Spatial scale influence 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 yet, 15 it is still unclear how the spatial scale of plant associations modulates foraging choice of animal; 16 an inherently spatial process in itself. Using a meta-analysis, we investigated how spatial scale 17 modifies associational effects of neighboring plants on the susceptibility to deer-sized herbivores. 18 From 2496 articles found in main literature databases, we selected 46 studies providing a total of 19 168 differences of means in damage or survival with and without neighboring plants. We tested 20 the impact of spatial scale, estimated as the distance between the focal plant and its neighbors, 21 and the type of associational on the effect sizes reported in these studies using a meta-analysis 22 mixed model. The strength of associational effects slightly increases between 0 and 1 m and 23 decrease at scales larger than 1 m. Associational defence (i.e. decrease in susceptibility with 24 repulsive neighbors) had stronger effects than any other type of associational effects, but was not 25 more frequent. Our study is the first addressing the magnitude of change in associational effects 26 with spatial scale. Further empirical studies should test associational effects between plants at 27 multiple spatial scales simultaneously. The high remaining heterogeneity between the studies 28 suggests that untested factors modulate associational effects, such as nutritional quality of focal 29 and neighboring plants or timing of browsing. Associational effects can be exploited as a 30 management tool to alleviate the effect of herbivores (e.g. planting susceptible plants under nurse 31 species) so understanding these intratrophic relationships shaping multitrophic interactions could 32 improve the utility of the tool. 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;