International Journal of Marine Science, 2025, Vol.15, No.2, 75-91 http://www.aquapublisher.com/index.php/ijms 76 Therefore, studying the origin and evolution, biological characteristics and response laws of Spanish mackerel fish is not only of scientific significance, but also helps to formulate effective fishery management and protection strategies. This study aims to review the "original and diffusion" of the genus Spanish mackerel, and comprehensively summarize the latest scientific research progress: mainly introduce the classification status, phylogenetic relationship and origin hypothesis of the genus Spanish mackerel; discuss the impact of paleogeography and climate change on the origin and distribution of genus Spanish mackerel; summarize the ecological physiological mechanism of Spanish mackerel adaptation to the environment; through the above content, we strive to reveal the survival picture of Spanish mackerel under the interweaving of the dual factors of evolution and human activities, and provide a scientific basis for fishery management and ecological protection of related species. 2 Phylogenetic and Origin of Scomberomorus spp. 2.1 Classification status and species diversity of the genus Spanish mackerel The Spanish mackerel belongs to the suborder of the Mackerel family Tuna, which is a specialized branch in the Mackerel family. The genus was first named in 1801 by French naturalist Lacepède based on specimens collected by Martinique. The Mackerel family is traditionally divided into several families according to its molecular and morphological characteristics. The Spanish mackerel belongs to the Scomberomorini family, which is parallel to the Mackerel (Scomber, such as Mackerel) and Tuna family (Thunnini). Currently, it is recognized that the genus Spanish mackerel contains about 18 effective species, commonly known as "mackerel" or "foxmackerel", and is distributed in warm waters around the world. These species are morphologically slender and streamlined, with sharp teeth and well-developed tail shank bulges, making a living by swiming at high speeds and preying on small fish. The main distinctive characteristics between different species include body lateral markings, scales and vertebrae number. For example, the body of the Japanese Spanish mackerel (S. niphonius) has blue-gray wavy markings, mainly produced in the northwest Pacific; the body of the narrow-band Spanish mackerel (S. commercial) has black stripes, which are widely distributed in the Indo-Western Pacific and invaded the Mediterranean Sea; while the Atlantic Spanish mackerel (S. maculatus) is scattered on the side, distributed along the Western Atlantic coast (Widayanti et al., 2024). Molecular phylogenetic analysis supports the effectiveness of species composition of Spanish mackerel species, but also suggests the possibility of hidden species. This suggests that species diversity in the genus Spanish mackerel may be underestimated, and that some widely distributed species have genetic differentiation within them. 2.2 Application of molecular phylogenetic analysis in origin research The development of modern molecular systems provides a powerful tool for exploring the origin and evolution of Spanish mackerel. Through mitochondrial DNA and nuclear gene sequence analysis, researchers were able to reconstruct the phylogenetic relationship within the genus Spanish mackerel and with other Spanish mackerel fishes, and calculate the differentiation time based on the molecular clock. Early phylogenetic research is mostly based on single gene sequences such as mitochondrial COI barcode or 16S. In recent years, it has gradually expanded to the combined analysis of multiple mitochondrial and nuclear genes. The results support the monolinearity of each known species of the genus Spanish mackerel, with clear lineage differentiation between Atlantic species (such as the Caribbean Mackerel S. regalis group) and Indo-Pacific species. Molecular clock analysis shows that the genus Spanish mackerel is likely to differentiate from other branches of the Spanish mackerel family from the late Paleogene to the early Neogene (about 30~25 million years ago), similar to the differentiation of the genus Tuna and Mackerel (Jeena et al., 2022). The genus has since experienced faster species radiation, forming the major current lineages during the Miocene to Pliocene. Genetic distance analysis of mitochondrial DNA sequences also reveals that some regional populations may have hidden taxons. For example, the narrowband mackerel samples collected in Australian waters are divided into two genetic branches, corresponding to the Australian endemic species S. queenslandicus and the wider narrowband mackerel, but these two species with similar morphology are difficult to distinguish molecularly. This finding prompts morphological review and re-evaluation of species boundaries (Zeng et al., 2022).
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