Intraguild Predation And Combine Release In The Phytoseiid Mites Amblyseius Swirskii And Neoseiulus Barkeri

Amblyseius swirskii is an exotic phytoseiid generalist,and Neoseiulus barkeri?Hughes?is a indigenous phytoseiid species which are widely used in China,both of which can be used as biocontrol agents of the Western flower thrips Frankliniella occidentalis?Pergande?and other pests.In this thesis,these two species of predatory mites and their shared prey?Extraguild prey,Extra-prey?F.occidentalis were used as the research system to studied the Intraguild predation?IGP?by a series of experiments in lab in order to provide the basis for the application of exotic A.swirskii and combined release of A.swirskii and N.barkeri in biocontrol.The main results were as follows:the predatory selection of phytoseuis between IG-prey and Extra-prey,Extra-prey density-dependent intraguild predation in the phytoseiid mites,The influence of female and male of three species of predatory mites on their IGP relationship,effect of IGP on the combined release of A.swirskii and N.barkeri,the research results provide A.swirskii basis for the application and combine release of locally.The main results are as follows:?1?In the predation orientation experiment between A.swirskii and N.barkeri:In the absence of Extra-prey,both of A.swirskii and N.barkeri would give priority to attackheterogenetic mite than conspecific mite?Breslow tests,A.swirskii:?²=33.728;df=1;P<0.001;N.barkeri:?²=39.421;df=1;P<0.001?.There was no significant difference in IGP level between A.swirskii and N.barkeri showing as as symmetric IGP in the absence of Extra-prey??²test:?²=0.076,df=1,P=0.782?.Thus,A.swirskii and N.barkeri were preferentially engaged in IGP rather than cannibalism.?2?In the selective experiments of IG-predator for IG-prey and Extra-prey:both the IG-predator A.swirskii or N.barkeri showed an significant preference for F.occidentalis over IG-prey when Extra-prey F.occidentalis and IG-prey coexisted?Kaplan-meier,both P's<0.05?,and rusulted that the predation risk of IG-predator for IG-prey was reduced.The further analysis by Cox risk regression model proved that A.swirskii and N.barkeri posed a serious threat to F.occidentalis?A.swirskii as IG-predator,R=-0.594,P<0.05;N.barkeri as IG-predator,R=10.608,P<0.05?whereas A.swirskii and N.barkeri posed no threat relationship with IG-prey?A.swirskii as IG-predator,R=-0.875,P>0.05;N.barkeri as IG-predator,R=-0.594,P>0.05?.?3?Extra-prey density-dependent Intraguild predation:With the increase of Extra-prey F.occidentalis density,the IGP between the two mite species was reduced gradually from significant asymmetric IGP in the absence of Extra-prey??²-test,?²=5.624,df=1,P=0.045?,to symmetry IGP in the presence of Extra-prey?In-sufficient,Sufficient???²-test,both P's>0.05?.Meanwhile,the predation of two species of IG-predators on Extra-prey increased significantly?T-test,all P's<0.001?,whereas the the predation on IG-prey decreased gradually?ANOVA,all P's<0.05?.There was a moderate negative correlation between the predation amount of IG-prey and the density of Extra-prey(Pearson,r_A.swirskii=0.593;r_N.barkeri=0.624).With the increase of density of Extra-prey of F.occidentalis,the IGP between A.swirskii and N.barkeri was relieved effectively because the predation risk of IG-predator for IG-prey was reduced gradually as a results of IG-predator shifting to prey on more Extra-prey.?4?Both of the survival rates of A.swirskii and N.barkeri were significantly different under the different density of Extra-prey(ANOVA,A.swirskii:F_2,87=139.24,P<0.001;N.barkeri:F2,87=275.62,P<0.001).The density of Extra-prey was positively correlated with the oviposition of A.swirskii and N.barkeri(Pearson,r_A.swirskii=0.654;r_N.barkeri=0.746).Ther were significantly difference in the survival rates of A.swirskii and N.barkeri under different density IG-prey(ANOVA,A.swirskii:F2,87=147.32,P<0.001;N.barkeri:F_2,87=155.64,P<0.001).The density of IG-prey was positively correlated with oviposition of A.swirskii and N.barkeri(Pearson,r_A.swirskii=0.874;r _N.barkeri=0.836).?5?The effects of sex of phytoseiid mites on IGP:The female adults of two phytoseiid species didn't prey on intraspecific female and male adults,and the female adults of two phytoseiid species did'n prey on the heterogeneous female adults,neither.But female adults of two kinds of mites only predated against male heterogeneous adults?Fisher's Exact test:?²=52.342,df=1,P<0.001?.?6?In the half natural experiments for evaluating the effect of combined release of A.swirskii and N.barkeri:there were significant effects of treatments on the population of F.occidentalis(GLM_adults:F=58.764,df=3,P<0.001).By kaplan-meier comparison of the survival time of F.occidentalis anmon3 bio-control groups,it was concluded that the single release of A.swirskii obtained the best control effect against prey?Breslow tests:all P's<0.05?,and the survival rate of predators in combined release reached the highest among three treatments.