Elm leaves 'warned' by insect egg deposition reduce survival of hatching larvae by a shift in their quantitative leaf metabolite pattern. (14th November 2015)

• Record Type: Journal Article
• Authors: Austel, Nadine; Eilers, Elisabeth J.; Meiners, Torsten; Hilker, Monika
• Is Part Of: Plant, cell and environment. Volume 39:Number 2(2016)
• Page Start: 366
• Page End: 376
• Publication Date: 2015-11-14
• Subjects: plant defence -- flavonoids -- herbivory -- nitrogen -- perennial plant -- phenolics -- quantitative nutritional pattern -- Ulmus minor -- Xanthogaleruca luteola; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.12619
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: Plants may take insect eggs on their leaves as a warning of future herbivory and intensify their defence against feeding larvae. Responsible agents are, however, largely unknown, and little knowledge is available on this phenomenon in perennial plants. We investigated how egg deposition affects the anti‐herbivore defence of elm against the multivoltine elm leaf beetle. Prior egg deposition caused changes in the quality of feeding‐damaged leaves that resulted in increased larval mortality and reduced reproductive capacity of the herbivore by harming especially female larvae. Chemical analyses of primary and secondary leaf metabolites in feeding‐damaged, egg‐free (F) and feeding‐damaged, egg‐deposited (EF)‐leaves revealed only small differences in concentrations when comparing metabolites singly. However, a pattern‐focused analysis showed clearly separable patterns of (F) and (EF)‐leaves because of concentration differences in especially nitrogen and phenolics, of which robinin was consumed in greater amounts by larvae on (EF) than on (F)‐leaves. Our study shows that insect egg deposition mediates a shift in the quantitative nutritional pattern of feeding‐damaged leaves, and thus might limit the herbivore's population growth by reducing the number of especially female herbivores. This may be a strategy that pays off in a long run particularly in perennial plants against multivoltine herbivores. Abstract : While plant anti‐herbivore defences are well known to be inducible by feeding damage, little knowledge is available as to how insect egg deposition preceding larval herbivory affects plant defence. Here we show that the defence of elm trees against elm leaf beetle larvae is improved when leaves received elm leaf beetle eggs prior to larval feeding. The egg deposition mediates a shift in the quantitative nutritional pattern of feeding‐damaged leaves, resulting in increased larval mortality which may be attributed to an increased larval uptake of a phenolic leaf compound harming the larvae. Hence, insect egg deposition functions as 'warning' which prepares the plant for improved anti‐herbivore defence.