Here, we explore the high-altitude adaptions and acclimatisation ofAporrectodea caliginosa. Population diversity is assessed through mitochondrial barcoding, identifying closely related populations across the island of Pico (Azores). We present the first megabase N50 assembly size (1.2 Mbp) genome forA. caliginosa. High- and low-altitude populations were exposed experimentally to a range of oxygen and temperature conditions, simulating altitudinal conditions, and the transcriptomic responses explored. SNP densities are assessed to identify signatures of selective pressure and their link to differentially expressed genes. The high-altitudeA. caliginosapopulation had lower differential expression and fewer co-expressed genes between conditions, indicating a more condition-refined epigenetic response. Genes identified as under adaptive pressure through F_stand nucleotide diversity in the high-altitude population clustered around the differentially expressed an upstream environmental response control gene, HMGB1. The high-altitude population ofA. caliginosaindicated adaption and acclimatisation to high-altitude conditions and suggested resilience to extreme weather events.This mechanisticunderstanding could help offer a strategy in further identifying other species capable of maintaining soil fertility in extreme environments.