Fig. 1

Geographic distribution of the five mtDNA phylogroups of the house mouse Mus musculus [3, 5], with their tentatively predicted homelands (a). Five distinct lineages are represented by the following taxon names: M. m. musculus (MUS), M. m. domesticus (DOM), M. m. castaneus (CAS), M. m. gentilulus (GEN), and the Nepalese lineage (NEP). Further subdivision of the MUS lineages into two others (MUS-1, MUS-2), and the MUS-1 sublineage, in turn, into three others (MUS-1a, MUS-1b, MUS-1c) was proposed in a previous study [5]. The sub-group types of MUS-1 and CAS (CAS 1–4) are shown in circles with letters or numerals, respectively [5]. A maximum likelihood tree based on mitochondrial cytochrome b gene sequences (13; Sakuma et al., unpublished data) (b). A median joining network is shown for haplotypes belonging to the mitochondrial subgroup CAS-1, which is thought to have experienced rapid expansion, perhaps associated with human activities related to agricultural development [5]. The scale bar shown below the tree represents genetic distance (c). The next range extension of the CAS-1 lineage is related to the CAS-1a group expansion, perhaps correlating with the spread of rice cultivation from South China to the Japanese Islands and the southern part of Sakhalin Island