International Journal of Aquaculture, 2025, Vol.15, No.3, 99-115 http://www.aquapublisher.com/index.php/ija 106 consistent with the environmental evolution of the late Cenozoic in the geological record. For example, many species within the broad-fronted Channa lineage (Gachua Formation) may have differentiated during the Pleistocene climate reversals within 2 Ma ~ 3 Ma (Sholihah et al., 2021). The stream isolation and water temperature fluctuations caused by the ice age provided an opportunity for the local differentiation of small Channa. Although these estimates have a certain error range, they generally outline the approximate time frame for the differentiation of the main lineages of the genus Snakehead. The division between Snakehead and its closest African genus Parachanna is speculated to be about 50 Ma ago, and can be traced back to the breakup of Gondwana at the end of the Cretaceous. This means that the ancestors of Asian and African Channa were on their own independent evolutionary paths as early as the end of the dinosaur age, and the subsequent plate drift and climate change shaped the discrete distribution pattern of Channa in Eurasia and Africa today. For the Snakehead genus, the differentiation node between the Southeast Asian and South Asian groups may be related to the transgression of the Indian Ocean and the Western Pacific Ocean in the middle Miocene, while the differentiation of the group within the Asian continent is related to events such as the uplift of the Qinghai-Tibet Plateau and the strengthening of the monsoon. For example, the formation period of the Argus Group coincided with the second stage of the uplift of the Qinghai-Tibet Plateau about 10 Ma, and the reorganization of the basin patterns of the Yangtze River and the Yellow River, which may have contributed to the northward spread and adaptive evolution of the ancestors of this lineage. Node analysis also revealed that the formation of the Snakehead genus may have undergone multiple fast radiations. Some nodes on the phylogenetic tree have low support values, suggesting that related species may have differentiated almost simultaneously in a short period of time on the geological time scale, making it difficult to distinguish the systematic relationship. This is particularly evident in small species of the Snakehead genus. For example, the relationship between multiple species in the broad-headedChanna group has long been controversial because they may have differentiated rapidly in a certain period of the Pleistocene, and the differences between genetic lineages are very small. This radiation may be driven by rapid climate fluctuations or the emergence of new ecological spaces. 5 Regional Comparisons and Lineage Patterns 5.1 Comparative sampling across Southeast Asia and South China The genus Snakehead is widely distributed in Southeast Asia and southern China, and the representative populations of these two regions show certain genetic differences. By comparing the mitochondrial DNA sequences of snakeheads in Southeast Asia and southern China, the characteristics of inter-regional lineage distribution can be revealed. Studies have shown that snakehead species in Southeast Asia (such as Thailand and Vietnam) are diverse, with multiple unique lineages, such as Channa striata and Channa micropeltes, which are both unique or mainly distributed species in the region. The mitochondrial sequences of these species are quite different from those of Chinese snakehead species, and they are in different branches on the phylogenetic tree. In contrast, the species of snakeheads in southern China are relatively limited, mainly Channa striata and Channa sinensis, which are closely related to some species in Southeast Asia in terms of phylogeny. For example, Channa striata and Channa lucius in Thailand belong to the same "Lucius Group" lineage. This suggests that there was species exchange and common ancestral lineages between southern China and Indochina. From the perspective of mitochondrial genetic distance, there is almost no difference between the individual sequences of Channa maculata collected from southern China and Vietnam and Laos, indicating that they belong to the same evolutionary unit and have no obvious differentiation. This is consistent with the distribution pattern of Channa maculata in South China and Indochina. In contrast, Channa argus is widely distributed in China, but it is not a native species in Indochina. There are only a few distribution records in northern Vietnam, which is speculated to be caused by artificial introduction or ancient human migration. Therefore, the lineage of Channa argus is almost limited to China, the Korean Peninsula, and the Russian Far East, and its mitochondrial type is rare in Southeast Asia. On the other hand, Indochina has some lineages of the genus Snakehead that are not
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