1 Introduction

Shrimp is one of the highest-yield and largest-trade aquatic products in the global aquaculture industry, with annual output of millions of tons. Among them, Whiteleg shrimp (Litopenaeus vannamei) and Giant tiger prawn (i.e., Penaeus monodon) are the two most widely cultivated varieties, accounting for the vast majority of the global farmed shrimp production. Due to its fast growth, strong adaptability and mature reproductive technology, Whiteleg shrimps have been introduced to breed by more than 70 countries and have now become the world's highest breeding shrimp species. The Giant tiger prawns are native to the Asia-Pacific region. Although the breeding volume is less than that of the South American whitening shrimps, they still occupy an important position in Southeast Asia and other places, and they have developed breeding in some countries through introduction. In addition, local varieties such as Chinese prawns and Japanese prawns have important ecological and economic value in inshore breeding and natural populations in countries such as China. The development of shrimp farming not only provides huge economic benefits, but also promotes employment and income in coastal communities (Kumar and Engle, 2016).

Global systematic geography research on shrimp species aims to reveal the genetic structure, lineage differentiation and historical diffusion processes of species in different geographical regions around the world. On the one hand, phylogenetics can combine molecular phylogenetic development with biogeographic distribution to clarify the relationship between species evolution and geological events and changes in the marine environment. This has important theoretical significance for understanding the formation mechanism of marine biodiversity (Farias et al., 2023).

On the other hand, in terms of application, understanding the genetic structure and gene flow pattern of farmed shrimp species has direct guiding significance for cross-regional seedling introduction and breeding management.

This study focuses on the global systematic geographical pattern and transmission model of commercial important shrimps: introduces the phylogenetic relationship and classification status of major farmed shrimps, including lineage differentiation of shrimp family and basal shrimps and the application of molecular markers; discusses the natural geographical distribution pattern and evolutionary history of native shrimp populations, focusing on the Indo-Pacific biodiversity hotspots, regional differences between the east and west oceans, and the impact of marine geographical barriers; analyzes the current global systematic geographical research status of typical farmed shrimp species through case analysis. Through the above structure, we hope to fully demonstrate the research progress of commercial important shrimp system geography in recent years and provide scientific reference for the next step of research and breeding management.

2 Phylogenetic and Classification of Major Commercial Shrimps

2.1 Main economic types and genealogy of the Penaeidae family

The Penaeidae family contains many important marine economic shrimps, and their systematic classification has long been controversial. Based on traditional morphological principles, large marine prawns are roughly divided into the genus Paleopause (Penaeus sensu stricto) and several subgenus, but different classification systems have different levels of genus levels. This chaos has sparked heated discussions over the past few decades about whether the genus Prawns should be split. Research based on molecular phylogenetic development in recent years has brought new insights into this issue. The researchers used large-scale data of mitochondrial and nuclear genes to reconstruct the phylogenetic tree of the main breeding species of the Shrimp Family, and the results supported the reintegration of the originally separated subgenus into the generalized genus Penaeus, thereby simplifying the classification system. The study suggests that the genus Penaeus name is reused to include all major breeding species including Chinese prawns, squid prawns, and white prawns in South America. The genus names such as Fenneropenaeus, Marsupinaeus, and Litopenaeus will no longer be used respectively. This classification adjustment is now gradually accepted by the industry, making the classification of shrimp families stable and consistent (Zhang et al., 2016). The major economic species form clear lineage branches on the systemic tree, such as the squid prawns and Mexican white shrimp (Farfantepenaeus genus), and the Whiteleg shrimp lineage is close to East Asian species such as Chinese shrimp.

2.2 Systematic classification and evolutionary relationship of Caridea family

Compared with the family Shrimp family, Caridea species such as Cyvador (i.e., non-prawns in the suborder of shrimp, including a variety of freshwater and seafood small shrimps) are commercially secondary, but their phylogenetic diversity is eye-catching. An important family under Caridea is the Palaemonidae family, which includes freshwater shrimps that have some significance for aquatic products (such as Japanese swamp shrimp). Molecular systems research in recent years has shown that the long-armed shrimp family is one of the most diverse species among basal shrimps, and can be divided into multiple branches on the phylogeny tree. Research experts conducted mitochondrial whole-genome sequencing and phylogenetic analysis of 14 species in the long-armed shrimp family, and the results support the existence of several evolutionary branches in this family, and proposed new insights into the unilinearity of certain genera (Figure 1) (Frolová et al., 2022). The phylogenetic tree they construct splits some genera in the traditional classification into two separate branches, prompting that the genus hierarchy may need to be re-divided. In addition, historical biogeographic analysis of marine basal shrimps shows that plate tectonics and strait changes have profound effects on their evolution. A study by Scientific Reports pointed out that the lineage evolution of oceanic basal shrimp globally is affected by major events such as Atlantic splitting, Eastern Pacific barrier, and Panguttis Sea closure, thus forming a current cross-ocean species distribution pattern (Chow et al., 2021).

2.3 Application of molecular markers in the study of shrimp phylogenetic

Molecular marking technology plays a key role in analyzing shrimp system relationships and genetic differentiation. Mitochondrial DNA is widely used in shrimp species identification and phylogenetic analysis due to its maternal inheritance and moderate evolution rate. For example, mitochondrial gene sequences such as 16S rRNA and COI have been successfully used to distinguish between relative shrimp species and construct intergenic phylogenies (Baeza and Fuentes, 2013). The acquisition of complete mitochondrial genome data has also gradually increased. For example, the entire mitochondrial genome of Chinese prawns and Pacific white shrimp has been recently measured, providing information for more refined systematic analysis. Nuclear DNA markers such as 18S rRNA, 28S rRNA, histone genes, etc. are also often combined with mitochondrial data to improve the reliability of phylogenetic trees. In addition, highly variable microsatellite (SSR) and single nucleotide polymorphism (SNP) markers are more used in population-level genetic structure research, but can also assist in the exploration of population differentiation history at a higher classification level. With the development of second-generation sequencing, methods such as RAD-seq, whole-genome resequencing of shrimps have also begun to be applied to systematic geography research, and can obtain thousands of SNP sites at the same time, greatly improving resolution. The application of these molecular marker tools has greatly promoted the research depth of shrimp phylogenetic and geographical evolution issues. For example, analyzing 21 globally cultivated Pacific white shrimp populations using high-density SNP chips found that their overall genetic diversity is still high, but there are structural differences between different source lines (Santos et al., 2018).

3 Natural Geographical Distribution and Evolution History of Native Populations

3.1 Indo-Pacific: biodiversity hotspots and origin center

A large number of studies have shown that the Indo-West Pacific (IWP) waters are the hot spots of biodiversity and the center of evolutionary origin of many marine shrimps. The region includes tropical waters in the Indian Ocean and the Western Pacific, with abundant coral reefs and mangrove ecosystems, providing a diverse habitat for shrimp. Phylogenetic and fossil evidence suggests that the common ancestors of many of the living prawnaceae species may have originated from Guttisyang, undergoing radiation evolution in the IWP region formed by plate drift. Historical biogeographic analysis by Frolová et al. (2022) suggests that the current diversity of basal shrimps such as the Long-armed Shrimp family originates to a large extent from the IWP region, and it is speculated that the main lineages have been nurtured in the Late Cretaceous (about 91 million years ago) and then spread outward (Frolová et al., 2022). Why IWP has become the center of shrimp origin and differentiation? On the one hand, the region has been connected for a long time in geological history. The Paleo-Mediterranean (Tetis Sea) period provided a stable and vast habitat for Indo-Pacific waters, which is conducive to the continuous evolution of species (Saulsbury and Baumiller, 2022). On the other hand, the IWP region has a warm climate, high productivity and diverse habitat types, which promotes high radiation adaptation of species. In addition, before the Late Miocene, the sea access from East Africa to the Western Pacific basically maintained unobstructed, allowing species to spread widely within the Indo-Pacific. This is also confirmed by the modern distribution pattern: many prawn and basal shrimp species have the greatest diversity in the Indo-Pacific Ocean, while relatively few species are found in the corresponding latitude areas of the Atlantic Ocean or the Eastern Pacific.

3.2 Comparison of regional characteristics between the Eastern Pacific and the Western Atlantic Ocean

The Eastern Pacific and Western Atlantic Oceans are two geographically isolated marine areas, and there are obvious differences in their shrimp regions and population characteristics. In terms of species composition, large marine shrimp species in the Eastern Pacific (especially the eastern coast of the American Pacific) are relatively poor, and are known as the "East Pacific Species Poverty Zone". Along the tropical coast of the Eastern Pacific, large shrimps with commercial value are mainly Pacific white shrimp (native to the eastern Pacific coast) and a few close species, In contrast, the corresponding latitudes of the western Atlantic (along the American Atlantic coast) are home to a variety of penaeid shrimp species, including the white shrimp (Penaeus setiferus), brown shrimp (Penaeus aztecus), and northern white shrimp (Penaeus schmitti). The formation of this difference is closely related to geological historical events (Valles-Jiménez et al., 2006). From the perspective of genetic diversity, western Atlantic shrimp populations tend to have higher genetic variations, while eastern Pacific side populations have shown signs of bottleneck in some studies. Take the Pacific white shrimp as an example. The native Eastern Pacific population has experienced fluctuations in population size in history, and its mitochondrial genetic diversity is lower than that established later in Asia. In terms of geographical distribution range, the distribution of many shrimp species in the Eastern Pacific is relatively narrow in the north and south, which is related to the narrow continental shelf and unique cold currents along the Eastern Pacific coast; while the continental shelf along the Western Atlantic coast is wide, providing a broader adaptable environment for shrimps (Farias et al., 2023).

3.3 The restrictive effect of marine geographical disorders on gene flow

Geographic barriers in the ocean play a significant restrictive role in genetic communication of shrimp populations. Famous marine barriers include vast ocean barrier-free areas, cold waters, ocean current boundaries, and land barriers. These factors can prevent shrimp larvae or adults from spreading freely between different regions, thereby contributing to population differentiation. The East Pacific Barrier refers to an open deep-sea area that lasts thousands of kilometers from the coast of Central America to the South Pacific Islands, and is an insurmountable barrier for nearshore creatures. This barrier has been around since the Cenozoic, preventing many Indo-Western Pacific species from naturally crossing the Eastern Pacific to reach the coast of the Americas, resulting in a relatively poor biological poverty in the eastern Pacific nearshores, known as one of the largest biogeographic barriers in the global ocean. For example, the Panama Isthmus finally closed about 3 million years ago, forming a solid land barrier that completely separates marine life from the Atlantic Ocean and the Pacific Ocean. This "hard barrier" directly terminates gene exchange between the two oceans, causing the once connected populations to evolve independently, and is considered to be the main reason for the formation of many shrimp "sister species" (McCartney et al., 2000). In addition, the Guttis Seaway between the Indian Ocean and the Atlantic gradually disappeared during the Miocene, resulting in biological isolation between the Indian Ocean and the Eastern Atlantic Ocean. There are also some "soft obstacles", such as cold water masses and ocean currents: for example, cold water at the southern end of Africa makes it difficult for shrimps in the Indian Ocean to bypass the Cape of Good Hope to enter the Atlantic Ocean, and the Patagonian cold current at the southern end of South America also limits tropical shrimps to cross the sides of South America. Salt jump layers, hypoxic zones, etc. in the marine environment may also constitute invisible obstacles.

4 Artificial Introduction and Cross-Continental Transmission Path Analysis

4.1 Review of the introduction history in global shrimp aquaculture

The global distribution pattern of shrimp species in large-scale introduction and breeding by humans has had a revolutionary impact. Since the second half of the 20th century, with the rise of aquaculture, major breeding shrimp species have been introduced to areas outside their origin for artificial breeding. The most typical one is the Whiteleg shrimp, which is native to the Pacific coast of the Americas. In the 1960s and 1970s, Southeast Asian countries began to develop local black tiger shrimp (spotted shrimp) farming, and at the same time tried to introduce different kinds of shrimp seedlings from neighboring countries to improve production. However, at that time, breeding technology was limited and the scale of transnational introduction was relatively small. The second stage was from the 1980s to 1990s. After the breakthrough in seedling cultivation and breeding technology, the tide of transcontinental introduction emerged. In 1988, China introduced the first Vannabin Prawn Prawn from Hawaii, USA, and successfully tried to raise it in Guangdong, kicking off the introduction of South American whitening prawns in Asia. In just over ten years, South American whitening prawns spread to the entire Asia-Pacific region through Taiwan, Thailand and other places. During the same period, India, Indonesia and others also introduced fine varieties of platylensis shrimp from their Asian neighbors to improve local germplasm (Tandel et al., 2017). Since the beginning of the 21st century, a global shrimp fry trade network has been formed, and some countries have begun to import shrimp fry from third countries in batches for breeding. For example, many Asian shrimp farmers choose to purchase SPF vannabean shrimp seedlings from the United States or Hawaii to reduce disease risk (Boyd and Jescovitch, 2020). Emerging breeders in Africa and the Middle East also purchase shrimp seedlings from Asia through international cooperation.

4.2 Global diffusion route for Litopenaeus vannamei

4.2.1 From the Eastern Pacific to Asia: the rise of seedling trade

Whiteleg shrimp are native to the eastern Pacific coast (from Peru to Mexico coast), and before the 1980s, their breeding was basically limited to the Americas. The truly large-scale transcontinental spread began in the late 1980s and early 1990s. At that time, due to the continuous outbreak of viral diseases (such as leukoplakia) of prawns cultivated in Asia, it was urgent to find alternative varieties. In 1988, Chinese scientific researchers introduced South American white prawn parents from the United States for trial breeding for the first time and achieved success, which aroused strong interest from Asian countries. Subsequently, Taiwan introduced a batch of Pacific white shrimp from Hawaii in 1990, quickly realizing artificial seedling cultivation and promoting breeding. During the same period, Thailand also obtained seedlings from the United States and Taiwan, and Malaysia, Indonesia, Vietnam and others followed suit to introduce them. In just a few years, South American white prawn farming technology has spread in Asia. Around 1995, Whiteleg shrimp replaced local prawns and became the dominant breeding farm in Southeast Asia. Seedling trade played a key role in this process - early Asian shrimp seedlings relied heavily on pro-shrimps airlifted from Florida, Hawaii and other places in the United States, and then gradually achieved self-sufficiency in local seedlings (Moss et al., 2010).

4.2.2 Rapid expansion and genetic convergence of high-density breeding areas in Asia

After the introduction of Whiteleg shrimp into Asia, countries quickly established high-density and intensive breeding systems, with rapid output growing, and problems such as genetic convergence and germplasm degradation have also occurred. From the late 1990s to the early 2000s, Thailand, mainland China, Vietnam and other places promoted the high-density breeding model of Whiteleg shrimp ponds on a large scale, with annual output hitting new highs. Taking China as an example, the total production of vannah shrimp has skyrocketed from thousands of tons in the early stages of introduction to millions of tons in the 2010s, and currently accounts for about two-thirds of global production. However, due to the relatively single source of the prawn germplasm introduced by most countries, and the lack of systematic breeding of good varieties during the breeding process, the genetic background of breeding groups in various places tends to be similar. The study found that the Pacific white shrimp population cultivated in different Asian countries has little difference in genetic markers such as microsatellites, and many of them originated from the offspring of the first batch of American-born shrimp. Long-term high-intensity artificial selection and incomparison also trigger germplasm degeneration: manifested as decreased growth rate, weakened disease resistance, and reduced fertility. At the end of the 20th century, the incidence and mortality of shrimp in some breeding areas in China increased year by year, which is believed to be related to germplasm aging. In response to these issues, Asian countries have begun to pay attention to genetic improvement and variety updates. On the one hand, since the 2000s, many countries have launched a breeding program for good breeding, cultivate new strains with fast growth and strong disease resistance through hybridization and family breeding, and introduce new wild germplasm to rejuvenate domestic groups. On the other hand, strengthen international cooperation and introduce new SPF pro-shrimps from origin or other countries to expand the gene pool (Li et al., 2024).

4.2.3 Communication dynamics and limiting factors to Africa and the Middle East

Under the demonstration effect of successful breeding in Asia, Whiteleg shrimp have gradually spread to Africa and the Middle East since the 21st century, becoming new breeding targets. However, this diffusion process is relatively slow, and its dynamics and limiting factors are worth discussing. In terms of power, the first is market-driven: With the growth of global demand for shrimp, some African coastal countries hope to develop shrimp farming to obtain export benefits, and have introduced the high-yield species of Pacific white shrimp (Tian et al., 2024). The second is technology promotion: Asian experts and enterprises bring breeding technology and management experience to Africa and the Middle East to help local infrastructure and technical teams. This "technical spillover" reduces the difficulty of starting a new region. In terms of restrictive factors, environmental conditions restrict: Whiteleg shrimp is suitable for tropical and subtropical warm waters, and in some areas of Africa introduced (lower water temperature or unstable climate) must overcome the problems of wintering and breeding cycles (Wang et al., 2020). Secondly, seedling supply bottlenecks: African and Middle Eastern countries lack local pro-shrimp cultivation systems, and often require airlifting shrimp from Asia or the Americas from a long distance, which is costly and has a high risk of mortality in the process. Disease prevention and control challenges: New breeding areas often have no history of shrimp farming and lack experience in quarantine and disease monitoring. If the virus is carried into the local waters during the introduction process, it may cause serious consequences (such as reports of white spot disease and other transmission into Africa). In fact, the first introduction in some countries has failed due to disease outbreaks. Finally, manpower and supporting: farming shrimp requires supporting support such as feed, power supply, and technicians, while some African countries have weak foundations in these aspects, which restricts the large-scale development of the industry (Pratiwi et al., 2021). Despite the above difficulties, South American whitening prawns have made some progress in Africa and the Middle East in recent years.

4.3 The spread mode of giant tiger shrimp (Penaeus monodon) in Asia and Africa

Giant tiger shrimp (i.e., Giant tiger prawn) is an important traditional breeding species in the Asia-Pacific region. Its transmission history is different from that of Whiteleg shrimp and has its own characteristics. The Giant tiger prawns are native to Southeast Asia to northern Australia and were mainly cultivated in extensive manner before the second half of the 20th century in native countries (such as Thailand, the Philippines, Indonesia, India, etc.). In the 1970s, Japan took the lead in conquering the full artificial seedling cultivation technology of prawns, releasing larvae to pond breeding, and driving Asian neighbors to imitate (Wong et al., 2021). In the following decades, the Giant tiger prawn farming technology spread throughout East and Southeast Asia, making it the highest-growing shrimp species in Asia in the early 1990s. However, unlike Vannephrod, the cross-continental transmission of the pimples is relatively limited. Until around 2000, only a few African countries (such as Madagascar and Mozambique) introduced prawns to breed them. Its propagation mode mainly presents two paths: one is propagation within the region. Seedlings and shrimps are frequently exchanged between Southeast Asian countries and Taiwan, China, to form an "Asian germplasm circle". Due to the similar geographical location, this transmission is relatively easy, resulting in little genetic differences in the prawn populations of the sputum in different regions. Some studies have found through sequence analysis of mitochondrial control zones that the wild population of pimples in different Southeast Asian countries is mixed in the same haplotype network, and there is no obvious regional clustering. This implies that historically they may have been connected by sea currents, or that in modern times, they were caused by the transport of parent shrimp in the area. The second is to spread to Africa. At the end of the last century, some aquatic companies were optimistic about the vast land and good water quality along the coast of Africa, and tried to breed Giant tiger prawns there. Madagascar introduced pimples from Asia in the late 1980s and established a breeding farm. It is still the only country in Africa to achieve a large-scale pimples export (the population of pimples that escape and reproduce in its wild waters have also been found). In addition, Mozambique, Tanzania and other places have also recorded sporadic introduction records, but due to technology and capital, no major industries have been formed. The spread of varnish shrimp in Africa is generally not as successful as that of varnish shrimp, which is related to the characteristics of varnish shrimp with higher environmental requirements, susceptibility to diseases, and longer growth cycles (Simtoe et al., 2025).

5 The Impact of Human Activities on Population Structure and Geographical Pattern

5.1 Genetic mixing and germplasm erosion driven by aquaculture

Large-scale aquaculture activities have had a profound impact on the genetic structure of shrimp populations. Artificial breeding often breaks down natural geographical barriers, mixing originally geographically isolated populations, resulting in intensifying genetic communication. In breeding practice, shrimp seedlings in different regions tend to circulate across regions. Most of the Pacific white shrimp strains cultivated in Asian countries originate from similar parental germplasms, which led to the "fusion" of the originally evolved Eastern Pacific lineage and the Asian native shrimp gene pool. Molecular testing found that some Asian Pacific white shrimp populations contain genetic components of multiple geographical origins, and their heterozygation is maintained at a moderate level, but the differences between populations are reduced. This shows that aquaculture activities have contributed to the mixed unity of germplasms from different sources (Wu et al., 2025). Secondly, aquaculture may cause germplasm erosion due to artificial selection and other reasons, namely, the decline in genetic diversity and the degradation of specific traits. High-intensity breeding and in-mating have reduced the effective population size of many breeding shrimp populations and lost allele. Domestic studies have shown that after continuous multigenerational breeding, the average heterozygous degree and allelic number of Pacific white shrimp farming population have significantly decreased compared with the wild population. Especially in the absence of a good breeding plan, breeders often repeatedly use a few parent shrimps to reproduce, resulting in a narrowing of the genetic background of offspring. The selection pressure of artificial environments is different from that of natural environments and may also lead to the differentiation of breeding populations from wild populations in terms of traits. Farming conditions are usually sufficient resources and have low predation pressure, so they may tend to retain genotypes that sacrifice stress resistance at the expense of high growth rates. Comparative studies found that the breeding of Pacific white shrimp population showed significant changes in allelic frequency on some genes related to immunity and metabolism, reflecting the role of artificial selection.

5.2 Ecological risks of escape populations and non-local spread

5.2.1 Examples of establishing wild populations in non-native places

Large-scale shrimp farming is accompanied by frequent escape events, and some alien species can survive and reproduce in wild environments in non-original places, forming new populations, posing a potential threat to the local ecology. A typical case is the "secondary wildization" of Whiteleg shrimp in Asia. Although Vannebane shrimps are native to the Americas, they have repeatedly escaped into the estuary and near the sea due to typhoons and dam damage. Wild breeding Pacific white shrimp populations have been monitored in China's Pearl River Estuary and the coast of Taiwan. They lay eggs and grow in warm seasons, and some individuals can even survive overwinter, indicating that the species has been successfully colonized in some new areas (Chavanich et al., 2016). Another case is the spread of prawns in Africa. The Giant tiger prawns at Madagascar farms once escaped to nearby bays. Local fishermen are now able to catch commercially valuable Giant tiger prawns, indicating that the species has established wild populations along Madagascar's coast. Even along the Brazilian coast of South America, records of invasion of prawns have been found: giant tiger shrimps have been continuously captured in the waters of northern Brazil since 1987, and are believed to have originated from the escape of the farm and reproduced smoothly.

5.2.2 Ecological impact on local species competition and habitat changes

After foreign shrimp species colonize non-native, they may affect the local ecology through various channels. First, compete with local species. Alien shrimp often share similar ecological niches with local close species, thus creating competition in food and space. For example, after the invasion of Brazil, the Giant tiger prawns were concerned about competing with local indigenous prawn species such as the Farfantepenaeus species (Petatán-Ramírez et al., 2020). If the invasive species have stronger adaptability or reproductive power, it may lower the local population (Figure 2). The second is predation and food web effects. Shrimps are both important predators and prey in the ecosystem. Foreign shrimp joining may change the original predation network. For example, after the Whiteleg shrimp escaped to the estuary of the Chinese river, it was reported that it fed benthic animals and young shrimp seedlings, which may affect benthic biome structure (Are and Apapa, 2014). The third is the role of habitat engineering. High-density shrimp may disturb the base material or affect the water quality. For example, crayfish will dig their holes and cause turbidity after invading freshwater, and the large number of seawater shrimps may also change the benthic environment through feeding and biological disturbances. Fourth, the risk of genetic pollution. If foreign species can hybridize with local relative species, it will lead to genetic confusion.

5.3 Co-concomitant spread mechanism of international trade and disease transmission

Global farming of shrimp is also accompanied by the global spread of pathogens, which is a serious challenge brought by international trade. Viruses, bacteria and parasites that are susceptible to shrimps can spread with the cross-border flow of live and fresh shrimps. The most prominent examples are the transcontinental transmission of prawns, white spot syndrome virus (WSSV) and Taola virus (TSV). TSV was originally only popular in the Americas, but with the introduction of Pacific white shrimp into Asia, shrimp seedlings that were infected around 1998 were introduced to Thailand, Taiwan, China and other places, resulting in a large-scale outbreak. The transmission path is believed to be caused by the transnational sale of infected shrimp seedlings. WSSV spread from Asia to the Americas in the 1990s, devastatingly hitting the shrimp industry in Ecuador and other countries. Research evidence shows that WSSV's global popular strains can be traced back to a few sources, and international seedling trade has accelerated its global spread (Figure 3) (Tandel et al., 2017). The mechanisms of co-dispersal of international trade in co-dispersal include: the export of seedlings carrying pathogens/shrimp-producing shrimps, the release of contaminated water bodies for transporting seedlings, and the entry of fresh product waste into the environment. Since shrimp seedlings require water medium transportation, pathogens can be hidden in water and cross-border (Prochaska et al., 2022).

6 Genetic Diversity Pattern and Molecular Ecological Signals

6.1 Application of mitochondrial DNA and microsatellites in geographic population research

By analyzing the mitochondrial DNA sequences and nuclear microsatellite markers of the population, the genetic diversity pattern of shrimp geographical populations can be revealed. Mitochondrial DNA is often used to analyze historical expansion and lineage geographical structure due to its single parent inheritance and small effective population size. Haplotype composition of mitochondrial COI sequences in different regions can indicate whether the population has experienced expansion bottlenecks. Studies show that the COI haplotypes in Chinese shrimp wild populations along the coast of China are highly diverse, while the number of haplotypes in artificial breeding populations is significantly reduced, indicating that the breeding process may have lost some haplotypes. Microsatellites (SSRs) are highly polymorphic loci in the nuclear genome because high mutation rates are suitable for reflecting recent gene flow and inbred conditions. Microsatellite analysis is also used to detect confounding and gene exchange among populations. Vu et al. (2020) study on Australian black tiger shrimp, through more than 100,000 SNPs and several microsatellites, they consistently revealed the three major genetic groups along the coast, and there are a small number of significant microsatellite sites with F__ST under different environmental conditions (Vu et al., 2020). Such sites may be related to local adaptation (such as salinity, temperature selection). Mitochondrial DNA can also bind to molecular clocks for population history simulation. By comparing the divergence of mitochondrial haplotypes in each population, the population expansion time can be estimated. A study of pimples using control zone sequences to infer that it experienced a significant population expansion in the late Pleistocene, and then the distribution contracted due to the decline of sea level during the glacial period. Mitochondria can also be used to identify hidden species: If distinct mitochondrial branches are found in the same domain population and the differences exceed the species level, it is often suggested that there is an implicit new species that are not described.

6.2 Population differentiation index (Fst) and gene flow assessment

The population differentiation index F_ST is an important indicator to measure the degree of genetic differentiation among different geographical populations and is often used to evaluate the gene flow level of shrimp populations. The F_ST value is 0 to 1. The higher the value, the greater the genetic difference between populations and the less gene communication. Many studies have revealed which geographical barriers significantly restrict gene flow by calculating the F_ST of different regional populations of shrimp. For example, analyzing the wild populations along the coast of Australia's black tiger shrimp was obtained with an average F_ST of about 0.05-0.10, indicating that there is a clear spatial genetic structure. The Chinese shrimp populations in the Bohai Sea and the Yellow Sea in China are often very low, meaning that seasonal currents make them closely connected. In addition, software that analyzes population structures (such as STRUCTURE) can be used to divide implicit groups through the F_ST matrix. Many shrimp studies have found that the genetic structure of the population often coincides with the marine geographical area. For example, the Indo-Pacific black tiger shrimp can be divided into 7 genetic groups, corresponding to East Africa, Indo-Sri Lanka, Southeast Asia, northern Australia and other regions. The F_ST values ​​between these groups range from 0.05 to 0.25, reflecting different regional isolation.

6.3 Construction of haplotype network and historical diffusion model

Haplotype network analysis is a method to visually display the evolutionary relationship of mitochondria or other haplotype sequences, which is quite useful in the historical inference of shrimp populations. By drawing haplotype networks of different geographical groups, the clustering, frequency and geographical distribution of haplotypes can be observed, thereby inferring historical population expansion, migration routes, etc. Aguirre-Pabón constructed a network of COI haplotypes of invasive platylensis shrimp in Colombia. The results showed that the two major lineages (Lineage I and II) differed by 7.7% from each other, each containing multiple shared haplotypes from Asian and African countries. This suggests that these invading groups are derived from repeated introductions from multiple regions, rather than from a single source. Similarly, a global analysis of mitochondrial haplotypes of wild and farmed shrimps in Pacific white shrimps found that the haplotypes in the American sample were relatively concentrated, while the Asian breeding population showed a pattern of dominance of several major haplotypes, suggesting that the Asian breeding population may have experienced bottlenecks (Yudhistira and Arisuryanti, 2019). In addition to qualitative observation, the historical diffusion process of shrimp can also be quantitatively reconstructed with the help of statistical diffusion models. Commonly used methods include discrete geographical diffusion models based on Bayesian analysis, where molecular clocks can be used to estimate the time and diffusion order of the occurrence of ancestral nodes in each region. For example, Frolová et al. (2022) used BEAST to perform spatiotemporal diffusion simulation of Pon-I taxa in the long-armed family. The results supported that the taxa spread from the IWP to the eastern Pacific Ocean about 55 million years ago, and then crossed the nascent Panama Isthmus into the Atlantic Ocean. This model provides us with a timeline for the macroscopic diffusion of species. Similar methods can also be used for recent human-proliferation events.

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 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 from Asia to the Americas. The high level of haplotype diversity in the invading population and the coexistence of the two major differentiation lineages further reveal the genetic traces of multiple and multi-source introductions.

8.3 Chinese prawns (Fenneropenaeus chinensis): conservation pressure of nearshore habitat populations

Chinese prawns are large shrimps unique to the nearshore waters of the Northwest Pacific. They were once an important target of traditional Chinese sea capture and breeding. However, in recent years, due to overfishing and environmental changes, their wild populations have faced great conservation pressure. Systematic geography research provides scientific basis for understanding the population structure of Chinese shrimp and formulating conservation measures. The natural distribution of Chinese prawns is concentrated in shallow sea areas such as the Yellow Sea and the West Coast of the Korean Peninsula. Its life cycle includes nearshore egg laying, larval development, autumn migration and wintering. Genetic studies have shown that genetic differentiation among different egg-laying populations is low, which is related to their annual migration and confounding. Sun Song et al. identified the proportion of release shrimp seedlings in the wild captured samples through SSR and mitochondrial markers, and for the first time some release individuals successfully survived and participated in reproduction (Sun et al., 2024). This study provides direct evidence for the effectiveness of proliferation and release. But at the same time, some scholars have suggested that the genetic differences between release seedlings and wild populations may affect their adaptability, and if the release seedlings degrade, the effect will be reduced. Therefore, in recent years, the breeding department has focused on improving the quality of release seedlings, such as using wild shrimp breeding or hybridization to improve stress resistance. In addition to the decline in genetic diversity, environmental deterioration and diseases are also threats to Chinese prawns. After the white spot disease was introduced to China's coast in the 1990s, it also had a huge impact on wild Chinese shrimps, and the population was once sharply reduced. Climate warming and inshore eutrophication lead to changes in shrimp seedling habitat (Figure 4), which may affect early survival rates (Liu, 2022). When the population is down, genetic diversity may further decline, forming a vicious cycle. Therefore, Chinese shrimps are listed as one of the marine organisms that need to be protected by key areas.

Acknowledgments

During the completion of this paper, we would like to thank Professor Cai J.J. for his patient guidance and help in various stages such as data interpretation and paper revision, and I would also like to thank the two peer reviewers for their suggestions.

Conflict of Interest Disclosure

The authors confirm that the study was conducted without any commercial or financial relationships and could be interpreted as a potential conflict of interest.

References

Are A.O., and Apapa O.O., 2014, Aspects of the biology of the tiger shrimp Penaeus monodon (FABRICIUS) offshore the Niger Delta Area of Nigeria, Nigerian Journal of Fisheries, 11(1-2): 678-683.

Baeza J., and Fuentes M., 2013, Exploring phylogenetic informativeness and nuclear copies of mitochondrial DNA (numts) in three commonly used mitochondrial genes: mitochondrial phylogeny of peppermint cleaner and semi‐terrestrial shrimps (Caridea: Lysmata Exhippolysmata and Merguia), Zoological Journal of the Linnean Society, 168: 699-722.

https://doi.org/10.1111/ZOJ.12044

Boyd C.E., and Jescovitch L.N., 2020, Penaeid shrimp aquaculture, Fisheries and Aquaculture, 9: 233.

https://doi.org/10.1093/OSO/9780190865627.003.0010

Chavanich S., Viyakarn V., Senanan W., and Panutrakul S., 2016, Laboratory assessment of feeding-behavior interactions between the introduced Pacific white shrimp Litopenaeus vannamei (Boone 1931) (Penaeidae) and five native shrimps plus a crab species in Thailand, Aquatic Invasions, 11: 67-74.

https://doi.org/10.3391/AI.2016.11.1.07

Chow L.H., De Grave S., and Tsang L.M., 2021, Evolution of protective symbiosis in palaemonid shrimps (Decapoda: Caridea) with emphases on host spectrum and morphological adaptations, Molecular Phylogenetics and Evolution, 162: 107201.

https://doi.org/10.1016/j.ympev.2021.107201

Farias M., Filho P., Pontes A., and Jacobina U., 2023, DNA barcode reveals high cryptic diversity in the commercially important Penaeini shrimps (Decapoda Penaeidae), Organisms Diversity and Evolution, 23: 857-869.

https://doi.org/10.1007/s13127-023-00616-9

Frolová P., Horká I., and Ďuriš Z., 2022, Molecular phylogeny and historical biogeography of marine palaemonid shrimps (Palaemonidae: Palaemonella–Cuapetes group), Scientific Reports, 12(1): 15237.

https://doi.org/10.1038/s41598-022-19372-5

Kumar G., and Engle C., 2016, Technological advances that led to growth of shrimp salmon and tilapia farming, Reviews in Fisheries Science and Aquaculture, 24: 136-152.

https://doi.org/10.1080/23308249.2015.1112357

Li Y., Cao S., Jiang S., Huang J., Yang Q., Jiang S., Yang L., and Zhou F., 2024, Comparative study of nutritional composition physiological indicators and genetic diversity in Litopenaeus vannamei from different aquaculture populations, Biology, 13(9): 722.

https://doi.org/10.3390/biology13090722

Liu Q., 2022, Temporal changes in genetic diversity of Fenneropenaeus chinensis populations from Jinzhou Bay: implications for management, Pakistan Journal of Zoology, 13(9): 722.

https://doi.org/10.17582/journal.pjz/20211104141137

McCartney M.A., Keller G., and Lessios H.A., 2000, Dispersal barriers in tropical oceans and speciation in Atlantic and Eastern Pacific Sea urchins of the genus Echinometra, Molecular Ecology, 9(9): 1391-1400.

https://doi.org/10.1046/j.1365-294x.2000.01022.x

Meng X., Wang Q., Jang I., Liu P., and Kong J., 2009, Genetic differentiation in seven geographic populations of the fleshy shrimp Penaeus (Fenneropenaeus) chinensis based on microsatellite DNA, Aquaculture, 287: 46-51.

https://doi.org/10.1016/J.AQUACULTURE.2008.10.030

Moss S., Moss D., Otoshi C., and Arce S., 2010, An integrated approach to sustainable shrimp farming, Asian Fisheries Science, 23: 591-605.

Petatán-Ramírez D., Hernandez L., Becerril-García E., Berúmen-Solórzano P., Auliz-Ortiz D., and Reyes‐Bonilla H., 2020, Potential distribution of the tiger shrimp Penaeus monodon (Decapoda: Penaeidae) an invasive species in the Atlantic Ocean, Revista De Biologia Tropical, 68: 156-166.

https://doi.org/10.15517/rbt.v68i1.37719

Pratiwi R., Sudiarsa I., Amalo P., and Utomo Y., 2021, Production performance of super intensive Vannamei Shrimp Litopenaeus vannamei at PT. Sumbawa sukses lestari aquaculture west nusa tenggara, Journal of Aquaculture and Fish Health, 11(1): 135-144.

https://doi.org/10.20473/jafh.v11i1.21143

Prochaska J., Poompuang S., Koonawootrittriron S., Sukhavachana S., and Na-Nakorn U., 2022, Evaluation of a commercial SPF Litopenaeus vannamei shrimp breeding program: resistance to infectious myonecrosis virus (IMNV) Taura syndrome virus (TSV) and white spot syndrome virus (WSSV) from laboratory challenges, Aquaculture, 554: 738145.

https://doi.org/10.1016/j.aquaculture.2022.738145

Santos C.A., Farias F., Teixeira A.K., Rocha J.L., Guerrelhas A.C., and Freitas P.D., 2018, Scientific notes polymorphism in Litopenaeus vannamei genes and cross-species amplification in other shrimp species, Pesquisa Agropecuária Brasileira, 53(01): 121-124.

https://doi.org/10.1590/s0100-204x2018000100014

Saulsbury J., and Baumiller T., 2022, Dispersals from the West Tethys as the source of the Indo-West Pacific diversity hotspot in comatulid crinoids, Paleobiology, 49: 39-52.

https://doi.org/10.1017/pab.2022.23

Simtoe A.P., Lugendo B.R., and Mgaya Y.D., 2025, Assessment of food sources for juvenile and adult Penaeus monodon in Tanzania Coastal Waters, Aquaculture Fish and Fisheries, 5(1): e70041.

https://doi.org/10.1002/aff2.70041

Sun S., Lyu D., Jin X., Shan X., and Wang W., 2024, Parent-offspring relationship recognition based on SSR and mtDNA confirmed resource supplement effect of Fenneropenaeus chinensis release, Acta Oceanologica Sinica, 43: 156-160.

https://doi.org/10.1007/s13131-023-2219-1

Tandel G., John K., Rosalind george M., and Jeyaseelan M.J.P., 2017, Current status of viral diseases in Indian shrimp aquaculture, Acta virologica, 61(2): 131-137.

https://doi.org/10.4149/av_2017_02_01

Tian J.T., Wu W., Li J.W., Wan X.Y., Zhao Z.M., Xi R., Hu X.L., Pan M.C., Xue Y.G., and Yu W.S., 2024, Development dilemma of Litopenaeus vannamei industry in China current countermeasures taken and its implications for the world shrimp aquaculture industry, Israeli Journal of Aquaculture - Bamidgeh, 76(3): 122102.

https://doi.org/10.46989/001c.122102

Valles-Jiménez R., Gaffney P., and Pérez-Enríquez R., 2006, RFLP analysis of the mtDNA control region in white shrimp (Litopenaeus vannamei) populations from the eastern Pacific, Marine Biology, 148: 867-873.

https://doi.org/10.1007/S00227-005-0122-2

Vu N., Zenger K.R., Guppy J.L., Sellars M.J., Silva C.N.S., Kjeldsen S.R., and Jerry R.D., 2020, Fine-scale population structure and evidence for local adaptation in Australian giant black tiger shrimp (Penaeus monodon) using SNP analysis, BMC Genomics, 21(1): 669.

https://doi.org/10.1186/s12864-020-07084-x

Wang Z., Zhou J., Li J., Lv W., Zou J., and Fan L., 2020, A new insight into the intestine of Pacific white shrimp: regulation of intestinal homeostasis and regeneration in Litopenaeus vannamei during temperature fluctuation, Comparative Biochemistry and Physiology, 35: 100687.

https://doi.org/10.1016/j.cbd.2020.100687

Wong L., Chun L., Deris Z., Zainudin A., Ikhwanuddin M., Iehata S., Rahman M., and Asaduzzaman M., 2021, Genetic diversity and population structure of wild and domesticated black tiger shrimp (Penaeus monodon) broodstocks in the Indo-Pacific regions using consolidated mtDNA and microsatellite markers, Gene Reports, 23: 101047.

https://doi.org/10.1016/J.GENREP.2021.101047

Yudhistira A., and Tuty D., 2019, Preliminary findings of cryptic diversity of the giant tiger shrimp (Penaeus monodon Fabricius 1798) in Indonesia inferred from COI mitochondrial DNA, Genetika, 51(1): 251-260.

https://doi.org/10.2298/GENSR1901251Y

Zhang D., Huang J., Zhou F., Gong F., and Jiang S., 2016, The complete mitochondrial genome of banana shrimp Fenneropenaeus merguiensis with phylogenetic consideration, Mitochondrial DNA, 27: 2606-2607.

https://doi.org/10.3109/19401736.2015.1041116

Zhang Z., Lu C., Lin K., You W., and Yang Z., 2023, Genetic diversity and genetic structure among four selected strains of whiteleg shrimp (Litopenaeus vannamei) using SSR markers, Fishes, 8(11): 544.

https://doi.org/10.3390/fishes8110544

Zhao F., and Wang F., 2024, Efficient gene transfer techniques in shrimp and their cellular applications, Genomics and Applied Biology, 15(2): 89-98.

https://doi.org/10.5376/gab.2024.15.0011