Human-induced landscape modification affects functional but not taxonomic or phylogenetic bird diversity in a mountain tropical region

Human-induced landscape modification is a major driver of global biodiversity patterns. This study compared the multifaceted bird diversity across three representative land-use scenarios within a variegated tropical mountain landscape. 2. The landscape consisted of a mosaic dominated by humid pine–oak forest, agricultural fields, cattle pastures, and orchards. Based on the proportion of remaining original vegetation cover, we defined three landscape scenarios: conserved, variegated, and fragmented. Within each scenario, we established a 100-ha square divided into 16 plots. Birds were surveyed using point counts. 3. We recorded species identity and abundance, and all diversity dimensions were expressed as Hill numbers 0D (no abundances considered), 1D (all the observed abundances considered), and 2D (only the abundances of dominant species considered). Functional diversity was assessed using a Gower trait similarity matrix; phylogenetic diversity was estimated from a preexistent phylogenetic tree. Sample completeness was evaluated using coverage estimates, and alpha and beta diversity profiles were calculated for all diversity dimensions. 4. Sample coverage was high across all scenarios (0.98–0.99). Taxonomic alpha diversity was greater in the fragmented than in the conserved scenario, whereas functional diversities 1D and 2D were lower in the conserved scenario than in the more modified ones. Phylogenetic alpha diversity did not differ among scenarios. Taxonomic and functional beta diversity were high between the conserved and modified scenarios, while phylogenetic beta diversity remained consistently low. 5. Our results suggest that, in variegated mountain landscapes, reductions in original vegetation cover may have stronger effects on beta diversity than on alpha diversity, likely through the replacement of specialist species and associated functional traits. In such contexts, forest cover loss does not necessarily imply a substantial decline in local bird diversity. In southern Mexico, the low-intensity land management practices of Indigenous communities may contribute to maintaining the multifaceted bird diversity.