Origin and radiation of the house mouse: clues from nuclear genes

Abstract

Although quite a lot is known about the genetic structure of the polytypic species Mus musculus at the periphery of its range, the centre of origin and dispersion of the species remains unknown. To investigate the amount of genetic subdivision that occurs in the central parts of its range, we analysed the genetic variation in four new samples of mice coming from Iran, Pakistan, northern and southern India using 3.5 autosomal protein loci and restriction fragment length polymorphisms of three genes of the Vg gene complex of the immune system. The variation was then compared with that found in the subspecies occupying the peripheral regions of the species range. The two samples from the northern part of the Indian subcontinent were shown to be more heterozygous than the samples from any of the other regions. They also contain the majority of the alleles that exist in the differentiated subspecies at the periphery of the species range. A neighbour-joining analysis on Nei's genetic distances and a factorial analysis of correspondences on the allelic composition of each sample both place the Pakistani and Indian populations in a phylogenetically and genetically central position compared to the peripheral subspecies. These results suggest that the populations in this geographically central area have retained most of the ancestral polymorphisms, which in turn indicates that the Indian subcontinent is probably the cradle of the species. The nature of the genetic relationships between the various populations throughout the species range and the possibility that they form an incipient ring species are also discussed. Our results are in agreement with the classical model of geographic differentiation where genetic divergence in allopatry is considered to be the prime cause of subspecies formation that may eventually lead to partial reproductive isolation on secondary contact.

On the subspecific origin of the laboratory mouse

“…Evolutionary models suggest that the three major mouse subspecies diverged simultaneously from a common ancestor or, alternatively, that M. m. musculus and M. m. castaneus diverged from a common ancestor shortly after the divergence of M. m. domesticus [26][27][28] . This history should be reflected in the distribution of SNPs that are specific to each of the subspecies.…”

Phylogeographic origin of Hokkaido house mice (Mus musculus) as indicated by genetic markers with maternal, paternal and biparental inheritance

“…Under this scenario, the derived MUS and BAC types developed in situ, each in different areas of the Indian subcontinent. However, MUS types later dispersed out from this region, again moving both west and east, where they eventually established secondary contact with the DOM and CAS populations, respectively Din et al, 1996). An alternative view, derived from analyses of mitochondrial and some nuclear gene sequences, postulates a Middle Eastern origin of M. musculus, with subsequent dispersal of DOM, MUS, CAS and GEN types to Western Europe, northern Eurasia, India and the Arabian Peninsula, respectively (note that sequence data generally fail to identify a separate BAC cluster).…”

“…Based on allozyme data sets, several research teams have proposed that M. musculus emerged in central Asia or India, and dispersed in both west and east, giving rise to DOM and CAS in Europe and East Asia, respectively Din et al, 1996). Under this scenario, the derived MUS and BAC types developed in situ, each in different areas of the Indian subcontinent.…”

Evidence for a mitochondrial lineage originating from the Arabian peninsula in the Madagascar house mouse (Mus musculus)

“…It can also be encountered in the countryside (rice fields, savannas, borders of marshes) but at very low densities. The house mouse (Mus musculus species complex) originated from the Indian subcontinent Din et al, 1996). It is assumed that it radiated approximately 0.5 million years ago in three directions, thus giving rise to the current subspecies (which some authors consider as proper species, see Sage et al, 1993) Prager et al (1998) suggested that a gentilulus lineage may exist on the Arabian peninsula (which would represent a subspecies according to the nomenclature adopted in the present article, but a species according to the original article), based on a divergent mitochondrial lineage recently described in Yemen.…”