The Phylogeographic Relationships and the Evolution History of Carassius Auratus Complex With a Newborn Homodiploid Crucian Carp-like Fish (2nNCRC)

Background: One of the important aspects of studying evolution is to understand how new species are formed and their uniqueness maintained. Hybridization can lead to the formation of new species with the reorganization of adaptive system and significant changes in phenotype. It is wondrous that eight stable strains of 2nNCRC derived from the interspecies hybridization have been established in our laboratory. To examine the phylogeographical pattern of the wildly distributed genus Carassius in the Eurasia, and investigate the possible hybrid origin of Carassius auratus lineage, in light of past climatic events, the mitochondrial genome (mtDNA) were used to reconstruct the phylogenetic relationship between the C. auratus complex and the 2nNCRC, and to assess how demographic history, dispersal and barriers to gene flow have led to the current distribution of mtDNA lineages for C. auratus complex. Results: : As expected, the 2nNCRC had a very close relationship with the C. auratus complex, which was distinctly separated with other three species of Carassius . The C. auratus lineage possibly originated from China during the Late Pliocene, far postdated the diversification of C . carassius in Europe and C . cuvieri in Japan. The admixture of mtDNA haplotype lineages of C. auratus detected across the whole Eurasia has experienced a rapid diversification since Early Pleistocene Conclusion: Combined the molecular dating analyses, species distribution modeling and ancestral area reconstruction, the speciation of C. auratus seemed not to be the processing of lineage diversification from the most recent common ancestor of C. carassius or C . cuvieri . The formation of 2nNCRC in our laboratory could be a good candidate explaining for the hybrid origin species for C. auratus lineage, as well as the paleoclimate oscillation and geological event during Pliocene and Pleistocene in China supplying an opportunity for the distant hybridization. The most wildly distributed C. auratus lineage could be attributed to the dispersal during the glacial period and the recent human-facilitated dispersal.