Population Genetic Structure And Biogeographic History Of Three Species Of Marine Fishes In The China Seas

Collichthys lucidus,Larimichthys polyactis and Trachurus japonicus are economically important marine fishes in the China seas.In the past several decades,some important economic species in the China seas have experienced rapid decline in body size and sharp decrease in fishing catch due to anthropogenic high fishing pressure and environmental pollution.In order to uncover the evolutionary response of marine fishes to human activities in the China seas,genetic structure and population historical dynamics of C.lucidus,L.polyactis and T.japonicus were examined based on different gene fragments of mitochondrial DNA.The main results are listed in the following:1.Population genetic structure and historical dynamics of C.lucidus from five sampling localities(Luchaogang,Zhoushan,Wenzhou,Fuzhou and Xiamen)in the East China Sea were studied based on mitochondrial Cytb and COI genes.The results showed that:(1)High genetic diversities of overall populations were revealed(Cytb gene,H_d=0.833±0.023,?=0.01582±0.00047;COI gene,H_d=0.782±0.021,?:=0.01054±0.00029);(2)Two genetic clusters including a northern group from Luchaogang,Zhoushan and Wenzhou and a southern group from Fuzhou and Xiamen were observed in reconstructed phylogenetic trees and haplotype networks;(3)Analysis of molecular variance(AMOVA)revealed main genetic variation occurring between above mentioned two groups(89.94%for Cytb gene and 88.26%for COI gene);(4)Neutral tests and unimodal pattern observed in mismatch distribution of C.lucidus indicated recent demographic expansions in each cluster.2.Genetic structure and population historical dynamics of L.polyactis were analyzed based on mitochondrial Cytb genes and D-loop sequences through sampling from eight coastal locations(Dalian,Shidao,Lvsi,Zhoushan,Xiangshan,Taizhou,Wenling,Wenzhou)in the China Sea.The results showed that:(1)High haplotype diversity(H_d)were observed in overall population(Cytb,H_d=0.993±0.002,?=0.00466±0.00018;D-loop,H_d=0.998±0.001,?=0.01218±0.00054);(2)A single star-like evolutionary lineage of L.polyactis was revealed in haplotype network and phylogenetic tree,respectively;(3)Analysis of molecular variance(AMOVA)showed that the main genetic variation of L.polyactis occurred within population(Cytb,99.73%;D-loop,100.12%)other than among populations;(4)Neutral tests and mismatch distribution analyses indicated that L.polyactis had experienced recent demographic expansion with genetic homogeneous population structure in the China seas.3.Genetic structure and population historical dynamics of T.japonicus in the coastal China seas were analyzed:(1)High haplotype diversity(Cytb gene,H_d=0.951±0.010;D-loop sequences,H_d=0.998±0.001)were observed;(2)A single star-shaped lineage was revealed from phylogenetic tree and haplotype network,respectively;(3)Analysis of molecular variance(AMOVA)among five sampling stations in the East China Sea continental shelf based on Cytb gene found that most of the genetic variation occurred within population(99.83%)instead of among populations.AMOVA among three geographic populations(East China Sea shelf,coastal Fujian province and Beibu Gulf)based on D-loop sequences revealed that most of the genetic variation also occurred within populations(99.39%)other than among populations;(4)Neutral tests and mismatch distribution analysis of T.japonicus suggested that recent demographic expansions had happened.In conclusion,high genetic diversity observed in L.polyactis and T.japonicus showed that some fishes in the coastal China seas still have strong recovery potential even facing high fishing pressure and strong human economical activities disturbance.Furthermore,L.polyactis and T.japonicus could be managed as a single genetic homogeneous population in the China seas,respectively.However,two identified genetic clusters(northern cluster and southern cluster)of C.lucidus can be regarded as two different significant evolutionary units in the future's fishery reserves design and management.A biogeographic boundary between coastal Wenzhou and Fuzhou cities likely exists to have influenced gene flow of marine species in the East China Sea,which should be confirmed through integrating physical-chemical oceanographic conditions and comparing phylogeographic patterns of different marine species in the China seas.