| Widely distributed in temperate and tropical coastal waters, Sparid fishes(Osteichthyes, Perciformes, and Percoidei) are one of the most economically important fish families in the world: most of them are delicious and of high nutritional value, and some species have high fishery landings and aquaculture yields. Sparid fishes are important subject of bottom trawl fisheries along the southeast coast of China, of which Pagrus major is listed as one of the “four most famous marine fishes” in China, and Pagrus major, Acanthopagrus schlegeli, and Rhabdosargus sarba etc are important mariculture. However in recent years, due to the increasingly impacts of nature and human factors, wild resources of A. schlegeli and R. sarba are rapidly depleted, and no fishing season can be found in P. major. As such, in this paper sequences of mitochondrial DNA D-loop control region of 11 populations(238 individuals) of P. majors, 12 populations(266 individuals) of A. schlegelis and 6 populations(137 individuals) of R. sarbas were analyzed to study genetic background of Sparid fishes along coastal waters of China, with an aim to provide a theoretical reference for the development of effective protection measures and sustainable exploitation of the germplasm. The results were as following:1. P. major. 1) High haplotype diversity and high nucleotide diversity(Hd= 0.996±0.001, π= 0.022±0.0004) have been shown. Of which, genetic diversity of Laizhou population in Bohai Sea(Hd= 0.533±0.032, π= 0.009±0.0043) is much poorer than the remaining populations(Hd: 0.989~1.000, π: 0.020~0.023). 2) There are 3 clades without obvious geographic structure in the neighbor-joining tree, and the deduced divergence time was about 0.5~0.13 million years ago in the pleistocene period, which might be related to climate fluctuation and glacial change. High differentiation(Fst: 0.240~0.399, P< 0.01) between Laizhou population and the remaining populations, and low degree of differentiation(Fst: 0.058~0.110, P< 0.05) between Beihai population in beibu gulf and Donggang, Laoshan, Korea and Daya Bay populations suggested that there might be some local adaptation or bottleneck in Bohai population, and Qiongzhou Strait might have had negative effects on gene flow. Neutrality tests, mismatch distribution and R2 test showed P. major overall and 3 clades have occurred population expansion about 0.303~0.078 million years ago, which probably related to the transgression of sea water during the late Pleistocene epochs. 3) With highest genetic diversity, Daya bay population is recommended to be protected in priority. Laizhou population with lowest genetic diversity should be protected too to avoid population collapse and eventual extinction.2. A. schlegeli. 1) A. schlegeli has high haplotype diversity and poor nucleotide diversity(Hd= 0.994±0.001, π= 0.0074±0.0002), among 12 populations, the genetic diversity of Yingkou population(Hd= 0.934±0.051, π= 0.0050±0.0006) is the poorest and Daya bay population(Hd= 0.986±0.013, π= 0.0085±0.0005) is the highest. 2) There is no obvious lineage and geographical structure in NJ phylogenetic tree of A. schlegeli; there is no significant differentiation within Bohai Sea and Yellow Sea populations, as well as East China Sea and South China Sea populations, but there do exist a low degree of differentiation between the two groups, suggesting that the Yangtze River diluted water might have had an important impact on the differentiation of A. schlegeli population in coastal waters of China. Neutrality tests, mismatch distribution and R2 test indicated that a population expansion has been occurred in A. schlegeli about 0.124~0.037 million years ago, which might be caused by the fluctuation of sea level due to the glacial and interglacial cycle during the Pleistocene epochs. 3) With highest genetic diversity, Daya bay population is recommended to be protected in priority. Yingkou population has the poorest genetic diversity, it should be also protected to avoid population collapse or even extinction.3. R. sarbas. 1) Genetic diversity of R. sarbas is similar to A. schlegeli, it’s also has high haplotype diversity(0.993~1.000) and poor nucleotide diversity(0.0063~0.0083). Of which, genetic diversity of Boao population(Hd= 1.000±0.020, π= 0.0063±0.0006) is the poorest and Daya bay population(Hd= 1.000±0.011, π= 0.0083±0.0009) is the highest. 2) NJ tree of R. sarbas is similar to A. schlegeli, lacking of obvious lineage and geographical structure. Deduced population expansion in R. sarbas occurred about 0.124~0.037 million years ago, also similar to that of A. schlegeli, indicated that they might have been affected by the same historical events. A certain degree of differentiation(Fst= 0.031, P< 0.01) between Boao and Huilai populations might be related to the reciprocal influence caused by ocean currents and along shore currents. 3) Genetic diversity of Fuqin and Huilai populations are relatively higher, demanding for protection in priority. |
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