Spatial scale influences the associational effects of neighbor plants

12 There is high intra-specific variability in susceptibility of plants to herbivores with potential 13 effects on the population dynamics of species, community composition, structure and function. 14 This variability can be partly explained by vegetation assemblages, i.e. associational effects, but 15 it is still unclear how the spatial scale of plant associations modulates foraging choice of 16 herbivores; an inherently spatial process in itself. Using a meta-analysis, we investigated how 17 spatial scale modifies associational effects of neighboring plants on the susceptibility to 18 browsing by herbivores with movement capacities similar to deer. From 2496 articles found in 19 main literature databases, we selected 46 studies providing a total of 168 differences of means in 20 damage or survival with and without neighboring plants. We tested the impact of spatial scale, 21 estimated as the distance between the focal plant and its neighbors, and the type of association 22 effect on the effect sizes reported in these studies using a meta-analysis mixed model. The 23 strength of associational effects slightly increases from 0 to 1 m and decreases at scales larger 24 than 1 m. Associational defence (i.e. decrease in susceptibility with avoided neighbors) had 25 stronger effects than any other type of associational effects, but was not more frequent. Our 26 study is the first addressing the magnitude of change in associational effects with spatial scale. 27 Further empirical studies should test associational effects between plants at multiple spatial 28 scales simultaneously. The high remaining heterogeneity between the studies suggests that 29 untested factors modulate associational effects, such as nutritional quality of focal and 30 neighboring plants and/or timing of browsing. Associational effects are already considered in 31 multiple restoration contexts worldwide, but a better understanding of these intratrophic 32 relationships could improve and generalize their use in conservation and exploitation. 33 . 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;