International Journal of Aquaculture, 2025, Vol.15, No.2, 88-98 http://www.aquapublisher.com/index.php/ija 96 as the evolutionary division of African catfish and Asian catfish), but also corrects several long-standing classification errors (such as the division of the genus of East Asian yellow catfish). The phylogenetic tree constructed by the mitochondrial genome is highly consistent with morphological evidence at the inter-family level, and reveals rich details and new discoveries at the intra-family level, including hidden species and complex phylogenetic structures. These advances have gradually improved the classification system of Siluriformes fish and laid a reliable systematic framework for evolutionary biology and ecological research. At the same time, the application of molecular clock and biogeographic analysis puts the diversification history of Siluriformes fish in the context of time and space, so that we have a preliminary answer to when and where this group appeared, how it spread and differentiated. For example, existing evidence supports that Siluriformes originated in South America in the Cretaceous, and then spread to the world through continental connection and drift events. The diversity of catfish on each continent was formed under the shaping of the geological history of the Cenozoic Era (such as the separation of Africa and South America, the evolution of the inland water system in Asia, etc.). This understanding is not only of academic value, but also provides a typical case for understanding the historical evolution of freshwater biota. Despite this, there are still some limitations and gaps in the current research, which is also the direction of future efforts. First, at the data level, although the currently public mitochondrial genome data of Siluriformes covers most families, some rare or restricted distribution groups are still undersampled. For example, some small families in Africa and cave catfishes in the Andes region of South America lack genome data, making some branches of the phylogenetic tree still incomplete. In the future, it is necessary to strengthen the genome sequencing of these unsampled groups through international cooperation to achieve comprehensive coverage of the main evolutionary lineages of Siluriformes. For the cryptic lineages that have been discovered, their taxonomic status should be further confirmed through multi-gene data and morphological evidence. For example, whether those MOTUs of the genus Siluriformes correspond to new species needs to be comprehensively described and named. Second, at the methodological level, although a single mitochondrial genome has a large amount of information, it only represents the maternal lineage after all. With the reduction of the cost of sequencing technology, it is a general trend to introduce nuclear genome data (such as transcriptomes, ultra-conserved elements, UCEs, etc.) into the phylogeny of Siluriformes. Nuclear genes have a genetic history independent of mitochondria, which can provide independent verification for phylogenetic trees and solve the possible inconsistencies between mitochondria and species trees (such as hybridization, maternal bias, etc.). Future taxonomic reconstruction work should integrate evidence from mitochondria and nuclear genes to build a more robust comprehensive phylogenetic framework. Third, in terms of analytical methods, in addition to traditional sequence alignment and tree construction, new models and computational methods are worth trying. For example, the application of Bayesian models of biogeography (such as BioGeoBEARS software) can quantify the possibility of different distribution models and accurately reconstruct the ancestral geographical range of each node of the catfish family. For another example, the use of molecular clocks at the whole genome level (such as substitution rate drift models) can better characterize the differences in evolutionary rates between lineages and provide a basis for understanding the "slow clock" or "fast clock" phenomenon of certain lineages. The study of phylogenetic and taxonomic reconstruction of the catfish family (Siluriformes) is entering a new stage of integrating multi-source data and analyzing deep problems. The fruitful results achieved in mitochondrial genome research in the past few years have laid a solid foundation for this field and inspired new scientific problems. Looking into the future, we look forward to further revealing the unsolved mysteries in the catfish evolutionary tree through more comprehensive genomic data, more advanced analytical methods and closer interdisciplinary collaboration. Acknowledgments We are grateful to Dr. W. Liu for his assistance with the serious reading and helpful discussions during the course of this work. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.
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