Here we provide R scripts used to select and analyze data to investigate the role of community size in mediate the strength of ecological drift and environmental selection in driving community spatial variation in metacommunities. We selected fish abundance data publicly available and measured community size to model against beta diversity and beta deviation metrics (Shannon and Jaccard-Chao) and against other communities descriptors (evenness, rank difference and richness difference). We also selected environmental variables to measure the strength of community-environment relationships using Hierarchical Modelling of Species Communities and model against community size.

C.M.J. was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil (CAPES) - Finance Code 001 for funding. T.S. was supported by grant #21/00619-7, São Paulo Research Foundation (FAPESP) and by grant #309496/2021-7, Brazilian National Council for Scientific and Technological Development (CNPq).