Spatial extent of neighboring plants influences the strength of associational effects on mammal herbivory. Insights from a meta-analysis

11 There is high variability in the level of herbivory between individual plants from the same 12 species with potential effects on population dynamics, community composition, and ecosystem 13 structure and function. This variability can be partly explained by associational effects i.e. the 14 impact of the presence of neighboring plants on the level of herbivory experienced by a focal 15 plant, but it is still unclear how the spatial scale of plant neighborhood modulates foraging choice 16 of herbivores; an inherently spatial process in itself. Using a meta-analysis, we investigated how 17 spatial scale modifies associational effects on the susceptibility to browsing by herbivores with 18 movement capacities similar to deer. From 2496 articles found in literature databases, we 19 selected 46 studies providing a total of 168 differences of means in damage by herbivores or 20 survival to woody plants (mostly) with and without neighboring plants. Spatial scales were 21 reported as distance between plants or as plot size. We estimated the relationships between the 22 effect sizes and spatial scale, type of associational effects and nature of the experiment using 23 meta-analysis mixed models. The strength of associational effects declined with increasing plot 24 size, regardless of the type of associational effects. Associational defences (i.e. decrease in 25 herbivory for focal plants associated with unpalatable neighbors) had stronger magnitude than 26 associational susceptibilities. The high remaining heterogeneity among studies suggests that 27 untested factors modulate associational effects, such as nutritional quality of focal and 28 neighboring plants, density of herbivores, timing of browsing, etc. Associational effects are 29 already considered in multiple restoration contexts worldwide, but a better understanding of 30 these relationships could improve their use in conservation, restoration and forest exploitation 31 when browsing is a concern. This study is the first to investigate spatial patterns of associational 32 effects across species and ecosystems, an issue that is essential to determine differential 33 herbivory damages among plants. 34 . CC-BY-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/019935 doi: bioRxiv preprint first posted online May. 28, 2015;