Contrasting responses of amphibian taxonomic and functional diversity to agriculture and silviculture in subtropical fragmented landscapes

Agricultural intensification is a major driver of biodiversity loss, yet its consequences for the functional structure and resilience of amphibian communities remain incompletely understood. We evaluated how conversion of native forest to agriculture and commercial silviculture reshapes anuran assemblages across 30 breeding sites in southern Brazil (10 sites per habitat type). We quantified taxonomic diversity, complementary facets of functional diversity, community-weighted traits, and environmental conditions. Coverage-standardized taxonomic diversity was consistently higher in silviculture than in agriculture, whereas native forest showed intermediate values and overlapped with both converted habitats. Nevertheless, native forest retained forest-associated species that were rare or absent from production systems, demonstrating that similar local diversity does not imply equivalent conservation value. Functional richness and evenness were broadly maintained across habitats, whereas functional dispersion varied among land uses. Individual community-weighted traits also showed substantial overlap, although ordinations indicated compositional and functional reorganization associated with land cover, shading, and environmental heterogeneity. The abundance of the invasive Lithobates catesbeianus was not associated with taxonomic or functional diversity in site-level regressions. Our findings show that agriculture and silviculture impose contrasting, non-monotonic filters on anuran assemblages. They further demonstrate that effective species diversity alone is insufficient to characterize land-use effects, because species identity, functional organization, and habitat context provide complementary information. Conservation strategies should therefore prioritize native-forest breeding sites while maintaining riparian vegetation, wetland integrity, terrestrial refuges, and landscape connectivity within production mosaics.