Drought and plant neighbourhood interactively determine herbivore consumption and performance

11 páginas, 4 figuras y 1 tablaBoth plant neighbourhood composition and drought have well-known independent effects on insect herbivore performance, but their interactive effects remain elusive. In this study we performed a laboratory experiment to investigate the independent and combined effects of plant neighbourhood composition and drought on the performance of Gypsy moth larvae (Lymantria dispar) feeding on silver birch (Betula pendula) leaves. For this, we collected leaf samples from birch trees growing in a field experiment where we manipulated both host-tree species diversity (three levels: birch monocultures, two-species mixtures associating birch with the pedunculate oak Quercus robur or maritime pine Pinus pinaster, and three-species mixture with pedunculate oak, the maritime pine and birch) and water availability (two levels: irrigated vs. non-irrigated). In most cases, plant neighbourhood composition and irrigation treatments independently and interactively affected herbivore performance traits, especially those related to growth and food (i.e. birch leaves) processing. By addressing the interactive effects of tree species diversity and drought on insect herbivory from the herbivore’s point of view, our study builds toward a better understanding of the multiple ecological drivers of plant-insect interactions.Te research in ORPHEE was funded by the GIP-ECOFOR program from the French Ministry of Ecology, under the project BIOPICC ECOFOR-2014-15. We thank Angelina Ceballos Escalera, Inge van Halder, Martine MartinClotté and Fabrice Vétillard for their help in the feld and laboratory tasks, and Maurane Buradino from INRA UE0348 for providing Gypsy moth egg masses. Te ORPHEE experiment is managed by INRA Experimental Unit Forêt-Pierroton, and in particular by Bernard Issenhuth. XM was supported by a grant from the Regional Government of Galicia (IN607D 2016/001), a Spanish National Research Grant (AGL2015-70748-R) and the Ramón y Cajal Research Programme (RYC-2013-13230). Collaboration between BC and XM was supported by a grant from the iLINK+ CSIC Program (I-LINK 1221).Peer reviewe