The Reproductive Fitness Of Mating Behaviour In Encarsia Sophia

Bemisia tabaci MED/MEAM1 is a worldwide invasive insect pest which causes serious economic losses in China.The massive usage of chemical insecticides has resulted in high level of resistance.Biological control using parasitoids is the alternative and effective way to control B.tabaci sustainably.Encarsia sophia,a heteronomous hyperparasitoid,is one of the dominant natural enemies of B.tabaci.Its fertilized eggs are laid in the nymphs of B.tabaci and developed to diploid females,while the unfertilized eggs were laid on the conspecific or heterospecific larvae which parasitized in whitefly nymphs and developed to haploid males.This sex-specific host relationship and development has brought up mass rearing problems in biocontrol applications,such as the divergence of emergence time between sexes and the diversity of sex ratio.In this thesis,we mainly focused on the effects of multiple mating and inbreeding on the reproductive fitness of E.sophia.The main results and conclusions are as follows: 1.Multiple mating behavior and reproductive benefitsMales can quickly re-mate after the first mating,with a re-mating rate of 76.7% in 2 hours interval between first and second mating.The duration of re-mating behavior(25.5 seconds)is significantly longer than the first mating(20.1 seconds).The multiple mating acceptance of females is related to the oviposition experience,only if the females have oviposition experience can re-mate.The re-mating rate was 72.8% within 24 hours after the first mating,and there was no significant difference in mating duration.Multiple mating of males had no significant effect on their own lifespan and their spouse's parasitism number,while multiple mating of females enhanced their reproductive ability significantly.The oviposition period and lifetime parasitism of females mated twice was 17.1 ± 0.7 days and 76.4 ± 5.9,respectively,while that of females mated once was 13.3 ± 0.6 days and 53.1 ± 3.8,respectively.2.Effect of inbreeding and secondary hosts of males on reproductive fitnessMales were from two different secondary hosts,conspecific secondary hosts(E.sophia female prepupae)and heterospecific secondary hosts(Encarsia formosa larvae).Females were mated with siblings from both conspecific and heterospecific secondary hosts,and with unrelated males from both conspecific and heterospecific secondary hosts.The observation of parental mating behavior and female reproduction showed that: females mated with siblings had longer duration time of mating and lower rate of successful mating,as compared to mated with unrelated males;females mated with males from conspecific secondary hosts had shorter duration time of mating,higher rate of successful mating,and lower lifetime reproduction of females,as compared to mated with males from heterospecific secondary hosts.For the F1 female progeny,inbreeding prolongs the pre-adult stage as compared with the mating treatments between no-related female and male.In the conspecific secondary hosts originated males group,the pre-adult development time of inbred F1 females was 15.3 ± 0.04 days,while that of the crossed mating was 13.7 ± 0.17 days.F1 females obtained from the four mating combination treatments were provided with unrelated males from heterospecific secondary hosts.The observation of F1 females mating behavior and reproduction showed that: inbreeding F1 females had shorter mating duration time,lower successful mating rate,shorter longevity and oviposition period,and lower reproduction as compared with crossed F1 females.This negative effects was more obvious when the female progeny was produced by mother that mated with conspecific secondary originated males.3.The influence of mating experience and kinship on mating selectionMales prefer to mate females without mating experience,while virgins are more likely to choose males with mating experience for mating,which increases the probability of males multiple mating.Males originated from conspecific and heterospecific secondary hosts were provided with sibling unrelated females for mating selection.Males showed no preference for mating with females with or without kinship.In summary,multiple mating and inbreeding of E.sophia affected its reproductive fitness.The multiple mating of females prolonged the oviposition period,increased the lifetime parasitism,thus had a positive impact on the reproductive fitness of this parasitoid.However,inbreeding of parasitoids has a negative impact on the reproductive fitness,showing a prolonged development time,reduced longevity and oviposition period,and reduced lifetime parasitism of F1 females.This negative effects are more obvious when there was no heterospecific secondary hosts involved.The results indicated that we should avoid inbreeding and utilize heterospecific secondary hosts in mass rearing of E.sophia,and male adults should be supplied to increase multiple mating of females thus enhance parasitism in the rearing and release of E.sophia in biocontrol applications.