Environmental and climatic variables
The same plant species analysed were previously described in term of their climatic niche, as well as in term of their growth-related functional traits (Defossez et al. 2018). We therefore used species’ average of several functional traits related to natural herbivore damage 1) % damage, and to growth; 2) specific leaf area (SLA), 3) plant biomass, 4) plant height, 5) chlorophyll content, and 6) leaf toughness, to assess a potential correlation between plant growth forms and GSL diversity. In short, herbivore damage was measured as percent increments on 10 randomly-sampled plants per species in their natural environment. SLA (mm2 mg-1DW), was measured as the area of a 1 cm leaf disc divided by its dry mass; chlorophyll content was measured as SPAD values using a SPAD 502 Plus Chlorophyll Meter (Konica, Minolta, Tokyo Japan); leaf toughness (g mm2) was measured with a custom made hole puncher; weight (g) was measured as the total dry aboveground plant biomass, and height (cm) was measured from the soil till the highest leaf (n = 10 plants per species and per trait; Table S1 in Supplementary material).