Research on Phylogenesis and Species Definition of <i>Oxyeleotris marmoratus</i> Based on Mitochondrial Genome

Marble goby ( Oxyeleotris marmorata ) is a freshwater fish with high economic value in aquaculture and widespread distribution in Southeast Asia. In this study, phylogenetic analysis of marble goby and related groups was performed using mitochondrial genome data from previous studies, and molecular population genetics was used to explore their species boundaries. Many results showed that the mitochondrial genome of marble goby is about 16.5 kb in length, encoding 13 protein genes, 22  tRNA  genes and 2  rRNA  genes, and the gene structure is consistent with that of typical bony fish. The phylogenetic tree shows that marble goby belongs to the family Channidae of the suborder Goby in fish classification, and is clearly differentiated from closely related groups such as the family Oxyeleotris (mudskippers, etc.) and the family Goby. The mitochondrial genetic differences between different geographical populations within the species are low (for example, the COI genetic distance between the artificially cultured population and the wild population is only 0.66%), but obvious genetic differentiation is still observed between the large river basins, suggesting the possible existence of cryptic lineages. Closely related species that are difficult to distinguish by morphological identification can be identified by molecular data. Species delimitation analysis based on mitochondrial sequences supports that the marble goby is a single species, but it is recommended to combine nuclear genome data for comprehensive taxonomic verification. This study emphasizes the importance of combining morphological characteristics with molecular evidence for species delimitation, and puts forward conservation and management recommendations for the phylogeographic pattern of marble goby in the Mekong region. The research results provide a scientific basis for fish taxonomy, species conservation and aquaculture breeding.