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1.
Genetic studies on the endangered African wild dog (Lycaon pictus) have primarily focused on the few remaining large and viable populations. However, investigations on the many isolated small African wild dog populations might also be informative for species management because the majority of extant populations are small and may contain genetic variability that is important for population persistence and for species conservation. Small populations are at higher risk of extinction from stochastic and deterministic demographic processes than larger populations and this is often of more immediate conservation concern than loss of genetic diversity, particularly for species that exhibit out-breeding behaviour such as long distance dispersal which may maintain gene flow. However, the genetic advantages of out-breeding behaviour may be reduced if dispersal is compromised beyond reserve borders (edge effects), further weakening the integrity of small populations. Mitochondrial DNA and 11 microsatellite genetic markers were used to investigate population genetic structure in a small population of out-breeding African wild dogs in Zambia, which occupies an historical dispersal corridor for the species. Results indicated the Zambian population suffered from low allelic richness, and there was significant evidence of a recent population bottleneck. Concurrent ecological data suggests these results were due to habitat fragmentation and restricted dispersal which compromised natural out-breeding mechanisms. This study recommends conservation priorities and management units for the African wild dog that focus on conserving remaining levels of genetic diversity, which may also be applicable for a range of out-breeding species.  相似文献   

2.
Restocking and stock enhancement programs are now recognized as an important tool for the management of fishery resources. It is important, however, to have an adequate knowledge on the genetic population structure of both the released stock and the wild population before carrying out such programs. In this study, random amplified polymorphic DNA (RAPD) markers were applied to assess genetic diversity and population structure of wild and hatchery populations of the white seabreamDiplodus sargus and the common two-banded seabreamD. vulgaris (Sparidae). The estimated values for intrapopulation genetic variation, measured using the percentage of polymorphic loci (%P), Shannon indexH’, and Nei’s gene diversity (h), showed high values for all populations. The percentage of genetic variation withinD. sargus andD. vulgaris populations, based on coefficient of gene differentiation, reached 82.5% and 90% of the total genetic variation, respectively. An undeniable decrease in genetic variation was found in both hatchery populations, particularly inD. sargus, compared to the wild ones. However, the high values of variation within all populations and the low levels of genetic variation among populations did not indicate inbreeding or depression effects, thus indicating a fairly proper hatchery management. Nevertheless, the results of this study highlight the importance of monitoring the genetic variation of hatchery populations, particularly those to be used in restocking programs. The creation of a genetic baseline database will contribute to a more efficient conservation management and to the design of genetically sustainable restocking programs.  相似文献   

3.
Catfishes of the family Pangasiidae are an important group that contributes significantly to the fisheries of the Mekong River basin. In recent times the populations of several catfish species have declined, thought to be due to overfishing and habitat changes brought about by anthropogenic influences. The Mekong giant catfish Pangasianodon gigas Chevey, 1913 is listed as Critically Endangered on the IUCN Red List. In the present study, we assessed the level of genetic diversity of nine catfish species using sequences of the large subunit of mitochondrial DNA (16S rRNA). Approximately 570 base pairs (bp) were sequenced from 672 individuals of nine species. In all species studied, haplotype diversity and nucleotide diversity ranged from 0.118±0.101 to 0.667±0.141 and from 0.0002±0.0003 to 0.0016±0.0013, respectively. Four haplotypes were detected among 16 samples from natural populations of the critically endangered Mekong giant catfish. The results, in spite of the limited sample size for some species investigated, indicated that the level of genetic variation observed in wild populations of the Mekong giant catfish (haplotype diversity=0.350±0.148, nucleotide diversity=0.0009±0.0008) is commensurate with that of some other related species. This finding indicates that (1) wild populations of the Mekong giant catfish might be more robust than currently thought or (2) present wild populations of this species carry a genetic signature of the historically larger population(s). Findings from this study also have important implications for conservation of the Mekong giant catfish, especially in designing and implementing artificial breeding programme for restocking purposes.  相似文献   

4.
In salmonids, the release of hatchery-reared fish has been shown to cause irreversible genetic impacts on wild populations. However, although responsible practices for producing and releasing genetically diverse, hatchery-reared juveniles have been published widely, they are rarely implemented. Here, we investigated genetic differences between wild and early-generation hatchery-reared populations of the purple sea urchin Paracentrotus lividus (a commercially important species in Europe) to assess whether hatcheries were able to maintain natural levels of genetic diversity. To test the hypothesis that hatchery rearing would cause bottleneck effects (that is, a substantial reduction in genetic diversity and differentiation from wild populations), we compared the levels and patterns of genetic variation between two hatcheries and four nearby wild populations, using samples from both Spain and Ireland. We found that hatchery-reared populations were less diverse and had diverged significantly from the wild populations, with a very small effective population size and a high degree of relatedness between individuals. These results raise a number of concerns about the genetic impacts of their release into wild populations, particularly when such a degree of differentiation can occur in a single generation of hatchery rearing. Consequently, we suggest that caution should be taken when using hatchery-reared individuals to augment fisheries, even for marine species with high dispersal capacity, and we provide some recommendations to improve hatchery rearing and release practices. Our results further highlight the need to consider the genetic risks of releasing hatchery-reared juveniles into the wild during the establishment of restocking, stock enhancement and sea ranching programs.  相似文献   

5.
Genetic rescue is an increasingly considered conservation measure to address genetic erosion associated with habitat loss and fragmentation. The resulting gene flow from facilitating migration may improve fitness and adaptive potential, but is not without risks (e.g., outbreeding depression). Here, we conducted a test of genetic rescue by translocating ten (five of each sex) brook trout (Salvelinus fontinalis) from a single source to four nearby and isolated stream populations. To control for the demographic contribution of translocated individuals, ten resident individuals (five of each sex) were removed from each recipient population. Prior to the introduction of translocated individuals, the two smallest above‐barrier populations had substantially lower genetic diversity, and all populations had reduced effective number of breeders relative to adjacent below‐barrier populations. In the first reproductive bout following translocation, 31 of 40 (78%) translocated individuals reproduced successfully. Translocated individuals contributed to more families than expected under random mating and generally produced larger full‐sibling families. We observed relatively high (>20%) introgression in three of the four recipient populations. The translocations increased genetic diversity of recipient populations by 45% in allelic richness and 25% in expected heterozygosity. Additionally, strong evidence of hybrid vigour was observed through significantly larger body sizes of hybrid offspring relative to resident offspring in all recipient populations. Continued monitoring of these populations will test for negative fitness effects beyond the first generation. However, these results provide much‐needed experimental data to inform the potential effectiveness of genetic rescue‐motivated translocations.  相似文献   

6.
Roads exert various effects of conservation concern. They cause road mortality of wildlife, change the behaviour of animals and lead to habitat fragmentation. Roads also have genetic effects, as they restrict animal movement and increase the functional isolation of populations. We first formulate theoretical expectations on the genetic effects of roads with respect to a decrease in genetic diversity and an increase in genetic differentiation or distance of populations or individuals. We then review the empirical evidence on the genetic effects of roads based on the available literature. We found that roads often, but not always, decrease the genetic diversity of affected populations due to reduced population size and genetic drift. Whether the reduction in genetic diversity influences the long-term fitness of affected populations is, however, not yet clear. Roads, especially fenced highways, also act as barriers to movement, migration and gene flow. Roads therefore often decrease functional connectivity and increase the genetic differentiation of populations or the genetic distance among individuals. Nevertheless, roads and highways rarely act as complete barriers as shown by genetic studies assessing contemporary migration across roads (by using assignment tests). Some studies also showed that road verges act as dispersal corridors for native and exotic plants and animals. Genetic methods are well suited to retrospectively trace such migration pathways. Most roads and highways have only recently been built. Although only few generations might thus have passed since road construction, our literature survey showed that many studies found negative effects of roads on genetic diversity and genetic differentiation in animal species, especially for larger mammals and amphibians. Roads may thus rapidly cause genetic effects. This result stresses the importance of defragmentation measures such as over- and underpasses or wildlife bridges across roads.  相似文献   

7.
Pedigrees of broodstock with unknown relationship of the critically endangered Chinese sturgeon, Acipenser sinensis, was evaluated using microsatellite markers to facilitate genetic management in restocking programs with small broodstock size. We characterized the distributions of relatedness values to reconstruct kin groups in four hatchery families with known pedigrees using microsatellites. The distributions of relatedness values for kin classes were used for partitioning full sibling groups of wild A. sinensis broodstock kept in two hatcheries, resulted in 13 full sibling clusters, four of which containing 62% of all the wild individuals. This indicates high probability of choosing close related breeder pairs in random mating, thus selective breeding is necessary to minimize inbreeding and maintain genetic diversity. This study provides a useful tool for genetic management in conservation programs of A. sinensis in aim of preserving self‐sustained wild populations.  相似文献   

8.
1. An important goal of conservation biology is to preserve the evolutionary potential of a species by maintaining natural levels of genetic diversity. Here, we assess the population differentiation in the Atlantic salmon, Salmo salar, listed in Annex II of the European Habitats Directive, to provide valuable information for its conservation in Normandy (France).
2. Samples collected from 10 natural sites revealed that 13 of 14 microsatellite loci were polymorphic. Significant differentiation among populations was detected ( F ST = 0.054, P  <   0.001), and all F ST pairwise comparisons except one were significant. A genetic split was observed between populations inhabiting streams with limestone geology compared to those inhabiting streams with siliceous geology, which could reflect adaptative differences.
3. Hatchery stocks used for the restocking of two rivers were genetically distinct from native stocks.
4. Analysis of three stream habitats restored in 1995 showed that all were recolonized naturally by wild salmon from geographically close populations and no founder effects were detected. Allelic richness was similar between recolonized and wild populations.
5. From a management perspective, our study revealed that restoration of habitat is very effective to recreate new populations in rivers from which salmon have disappeared and that natural recolonization can be fast and effective in terms of genetic diversity.  相似文献   

9.
King KC  Lively CM 《Heredity》2012,109(4):199-203
It is a commonly held view that genetically homogenous host populations are more vulnerable to infection than genetically diverse populations. The underlying idea, known as the 'monoculture effect,' is well documented in agricultural studies. Low genetic diversity in the wild can result from bottlenecks (that is, founder effects), biparental inbreeding or self-fertilization, any of which might increase the risk of epidemics. Host genetic diversity could buffer populations against epidemics in nature, but it is not clear how much diversity is required to prevent disease spread. Recent theoretical and empirical studies, particularly in Daphnia populations, have helped to establish that genetic diversity can reduce parasite transmission. Here, we review the present theoretical work and empirical evidence, and we suggest a new focus on finding 'diversity thresholds.'  相似文献   

10.
Red sea cucumber Stichopus japonicus is the most important and valuable commercial sea cucumber species in Korea. Its farming and stock enhancement started in the early 2000s and is still rapid expansion in Korea. Therefore, the analyses of genetic status of wild and hatchery populations are necessary to maintain the genetic diversity of this valuable marine resource. In this study, possible genetic similarity and differences between the wild population and hatchery population in Jeju, Korea were accessed using multiplex assays with eight highly polymorphic microsatellite loci. High levels of polymorphism were observed between the two populations. A total of 93 different alleles were found. Although a considerable loss of unique alleles and relatively high inbreeding coefficient value were observed in the hatchery samples, no statistically significant reductions were found in heterozygosity or allelic diversity in the hatchery population, compared with the wild population. However, significant genetic heterogeneity was found between two populations. These results suggest that genetic drift has probably promoted differentiation between populations, and stocking intensity in wild populations may correlate with loss of genetic integrity. Therefore, the sustainable exploitation plans of the fishery resource should be developed by applying basic genetic principles combined with molecular monitoring. This genetic baseline information of Korean red sea cucumber has important implications for designing of genetically sustainable restocking programs and more efficient conservation management guidelines for these valuable genetic materials.  相似文献   

11.
Gila trout (Oncorhynchus gilae gilae) was federally protected in 1973 because of severe declines in abundance and geographic range size. At present, four relict genetic lineages of the species remain in mountain streams of New Mexico and Arizona, USA. Management actions aimed at species recovery, including hatchery production and restocking of formerly occupied streams, have been guided by information from non-functional genetic markers. In this study, we investigated genetic variation at exon 2 of the major histocompatibility complex (MHC) class II β gene that is involved in pathogen resistance and thus presumably under natural selection. Phylogenetic analysis revealed trans-species polymorphism and a significantly high ratio of non-synonymous to synonymous amino acid changes consistent with the action of historical balancing selection that maintained diversity at this locus in the past. However, Gila trout exhibited low allelic diversity (five alleles from 142 individuals assayed) compared to some other salmonid fishes, and populations that originated exclusively from hatcheries possessed three or fewer MHC alleles. Comparative analysis of genetic variation at MHC and six presumably neutrally evolving microsatellite loci revealed that genetic drift cannot be rejected as a primary force governing evolution of MHC in contemporary populations of Gila trout. Maintenance of diversity at MHC will require careful implementation of hatchery breeding protocols and continued protection of wild populations to prevent loss of allelic diversity due to drift.  相似文献   

12.
Disruption of naturally evolved spatial patterns of genetic variation and local adaptations is a growing concern in wildlife management and conservation. During the last decade, releases of native taxa with potentially non-native genotypes have received increased attention. This has mostly concerned conservation programs, but releases are also widely carried out to boost harvest opportunities. The mallard, Anas platyrhynchos, is one of few terrestrial migratory vertebrates subjected to large-scale releases for hunting purposes. It is the most numerous and widespread duck in the world, yet each year more than three million farmed mallard ducklings are released into the wild in the European Union alone to increase the harvestable population. This study aimed to determine the genetic effects of such large-scale releases of a native species, specifically if wild and released farmed mallards differ genetically among subpopulations in Europe, if there are signs of admixture between the two groups, if the genetic structure of the wild mallard population has changed since large-scale releases began in the 1970s, and if the current data matches global patterns across the Northern hemisphere. We used Bayesian clustering (Structure software) and Discriminant Analysis of Principal Components (DAPC) to analyze the genetic structure of historical and present-day wild (n?=?171 and n?=?209, respectively) as well as farmed (n?=?211) mallards from six European countries as inferred by 360 single-nucleotide polymorphisms (SNPs). Both methods showed a clear genetic differentiation between wild and farmed mallards. Admixed individuals were found in the present-day wild population, implicating introgression of farmed genotypes into wild mallards despite low survival among released farmed mallards. Such cryptic introgression would alter the genetic composition of wild populations and may have unknown long-term consequences for conservation.  相似文献   

13.
J Guo  Y Liu  Y Wang  J Chen  Y Li  H Huang  L Qiu  Y Wang 《Annals of botany》2012,110(4):777-785
Background and Aims Wild soybean (Glycine soja), a native species of East Asia, is the closest wild relative of the cultivated soybean (G. max) and supplies valuable genetic resources for cultivar breeding. Analyses of the genetic variation and population structure of wild soybean are fundamental for effective conservation studies and utilization of this valuable genetic resource. Methods In this study, 40 wild soybean populations from China were genotyped with 20 microsatellites to investigate the natural population structure and genetic diversity. These results were integrated with previous microsatellite analyses for 231 representative individuals from East Asia to investigate the genetic relationships of wild soybeans from China. Key Results Analysis of molecular variance (AMOVA) revealed that 43·92 % of the molecular variance occurred within populations, although relatively low genetic diversity was detected for natural wild soybean populations. Most of the populations exhibited significant effects of a genetic bottleneck. Principal co-ordinate analysis, construction of a Neighbor-Joining tree and Bayesian clustering indicated two main genotypic clusters of wild soybean from China. The wild soybean populations, which are distributed in north-east and south China, separated by the Huang-Huai Valley, displayed similar genotypes, whereas those populations from the Huang-Huai Valley were different. Conclusions The previously unknown population structure of the natural populations of wild soybean distributed throughout China was determined. Two evolutionarily significant units were defined and further analysed by combining genetic diversity and structure analyses from Chinese populations with representative samples from Eastern Asia. The study suggests that during the glacial period there may have been an expansion route between south-east and north-east China, via the temperate forests in the East China Sea Land Bridge, which resulted in similar genotypes of wild soybean populations from these regions. Genetic diversity and bottleneck analysis supports that both extensive collection of germplasm resources and habitat management strategies should be undertaken for effective conservation studies of these important wild soybean resources.  相似文献   

14.
Randi E 《Molecular ecology》2008,17(1):285-293
The widespread occurrence of free-ranging domestic or feral carnivores (dogs, cats) or ungulates (pigs, goats), and massive releases of captive-reproduced game stocks (galliforms, waterfowl) is raising fear that introgressive hybridization with wild populations might disrupt local adaptations, leading to population decline and loss of biodiversity. Detecting introgression through hybridization is problematic if the parental populations cannot be sampled (unlike in classical stable hybrid zones), or if hybridization is sporadic. However, the use of hypervariable DNA markers (microsatellites) and new statistical methods (Bayesian models), have dramatically improved the assessment of cryptic population structure, admixture analyses and individual assignment testing. In this paper, I summarize results of projects aimed to identify occurrence and extent of introgressive hybridization in European populations of wolves (Canis lupus), wildcats (Felis silvestris), rock partridges and red-legged partridges (Alectoris graeca and Alectoris rufa), using genetic methods. Results indicate that introgressive hybridization can be locally pervasive, and that conservation plans should be implemented to preserve the integrity of the gene pools of wild populations. Population genetic methods can be fruitfully used to identify introgressed individuals and hybridizing populations, providing data which allow evaluating risks of outbreeding depression. The diffusion in the wild of invasive feral animals, and massive restocking with captive-reproduced game species, should be carefully controlled to avoid loss of genetic diversity and disruption of local adaptations.  相似文献   

15.
Genetic tools are increasingly valuable for understanding the behaviour, evolution, and conservation of social species. In African elephants, for instance, genetic data provide basic information on the population genetic causes and consequences of social behaviour, and how human activities alter elephants' social and genetic structures. As such, African elephants provide a useful case study to understand the relationships between social behaviour and population genetic structure in a conservation framework. Here, we review three areas where genetic methods have made important contributions to elephant behavioural ecology and conservation: (1) understanding kin-based relationships in females and the effects of poaching on the adaptive value of elephant relationships, (2) understanding patterns of paternity in elephants and how poaching can alter these patterns, and (3) conservation genetic tools to census elusive populations, track ivory, and understand the behavioural ecology of crop-raiding. By comparing studies from populations that have experienced a range of poaching intensities, we find that human activities have a large effect on elephant behaviour and genetic structure. Poaching disrupts kin-based association patterns, decreases the quality of elephant social relationships, and increases male reproductive skew, with important consequences for population health and the maintenance of genetic diversity. In addition, we find that genetic tools to census populations or gather forensic information are almost always more accurate than non-genetic alternatives. These results contribute to a growing understanding of poaching on animal behaviour, and how genetic tools can be used to understand and conserve social species.  相似文献   

16.
Lemer S  Planes S 《Molecular ecology》2012,21(12):2949-2962
Translocation has been widely studied as a tool for conservation management to restore or enhance degraded populations. On the contrary, few studies have been conducted on translocation for commercial purposes. In this study, we evaluate the genetic consequences of translocation of wild individuals of Pinctada margaritifera on farmed and adjacent wild populations. We tested the hypotheses that translocations would induce high genetic heterogeneity in farmed populations and this heterogeneity would then leak into the adjacent wild populations. In fact, farmed samples exhibit high levels of heterogeneity and low pairwise relatedness compared to wild populations, highlighting the pooling of genetically divergent populations into farms. We also demonstrate that this heterogeneity is transmitted to adjacent wild populations as a result of interbreeding. Adjacent wild populations tend to have higher genetic diversity values and greater pairwise relatedness coefficient with farmed populations than wild populations. Overall, pearl culture in French Polynesia promotes the mixing of unrelated individuals in farmed locations and reduces genetic divergence among geographically distant populations as well as among farmed and wild populations of a same lagoon. We also studied for the first time a farmed population originating from spat collected in a lagoon where release of hatchery-produced larvae occurred 10 years ago and we were able to identify four distinct genetic groups. These groups contribute highly to reproduction and caused considerable genetic drift in the lagoon, suggesting that hatchery-produced larvae are neither sustainable method for pearl culture nor for conserving the diversity of P. margaritifera in French Polynesia.  相似文献   

17.
Genotyping faeces links individuals to their diet   总被引:2,自引:0,他引:2  
The detection of individual variation in foraging behaviour within wild mammal populations requires large sample sizes and relies on the multifold re-sampling of individuals. However, limits for observational studies are posed by the rarity and nocturnal or otherwise elusive habits of many mammals. We propose that the detection of foraging variation within populations of mammals may be facilitated if conventional diet analysis from faeces is combined with DNA-based individual identification methods using "genetic fingerprinting" from faeces. We applied our approach to a coyote ( Canis latrans ) population, and showed how individuals may vary from one another in their diet profiles. Two main groups of coyotes were distinguished on the basis of their relative use of small mammals and "other vertebrates" as primary food sources, and these two groups were further subdivided on the basis of their relative use of "other vertebrates" and fruit as secondary food sources. We show that, unless a faecal sampling scheme is used that maximizes the number of different individuals included in a survey, individual foraging variation that is left unaccounted for may result in downwardly biased faecal diet diversity estimates. Our approach allows the re-sampling of individuals over time and space, and thus may be generally useful for the testing of optimal foraging theory hypotheses in mammals and also has conservation applications.  相似文献   

18.
Dendrobium officinale (Orchidaceae) is an endangered plant species with important medicinal value. To evaluate the effectiveness of ex situ collection of D. officinale genetic diversity, we developed 15 polymorphic trinucleotide microsatellite loci of D. officinale to examine the genetic diversity and structure of three D. officinale germplasm collections comprising 120 individuals from its germplasm collection base and their respective wild populations consisting of 62 individuals from three provinces in China. The three germplasm collections showed reductions in gene diversity and average number of alleles per locus, but an increase in average number of rare alleles (frequency?≤?0.05) per locus in comparison to their wild populations. However, the differences in gene diversity between the germplasm collections and wild populations were not statistically significant. The analysis using STRUCTURE revealed evident differences in genetic composition between each germplasm collection and its wild population, probably because the D. officinale individuals with distinct genotypes in each wild population were unevenly selected for establishing its germplasm collection. For conservation management plans, we propose that D. officinale individuals with rare alleles need to be conserved with top priority, and those individuals with the most common alleles also should be concerned. The 15 new microsatellite loci may be used as a powerful tool for further evaluation and conservation of the genetic diversity of D. officinale germplasm resources.  相似文献   

19.
小麦族中间鹅观草不同居群的形态多样性分析   总被引:2,自引:0,他引:2  
小麦族(Triticeae)植物的野外调查、收集通常是以形态学为依据的。为了探讨小麦族植物在野外调查、收集的科学取样策略,本项研究以小麦族具有自花授粉习性的3个中间鹅观草(Roegneria sinica.vat.media Keng)居群、每个居群30个单株为材料,对11个形态学性状的多样性进行了分析。结果表明,3个居群的总遗传多样性指数为1.991,遗传多样性主要集中于居群内(91.76%),而居群间的遗传变异(8.24%)相对较小;不同取样梯度下的遗传多样性指数随单株取样数目的增加呈现增大趋势,但当取样数目达到18株时,遗传多样性指数达到最高值。上述结果说明,对于小麦族自花授粉植物野外调查、收集时,应以居群为单位,而且每一居群至少应调查、收集18个单株,才能代表居群的遗传多样性。以形态学为依据的取样策略的建立,对于指导野外调查、收集具有现实意义。  相似文献   

20.
The pullet carpet shell Venerupis senegalensis (=V. pullastra) is a commercially important species in Portugal, Spain, France, and Italy. In Portugal, this species was once abundant in the Ria Formosa (southern Portugal). However, in the early 1980s, its abundance declined dramatically due to overfishing. In order to reverse this negative trend, the genetic sustainable management of the wild stocks of V. senegalensis should be performed by promoting successful restocking actions and the development of an aquaculture commercial production program of this species. In order to find the best broodstock for aquaculture purposes and therefore minimize the deleterious effects of hatchery practices, we analyzed the genetic diversity of the natural population to be restocked (Ria Formosa) but also of another potential genetically close population (Ria de Aveiro) by RAPD. Similar and substantive percentage of polymorphic loci, effective number of alleles, Nei’s gene diversity, and Shannon’s diversity index was found within both populations. This high genetic variability within populations suggests that they might have a gene pool with sufficient genetic plasticity to support changes in the environmental conditions. Analyses of population genetic structure also revealed a small genetic differentiation between the two populations. The high genetic variability of the natural population to be restocked makes it the preferential broodstock for aquaculture purposes. However, the Ria de Aveiro population could also be a viable alternative, due to its genetic plasticity and the genetic similarity of both populations. The results of this study can be useful to the sustainable management of wild stocks as well as in promoting successful restocking actions based on aquaculture production.  相似文献   

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