Evolutionary and ecological processes drive the global diversity of the avian family Paridae

Understanding how biodiversity is formed and maintained, is a key topic in both ecology and conservation biology. Both ecological and evolutionary processes jointly shape community assembly and maintain biodiversity, often through complex interactions. This study aims to examine how ecological and evolutionary processes jointly shape the global and regional distribution patterns of diversity in the avian family Paridae, focusing on assembly and species pairwise levels. We integrated phylogenetic information, environmental variables (net primary productivity and environmental heterogeneity), and species traits (plumage, song, and morphometrics). We applied structural equation modeling to evaluate how these evolutionary and ecological factors integratively influence the parids diversity. We also used the Bayesian generalized linear mixed model MCMCglmm to assess how these factors affect range overlap between species pairs and, ultimately, patterns of sympatry. The result shows that diversity patterns in Paridae are shaped by both ecological and evolutionary drivers, with mechanisms differing regionally. Patterns of sympatry largely reflect secondary contact, with a pronounced tendency for sympatry among close relatives, and no evidence of character displacement. In Eastern Eurasia, particularly in the diversity center of the Sino-Himalayan mountains, speciation rate is constrained, and richness pattern is strongly influenced by environmental factors and plumage color diversity, possibly due to the relatively saturated ecological niches resulting from a long evolutionary history. In contrast, in the Western region, centered on Europe, where ecological niche space is thought to remain more available, rapid speciation plays a greater role in generating the richness pattern. Here, variation in plumage and morphometric traits further promote species coexistence and diversity. Our findings underscore the need to integrate evolutionary history, contemporary ecological dynamics, and phenotypic traits to understand the mechanisms that shape global diversity patterns of parids. Regional differences in assembly processes, niche saturation in areas with long evolutionary history versus speciation-driven richness in niche-available regions highlight the complex interplay of ecology and evolution in maintaining such the diversity.