Occurrence data and range maps in endemicity analysis: Data choice matters

The reliability of biogeographic analyses depends strongly on the type and quality of species distribution data. We compared point-based occurrence records and polygonal range maps for 160 species of the lizard genus Liolaemus, assessing their influence on the identification of areas of endemism across three spatial scales using endemicity analysis. Our results show that range maps consistently overestimate distributions, often identifying broad endemic areas with low species overlap-patterns likely inflated by commission errors. In contrast, occurrence data yield fewer but more localized and compositionally distinct areas of endemism, especially at finer spatial scales, capturing spatial discontinuities and narrow-range endemism more effectively. Occurrence data also proved to be more sensitive to spatial scale, revealing fine-grained biogeographic patterns often missed by range maps, particularly in mountainous or environmentally heterogeneous regions. Despite potential biases from uneven sampling, occurrence data provide a more ecologically meaningful representation of endemism, especially for habitat specialists or narrowly distributed species. These findings highlight that data choice significantly affects the detection of endemism, with direct implications for biodiversity assessments and conservation planning. Researchers should carefully consider data sources in light of their study taxa's ecological and geographic traits to ensure robust and scale-appropriate analyses.