Impact of a native hemiparasitic plant on invasive and native hosts in the field.

Abstract

There is increasing evidence that native parasitic plants are showing potential as biocontrols for plant invasions which are a major global threat to biodiversity. However, for this potential to be realised, the range of invasive hosts that can be controlled needs to be identified while also evaluating any potential off-target effects the parasite may pose. To address this, we investigated the impact of the Australian native shoot hemiparasitic plant, Cassytha pubescens on the major invasive species Rubus anglocandicans and two native shrubs, Acacia pycnantha and Bursaria spinosa in naturally occurring populations in southern Australia. We measured foliar predawn and midday quantum yield, electron transport rate (ETR), stomatal conductance (gs), carbon isotope composition and foliar nitrogen concentration [N] of uninfected and infected plants and, apart from gs, also for C. pubescens. Infection significantly decreased predawn and midday quantum yield, ETR and gs of invasive R. anglocandicans. In contrast, infection had no effect on predawn and midday quantum yield, ETR or carbon isotope composition of the native hosts. However, C. pubescens had a significant negative effect on native host gs, and a positive effect on host [N]. Parasite stem [N] was significantly higher when infecting A. pycnantha than B. spinosa. These results strengthen evidence for native parasitic plants having greater impact on invasive hosts while having mild off-target effects on native hosts and thus, show potential to mitigate plant invasions and help protect biodiversity.