Intraguild predation alters life histories in Neoseiulus barkeri and Scolothrips takahashii : asymmetric effects on development and reproduction

Abstract Background Intraguild predation (IGP) regulates predator populations through direct predation and risk effects, shaping the life‐history traits of intraguild prey. This study examines the impacts of IGP on life‐history traits of two biocontrol agents, Neoseiulus barkeri and Scolothrips takahashii , reared on their shared prey Tetranychus urticae , using age‐stage, two‐sex life‐table analysis and computer simulations. Results Life‐table analysis revealed that IGP significantly reduced pre‐adult survival of both predators. Neoseiulus barkeri developed faster, but exhibited reduced fecundity under IGP, which resulted in declines in its net reproductive rate ( R 0 , from 30.76 to 10.51 offspring per individual), intrinsic rate of increase ( r , from 0.2555 to 0.1872 day −1 ), and finite rate of increase ( λ , from 1.2911 to 1.2059 day −1 ). Conversely, S. takahashii maintained stable development and fecundity, showing no significant differences in R 0 , r , λ and mean generation time ( T ) between IGP and control groups. The net predation rate ( C 0 ) of N. barkeri decreased from 381.00 to 172.97 prey per individual, and that of S. takahashii from 416.58 to 25.31, under IGP. Computer simulations indicated that IGP led to smaller populations and reduced predation potential for N. barkeri , whereas S. takahashii showed an increase in both. Conclusion IGP differentially alters the population parameters and predation capacity of these two species. Neoseiulus barkeri experiences a decline in population growth, whereas S. takahashii benefits from IGP. These findings highlight species‐specific adaptive strategies in response to IGP, providing insights for designing compatible multipredator application programs in biological control. © 2026 Society of Chemical Industry.