Behavior of higher trophic levels associated with an invasive plant varies among populations.

ABSTRACT

Invasive plants from their native and introduced ranges differ in their interactions with herbivores but it is not known whether they also vary in their interactions with herbivore natural enemies. Here, we used olfactometer bioassays and cage experiments to investigate how foraging behaviors of 2 parasitoid and 1 hyperparasitoid species depended on plant population origin. Triadica sebifera (Euphorbiaceae) is native to China but invasive in the United States. In China, it is fed on by a specialist noctuid Gadirtha fusca (Lepidoptera Nolidae), which hosts a parasitoid Apanteles sp. (Hymenoptera Microgastinae) and hyperparasitoid (Hymenoptera Eurytomidae) plus a generalist aphid Toxoptera odinae (Homoptera Aphidiidae) parasitized by Lysiphlebus confusus (Hymenoptera Aphidiinae). Both parasitoids preferred plants infested by their host over herbivore-free plants in olfactometer bioassays. Apanteles sp. and Eurytomid wasps preferred G. fusca infested plants from China populations over those from US populations in olfactometer bioassays but L. confusus wasps did not discriminate between T. odinae infested plants from China vs. US populations. Similarly, G. fusca caterpillars on China population plants were more likely to be parasitized than ones on US population plants when they were in the same cage but odds of parasitism for T. odinae did not differ for those on China vs. US population plants. These results suggest that populations from the native and introduced ranges may differ in traits that impact higher trophic levels. This may have implications for successful control of invasive plants as biocontrol agents are introduced or herbivores begin to feed on them in their introduced ranges.