Distribution and Biogeographic Patterns of the Dwarf Snake’s Genus Eirenis (Ophidia: Colubridae) in Iran

The dwarf snake’s genus Eirenis Jan, 1863 (Colubridae), comprising about 23 valid species, is distributed across North Africa, Southern Europe, Southwest Asia, Central Asia, and the Middle East. Among non-venomous colubrid snakes, the genus Eirenis is distinguished by morphological characteristics such as 15 or 17 dorsal scales (two subgenera based on the number of dorsum scales), fewer than nine supralabial scales, and fewer than 190 ventral scales. While the evolutionary history of this genus is well-documented, the specific biogeographic patterns and distribution dynamics within the Iranian Plateau remain insufficiently characterized. This study aims to map the spatial distribution of Eirenis species in Iran and analyze their biogeographic patterns. By synthesizing comprehensive bibliographic records with new field observations, we assessed the occurrence of 15 species within the region. Our results show that E. punctatolineatus possesses the most extensive distribution and highest habitat diversity, whereas E. kermanensis, E. rechingeri, E. rafsanjanicus, and E. yassujicus are strictly endemic to specific mountain and steppe ecosystems. Furthermore, E. occidentalis and E. thospitis exhibit highly localized ranges along the western and northwestern borders, respectively. These findings reveal a high degree of regional endemism and suggest that the complex topography of Iran plays a crucial role in shaping the biogeographic structure of the genus. This study provides essential baseline data for understanding the spatial ecology of Eirenis and highlights the need for targeted conservation efforts in Iran’s high-endemism zones.