Taxonomic Status Research Of Hapalogenys And Divergence Time Estimates For Perciformes

The Hapalogenys genus fish belongs to Perciformes, Percoidei, and Haemulidae, and it is a worldwide temperate and tropical coastal fish. It had obvious regional distribution characteristics and limitations, and had been become good materials for phylogenetic relationships, origin and evolution of fish. The Hapalogenys genus was still not clear in its phylogenetic position of Percoidei so far. Therefore, this study determined four complete mitochondrial genome sequences of Perciformes fish, and analyzed sequence features for coding and non-coding region.We used62whole mitochondrial genome sequences by Maximum likelihood and Bayesian method to solve Hapalogenys germs classification status in Percoidei suborder. A loose molecular clock method was used for estimating origin time for Perciformes fish, and expecting to accumulate theory material for Perciformes fish. The main studies are as follows:(1) This paper determined four complete mitochondrial genome sequences of Perciformes fish (Hapalogenys analis, Grammistes sexlineatus, Psenes pellucidus, Chaeturichthys stigmatias), and analyzed mitochondrial genome structural. We found that mitochondrial genome base composition and gene order were more conservative, as was similar to that in the bony fish. Specifically, the lacking of tRNA-Pro gene was found in mitochondrial genome of Hapalogenys analis. Four kinds of fish mitochondrial genome sequence length was difference, mainly due to the length of the control region. Replication origin region of the light chain (OL) could form a stable stem-loop secondary structure, and there were three conserved sequence:5’-GCCGG-3’,5’-TCCGG-3’and5’-GCGGG-3in arm structure. Most species identified termination-associated sequences, but the central conserved domain and conserved sequence block varied greatly and lost in fish mitochondrial genome for this study.(2) The Hapalogenys molecular phylogenetic tree was constructed by Maximum likelihood and Bayesian method based on62complete mitochondrial genome sequences. Results showed that Hapalogenys was removed from Haemulidae family and clustered Lethrinidae and Sparidae together. However, the Haemulidae family clustered Monodactylidae to constitute the sister group. This result supported Hapalogenys was separated from Haemulidae and it was upgraded to a family rank titled Hapalogenyidae of Percoidei.(3) We used a loose molecular clock constraint analysis to estimate divergence time for Perciformes fish. The result indicated it dated back160million years ago, the Jurassic period, and it was older than the ancient old fossil record. Meanwhile, certain groups of Perciformes radiation evolutionary time dated back between the Cretaceous and Tertiary. We speculated that the climate environment has an influence on Periformes fish evolution.