Genetic Diversity Of Siganus Fuscescens In Coastal Waters Of China Based On Mitochondrial Control Region Sequences

With delicious taste and colorful patterns,Siganus fuscescens(Actinopterygii: Perciformes: Serranidae)has high market value and ornamental value throughout South China,Singapore,Philippines and other Southeast Asian countries.In recent years,due to overfishing and environmental pollutions etc,the catches of wild S.fuscescens along China’s coastal waters have dropped sharply,demanding for effective measures to be taken for sustainable utilization of the wild resources.Genetic diversity is prerequisite to species protection and utilization.In the present study,sequences of mtDNA control region of 12 S.fuscescens populations,including Wenzhou in Zhejiang Province;Ningde and Pingtan in Fujian Province;Shantou,Zhaopo,Naozhou Island,Wushi in Guangdong Province;Tanmen,Lingshui,Xingying,Dongfang in Hainan Province;Hepu in Guangxi Province were sequenced to sudy genetic diversity and phylogeographic patterns in S.fuscescens in coastal waters of China.The results are as follows:1)92 variable sites and 62 Parsimony informative sites were found in 741 bp segement of mtDNA control region from 297 specimens,accounting for 12.42% and 8.37% of the full length of the nucleotide sequences,respectively.Overall high genetic diversity and low nucleotide diversity(Hd =0.926±0.005,π=0.017±0.023)were observed in S.fuscescens,of which Shantou(Hd=0.917±0.024,π=0.007±0.0129)and Zhapo(Hd =0.867±0.029,π=0.009±0.0165)exhibited the lowest genetic diversity,and the highest genetic diversity occurred in Hepu(Hd=0.956± 0.017,0.022 ±0.0212)and Tanmen(Hd =0.917±0.024,π =0.022±0.0024).2)3 clades and two groups,all mixed individuals from different populations,were shown in the NJ tree and the haplotype network,and the divergence between the groups was about 72.6~21.8 million years.Clade A diverged from Clade B since 49.48~14.84 million years ago,and the divergence of Clade C from Clade A and Clade B were both within the Middle Pleistocene period,between 83.22~249,700 Years ago,which may have been influenced by the Pleistocene glacial events.3)Overall moderate differentiation occurred between Shantou and Naozhou Island,Ningde(FST: 0.112~0.134,0.01<P<0.05,Nm: 3.234~3.965).Mild and significant differentiation were found between Shantou and all other populations excluding Pingtan and Ningde(FST:0.039~ 0.100,0.01<P<0.05),similar differentiation also found between Zhapo and other 7 populations,i.e.Ningde,Pingtan,Shantou,Naozhou Island,Tanmen,Lingshui,and Hepu(FST:0.039~0.100,0.01<P<0.05).As for Clade A,moderate and significant differentiation occurred between Hepu and the Dongfang(FST: 0.120,P<0.05,Nm = 3.67);mild differentiation occurred between Ningde and Pingtan,Shantou,Naozhou Island(FST: 0.052~0.091,Nm: 5.02~9.08).Slight differentiation were found between Zhapo and Pingtan,Shantou,Naozhou Island(Fst: 0.009~0.073,0.01<P<0.05).Low differentiation(FST: 0.008~0.120,P<0.5)were shown between Hepu and Wenzhou,Naozhou Island and Tanmen Hepu.These differentiations might have been caused by seascapes such as Taiwan Strait,Qiongzhou Strait,coupled with China coastal currents and the warm current from South China Sea,oceangraphic circulations,and distinctive nearshore water masses,plus their unique eco-physiogical factors.4)Neutral test,mismatch distribution analysis and test of Ramos-Onsins & Rozas’ s R2 showed that the overall expansion time was 15.23~457 million years.The expansion of Group 1 and Group 2 occurred 10.85~3.26 million years ago,8.153~2.446 million years ago,respectively.The expansion time of Clade A and Clade C is 14.19~4.26 million years ago,8.15~2.44 million years ago,respectively,i.e.,in Pleistocene glacial period with sea level fluctuations,retaining the genetic signature that mainly affected by marine transgression or regression in S.fuscescens.5)Based on the genetic differentiation and genetic diversity of S.fuscescens in coastal waters of China,Hepu and Tanmen should be protected in priorioty,and Shantou and Zhapo be protected too.