Background and Aims Invasive plants can be released from specialist herbivores and encounter novel generalists in their introduced ranges, leading to variation in defence among native and invasive populations. However, fewstudies have examined how constitutive and induced indirect defences change during plant invasion, especially during the juvenile stage. 

Methods Constitutive extrafloral nectar (EFN) production of native and invasive populations of juvenile tallowtree (Triadica sebifera) were compared, and leaf clipping, and damage by a native specialist (Noctuid) and two native generalist caterpillars (Noctuid and Limacodid) were used to examine inducible EFN production. 

Key results Plants fromintroduced populations had more leaves producing constitutiveEFNthan did native populations, but the content of soluble solids ofEFNdid not differ. Herbivores inducedEFNproductionmore than simulated herbivory. The specialist (Noctuid) induced more EFN than either generalist for native populations. The content of soluble solids in EFN was higher (2.1 times), with the specialist vs. the generalists causing the stronger response for native populations, but the specialist response was always comparable with the generalist responses for invasive populations. 

Conclusions These results suggest that constitutive and induced indirect defences are retained in juvenile plants of invasive populations even during plant establishment, perhaps due to generalist herbivory in the introduced range. However, responses specific to a specialist herbivore may be reduced in the introduced range where specialists are absent. This decreased defence may benefit specialist insects that are introduced for classical biological control of invasive plants.