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Background: An important aspect of studying evolution is to understand how new species are formed and their uniqueness is maintained. Hybridization can lead to the formation of new species through reorganization of the adaptive system and significant changes in phenotype. Interestingly, eight stable strains of 2nNCRC derived from interspecies hybridization have been established in our laboratory. To examine the phylogeographical pattern of the widely distributed genus Carassius across Eurasia and investigate the possible homoploid hybrid origin of the Carassius auratus complex lineage in light of past climatic events, the mitochondrial genome (mtDNA) and one nuclear DNA were used to reconstruct the phylogenetic relationship between the C. auratus complex and 2nNCRC and to assess how demographic history, dispersal and barriers to gene flow have led to the current distribution of the C. auratus complex. Results: As expected, 2nNCRC had a very close relationship with the C. auratus complex and similar morphological characteristics to those of the C. auratus complex, which is genetically distinct from the other three species of Carassius. The estimation of divergence time and ancestral state demonstrated that the C. auratus complex possibly originated from the Yangtze River basin in China. There were seven sublineages of the C. auratus complex across Eurasia and at least four mtDNA lineages endemic to particular geographical regions in China. The primary colonization route from China to Mongolia and the Far East (Russia) occurred during the Late Pliocene, and the diversification of other sublineages of the C. auratus complex specifically coincided with the interglacial stage during the Early and Mid-Pleistocene in China. Conclusion: Our results support the origin of the C. auratus complex in China, and its wide distribution across Eurasia was mainly due to natural Pleistocene dispersal and recent anthropogenic translocation. The sympatric distribution of the ancestral area for both parents of 2nNCRC and the C. auratus complex, as well as the significant changes in the structure of pharyngeal teeth and morphological characteristics between 2nNCRC and its parents, imply that homoploid hybrid speciation (HHS) for C. auratus could likely have occurred in nature. The diversification pattern indicated an independent evolutionary history of the C. auratus complex, which was not separated from the most recent common ancestor of C. carassius or C. cuvieri. Considering that the paleoclimate oscillation and the development of an eastward-flowing drainage system during the Pliocene and Pleistocene in China provided an opportunity for hybridization between divergent lineages, the formation of 2nNCRC in our laboratory could be a good candidate for explaining the HHS of C. auratus in nature. [ABSTRACT FROM AUTHOR]

Reducing carbon emissions and increasing carbon sinks are key strategies to effectively remove greenhouse gases from the atmosphere. Assessing the current carbon emission status and predicting future carbon emission scenarios could help formulate effective regional carbon emission reduction targets. However, it is necessary to enhance the carbon sink capacity of terrestrial ecosystems and improve forest management methods to promote greenhouse gas absorption. In this study, the spatiotemporal characteristics and dynamic evolution of fossil fuel CO 2 (FFCO 2) emissions in China from 2000 to 2019 were analyzed using the standard deviation ellipse, kernel density of emissions, and Theil index. A backpropagation (BP) neural network optimized with a genetic algorithm (GA) was used to predict FFCO 2 emission during 2020–2030. The biomass increment methodology was used to predict the potential carbon sinks generated by Chinese Certified Emission Reduction (CCER) carbon-sink forestry projects during 2020–2030. The results showed that China's FFCO 2 emissions exhibited a gradual increasing trend during 2000–2019, with an average annual growth rate of 6.29%. China's FFCO 2 emissions show a greater distribution on the southeastern coast than in the northwestern interior. The GA-BP prediction shows that China's FFCO 2 emissions will continue to fluctuate and increase between 2020 and 2030. The potential of carbon sinks will be 0.69 × 108 Mg C generated by the CCER carbon-sink forestry projects during 2020–2030, which could offset 0.56% of FFCO 2 emissions. In the future, imbalances in regional development should be considered when formulating carbon-reduction strategies. Moreover, using carbon-sink of forestry projects of CCER to balance economic development including poverty eradication and environmental conservation should be considered. Specifically, establishing a methodology of projects for the management of natural forests' carbon-sink will be an important future strategy. • China's FFCO 2 emissions rose in volatility with an average growth rate of 6.29%. • The spatial differences of FFCO 2 emissions are gradually narrowing. • FFCO 2 emissions will continue to rise in the future. • Carbon-sink forestry project is ideal approach to offset carbon emission. • The Methodology of Forests Management for natural forest should be focused. [ABSTRACT FROM AUTHOR]