Ficus trees with upregulated or downregulated defence did not impact predation on their neighbours in a tropical rainforest

Mäntylä, E., Jorge, L.R., Koane, B., Sam, K., Segar, S.T., Volf, M., Weinhold, A. and Novotny, V. (2022) Ficus trees with upregulated or downregulated defence did not impact predation on their neighbours in a tropical rainforest. Arthropod-Plant Interactions.

Simon Segar Ficus trees UPLOAD 2.OCR.pdf - Accepted Version

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Trees can emit volatile organic compounds (VOCs) when under attack by herbivores, and these signals can also be detected by natural enemies and neighbouring trees. There is still limited knowledge of intra- and inter-specific communication in diverse habitats. We studied the effects of induced VOC emissions by three Ficus species on predation on the focal Ficus trees in a lowland tropical rainforest in Papua New Guinea. Further we assessed predation across a phylogenetically diverse set of neighbouring tree species. Two of the focal tree species, Ficus pachyrrhachis and F. hispidioides, have strong alkaloid-based constitutive defences while the third one, F. wassa, is lower in constitutive chemical defences. We experimentally manipulated the jasmonic acid signalling pathway by spraying the focal individuals with either methyl jasmonate (MeJA) or diethyldithiocarbamic acid (DIECA). These treatments induce increases or decreases in VOC emissions, respectively. We tested the possible effects of VOC emissions on each focal Ficus tree and two of its neighbours by measuring the predation rate of plasticine caterpillars. We found that predation increased after the MeJA application in only one focal tree species, F. wassa, while the DIECA application had no effect on any of the three focal species. Further, we did not detect an effect of our treatments on predation rates across neighbouring trees. Neither the phylogenetic distance of the neighbouring tree from the focal tree nor the physical distance from the focal tree had any effect on predation rates for any of the three focal Ficus species. These results suggest that even congeneric tree species vary in their response to the MeJA and DIECA treatment and subsequent response to VOC emissions by predators. Our results also suggest that MeJA effects did not spill over to neighbouring trees in highly diverse tropical rainforest vegetation.

Item Type: Article
Keywords: Diethyldithiocarbamic acid, Herbivory, Methyl jasmonate, Plant-to-plant communication Predation, Olfaction, Volatile organic compounds
Divisions: Agriculture and Environment (from 1.08.20)
Depositing User: Mrs Rachael Giles
Date Deposited: 10 May 2022 10:33
Last Modified: 27 Mar 2023 03:30

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