Asian Mus musculus: subspecies divergence, genetic diversity, and historical biogeography

Abstract

The House Mouse, Mus musculus, is a model organism that has greatly contributed to evolutionary research. Despite its significance, there remain gaps in our understanding of its phylogeography and population genetic structure in Asian regions. This comprehensive study aims to elucidate the evolutionary history, genetic diversity, and distribution patterns of M. musculus. A diverse data set of 281 M. musculus samples was collected from across Asia, covering 101 localities in 19 countries. Phylogenetic analysis using Cytochrome b and D-Loop region unveiled well-supported lineages. These lineages correspond to: M. m. musculus, M. m. domesticus, M. m. castaneus, and M. m. bactrianus. Also, validity of M. m. bactrianus was questioned. The analysis suggests a monophyletic origin of these subspecies approximately 0.59 million years ago (Mya), followed by 2 main lineages—one consisting of M. m. domesticus (~0.59 Mya) and the other comprising M. m. castaneus, M. m. bactrianus, and M. m. musculus (~0.56 Mya). Genetic diversity varied among subspecies, with M. m. domesticus exhibiting the highest diversity due to its extensive global distribution and M. m. bactrianus exhibiting the lowest diversity due to restriction in southwest Asia. Pairwise genetic distances and Fst values confirmed significant genetic differentiation among the subspecies, underlining their historical isolation. Additionally, a Mantel test indicated that geographical distance played a pivotal role in shaping genetic differentiation. Demographic analysis revealed evidence of population expansions in M. m. domesticus, M. m. musculus, and M. m. castaneus, while M. m. bactrianus showed characteristics of neutral selection and genetic drift. Species distribution modeling, assessing both Current Conditions and the Last Glacial Maximum, indicated habitat shifts and losses during glacial periods, particularly in the eastern and northern regions of Asia. However, each subspecies displayed unique responses to climatic changes, reflecting their distinct ecological adaptations. Historical biogeography analysis pointed to complex origins and a network of dispersal and vicariance events that led to the contemporary distribution of subspecies. Deserts and xeric shrublands emerged as critical areas for diversification and speciation. This study contributes to our understanding of the phylogeography and population genetics of M. musculus in Asia, highlighting the significance of geographical factors and climatic fluctuations in shaping its evolutionary history and genetic diversity.