| I.aegyptiaca is a kind of garden plant pest widely distributed in the tropics and subtropics.The insect is omnivorous and has a host plant of up to 59 families and 113 genera.In the 1980 s,the insect was listed as one of the dangerous garden pests in Guangzhou.I.purchasi is distributing in 125 countries in the world,mainly in tropical and subtropical regions.The hosts of I.purchasi include plants of 167 genera in 68 families.I.purchasi is very omnivorous,which mainly damages citrus in China.In the last century,it caused damage to citrus in the south.I.purchasi also damages fruit trees such as litchi,longan,mango,peach,plum,pear and persimmon.In recent years,it has caused great damage to the garden tree species of Pittosporum tobira.In order to grasp the invasion risk of the two Icerya species in the world and China,this paper uses Max Ent niche model to predict the current and future(2050 and 2070)potential distribution areas of the two species in China and the world.The results can provide a theoretical basis for controlling the spread and early warning of the two species.In order to find out the invasion source and diffusion path of the two species in China,and strengthen the quarantine work of the related departments,this study intends to use the ISSR Molecular marker method to analyse the genetic diversity and genetic structure of the two Icerya species in China.To make clear the genetic diversity and lineage among different geographic populations,to understand the invasion pathway and population differentiation of the two Icerya species in China.The main results are as follows:(1)The average AUC and AUC ratio of Max Ent global prediction model of I.aegyptiaca are 0.932 and 1.58,and the average AUC and AUC ratio of China model are 0.982 and 1.74,which shows that the modeling results are good and the accuracy is high.The global potential distribution area of I.aegyptiaca includes a wide range of tropical and subtropical areas,mainly between 10°S-30°N,and the main areas include southern Asia,central and northern Africa,southern North America,northern South America and tropical Pacific.In the future climate,the location of the global habitable area of the scale is not much different from that in the current climate,but the total habitable area is increase.The order of the area is as follows: 2070rcp4.5 > 2050rcp4.5 > 2050rcp8.5 > current > 2070rcp8.5.The potential distribution areas of I.aegyptiaca in China include all areas of South China,central China and southwest China,mainly in the areas of longitude 98°E-123°E and Latitude 20°N-30°N,and its suitable areas are mainly in the south of China.In the future climate,the area of the scale in the suitable area of China will move northward and increase,and the area will reach the maximum in 2070rcp8.5 model.(2)The average AUC and AUC ratio of Max Ent global prediction model of I.purchasi was 0.865 and 1.36,and the average AUC and AUC ratio of China model were 0.974 and 1.79.The AUC of all modelling results is greater than 0.8,and the AUC ratio is greater than 1,which shows that the prediction results of this experiment are excellent and have high reliability.The potential distribution areas of I.purchasi mainly include Australia,South America,most of Africa and Europe,South America and South Central Asia.Under the future climate conditions,the location of the habitable areas of the global model habitable area has changed obviously,especially in the highly habitable areas.Compared with the current climate model,the total area of the habitable region under the future climate model will increase,and the area of the habitable region in 2070 will be larger than that in 2050.The total suitable habitat area of different climate models in the world is as follows: 2070rcp8.5 > 2070rcp4.5 > 2050rcp8.5 > 2050rcp4.5 > current.In the future,the suitable habitat area of Asia,North America and Europe will increase,and the high and middle habitat area of North America and Europe will increase significantly.The potential distribution area of I.purchasi in China includes a wide range of southern areas,mainly in the areas with the longitude of 95°E-123°E and the latitude of 20°N-35°N,its suitable area is mainly in the southeast of China,and the climate is relatively humid and warm.Compared with the current climate,the potentially suitable area in the future of I.purchasi in China will not change much,the suitable area will spread to the north,the total suitable area will increase,and the suitable area will reach the maximum under 2070rcp8.5 model.(3)Based on the genetic diversity and differentiation analysis of 46 samples of I.aegyptiaca from Guangdong and Yunnan populations,21 ISSR primers were screened,and the percentage of polymorphic loci was 73.24%.The results of genetic diversity analysis showed that the genetic diversity of the population in Yunnan was higher than that in Guangdong,and the genetic differentiation analysis showed that the genetic differentiation level was higher and the gene flow was larger.The results of AMOVA showed that the variation within the population was larger than that between populations.Genetic similarity and cluster analysis also support that the two geographic populations are more differentiated and far away.Based on the above results,it was analysed that the geographical population of the two populations were different.Yunnan was directly introduced from Southeast Asia,while Guangdong was indirectly introduced from Southeast Asia through Taiwan.(4)Genetic differentiation and diversity analysis of I.purchasi about 80 samples from Guizhou,Fujian,Shaanxi,Zhejiang and Guangdong were carried out.The percentage of 24 ISSR primer polymorphisms was 56.36%.The genetic diversity of the five geographical populations was in the order of Guizhou,Fujian,Guangdong,Zhejiang and Shaanxi.The results of genetic differentiation analysis showed that the genetic differentiation degree among geographical populations was high,and the gene exchange among different populations was low.The results of AMOVA showed that the various populations of I.purchasi were larger than between populations.The results of genetic similarity and cluster analysis showed that the genetic distance between the geographical populations of I.purchasi did not reach the subspecies level,and the results supported that the five geographical populations were classified into three groups,and Guizhou constituted one group,Fujian constitutes a group,Shaanxi,Zhejiang and Guangdong constitute a group.It is suggeste that the population of Shaanxi and Zhejiang may be formed by the invasion of Guangdong population,Fujian population may be directly introduced from Taiwan,while Guizhou Population formation is not sure where the population was introduced,which needs more regional data to support the interpretation. |
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