The Influence Of Non-consumptive Effects Of Harmonia Axyridis On Fitness Of Acythosiphon Pisum

Predation relationship is a common interaction in ecosystem and it play an important role in regulating community structure and stability.Predators not only directly affect the prey population and distribution through consumptive effects(CEs),but also indirectly influence the behavior,development or physiological state of prey through non-consumptive effects(NCEs).The effect which reduce prey fitness,but not directly result in the death of prey is defined NCEs.The NCEs of coccinellid have the potential to further differentiate their relative impacts on aphid populations.Moreover,aphid alarm pheromone((E)-β-farnesene,EBF)is an important factor when ladybirds produce non-consumptive effects on aphids.In this study,a system that consisted of Harmonia axyridis(Pallas)and Acyrthosiphon pisum(Harris)was used to study the effect of NCEs on the performance of A.pisum.The main research contents include two aspects:(1)The effect of NCEs of ladybird with low,medium and high densities on the nymph development duration,weight grown and the number of offspring of three generations of aphid.(2)The effect of five concentrations of EBF on the fitness of two generations of aphid were investigated through the establishment of the aphid life table.The main findings are as follows:(1)The NCEs of different densities of ladybird could affect the fitness of A.pisum,and its influence is related to the generation of A.pisum.The low-density ladybird had no significant effect on the fitness of the multiple generation of A.pisum.The mid-density ladybird could prolong the nymph development duration of the second generation and the third generation of A.pisum,and reduce the weight grown of the second generation of A.pisum.Finally,the high-density ladybird could increase the number of offspring of the second generation of A.pisum.(2)The EBF of different concentrations could affect the fitness of A.pisum,and its influence is related to the generation of A.pisum.The development time of the third instar nymph,lifetime,and generation time of the first-generation of A.pisum significantly shortened in 1000 ng/μL EBF treatment.The intrinsic rate of increase and finite rate of increase of the first generation of A.pisum were significantly reduced in the 1000 ng/μL EBF treatment.The development time of the first instar nymph of the second-generation of A.pisum was significantly increased after 50 ng/μL,250 ng/μL and 500 ng/μL EBF treatment,and lifetime was significantly reduced after 10 ng/μL EBF treatment.The net reproductive rate and fecundity of the second generation of A.pisum was significantly reduced after 10 ng/μL,250 ng/μL and 500 ng/μL EBF treatment.In conclusion,the NCEs of different density predators and different EBF concentrations have an impact on the fitness of A.pisum.The NCEs of ladybirds of different densities and low concentration of EBF have no effect on the fitness of the first generation of A.pisum.The NCEs of the mid-density ladybirds can prolong the nymph development duration of the second and third generation of A.pisum,and reduce the weight grown of the second generation of A.pisum.NCEs of high-density ladybirds can increase the number of offspring of the second generation of A.pisum.The concentrations of EBF was not linearly related with the development of A.pisum,and high concentration of EBF can significantly reduce the fitness of A.pisum.