Difference in frequency of traits across beach levels
We evaluated the differences in frequency of five traits related and one trait unrelated to hydrodynamics across beach levels. For each trait, we fitted a generalized linear mixed effect model (GLMM) using the proportion of species that present each trait at each sample as a response variable, the beach level as predictor, and the identity of each beach as a random effect. We selected a binomial(logit) family model to account for proportion data, using the function ‘cbind’. The GLMM were run with the function ‘glmer’ in the R package ‘stats’ of the R core team. We tested significance of models for pairwise differences across habitats by comparing marginal means between the three beach levels using a Tukey HSD test as implemented in the functions ‘glht’ in the R package ‘multcomp’ v. 1.8.1-1 (Hothorn et al., 2008). The results were then represented using box plots drawn using the R package ggplot2, and Type II ANOVA tables from the R package car to produce output tables from GLMM with both categorical and continuous predictors.
A reproducibility checklist for the study (Palacio et al., 2022) including detailed information on sample size, number of traits, and statistical procedures is available in Supplementary material (Supplementary Table S4).