Landscape heterogeneity sustains taxonomic and functional bird diversity in Mediterranean agroecosystems: an integrated diagnostic approach

Agricultural intensification is a major driver of biodiversity loss. Taxonomic indicators alone may not capture community responses to landscape simplification. We applied an integrated diagnostic approach combining univariate and multivariate taxonomic and functional analyses to study bird communities in Mediterranean agricultural landscapes. Ornithological censuses were conducted at 20 sites distributed across specialised agroecosystems ( n = 5), agroecological mosaics ( n = 7), and natural ecosystems ( n = 8), recording a total of 80 species. Taxonomic diversity was assessed using species richness (S) and the Shannon diversity index (H′). Functional diversity was assessed using functional richness (FRic), functional evenness (FEve), Rao's quadratic entropy (RaoQ), and trait-based multivariate analyses. Species richness and Shannon diversity index differed significantly across landscape contexts ( p < 0.001), with specialised agroecosystems showing lower diversity than the other two landscapes. Functional richness also varied significantly ( p = 0.0057), while FEve and RaoQ remained relatively stable, indicating that landscape simplification primarily reduced the breadth of ecological strategies, rather than completely restructuring trait distribution and functional redundancy. Community composition differed significantly across landscape contexts (PERMANOVA: p < 0.001). Trait-based analyses identified beak morphology and primary lifestyle as the traits most closely associated with landscape differentiation. Agroecological mosaics were shown to be key drivers of biodiversity within agricultural matrices, with taxonomic diversity comparable to that of natural ecosystems while remaining distinct from them in terms of composition and functional identity. By integrating complementary analytical approaches, this diagnostic approach provides a practical and transferable tool for biodiversity monitoring, conservation planning, and landscape assessment across diverse taxonomic and ecological contexts.