Molecular Barcoding And Phylogeography Of Acanthogobius And Tridentiger (Teleostei: Gobiidae) Of Zhejiang Coast

The suborder Gobioidei (gobies) is the most speciese fish group in presently livingPerciformes. They are widely distributed and adaptable, due to their small size anddifficulty to identify, research on gobies is limited. In this study, we used DNA sequences toinfer molecular barcodes and phylogeography of Acanthogobius and Tridentiger ofZhejiang Coast. The results are summarized as follows:We analyzed615bp DNA sequences of mitochondrial cytochrome C subunit I (COI)for a total of30Acanthogobius samples collected from coastal areas of Zhejiang Coast. Thenumber of variable (polymorphic) sites in the COI sequences is10. The haplotype (Hd) andnucleotide diversity (π) are0.69and0.0033, respectively. On average, the distance ofKimura-2-parameter (K-2-P) is0.007within species, and0.186between congeners withinAcanthogobius. The intraspecific distances are significantly lower than congenericdistances (approximately1to27). DNA barcoding analysis indicates that a total of7haplotypes of Acanthogobius of Zhejiang Coast belong to a single species of A. ommaturus.In addition, COI gene sequence analysis suggests that A. ommaturus, A. hasta, andSynechogobius ommaturus are probably a synonym.A582bp DNA sequence of COI gene fragment and789bp DNA sequence of Ryr3were aligned and barcoded for203Tridentiger samples. A total of27distinct COIhaplotypes and40distinct Ryr3alleles were observed in203samples. In addition to T.barbatus and T. trigonocephalus, the analyses identified a third species, T. bifasciatus inZhejiang Coastal Waters. The number of samples is21for T. barbatus,40for T.trigonocephalus, and142for T. bifasciatus. Based on COI data, the distance ofKimura-2-parameter (K-2-P) is from0.001to0.003between T.trigonocephalus, and from0.001to0.011between T.bifasiatus. the distance of Kimura-2-parameter (K-2-P) is from0to0.001within T.trigonocephalus, and from0.001to0.006within T.bifasiatus. Based onRyr3data, the distance of Kimura-2-parameter (K-2-P) is from0.002to0.003betweenT.trigonocephalus, and0.001between T.bifasiatus. the distance of Kimura-2-parameter(K-2-P) is0.001within T.trigonocephalus, and0.001within T.bifasiatus. Bayesianphylogeny suggests that T.bifasiatus is more closely related to T.trigonocephalus than to T.barbatus. The result agrees with Taiwan Fish Taxonomy that T.barbatus should beclassfied in a different genus.COI and Ryr3DNA sequence data indicated that the levels of genetic diversity ofT.trigonocephalus and T.bifasiatus are lower. COI and Ryr3gene haplotype networkdiagram showed that no haplotypes of either T.trigonocephalus or T.bifasiatus formpopulation-specific groups. COI-based FSTis0.015-0.859and-0.006-0.686amongpopulations of T.trigonocephalus and of T.bifasiatus, respectively; Ryr3-based FSTis0.037-0.231and-0.004-0.299among populations of T.trigonocephalus and of T.bifasiatus,respectively. The results suggest that the levels of genetic divergence among geographicalpopulations are insignificant. There are several possible hypotheses,(1) the isolationbetween populations of same species took place recently;(2) the barrier-free coastal areaallows marine organisms within a very broad distribution to have low levels of divergence;(3) in addition, Taiwan Warm Current, the Yangtze River, and the Qiantang River meet inthe waters, and together they contribute to the proliferation and exchange of eggs, larvaeand adult of marine life.