Biogeographical variation in plant defence and performance of Carpobrotus edulis against generalist and specialist herbivores

RODRÍGUEZ J; NOVOA A; SOTES GJ; PAUCHARD A; GONZÁLEZ L

Vodice

Congreso; 11th International Conference in Biological Invasions; 2020

Carpobrotus edulis is a perennial succulent plant that was intentionally introduced to many Mediterranean-climate coastal regions for gardening, and sand and dune stabilization. In the introduced ranges, C. edulis could benefit from reallocating the resources previously used to resist the attack of their specialist herbivores, to tolerate the effects of generalist enemies (Shifting Defence Hypothesis, SDH). Currently, both generalist and specialist herbivore species are known to feed on C. edulis in both native and introduced ranges. Nevertheless, it is not known if C. edulis has a different response in plant defence and performance according to the origin.Here, we test the SDH by examining the performance and resistance of C. edulis from different origins (native vs invaded) when it is being attacked by both generalist and specialist species. We collected seeds of C. edulis from native (South Africa) and introduced (Chile and Spain) ranges, and a generalist (Philaenus spumarius) herbivore native to Europe and a specialist (Pulvinariella mesembryanthemi) herbivore native to South Africa as herbivore treatment (collected in areas invaded by C. edulis in NW Spain).In a greenhouse experiment in Spain, we grew 90 individuals of C. edulis(30 individuals per origin) for 3 months, which were subsequently inoculatedwith the respective herbivory treatments for another 3 months.Our results do not fully support the SDH. Regardless of its origin,the attack of the specialist enemy causes severe damage to C. edulis, even death.However, the attack of the generalist enemy does not affect the performance, it does not trigger either any defence mechanisms in the invasive plant. We conclude that the performance of C. edulis is affected by the presence of the specialist herbivore, but not by the attack of the generalist. Thus, we recommend implementing management strategies using the specialist as biological control.