International Journal of Marine Science, 2025, Vol.15, No.2, 92-106 http://www.aquapublisher.com/index.php/ijms 102 7 Environmental Adaptability and The Geographical Driving Role of Ecological Factors 7.1 Shaping of population structure by salinity, temperature and ocean current systems Environmental factors play a key driving role in shaping shrimp population structure and geographical distribution. Among them, seawater salinity and temperature are the two main ecological factors that affect shrimp survival and reproduction. Different populations may form local adaptation to salinity and temperature during long-term adaptation, thereby forming a genetic differentiation pattern in space. Australian black tiger shrimps form significantly different genetic groups in the northern tropical waters and the western semi-temperature waters, partly due to the different annual cycles of water temperatures in the two places. Experts found that the population diversity of black tiger shrimps in areas with higher water temperatures and stable waters along North Australia is relatively low, while the population genetic diversity of colder waters in Western Australia is speculated that the latter is limited by the low-temperature environmental pressure. In terms of salinity, some shrimp species have adaptive differentiation to the nearshore low-salt estuary environment. Chinese shrimps breed in brackish water environments such as the Bohai Bay. Their population may have stronger low salt tolerance, which has physiological differences from the Yellow Sea offshore population. The current flow system determines the path and distance of floating and dispersed shrimps in their early life history, which in turn affects the range of gene communication. Taking Chinese shrimp as an example, the warm current of the Yellow Sea transports overwinter shrimp seedlings from the Bohai Bay to the northern part of the Yellow Sea every winter, forming a so-called "overwintering southward and going northward in spring" migration cycle, and the local groups are therefore closely connected (Meng et al., 2009). The Giant tiger prawn population in some closed bays in southern Japan shows genetic differences from the outshore population, which is believed to be the isolation effect caused by the bay circulation. In addition to warm salts and ocean currents, topographic factors such as the width of the continental shelf also have an impact. Shrimp fowls with wide continental shelf can spread on a large scale along the coast, while the diffusion radius of fjords and coral reefs surrounding the areas are smaller, which will be reflected in the genetic structure. 7.2 Genetic basis of environmental selection and local adaptation Selective pressures exerted by different habitat environments on shrimp populations may drive adaptive differentiation of specific genes or genomic regions. This local adaptation can be detected by molecular means, such as finding allele frequency changes associated with environmental variables. In recent years, genome studies of shrimp have begun to reveal the genetic basis of environmental adaptation. Vu et al. (2020) used genome-wide SNP to conduct an outlier analysis of the black tiger shrimp population in the India-Western Pacific region and found that about 26 SNPs were significantly correlated with the highest/lowest temperature of the seawater surface. The genetic functions of these sites involve cell metabolism, pigment, immunity, etc., indicating that temperature selection may act on a wide range of physiological processes (Vu et al., 2020). Similarly, in the genetic improvement of Pacific white shrimp, people have noticed family differences in traits such as low-salt resistance and disease resistance, and key genes are currently being locked through QTL localization and gene editing. Environmental selection is often intertwined with genetic drift and gene flow, posing challenges to detection methods. Modern analyses usually use two types of methods, “differentiation-based” (PD) and “environmental association” (EA) to identify adaptive sites. Combining the two can improve reliability. Research on shrimps shows that due to long-term artificial breeding, some adaptability is different from that of the wild environment. 7.3 Reconstruction of distribution pattern and suitable breeding areas by climate change Global climate change is increasingly becoming a key background factor affecting the distribution of shrimp and the pattern of aquaculture. The warming of the ocean surface, changes in salinity, and increased extreme weather will have a long-term impact on the geographical distribution range and suitable breeding areas of shrimp species. Rising water temperatures may drive tropical shrimps to expand to higher latitudes. In recent years, some prawn species that were originally limited to the tropical region have been observed in temperate waters. For example, the success rate of overwintering of Whiteleg shrimp in northern China has increased, which is due to the rise in sea water temperature in winter. Climate models predict that the average global ocean temperature will rise by
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