Efeitos do gradiente altitudinal na diversidade taxonômica, filogenética e funcional de assembleias de aves na Chapada Diamantina, Bahia

Abstract

Altitude is a key ecological factor that shapes the patterns of biological diversity. In this study, we analyzed the patterns of taxonomic, phylogenetic, and functional alpha diversity of bird assemblages across an altitudinal gradient in the Chapada Diamantina at eastern Brazil. The sampling was carried out at five levels of altitude with three replicates per level, covering 15 sampling points in total: 400-500 m, 600-700 m, 800-900 m, 1000-1100 m and 1200-1300 m. Bird assemblages were gathered using mist nets and point counts at each altitudinal level. The relationship between altitude and bird diversity (taxonomic, phylogenetic and functional) was obtained using linear regression. We also analyzed the relationship between species diversity and environmental variables (temperature, precipitation, solar radiation, wind speed, water vapor and habitat heterogeneity) were analyzed using Generalized Linear Models (GLMs). A total of 162 bird species were recorded, distributed over 43 families. The 400-500 m level showed the highest richness (104 species), followed by the 600-700 m range (99 species), 800-900 m range (82 species), and 1000-1100 range (76 species). The 1200-1300 level showed the lower species richness (51 species). We found a significant decrease in richness (R² 0.76, p < .001), PD (phylogenetic diversity) (R² 0.607, p < .001), FRic (functional richness) (R² 0.319, p < .001), and FDiv (functional divergence) (R² 0.541, p < .001) indices with altitude; however, the MNTD (mean nearest taxon phylogenetic distance) index (R² 0.566, p < .001) revealed a positive relationship with altitude. Mean annual temperature exhibited a significant effect on diversity indices along the gradient. The higher phylogenetic diversity at higher altitudes and the significant influence of temperature on diversity patterns underscore the importance of climate for bird communities in such environments. This highlights the sensitivity of these communities to climate change and the potential impacts thereof.