| Amur tiger(Panthera tigris altaica),which is the northernmost subspecies of tiger and also a Class I protected animal in China,once was widely distributed across northeastern China,the Korean Peninsula,and Russian Far East.After the middle of the 20th century,excessive poaching,habitat loss,and habitat fragmentation led to a rapid decrease in population numbers and habitat range,leaving Amur tiger on the verge of extinction due to their small and isolated population.For the sustainable growth of the population,it is necessary to have an in-depth understanding on the genetic status of the Amur tiger in China,therefore,this study uses genetic data to explore the spatial dispersal of Amur tiger,the inbreeding degree and its impact;and meanwhile,to detect the structure and function differences in the gut microbiota between wild and captive Amur tigers for preparing the reintroduction.The main results and findings were as follows:1 Dispersal of Amur tiger population within the northern Changbai mountain based on spatial distribution and genetics analysisPopulation dispersal and migration are important means to expand habitat and reduce inbreeding probability,and to some extend reflects improvement in the condition of the population.Amur tiger in China is mainly distributed in the Sino-Russian border area,it is crucial for the persistence of the whole Amur tiger population in China that whether they could spread smoothly into Chinese interior.In recent years,many studies have proved the rapid recovery of the number of Amur tiger individuals in China,but the information on spatial distribution dynamics and population dispersal has not received enough attention.In this study,occurrence data and fecal samples of Amur tigers in the northern part of Changbai mountains in China from 2003 to 2016 were collected to analyze the spatial distribution and dispersal of Amur tiger in China.Our results showed that,from 2003 to 2016,the Amur tiger population in this area was spreading westward at a speed of 12.83 ± 4.41 km every three years.Comparing with the adjacent southwest Primorye of Russia,the genetic diversity of these two populations were not significantly different and the proportion of the potential migration individual between these two populations was calculated to be about 13.04%,indicated that there were some serious geographical or artificial barriers limited the westward spread of Amur tiger.In addition,there is a significant positive correlation between genetic distances and spatial distances among different individuals of Amur tigers in north of Changbai mountains in China.Our research proved important information about the westward spread and transboundary movement of Amur tigers in north of Changbai mountains in China,and showed the emergency nessesary on habitat recovery by Amur tigers in China,ecological corridor research and construction should be conducted as soon as possible to eliminate dispersal barriers,and international cooperation should be strengthened to promote transboundary movement of Amur tiger.2 Inbreeding of Amur tiger population and its influenceInbreeding,mating and breeding between closely related individuals,clumps harmful mutations together and reduces the fitness and viability of the population.In addition,genetic erosion,inbreeding depression and allelic effects caused by inbreeding can eventually lead to isolated small populations more vulnerable to extinction.Wild Amur tiger in China has been in a small state for a long time,and the individual exchange with the Russian population is restricted by the border management between China and Russia,all these factors are more likely to cause inbreeding,but the relevant research is still not been conducted.In order to understand the inbreeding status of wild Amur tigers in China and the harmful effects of inbreeding,we used the most polymorphic markers to evaluate the inbreeding degree and the relatedness of Amur tigers in China.Then,we analyzed whether there were significant differences in MHC polymorphisms and gut microbiota between inbred and non-inbred group,and the relationship between inbreeding and intestinal parasites.The result showed that the relatedness of more than 50%individuals belong to cousin or half-sister relationship,and the inbreeding coefficients of 22.73%individuals were bigger than 0.125.There was no significant difference in MHC polymorphism between inbred and non-inbred groups,however,individual's inbreeding coefficient have significant correlation with Toxocara cati load,U test have identified the difference of MHC diversity between infection and non-infection parasite groups,while,no significantly association were found between special MHC allele and parasite prevalence.For the gut microbiota,multi-taxa microbiota and microbiota functions have impact by inbreeding.These results clearly indicated that a moderate inbreeding level have existed in Amur tiger population.Although,current inbreeding conditions did not lead to a significant difference in MHC diversity,it significantly correlated to intensity of parasite infection.In addition,inbreeding also changes the structure and function of the gut microbiota,increasing the abundance of pathogenic bacteria and affecting the body's functions of biosynthesis,degradation and utilization.3 Comparative analysis of gut microbial community structure and function of wild and captive Amur tiger populationReintroduction,as an effective strategy for wild population recovery and genetic diversity maintenance for endangered populations,is an effective method to relieve the inbreeding pressure of the Amur tiger population and quickly restore the individual numbers in other patches.Although our country has the world's largest Amur tiger breeding base,previous studies have also shown that the captive Amur tigers still retain the ability of recogniting its natural prey,but environment and food composition differences between wild and captive Amur tigers not only affects their behavior and survival ability,but also lead to the change of gut microbiota.Gut microbiota is important for host health,composition changes in the gut microbial community might increase host's susceptibility to infection and reduce its adaptability to environment.Well understand on the composition and function differences of gut microbiota between captive and wild Amur tigers,could provide important data support for the captive individuals rewilding.In this study,high throughput sequencing of the 16S ribosomal RNA(rRNA)(amplicon sequencing)and metagenomics were used to analyze the composition and function differences of gut microbiota communities between captive and wild Amur tiger population based on total 35 fecal samples(13 from captive tigers and 22 from wild tigers).Our results showed that captive Amur tigers have higher Alpha diversity in gut microbiota,but the average unweighted UniFrac distance of bacterial taxa among wild Amur tigers was much larger than captive.The function differences involve most aspects of metabolism,cellular processes and environmental information processing,such as glycanbiosynthesis and metabolism,cell motility,signaling molecules and interaction.It was indicated that the diet habit and environment difference between captive and wild population lead to composition differences of gut microbiota and then resulted in significant differences in function.Based on DNA data,this study systematically analyzed the dispersal of wild Amur tigers,influence of inbreeding degree and its influences,and identified the differences of wild and captive Amur tigers in the gut microbiota composition and function,this study is important for Amur tiger protection management and policy decision. |
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