Herbivory and pollination impact on the evolution of herbivore-induced plasticity in defense and floral traits

Abstract

Theory predicts that herbivory should primarily determine the evolution of herbivore-induced plasticity in plant defenses, but little is known about the influence of other interactions such as pollination. Pollinators may exert negative selection on the herbivoreinduced plasticity of chemical defenses when floral signals and rewards are indirectly affected, provoking deterrent effects on these mutualists. We investigated the influence of constant herbivory and pollination on the evolved patterns and degree of herbivoreinduced plasticity in chemical plant defenses and floral morphometry and volatiles in fast-cycling Brassica rapa plants. To do this, we used plants from an evolution experiment that had evolved under bee/hand pollination and herbivory manipulated in a 2 × 2 factorial design during six generations, producing four selection treatments. We grew sibling plant pairs from each of the four selection treatments of the last generation and infested one group with herbivores and left the other uninfested. Herbivore-induced plasticity was analyzed within-and between-selection treatments. We found support for the hypothesis that constant herbivory favors the evolution of higher constitutive yet lower herbivore-induced plasticity in defenses. However, this only occurred in plants that evolved under hand pollination and constant herbivory. Bee pollination had a strong influence on the evolution of herbivoreinduced plasticity of all traits studied. Plants that evolved under bee pollination, with and without constant herbivory, showed remarkably similar patterns of herbivore-induced plasticity in their defense-and floral traits and had a higher number of plastic responses compared to plants with hand pollination. Such patterns support the hypothesis that bee pollination influenced the evolution of herbivore-induced plasticity, most likely via indirect effects, such as links between defense-and floral traits. We conclude that interactions other than herbivory, such as pollination, may impact herbivore-induced plasticity, through indirect effects and metabolic trade-offs, when it contributes to trait evolution in plants.

Humans Share More Preferences for Floral Phenotypes With Pollinators Than With Pests

“…Furthermore, using the same system it has been shown that floral attractiveness i.e., they were more fragrant and displayed larger flowers when evolving in the presence of bumblebees as pollinators. In contrast, when plants grow in the presence of bumblebees and the hervibore Pieris brassicae ( Ramos and Schiestl, 2019 , 2020 ), volatile evolution, production of glucosinolates and autogamy evolve differently. The current emerging hypothesis is a possible coevolution of floral and defense traits.…”

Phenotypic plasticity guidesMoricandia arvensisdivergence and convergence across the Brassicaceae floral morphospace

“…Under this idea, floral traits change due to external factors such as environmental stimuli, biotic stressors, etc. (Rusman et al, 2019a,b;G omez et al, 2020;Ramos & Schiestl, 2020). When this process takes place within dense morphospaces, plastic phenotypes may converge with nonrelated flowers rather than arising as novelties.…”

On the capacity for rapid adaptation and plastic responses to herbivory and intraspecific competition in insular populations of Plectritis congesta

“…congesta displays marked local adaptation to browsing and context‐dependent trade‐offs in the fitness value of traits shown to drive population growth and persistence in the presence or absence of deer (Skaien & Arcese, 2020), a pattern thought to occur in other plant‐herbivore systems (e.g. López‐Goldar & Agrawal, 2021; McGoey & Stinchcombe, 2009; Ramos & Schiestl, 2020; Wenk & Falster, 2015).…”