Effect of novel competitors
We tested if species’ demographic response to novel competitors depended on their trait values. We built a LMM of the species’ cover or frequency in 2020 as a function of the cover/frequency in 2017, competitor treatment (alpine vs novel), the four trait axes of the PCA including all traits, and the two-way interactions between competitor treatment and the trait axes.
Species identity was a random effect in all LMMs. Model assumptions were validated by examining plots of residuals against fitted values for the homoscedasticity of residuals, and a Quantile‐Quantile plot for the normal distribution of the residuals. Analyses were conducted in the R version 3.6.2 (R Core Team 2018).
Results