set
Whilst conservation measures have been put in place to protect some Qinghai-Tibet Plateau (QTP) freshwater fishes and S. waltoni in particular, such actions are unlikely to safeguard the long-term www.nature.com/scientificreports future of this species
Summary
Fishes are the most abundant group of vertebrates, and nearly half of their number are found in freshwater systems that constitute < 0.01% of the earth’s water[1]. In the new Red List of China’s Vertebrates[17], S. waltoni is assessed as Vulnerable It is one of the most important commercial fishes of this region and is fished mainly by set gill nets and electrofishing. It is long-lived, cold-adapted, has a slow growth rate, late sexual maturity and low fecundity[9,18], and is especially vulnerable to human activities such as overfishing, biological invasion by exotic fishes and construction of hydroelectric dams[18,19,20]. Understanding the level of genetic diversity and population genetic structure of S. waltoni is important for the effective conservation (e.g. hatchery production of juveniles from appropriate stocks) and management (e.g. restrictions on fishing activities) of the species
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