International Journal of Marine Science, 2025, Vol.15, No.2, 92-106 http://www.aquapublisher.com/index.php/ijms 103 1 °C~3 °C by the end of this century, which will significantly change the distribution pattern of warm and cold water mass. The survival line of temperature-sensitive species such as shrimp will also be moved accordingly. Changes in rainfall and land-source freshwater input patterns affect coastal salinity, putting pressure on shrimps in nearshore spawning grounds. Many shrimp larvae are highly sensitive to salinity gradients. Extreme rainfall and drought caused by climate change may lead to excessive or salty salty water in the estuary, which will affect the reproductive success rate and survival of larvae. Again, marine circulation may change due to warming, thereby changing the diffusion path of shrimp seedlings. Some predictions suggest that changes in frequency of events such as El Niño and changes in current intensity may reshape the seedling delivery pattern. In the aquaculture industry, climate change also brings opportunities and challenges: new high-latitude areas may become suitable for breeding tropical shrimp, providing the possibility for northward migration of industries; the increase in extreme weather (typhoons, heat waves) will increase breeding risks. 8 Global Systematic Geography Study of Typical Shrimps 8.1 Whiteleg shrimp: high diffusion and artificial selection interaction The global transmission and artificial breeding process of Whiteleg shrimp (Litopenaeus vannamei) make it a typical case of studying the interaction between human activities and systematic geographical patterns. In natural state, Pacific white shrimp are native to narrow areas of the Eastern Pacific, with limited genetic diversity and simple population structure. However, after human introduction and spread, the species has now formed new populations in Asia and Africa and has experienced strong artificial selection in breeding environments. In this process, the high degree of diffusion and artificial selection interaction shapes its unique genetic pattern. On the one hand, Pacific white shrimp has physiological adaptability to the environment with wide salt and high temperature. In addition, humans assist in transoceanic transportation, their geographical diffusion ability is extremely strong. On the other hand, artificial breeding exerts directional selection pressure on Pacific white shrimp in different regions. In order to improve yield and disease resistance, countries have established breeding groups for generations to select, such as the "Guihua No. 2" strain selected for growth rate. Artificial selection leads to rapid increase in frequency of certain trait-related genes in breeding populations, resulting in significant gene frequency shifts from wild ancestral populations. Zhang et al. (2023)'s study compared four breeding Pacific white shrimp lines through SSR markers and found that they all maintain moderate genetic diversity, but exhibited a relatively consistent allelic frequency at growth-related sites, suggesting that breeding programs in different regions converge to increase the frequency of certain key growth genes (Zhang et al., 2023). This shows that artificial selection offsets geographical environment differences to a certain extent, making the genetic composition of breeding populations converge in the direction of high yields. 8.2 Giant tiger prawn: native populations and diffusion genetic traces in Southeast Asia As an indigenous shrimp species in Southeast Asia-Western Pacific, Penaeus monodon has rich genetic diversity and complex population structure within its native range, and has left certain genetic traces after artificial introduction to other regions (such as South Asia and Africa). Studies on native populations in Southeast Asia show that Giant tiger prawn may have hidden genetic differentiation in this area. The wide distribution of Giant tiger prawn (from East Africa to southern Japan) does have regional differentiation, such as the Indian Ocean population and the Western Pacific population showing differentiation (but not to a deep degree) on microsatellites and mtDNA, which is related to the presence of partial isolation barriers in places such as the Indian Peninsula. When the Giant tiger prawn is introduced into non-original farming, its genetic traces can also be detected. Among the Madagascar wild Giant tiger prawn population in Africa, genetic analysis showed that it was extremely approximate to the Asian population (Wong et al., 2021). On the one hand, this is because the origin of the Giant tiger prawn in Madagascar is Asian seedlings (without genetic uniqueness). On the other hand, it also shows that no significant mutation accumulation occurred shortly after the introduction, and the genetic characteristics of the source population are still retained. Another trace of genetic diffusion is reflected in invasive species detection. Experts have identified a variety of Asian haplotypes in invasive Giant tiger prawn along Colombia, South America. In particular, some haplotypes were found to be common in the breeding populations in Thailand and Taiwan, which clearly documented the process of human activities transporting these genotypes
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