International Journal of Aquaculture, 2025, Vol.15, No.2, 88-98 http://www.aquapublisher.com/index.php/ija 94 the vast majority of species, began to diversify rapidly about 94 million years ago. The timing of this series of differentiation events is very close to the final separation of South America and Africa (about 100 million years ago). Therefore, it can be inferred that the global radiation of Siluriformes fish is closely related to the isolation of continental plates in the middle and late Cretaceous period. After South America split from Africa, catfish populations on different continents evolved independently, gradually forming two major branch patterns of "African system" and "South American system". 6.2 Origin and dispersal routes of major Siluriformes lineages In addition to clarifying the macroscopic evolutionary time of the entire Siluriformes, molecular clock analysis can also be used to compare the evolutionary rates of specific families or genera and study the rate of speciation. For example, some scholars have focused on the rate of body size evolution of Siluriformes fish. By plotting body length traits on a time-corrected tree, they found that in the past 100 million years of evolution, the body size changes of different lineages were not in a single direction, but showed 16 significant large-scale evolutionary events and 11 small-scale evolutionary events, and there was no overall trend of continuous increase or decrease. This result negates simple hypotheses such as the "large-scale trend", indicating that the body size evolution of catfish is driven by niche diversification, and different branches may evolve their body size in different directions according to environmental selection pressure. For example, the body mass index of the Piraíba giant catfish increased by 5.65 times in about 40.8 million years, while the cave catfish of another lineage evolved a dwarfed body shape. These trait evolution analyses based on time trees demonstrate the power of the molecular clock combined with phylogeny, that is, the rate and period of trait change can be quantitatively characterized, thereby inferring possible factors driving evolution (Kishimoto et al., 2020). 6.3 Influence of geological and climatic events on lineage formation Historical biogeographic analysis is another important component of phylogenetic research. It attempts to link the branching of phylogenetic trees with geographical distribution, reconstruct the distribution range of the ancestors of species or groups, and infer events such as migration and isolation. In Siluriformes fish, historical biogeographic analysis has revealed many interesting patterns. For example, the aforementioned study of the genus Silurus showed that its ancestors probably originated from the East Asian continent and spread to other parts of Eurasia many times. This conclusion provides a basis for explaining the east-west distribution pattern of the genus Silurus. Similarly, at the family level, the North American Siluridae and the Chinese Siluridae form sister groups. The analysis of the ancestral distribution area speculates that their most recent common ancestor may have lived in the northern part of the ancient Laurasia in the late Cretaceous, and then separated into the east and west due to the breakup of the continent (Zhang et al., 2024). For example, the Clariidae from Africa and the Heteropneustidae from South Asia form sister groups. Their most recent common ancestor is presumed to be on the African-South Asian plate, which was still connected at the end of the Cretaceous. Later, as the plates separated, they evolved into today's distribution. These inferences need to be combined with paleogeographic evidence and fossil records for comprehensive judgment, but mitochondrial phylogeny provides key evolutionary sequence information. Historical biogeographic analysis can also test regional diversification hypotheses. For example, for small catfishes (such as Glyptothorax) in the rapids environment of the Asian Plateau, a study combined phylogenetic and geographic information and found that their diversification is highly consistent with the uplift event of the Qinghai-Tibet Plateau, that is, the geologically new river network provided a large number of new habitats for these mountain stream fish, driving the rapid differentiation of species (He et al., 2020). This "large-scale radiation" pattern is also reflected in other groups of Siluriformes, such as small electric catfish and hook catfish in the Congo River basin in Africa (Day et al., 2023). 7 Broader Implications for Evolution and Biodiversity 7.1 Origin and dispersal pathways of Siluriformes diversity The results of phylogenetic and taxonomic reconstruction studies of Siluriformes fish have far-reaching significance for understanding the evolutionary mechanism of fish and biodiversity conservation. At the level of evolutionary biology, a complete phylogenetic tree is the basis for analyzing the evolutionary pattern of traits. By
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