Biogeographia – The Journal of Integrative Biogeography

Türkiye represents one of the most important biogeographic transition areas in the Mediterranean Basin, linking Mediterranean, Euro-Siberian, and Irano-Turanian biotas. Owing to its complex topography, climatic heterogeneity, and geological history, the country harbors exceptionally diverse reptile assemblages. However, large-scale quantitative analyses of reptile community structure across Türkiye remain limited. In this study, I used cleaned occurrence records obtained from the Global Biodiversity Information Facility (GBIF) to investigate spatial patterns of reptile assemblages across Türkiye using a grid-based macroecological framework. A total of 6609 occurrence records representing 139 reptile taxa (138 named species and one genus-level unit) were analyzed within 50 × 50 km grid cells. Of the 151 species included in the harmonized union of the two most recent national checklists, 131 (86.8%) were represented in the dataset. Species richness analyses, beta diversity decomposition, non-metric multidimensional scaling (NMDS), and hierarchical clustering approaches were used to evaluate assemblage differentiation and identify major reptile bioregions. Reptile species richness exhibited strong spatial heterogeneity across Türkiye, with highest richness values concentrated primarily along Mediterranean coastal regions and parts of southeastern Anatolia. Total beta diversity among assemblages was high (mean βSOR = 0.878), with species turnover accounting for approximately 85.9% of total beta diversity, whereas nestedness contributed only 14.1%. Null-model analyses confirmed that observed turnover values exceeded random expectations (SES = 14.61, p < 0.001), indicating that reptile assemblages across Türkiye are primarily structured by deterministic processes of spatial species replacement rather than stochastic assembly or ordered species loss. Ordination and clustering analyses additionally revealed distinct assemblage regions broadly corresponding to Mediterranean coastal systems, central Anatolian steppes, eastern Anatolian highlands, and Black Sea-associated regions. Overall, the findings demonstrate that reptile assemblages across Türkiye exhibit pronounced compositional turnover and strong spatial structuring associated with major environmental and biogeographic gradients. This study additionally highlights the utility of GBIF-based macroecological approaches for investigating large-scale biodiversity patterns and provides a quantitative framework for future biogeographic and conservation studies in the region.