Data from: The effect of root-associated microbes on plant growth and chemical defence traits across two contrasted elevations,

1. Ecotypic differences in plant growth and anti-herbivore defence
phenotypes are determined by the complex interactions between the abiotic
and the biotic environment. 2. Root-associated microbes (RAMs) are
pervasive in nature, vary over climatic gradients, and have been shown to
influence the expression of multiple plant functional traits related to
biomass accumulation and biotic interactions. We addressed how variation
in climatic conditions between lowland and sub-alpine habitats in the Alps
and RAMs can independently or interactively affect plant growth and
anti-herbivore defence trait expression. 3. To address the contribution of
climate and RAMs on growth and chemical defences of high- and
low-elevation Plantago major ecotypes, we performed a full-factorial
reciprocal transplant field experiment at two elevations. We coupled it
with plant functional trait measurements and metabolomics analyses. 4. We
found that local growing climatic conditions mostly influenced how the
ecotypes grew, but we also found that the high- and low-elevation ecotypes
improved biomass accumulation if in the presence of their own-elevation
RAMs. Second, we found that while chemical defence expression was affected
by climate, they were also more highly expressed when plants were
inoculated with low elevation RAMs. 5. Synthesis – Our research
demonstrated that RAMs from contrasted elevations impact how plants grow
or synthesize toxic secondary metabolites. At low elevation, where biotic
interactions are stronger, RAMs enhance plant biomass accumulation and the
production of toxic secondary metabolites.