Climate Warming Drives Northward Contraction and Genetic erosion in a Cold‐Adapted Soil Worm Species

Aim Climate‐driven range fluctuations since the Pleistocene have repeatedly reshaped species distributions and population structures, with lasting consequences for genetic diversity. Contemporary warming causes similar pressures, yet most work emphasizes range shifts and gives less attention to genetic outcomes. We aim to assess the past, present and future geographical distribution and patterns of genetic diversity of an important cold‐adapted soil worm under global climate change. Location Global. Major Taxa Studied The cold‐adapted soil worm Henlea perpusilla (Clitellata: Enchytraeidae). Methods We combined species distribution models with population genetic analyses to: (1) reconstruct past, present and future potential distributions; (2) identify the major environmental factors driving its distribution and infer potential refugia; (3) assess potential loss of its genetic diversity under future climate warming. Results We found that temperature is the primary environmental factor determining the distribution of H. perpusilla , occurring widely in temperate and subarctic regions. Current populations exhibit high haplotype diversity and clear geographic clustering, consistent with strong geographic isolation and historical legacies. The past distribution ranges have undergone multiple contractions and expansions since the Last Glacial Maximum (LGM, with suitable areas estimated to be 44%–67% of the current distribution; mountain regions in western and central Europe were identified as the main long‐term refugia. Under future climate scenarios, suitable areas are predicted to contract and shift northward, with 28% loss under low‐emissions (SSP1‐2.6) and 30% under high‐emissions (SSP5‐8.5). Such contractions may result in a substantial loss of genetic diversity, with 14 (18%) and 17 (22%) unique haplotypes at high risk of loss under two scenarios, respectively. Main Conclusions Past climate changes have shaped the current distribution and genetic structure of H. perpusilla , and the future warming threatens the survival of this cold‐adapted species. Our study provides new insights into the biogeography of soil invertebrates under past and ongoing global change.