Abstract
Biotic stress can induce plastic changes in fitness-relevant plant traits. Recently, it has been shown that such changes can be transmitted to subsequent generations. However, the occurrence and extent of transmission across different types of traits is still unexplored. Here, we assessed the emergence and transmission of herbivory-induced changes in Brassica rapa and their impact on interactions with insects. We analysed changes in morphology and reproductive traits as well as in flower and leaf volatile emission during two generations with leaf herbivory by Mamestra brassicae and Pieris brassicae and two subsequent generations without herbivory. Herbivory induced changes in all trait types, increasing attractiveness of the plants to the parasitoid wasp Cotesia glomerata and decreasing visitation by the pollinator Bombus terrestris, a potential trade-off. While changes in floral and leaf volatiles disappeared in the first generation after herbivory, some changes in morphology and reproductive traits were still measurable two generations after herbivory. However, neither parasitoids nor pollinators further discriminated between groups with different past treatments. Our results suggest that transmission of herbivore-induced changes occurs preferentially in resource-limited traits connected to plant growth and reproduction. The lack of alterations in plant-insect interactions was likely due to the transient nature of volatile changes.
Highlights
Biotic stress can induce plastic changes in fitness-relevant plant traits
Within the four plant generations, four different responses to herbivory were recorded across all twenty-two measured traits (Fig. 1a–d): While seven traits were invariable, herbivory by Pieris brassicae and Mamestra brassicae induced transient changes in six, short-term effects in three and long-term effects in five traits
Responses varied strongly between trait types: While transient effects were mostly present among leaf and flower volatile organic compounds (VOCs), short and long-term effects were exclusively recorded among morphological and reproductive traits and completely absent among VOCs
Summary
Biotic stress can induce plastic changes in fitness-relevant plant traits. Recently, it has been shown that such changes can be transmitted to subsequent generations. The lack of alterations in plant-insect interactions was likely due to the transient nature of volatile changes To maximize their fitness, sessile organisms such as plants need to quickly respond to environmental stresses by readjusting the appropriate phenotypic traits[1,2,3,4]. Communication with insect visitors is one of the most specific plant-environment interactions Processes such as the attraction of pollinators or the deterrence of herbivores are mediated by orchestrated signalling of different trait types, e.g. visual perception of morphological traits and olfactory recognition of leaf and flower volatiles[11,12]. To reduce damage caused by these herbivores, B. rapa relies on the attraction of specialized natural enemies such www.nature.com/scientificreports/
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