Expected impacts of climate change on tree ferns distribution and diversity patterns in subtropical Atlantic Forest

Tree ferns are common elements in subtropical Atlantic Forest, sometimes reaching more than half of dominance at forest sites. Climate change could impact the distribution and diversity of tree ferns, hence impacting the ecological processes provided by them. We investigate the impacts of future climate changes in the potential distribution of tree fern species, as well as in the α- and β-diversity. Our first hypothesis (H1) is that warmer climate in the future will increase the distribution of Cyatheaceae species and decrease the distribution of Dicksoniaceae species. Due to a larger number of Cyatheaceae than Dicksoniaceae, the richness will tend to increase. However, the increase in richness might lead to homogenization, consequently decreasing β-diversity (H2). To test these hypotheses, we used distribution models to predict the potential species distribution in the present and future. Then, we calculated the changes in potential distribution areas, α-, and β-diversity components between scenarios. Finally, we assessed the impact of these changes within Protected Areas. We found that Dicksoniaceae distribution tends to shrink in the future, while half of Cyatheaceae tend to lose distribution. Species richness tends to decrease in the future, as well as β-diversity. At least 43% of the sites tend to have their species richness reduced, while only 26% of sites tend to gain species. Our results suggest that species associated with cold environments will lose suitable areas and are more threatened. Richness tends to decrease mainly in sites with high precipitation seasonality. Furthermore, the tree ferns assemblage tends to homogenize.