| Predacious natural enemies or mites play an important role in the biological control strategies.Understanding the population dynamics of pests in long term series,including the population numerical and structural dynamics,is the key to determine the most effective time of spraying pesticides and releasing biological control agents,and also is the key to avoid pesticide abuse and lower control effectiveness of biological control strategies.Current studies mostly focus on the population dynmaics and regularation mechanism of the pest,whereas those of natural enemies with higher trophic level are limited.Therefore,this study selected the commercialized productive biological control agent,Neoseiulus barkeri,key pest spider mite species,Panonychus citri and Eotetranychus kankitus,native natural enemy in Chongqing and Sichuan,Euseius nicholsi,alternative prey,Tyrophagus putrescentiae as the object mites,to systematicly and comprehensively illuminate the population regulation and dispersal mechanism of N.barkeri,on basis of two sex life table theory,predation analysis,population numerical and structural dynamics,interactions between natural enemies,walking dispersal of different coexistence systems.The major contents are as follows: 1 Age-stage,two sex life table constructions of N.barkeri fed on one alternative prey specie and three target spider mtie species.Using life table theory and survival analysis technology,age-stage,two sex life tables of N.barkeri fed on one alternative prey species,T.putrescentiae,and three target spider mite species,T.urticae,P,citri,and E.kankitus,and the life history traits,e.g.develop,survival,fecundity,and the population parameters,e.g.intrinsic rate of increase,finate rate of increase,net reproductive value,mean generation time,were compared.When fed on T.urticae,the longevity of pre-adults,adult females and adult males,and mean longevity of N.barkeri were longest.When fed on E.kankitus,the survival rates of N.barkeri adult males were nearly to that of females,whereas the survival rates of N.barkeri adult males were substantially higher than those of adult females when fed on P.citri.Although the survival rates of N.barkeri adult females fed on P.citri,the age-specific fecundies of that adult femals were substantially higher than those when fed on T.putrescentiae and E.kankitus.When fed on T.putrescentiae,the intrinsic rate of increase and finate rate of increase of N.barkeri population were the highest,whereas when fed on T.urticae,net reproductive value and mean generation time of N.barkeri population were the highest.According to the comprehensive analysis of the prey preference predation and preference index of N.barkeri on four prey specises,the prey preference ranking from high to low was as follows: E.kankitus > P,citri > T.urticae > T.putrescentiae.2 Population projection of N.barkeri on basis of two sex life table theory and Timing model construction.Based on functional response and mix-stages predation analysis,predation capacity of N.barkeri on E.kankitus was evaluated.Results showed that N.barkeri was able to develop and reproduce when fed on E.kankitus.The functional responses of N.barkeri on different stages of E.kankitus all fit the Holling II disc equation.When mixed stages of E.kankitus coexisted,N.barkeri mainly consumed larvae and nymphs,and seldomly consumed adults and eggs.The total number of E.kankitus preyed upon during the nymphal,adult female,and adult male stages by N.barkeri were 16.1,134.9,and 127.5 individuals,respectively.The cxj of N.barkeri adult females reached a peak of 21.7 at 51 d,8 at 38 d,4 at 39.5 d,and 25 at 51 d,when consuming larvae,nymphs,adults,and total individuals of E.kankitus,respectively.Using Timing model theory technology,the population projection of N.barkeri was constructed to quantify the population growth rate,population numerical and structural dynamics under different simulation conditions.Through the population projection,it is found that the population of E.kankitus will spend longer time to reach stable age structure distribution than that of N.barkeri.Although E.kankitus had the higher growth rate,an E.kanktus population initial with sixty females,forty males and twenty eggs was maintained at a low population level for several weeks after release of N.barkeri with initial population of five females and five males.The population vertification experiments showed that the population projection value of E.kankitus was overvalued when compared the ture values of vertification experiment;population projection value of N.barkeri with initial population of five females and five males,and with initial population of ten females and ten males was allowed 10 % error range when compared the ture values of vertification experiment;population projection value of N.barkeri with initial population of twenty females and twenty males was over than 10 % error range when compared the ture values of vertification experiment,except the projection of nymph stage which was 9 %.3 Patterns of coexistence or exclusion in an intraguild predator-prey system between N.barkeri and E.nicholsi.Cannibalism predation(CBP)and intraguild predation(IGP)betweent different stages and sexes of N.barkeri and E.nicholsi were evaluated.CBP level of N.barkeri in 6 h was low,and significantly increased in 24 h.All predacious stages of N.barkeri did not cannibalism consume eggs in 24 h.54 % combinations of E.nicholsi occurred CBP,which was substantially higher than CBP combinations of N.barkeri(33 %).The predacious stages of E.nicholsi did not cannibalism consume eggs in 6 h,but did cannibalism consume eggs in 24 h.83 % combinations occurred IGP between the two predatory mite species,of which bidirectional IGP took up 67 % and unidirectional IGP took up 33%.Unidirectional IGP index of N.barkeri was 2.7 fold higher than that of E.nicholsi,indicating that N.barkeri was the IG-predator,whereas E.nicholsi was the IG-prey.Besides,all E.nicholsi did not consume eggs of N.barkeri,whereas deutonymphs and adult males of N.barkeri could consume eggs of E.nicholsi.When extraguild prey,P.citri,was added into the IGP system,IGP level of E.nicholsi to N.barkeri was substantially decreased both in 6 h and 24 h.In contrast,IGP level of adult females and males of N.barkeri was not affected by the presence of P.citri,and reached to a high level of 80 % when five extraguild preys were added in 24 h.The similar phenomenon was also observed in bidirectional IGP between the two predatory mtie specises.Survival and fecundity of N.barkeri and E.nicholsi in the coexistence system of extraguild preys,or intraguild preys,or cannibalism preys,were evaluated.When coexisted with extraguild preys,both two predatory mite specises had significantly higher predation rate and daily fecundity.The predation,survival and fecundity of N.barkeri between IGP coexistence system and cannibalism coexistence system were not significantly different.However,those of E.nicholsi in the cannibalism system were significantly higher than those of E.nicholsi in the IGP system.These results indicated that when the productive level of extraguild preys was low,E.nicholsi may increase cannibalism predation to obtain nutrition and survival through,to decrease population density and keep population sustainability.4 Walking dispersal of N.barkeri between habitat patches with different productive levels in three coexistence systemsUsing experimental simulation of dispersal pressure,heterogenelty of habitat patches,and interspecific interactions,walking dispersal of different stages and sexes of N.barkeri in the coexistence system of extraguild preys,P.citri,or alternative preys,T.putrescentiae,or intraguild preys,E.nicholsi,were measured.Walking dispersal stages of N.barkeri was nymph,adult female and adult male,whereas larva stage of N.barkei did not play roles in dispersal.Dispersal of N.barkeri in horizontal direcitons was random.Dispersal of N.barkeri adult males between presence and absence of extraguild preys had no significant difference,and was higher than dispersal of other stages in 1 h.3 h later,dispersal number of N.barkeri female adults in habitat patches with extraguild preys was significantly higher than that without extraguild preys.When alternative preys coexisted in the system,dispersal of N.barkeri between different patches was not affected.However,when intraguild preys coexisted in the system,dispersal number of adult females of N.barkeri to patches with extraguild preys increased in 3 h and decreased thereafter.Package release experiments in citrus orchards showed that N.barkeri had low dispersal within 24 h,and its dispersal peaked from 24 h to 53 h.The horizontal dispersal of N.barkeri on citrus tree was also random,whereas vertical dispersal of N.barkeri on citrus tree hold a trend to middle crown and upper crown of citrus tree,and the grassland under the tree also had some certain lever of dispersal. |
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