Animal adaptation to environmental challenges is a complex process involving intricate interactions between the host genotype and gut microbiome composition. The gut microbiome, highly responsive to external environmental factors, plays a crucial role in host adaptability and may facilitate local adaptation within species. Concurrently, the genetic background of host populations influences gut microbiome composition, highlighting the bidirectional relationship between host and microbiome. Despite this, our understanding of gut microbiome plasticity and its role in host adaptability remains limited, particularly in reptiles. To clarify this issue, we conducted a reciprocal translocation experiment with gravid females of the Qinghai toad-headed lizards (