Abstract

Parasitic plants, those that directly acquire resources from other plants, are distributed across all biomes on earth. They can be restricted to a single host, or they can be generalists, but with preferences. Tristerix corymbosus (Loranthaceae) is a native generalist hemiparasite in Chile but infests many nonnative tree species and appears to suppress them more than its native hosts, indicating its potential to provide substantial ecological resistance. These patterns suggest the novel phenomenon of native hemiparasite host switching from slow-growing native hosts to fast-growing nonnatives, which may provide substantial biotic resistance to invasion, but they also have fascinating ecological, physiological, and evolutionary implications. For example, resistance to invasion contrasts with traditional views of parasitic plants as forest plagues. Instead, Tristerix may function in invaded forests as a keystone species with negative direct effects on invaders and positive indirect interactions with natives. The negative effects of Tristerix on nonnative species provide a more complete understanding of the various roles native parasitic plants can have in resistance to invasion. © 2025 The Author(s). New Phytologist © 2025 New Phytologist Foundation.