Increased host investment in extrafloral nectar (EFN) improves the efficiency of a mutualistic defensive service.

Extrafloral nectar (EFN) plays an important role as plant indirect defence through the attraction of defending ants. Like all rewards produced in the context of a mutualism, however, EFN is in danger of being exploited by non-ant consumers that do not defend the plant against herbivores. Here we asked whether plants, by investing more in EFN, can improve their indirect defence, or rather increase the risk of losing this investment to EFN thieves.

Divergent investment strategies of Acacia myrmecophytes and the coexistence of mutualists and exploiters.

Ant-plant interactions represent a diversity of strategies, from exploitative to mutualistic, and how these strategies evolve is poorly understood. Here, we link physiological, ecological, and phylogenetic approaches to study the evolution and coexistence of strategies in the Acacia-Pseudomyrmex system. Host plant species represented 2 different strategies.

Herbivore-induced volatiles as rapid signals in systemic plant responses: how to quickly move the information?

Plants respond to local herbivory or pathogen infection with phenotypic changes, which reduce the danger of future attack. This so-called induced resistance is usually not restricted to the attacked plant organ but is also expressed in distant, so far undamaged parts of the plant. Signaling compounds such as jasmonic acid and salicylic acid have been discovered that move within the plant via the xylem or the phloem and elicit the resistance, thus acting as plant hormones.

Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature.

Plants respond to herbivore attack with the release of volatile organic compounds (VOCs), which can attract predatory arthropods and/or repel herbivores and thus serve as a means of defense against herbivores. Such VOCs might also be perceived by neighboring plants to adjust their defensive phenotype according to the present risk of attack. We exposed lima bean plants at their natural growing site to volatiles of beetle-damaged conspecific shoots.