Multiple Attack to Inflorescences of an Annual Plant Does Not Interfere with the Attraction of Parasitoids and Pollinators

Abstract

Plants in the flowering stage need to ensure reproduction by protecting themselves from attack and by preserving interactions with mutualist pollinators. When different plant mutualists are using the same type of cues, such as volatile compounds, attraction of parasitoids and pollinators may trade off. To explore this, we compared volatile emission of Brassica nigra plants in response to single or dual attack on their inflorescences. Additionally, we recorded flower visitation by pollinators and the attraction of parasitoids in the greenhouse and/or field. Brassica nigra were exposed in the flowering stage to one or two of the following three attackers: Brevicoryne brassicae aphids, Pieris brassicae caterpillars, and Xanthomonas campestris pv. raphani bacteria. We found that single attack by caterpillars, and dual attack by caterpillars plus aphids, induced the strongest changes in plant volatile emission. The caterpillars’ parasitoid C. glomerata did not exhibit preference for plants exposed to caterpillars only vs. plants exposed to caterpillars plus aphids or plus bacteria. However, the composition of the pollinator community associated with flowers of B. nigra was affected by plant exposure to the attackers, but the total number of pollinators visiting the plants did not change upon attack. We conclude that, when B. nigra were exposed to single or dual attack on their inflorescences, the plants maintained interactions with natural enemies of the insect attackers and with pollinators. We discuss how chemical diversity may contribute to plant resilience upon attack.

Odour-mediated Interactions Between an Apex Reptilian Predator and its Mammalian Prey

“…In fur seals for example, chemical fingerprints help to determine mother-offspring similarity and colony membership (Stoffel et al 2015), and in many other taxa infochemicals shape preferences for particular mates or ensure recognition and avoidance of individuals from species that are otherwise ecologically similar (Caspers et al 2009). Infochemicals also shape the outcomes of competitive, mutualistic, commensal, predatory, and parasitic interactions among species (e.g., Lewis et al 2013;Allen et al 2017;Chrétien et al 2021;Scogings et al 2021), and are being used increasingly in programs of conservation management (Norbury et al 2021).…”

Plant metabolism and defence strategies in the flowering stage: Time‐dependent responses of leaves and flowers under attack

“…In the flowering stage, attackers mainly feed on the reproductive parts of the plant and specialist herbivores are the most frequent and abundant (L. T. S. Chrétien, personal observation). From those specialist attackers, we selected two florivorous insects and one phytopathogenic bacterium based on their distinct modes of action and reported the effect on flowering B. nigra (Chrétien et al, 2018(Chrétien et al, , 2021: (1) the aphid B. brassicae (Hemiptera: Aphididae) as a phloem feeder, (2) the Lepidoptera P. brassicae (Lepidoptera: Pieridae) eggs that develop into chewing caterpillars, (3) the bacterium X. campestris pathovar raphani (Xcr) as a necrotrophic pathogen. Brevicoryne brassicae can sequestrate plant glucosinolates as defences against nonspecialized carnivores (Kos et al, 2012a).…”

Plant defence strategies to multi-herbivore attack

“…Herbivores induce dramatic changes in a plant phenotype and alter the way plants are perceived by other organisms thereby altering community dynamics. Importantly, herbivore-induced changes in plant phenotype strongly affect the foraging of later arriving herbivores, parasitoids and pollinators (Chrétien et al, 2021;Rusman et al, 2018;Soper Gorden & Adler, 2018). In chapter 5, I show that plants treated with herbivores were more attractive to a later arriving herbivore in the fi eld.…”

“…There is even modelling exercises made to assess the plant growth defence trade-off under conditions of herbivory and competition for light (de Vries et al, 2017(de Vries et al, , 2018(de Vries et al, , 2019. Second, the pollinator community of B. nigra plants, as well as the effects of single attack by different herbivores and the effects of dual attack on the pollinator community have also been explored (Chrétien et al, 2021;Rusman et al, 2018Rusman et al, , 2020. Third, there is information on how community complexity shapes selection on traits in B. nigra (Lankau & Strauss, 2008).…”

“…The increase in seed number may in turn attract seed-feeding herbivores (Pérez- Barrales et al, 2013;Steenhuisen & Johnson, 2012). Thus, direct and indirect interactions between herbivores and other community members affect the insect community associated with a plant, including other herbivores , parasitoids (Blubaugh et al, 2018;Bukovinszky et al, 2012), pollinators (Chrétien et al, 2021;Rusman et al, 2018), and can affect plant fi tness (Cozzolino et al, 2015;Soper Gorden & Adler, 2018). However, it is poorly understood how plants maximise fi tness when defending against attack by diverse assemblages of herbivores while maintaining the attraction of parasitoids/predators and pollinators.…”