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