Climatic niche
Niche differences (bio 1 and bio 12) between extinct and recruited species were tested using linear mixed effects models (LMM). As response variables, we used the mean niche value of the species that were either extinct or recruited in each census interval. We also estimated the temporal trends of the extinct and recruited species’ niches by including the interaction between status and year in the models. Because observations were nested within sites and within census intervals, we accounted for the random effects of site and census interval.
y ~ status*year (eqn 3)
Equation 3 describes the global niche model with all variables included in the R notation. Interaction effects are represented by “*”. Note that y is the mean values of bio 1 and bio 12, two dimensions of the climatic niches of extinct and recruited species.