Long‐Term Dispersal Ability and Climate Drive Genetic and Biogeographic Divergence in Two Lizards With Contrasting Distribution Ranges

ABSTRACT Aims Long‐term dispersal ability fundamentally shapes genetic structure and biogeographic patterns, yet its role in driving divergence between closely related species with contrasting ranges remains less explored. Here, we assess its influence on genetic differentiation and range dynamics in two Eremias lizards, the widespread E. argus and the narrowly distributed E. brenchleyi . Location Northeast, Central North, and Northwest China. Taxon Mongolia racerunner Eremias argus and Ordos racerunner Eremias brenchleyi (Sauria: Lacertidae). Methods We sequenced two mitochondrial (COI and cyt b ) genes from 240 E. argus and 98 E. brenchleyi adults across their Chinese ranges, performed phylogenetic analyses using Maximum Likelihood and Bayesian Inference, assessed genetic diversity and differentiation via haplotype metrics and pairwise F ST , and projected suitable habitats under past, present and future climates using ensemble species distribution models (SDMs). Results The two species diverged approximately 4.28 million years ago. Eremias brenchleyi exhibited strong isolation‐by‐distance, high genetic differentiation, and limited post‐LGM (Last Glacial Maximum) demographic expansion, indicating topography‐constrained dispersal. In contrast, E. argus showed higher genetic connectivity and rapid expansion from the late LGM to the post‐glacial period. SDMs indicate that E. argus expanded following the LGM, while E. brenchleyi persisted in restricted ranges. By 2070, both species are projected to expand northward under SSP2‐4.5 and SSP5‐8.5, with E. brenchleyi benefiting more from warming in net range gain. Main Conclusions Long‐term dispersal ability, interacting with landscape and climate, drives genetic and biogeographic divergence. Eremias brenchleyi remains vulnerable to isolation and genetic erosion, while E. argus is threatened by climate‐driven range loss. Their contrasting responses underscore the necessity of integrating genetic and environmental data to understand species resilience under climate change.