Forests and Mediterranean squamates: How does crown canopy impact species richness and phylogenetic diversity?

Abstract Intense human disturbances, including changes in the balance between open and forested habitats, have impacted squamate reptile populations in the western Mediterranean. This region has experienced a notable increase in woodland cover, driven by the gradual abandonment of traditional agriculture, native forest regeneration and intensive reforestation. Microclimatic changes associated with dense canopies in native forests or tree plantations could affect squamate assemblages. In this study, we tested the hypothesis that squamates (amphisbaenians, lizards and snakes) would respond negatively to denser crown canopies and taller vegetation. Our study focused on the Iberian and Italian Peninsulas and included 56 squamate species. The analyses indicated that forests (>50% canopy cover) support a limited number of squamate species (24–26 species). The greatest species richness and phylogenetic diversity were found in low woodland formations (2‒9.9 m stand height and 20‒49% canopy cover) and areas with scattered trees and shrubs (5‒19% canopy cover), supporting 40–46 species. To balance reforestation efforts with squamate conservation, areas with low diversity or lack of threatened species should be prioritised.