Genetic Diversity Of Eleutheronema In The East And South China Seas Based On Mitochondrial COI Gene Sequences Analysis

Eleutheronema fishes are valuable marine fish widely distributed in Indo-West Pacific, theyare also important aquacultural objects. Based on external morphological characteristics194specimens from9geographical populations, Partial mitochondrial cytochrome oxidase subunit1of some samples were sequenced via PCR amplification and DNA direct sequencing mothed.Combined with GenBank available homologous sequences from Indian Ocean, northern coast ofAustralia, Xisha Islands and Nansha Islands from China, altogether207Eleutheronema mtDNACOI sequences were analyzed to infer the genetic diversity and population structure. The resultswere as following:1. The species status of studied EleutheronemaThree significant genealogical branches were recognized on the neighbor-joining tree of theEleutheronema fishes. The results of genetic distances, genetic differentiation index, externalmorphological characteristics of the Eleutheronema and the historical material confirmed thespecies status. Most Eleutheronema fish in the East and South China Seas is E. rhadinum. Somespecimens distributed in Dongxing and Fuzhou,China, and all of the specimens in the north ofAustraliashoud be treated as a valid species E. coecus Macleay. In addition, there are largergenetic differentiation between groups from the coast of China and those from the coast ofnorthern Australian, indicating that there might exist a trend from them to become differentspecies.1specimens from Dongxing,China and all Indian Ocean specimens are E.tetradactylumaccording to the information of typotype.However, taking it into consideration that it is difficultto rule out the possibility of the existence of additional genealogical branches in this the vastwater area from Indian Ocean to the coastal of Dongxing,China.So here it is treated as E. cf.tetradactylum Temporarily.2. The genetic diversity and the genetic differentiation of EleutheronemaThe haplotype diversity (Hd) and nucleotide diversity (Pi) of E.rhadinum in the Southeastcoastal of China is0.5296±0.0888and0.001626±0.001240, respectively, indicating high levelhaplotype diversity and low level nucleotide diversity. Of which the haplotype diversity (Hd) and nucleotide diversity (Pi) of E.rhadinumin in the East coastal of China(Hd=0.6486±0.1023,Pi=0.002392±0.001673) are higher than those in the South coastal ofChina(Hd=0.3684±0.1350,Pi=0.000650±0.000703). The haplotype diversity (Hd) and nucleotidediversity (Pi) of Zhoushan group (Hd=0.6000±0.2152, Pi=0.001951±0.001658) are the highest,those of Dongtou second, and the lowest is Tanmen(Hd=0.2500±0.1802,Pi=0.000407±0.000577),which present a gradual reduction trend of thehaplotype diversity and nucleotide diversity from north to south. In addition, the results ofgenetic differentiation index and the genetic distances between populations suggest that therearen’t remarkable genetic differentiation among the groups of E.rhadinumin in the coastal ofChina.The haplotype diversity of E.coecus in the Southeast coastal of China and in the northcoastal of Australia are0.5029±0.1128and0.8195±0.0165, respectively, while their nucleotidediversity are0.000894±0.000859and0.002936±0.001886, respectively, indicating that bothhaplotype diversity and nucleotide diversity in Australia are higher than those in China. However,the results of haplotype diversity and nucleotide diversity of E.coecus Dongxing,China(Hd=0.5441±0.1110,Pi=0.000980±0.000917)are close to individual geographical populations inAustralia,Eighty-mile Beach (Hd=0.4302±0.0835,Pi=0.000767±0.000755),Arthur Creek（Hd=0.5323±0.0694,Pi=0.001041±0.000918) and Port Alma（Hd=0.6222±0.0705，Pi=0.001218±0.001017). In addition, The genetic differentiation index is0.86274±0.00000and thegenetic distances between populations is0.037,respectively,suggesting that there is remarkablegenetic differentiation among China and Australia groups.3.Demographic history of EleutheronemaAccording to nucleotide mismatch distribution, and the Tajiama’s value and Fu’s value ofEleutheronema, E.rhadinum in China have experienced a rapid Population expansion about61Ky ago, while it happened about250Ky ago in the eastern coastal of China,and it is39Ky agoin the southern coastal of China, i.e, southern coastal population expanded during the last glacialmaximum. However, the population of E.coecus in the coastal of Dongxing remained stable inhistory. There are obvious genetic differentiation between the population of Dongxing andAustralian, and the time is about1.7million years ago.4. The protection and management of the Eleutheronema in the coastal of China Three different species of Eleutheronema were found along the southeast coast of China,andthere are2species in the coastal of Dongxing, where should be protected in priority. Mostpopulations along the southeast coast of China are E.rhadinum, AMOVA analysis suggested thatmost genetic variation(97.68%) are found within population,and the genetic differentiation indexamong East China sea group and South China Sea group is0.02625±0.09910, what suggestedthat there are no obvious genetic differentiation among different population of E.rhadinum. Asgenetic diversity is higher in populations from the east coast of China than those from SouthChina sea, indicating that the former should be protected.