A study identifies that the common ancestor of zebrafish and pufferfish, which gave rise to approximately 22,000 ray-finned fish species, experienced a large-scale gene or complete genome duplication event. This event led to the retention of many duplicated genes in zebrafish, while pufferfish lost many of these duplicates. Phylogenetic and synteny analyses support this hypothesis, showing that zebrafish and pufferfish share duplicated genes, and that these duplications are not randomly distributed but clustered in specific genomic regions. The study also finds that many genes in zebrafish have orthologs in pufferfish, with some showing closer relationships to one zebrafish duplicate than the other. These findings suggest that the ancient fish-specific genome duplication event played a key role in the evolution of ray-finned fish. The study further demonstrates that genome duplication can lead to the creation of new gene functions, which is essential for evolutionary progress. The research also highlights the importance of combining phylogenetic and synteny data to understand genome evolution and the role of duplication in generating genetic diversity. The study provides evidence that genome duplication is a common and important mechanism in the evolution of many species, including fish. The results support the idea that genome duplication and speciation are closely linked, and that the duplication of genes can lead to the evolution of new functions. The study also shows that the zebrafish genome has a complex structure with multiple duplicated genes, and that these duplications are often located on the same chromosomes, suggesting that they may have been generated by a single duplication event. The study also finds that some genes, such as HspA1, were duplicated in fish before the divergence of the zebrafish and pufferfish lineages. The research provides insights into the evolutionary history of ray-finned fish and the role of genome duplication in their development. The study also highlights the importance of using multiple phylogenetic methods to accurately reconstruct the evolutionary history of genes and genomes. The findings contribute to the understanding of how genome duplication has shaped the evolution of vertebrates and other organisms.A study identifies that the common ancestor of zebrafish and pufferfish, which gave rise to approximately 22,000 ray-finned fish species, experienced a large-scale gene or complete genome duplication event. This event led to the retention of many duplicated genes in zebrafish, while pufferfish lost many of these duplicates. Phylogenetic and synteny analyses support this hypothesis, showing that zebrafish and pufferfish share duplicated genes, and that these duplications are not randomly distributed but clustered in specific genomic regions. The study also finds that many genes in zebrafish have orthologs in pufferfish, with some showing closer relationships to one zebrafish duplicate than the other. These findings suggest that the ancient fish-specific genome duplication event played a key role in the evolution of ray-finned fish. The study further demonstrates that genome duplication can lead to the creation of new gene functions, which is essential for evolutionary progress. The research also highlights the importance of combining phylogenetic and synteny data to understand genome evolution and the role of duplication in generating genetic diversity. The study provides evidence that genome duplication is a common and important mechanism in the evolution of many species, including fish. The results support the idea that genome duplication and speciation are closely linked, and that the duplication of genes can lead to the evolution of new functions. The study also shows that the zebrafish genome has a complex structure with multiple duplicated genes, and that these duplications are often located on the same chromosomes, suggesting that they may have been generated by a single duplication event. The study also finds that some genes, such as HspA1, were duplicated in fish before the divergence of the zebrafish and pufferfish lineages. The research provides insights into the evolutionary history of ray-finned fish and the role of genome duplication in their development. The study also highlights the importance of using multiple phylogenetic methods to accurately reconstruct the evolutionary history of genes and genomes. The findings contribute to the understanding of how genome duplication has shaped the evolution of vertebrates and other organisms.