Contrasting Environmental Factors Explain the Beta Diversity of Atlantic Forest Ferns and Lycophytes Among Different Spatial Scales

Aim Understanding β‐diversity patterns is essential for investigating the processes driving biodiversity and ecosystem dynamics, providing insights into the assembly and structure of ecological communities. Here, we used a large‐scale comparative approach to investigate β‐diversity patterns of ferns and lycophytes from a tropical forest and its ecoregions, across different spatial scales. We aimed to identify whether compositional changes are better explained by turnover or nestedness and evaluate which environmental and geographical variables are better at explaining dissimilarity in species composition. Location Atlantic Forest (Argentina, Brazil and Paraguay). Time Period Present. Major Taxa Studied Ferns and Lycophytes. Methods We created presence‐absence matrices using 327,613 occurrence points for 902 species of ferns and lycophytes. Considering turnover and nestedness, we evaluated the variation in α, β, and γ diversity within the Atlantic Forest and among ecoregions. Using generalised dissimilarity modelling, we also assessed the effect of environmental variations (climate and soil) and geographical distance in the β‐diversity patterns among ecoregions. Results We found different species compositions of ferns and lycophytes along the Atlantic Forest, and among and within ecoregions. Turnover was the main component explaining composition dissimilarities in the Atlantic Forest and within ecoregions, whereas nestedness was the main component explaining changes in composition among ecoregions. We also found that geographical distance, soil acidity and air temperature during the wettest quarter were the most important variables explaining changes in species composition for both ferns and lycophytes. Main Conclusions Our results provide valuable insights into the ecological processes that influence the diversity and composition of ferns and lycophytes in the Atlantic Forest. The ecological processes influencing beta diversity patterns differ between ferns and lycophytes, as well as across geographical and environmental scales. We further discuss the need to understand the environmental processes that shape current biodiversity patterns in the Atlantic Forest.