International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.3, 144-152 http://ecoevopublisher.com/index.php/ijmec 147 due to its high mutation rate, maternal monophyletic inheritance, and easy amplification, is a commonly used marker in fish systematics, such as COI, Cyt b, 16S rRNA, etc., which are widely used in the classification and identification of black fish (Praveenraj et al., 2020; Zhang et al., 2024). Nuclear genes provide parental genetic information, with representative markers including the first recombinant kinase gene (RAG1), nuclear 28S rRNA, and actin introns. These nuclear sequences evolve at a slower rate, but can reflect deeper divergence events. To balance information from different evolutionary levels, recent studies have often adopted a multi gene joint strategy, such as linking mitochondrial gene sequences with nuclear sequences such as RAG1 and Rh protein gene fragments for analysis, in order to improve the robustness of the phylogenetic tree (Britz et al., 2020; Britz et al., 2024). In terms of analysis methods, Bayesian inference (BI) and maximum likelihood (ML) are currently the mainstream methods for constructing phylogenetic trees. By selecting appropriate replacement models and hyperparameters, a highly reliable system topology can be obtained. Zhang et al. (2024) constructed COI gene trees using both BI and ML methods when studying a new species of Burmese dwarf snakehead, and both methods consistently clustered the new species into monophyletic branches. In addition, molecular systematics also utilizes some auxiliary methods. For example, using BEAST software for simultaneous inference of molecular clocks and phylogenetic trees, node ages can be directly annotated on the system tree; Using population genetic methods such as STRUCTURE to validate the corresponding cryptic units of system branches (Praveenraj et al., 2020); And explore the possible effects of hybridization and gene flow on system relationships through network analysis. 3.2 Phylogenetic tree construction results and major lineage divisions The new DNA analysis provides a more precise molecular basis for the classification of snakehead fish (Britz et al., 2020; Britz et al., 2024). One group lives in northern areas. This includes fish like Channa argus and Channa asiatica. They're mostly found in East Asia's cooler waters. The family tree shows these fish from northern China and the Yangtze River are closely related. The South Asian branch includes large species such as Channa punctata and Channa marulius, forming independent branches on the phylogenetic tree (Britz et al., 2020). These large fish species are concentrated in the river and lake systems of the South Asian subcontinent, and there are significant differences in habitat preferences and morphological characteristics compared to Southeast Asian groups. Its typical ecological characteristics include a preference for open water environments and adaptation to still or slow-moving habitats in plain areas. Southeast Asian subfamily (Gachua group, Lucius group, Micropeltes group, Striata group, etc.): This represents the most diverse and evolutionarily successful clade within the genus Channa, including numerous small and medium-sized species, distributed in Thailand, Indochina Peninsula, Malay Archipelago, and other places. The Gachua group includes many dwarf snakeheads with a body length of only over ten centimeters, such as C. gachua and C. andro, which are rich in species and mostly distributed in narrow areas (Bhardwaj et al., 2022). The Lucius group is represented by the Javanese snakehead (C. lucius), which is characterized by black spots on the head; The Micropeltes group is represented by the largest giant snakehead; The Striata group, on the other hand, includes the spotted snakehead and its related species, which are widely distributed in the wetlands of Southeast Asian plains (Britz et al., 2020). Molecular systematics supports the formation of several closely related monophyletic groups of these Southeast Asian blackfish species. The mitochondrial genome study by Sun et al. (2024) showed a close relationship between the yellow snakehead from Assam, India and the dwarf snakehead (C. burmanica) from Myanmar, both of which are close to the Jurassic snakehead group rather than the traditionally thought Yellow snakehead group. 3.3 Molecular clock estimation and spatiotemporal dispersion patterns of lineages Researchers used a molecular clock method to estimate when each Channa lineage branched off. This helps link blackfish evolution with Earth’s climate and geological history. It also lets scientists guess how these fish spread over time and space (Britz et al., 2020). In Asia, most of the major blackfish lineages began forming between the late Oligocene and early Miocene, which is around 18 to 30 million years ago (Kumar et al., 2021). The evolution
RkJQdWJsaXNoZXIy MjQ4ODYzNA==