Molecular Phylogeny Of Two Acartia Species In China Southeast Coastal Seas

Acartia spinicauda Giesbrecht 1889 and Acartia pacifica Steuer 1915 are the highly-abundant, widely-distributed, and characteristically estuarine holoplanktonic calanoid copepod in China sea, they had described from several estuaries. We have little knowledge on the significant problems as follow as the evolution relationship of these two Acartia species, taxonomic status of their intermediate forms, population geodiversity and differentiation. For this study, the molecular population genetic diversity of A. spinicauda and A. pacifica was described based on DNA sequence variation for mtCOI gene and mt16S rRNA gene. Based on the analysis and calculation of the mtCOI and mt16S rRNA sequences, we want to know the genetic diversity, population genetic structure, gene flow among Fujian coastal seas. The brief results are as follows1. 7 female individuals of A.spinicauda and 8 A.pacifica female individuals'mtCOI gene fragment sequences were obtained. The length of the sequence is 658 bp. We submited 4 sequences to the Genbank (assessing number: DQ665251, DQ665252, DQ6652513, DQ665251). We also obtained 30 mt16S rRNA sequences of these two Acartia species (17 individuals of A.spinicauda, 13 individuals of A.pacifica).2. The average genetic distance of A. spinicauda and A. pacifica based on the mtCOI (658bp) and mt16S rRNA (209bp) is 19.13% and 24.95%, respectively. It would be concluded that they are different species for a certainty. We also found two kinds of intermediate forms between these two species, and define their taxonomic status. As the result, we brought forward a new morphological taxonomic method to distinguish the two Acartia species and their intermediate forms.3. We obtained the mtCOI and mt16S rRNA gene fragment sequences of A. pacifica from Jiulong jiang estuary and Min jiang estuary, The average genetic distance is 1.28% and 1.80%, respectively. The value of Fst, 0.1306, was measured, and the value of Nm, 1.66, was estimated based on the value of Fst. The results revealed that A. pacifica from Fujian coastal waters was a population with high gene flow. There was still no population differentiation found in Fujian coastal waters by using Chi-square test and PM (permutation) test with P value > 0.05 (no signicant).4. DNA sequences of mtCOI genes differed between individuals of A. pacifica from south Taiwan strait and A. pacifica from Fujian coastal waters and supported their designation as distinct species: 31.6% for mtCOI. The gene flow pattern between them also shows highly isolation: Fst = 0.9462; Nm = 0.01.5. The evidence of mtCOI and mt16S rRNA sequences, morphological characteristics and ecology bring us a clearly conclusion: A. pacifica which is distributed in low salinity Fujian coastal waters is the same species to a new Acartia species which was reported from the Ariake Bay, Japan. The real A. pacifica of China sea is distributed in the high salinity waters of the south China sea.6. In order to further examine the pattern of evolution and phylogeny within Acartia, consensus mtCOI and mt16S rRNA sequences of Acartia spp. were used to reconstruct phylogenetic tree.