Serological survey of complement factor H in common laboratory and wild mice: a new third allotype

Antigenic specificities of complement factor H from mice were studied serologically. In addition to previously reported allotypes, referred to as H.1 and H.2, a new allotype of complement factor H, H.3, was identified in the BFM/2Ms strain derived from European wild mice. Using three different alloantisera raised against the various mouse factor H allotype, a serological survey of the common laboratory strains and wild-derived strains of Mus musculus and its relatives, Mus spretus, Mus spretoides, and Mus spicilegus was carried out. All of the common laboratory strains examined in this survey had the H.1 allotype except for STR/N which had H.2. The geographical distributions of factor H allotypes in M. musculus were specific to the subspecies. Mice derived from Mus musculus domesticus and Mus musculus castaneus had the H.1 allotype. Mice derived from M. m. musculus, Mus musculus bactrianus, and Mus musculus molossinus had the H.2 allotype. Only BFM/2Ms and BFM/1Mpl strains derived from M. m. domesticus had the novel H.3 allotype. Sera of mice from strains derived from M. spretoides and M. spicilegus cross-reacted with H.2-specific antiserum, and those from M. spretus cross-reacted with H.3-specific antiserum.     

Seroepidemiological Survey of Lymphocytic Choriomeningitis Virus in Wild House Mice in China with Particular Reference to Their Subspecies

Serum samples from 337 wild house mice (Mus musculus) from 35 sites in China, collected in 1992 and 1993, were examined for antibodies against lymphocytic choriomeningitis virus (LCMV). Ten samples from eight sites were found to contain such antibodies. Six of the eight positive sites were located in the territory of M. m. gansuensis. One of the other two sites was located in the territory of M. m. castaneus in southern China and the other site was in a habitat of M. m. castaneus which had invaded into the western end of the territory of M. m. homourus. It seems likely that LCMV is distributed in the territories of M. m. gansuensis and M. m. castaneus in China. This is the first report of detection of these antibodies in wild house mice in China and specifically in the territories of M. m. gansuensis and M. m. castaneus.     

Allelic variants of Ly-5 in inbred and natural populations of mice

Allelic variants of Ly-5 in inbred commensal and other natural populations of mice were analyzed by patterns of restriction fragment length polymorphisms (RFLP) and Southern hybridization using an Ly-5 cDNA probe and by cell-surface staining with a panel of antibodies directed against polymorphic and nonpolymorphic Ly-5 determinants. New Ly-5 alleles were defined by RFLPs generated by both Eco RI and Bam HI restriction enzyme digests. The Mus musculus subspecies and other species within the genus Mus showed a strong correlation between allelic variants defined by restriction enzymes and serologic specificities. The data also suggest the conservation of the Ly-5 gene throughout the genus Mus.     

Oestrous females investigate the unfamiliar male more than the familiar male in both commensal and non-commensal populations of house mice

We studied female preferences for familiar and unfamiliar males. The subjects were laboratory-born house mice: (1) non-commensal Mus musculus domesticus from the eastern part of Syria along the Euphrates River; and (2) commensal M. m. musculus from the Czech Republic. Pair-choice preference tests have revealed that oestrous females of both populations sniffed towards unfamiliar males more than familiar males. In the case of females exhibiting postpartum oestrus, this preference was less pronounced and statistically not significant. Thus, our mice clearly exhibited the behavioural pattern known from commensal populations of polygynous and/or promiscuous M. m. domesticus. We found no inverse tendency to seek proximity to the familiar male that has been previously reported from closely related and presumably monogamous aboriginal mouse Mus spicilegus. We conclude that neither commensal M. m. musculus, nor non-commensal M. m. domesticus, are likely to share a monogamous mating system with mound-building mice.     

Origin of the House Mice (Superspecies Complex Mus musculus sensu lato) from the Transcaucasia Region: A New Look at Dispersal Routes and Evolution

We analyzed our results and literature evidence on variability of nuclear protein genes in 39 populations of eight commensal and wild species of house mice (superspecies complexesMus musculus and M. spicilegus) from Transcaucasia, Eastern and Western Europe, Near and Middle East, Central, South, and East Asia, and Cuba. These data were for the first time ever combined into a single database by unification of nomenclature of 21 loci examined by different authors in 39 populations. Analysis of geographical allele distribution have shown that populations of domestic Transcaucasian mice are close to Indo-Pakistani populations of form oriental of the species M. castaneus, which preserved a high level of ancestral polymorphism. We concluded that a very heterogeneous, rich gene pool of house mice from Transcaucasia could not develop only by secondary contacts of differentiated M. musculus s. str. and M. domesticus forms, since it is similar to the ancestral gene pool of the superspecies complexes M. musculus and M. spicilegus. In this context, unique characteristics of some Central Asian populations were examined; these populations may have served as a transit station in the dispersal of commensal house mice forms. We suggest that the Transcaucasian populations are genealogically closely related to an early Near East form of M. musculus, which, as M. domesticus and M. castaneus, split from the common ancestor and preserved nondifferentiated pool of ancestral alleles of protein genes. This hypothesis admits the involvement of differentiated species M. musculus s. str. and M. domesticus in the ultimate formation of the gene pool of Transcaucasian house mice. Apparently, these populations resulted from alternation and (or) overlapping of different evolutionary processes. A scenario suggesting that hybrid events having occurred in Transcaucasia at different times, were superposed on the gene pool of the ancient autochtonous population of house mice from this region seems most plausible. Analysis of allozyme variability in the modern Transcaucasian Mus populations could not always distinguish between ancestral polymorphism and hybridization consequences.     

The musculus-type Y Chromosome of the laboratory mouse is of Asian origin

Mus musculus domesticus, M.m. bactrianus, M. m. musculus, M.m. castaneus, and M.m. molossinus wild mice were investigated for polymorphisms of the Y Chromosome (Chr) genes Zinc finger-Y (Zfy) and Sex-determining region-Y (Sry). Zfy divided the Y Chrs of these mice into domesticus- (domesticus) and musculus-types (musculus, castaneus, molossinus). M.m. bactrianus specimens had both Y Chrs, possibly owing to the introgression of a musculus-type Y into this population. Sry identified a subpopulation of musculus-type Y chromosomes. This subpopulation, designated the molossinus-type, was found in M.m. molossinus, a M. musculus subspecies specimen from northern China (Changchun), and laboratory mice. The cumulative data suggest that M.m. musculus of northern China and Korea are subpopulation distinct from M.m. musculus of Europe and central China and that this subpopulation invaded Japan, giving rise to M.m. molossinus. Furthermore, the data suggest that the musculus-type Y of the laboratory mouse originated from this subpopulation, corroborating early historical record reporting that Chinese and Japanese mice that were imported into Europe for the pet trade contributed to the genome of the laboratory mouse.     

Clonal and atypical Toxoplasma strain differences in virulence vary with mouse sub-species

The severe virulence of Toxoplasma gondii in classical laboratory inbred mouse strains contradicts the hypothesis that house mice (Mus musculus) are the most important intermediate hosts for its transmission and evolution because death of the mouse before parasite transmission equals death of the parasite. However, the classical laboratory inbred mouse strains (Mus musculus domesticus), commonly used to test Toxoplasma strain differences in virulence, do not capture the genetic diversity within Mus musculus. Thus, it is possible that Toxoplasma strains that are severely virulent in laboratory inbred mice are avirulent in some other mouse sub-species. Here, we present insight into the responses of individual mouse strains, representing strains of the genetically divergent Mus musculus musculus, Mus musculus castaneus and Mus musculus domesticus, to infection with individual clonal and atypical Toxoplasma strains. We observed that, unlike M. m. domesticus, M. m. musculus and M. m. castaneus are resistant to the clonal Toxoplasma strains. For M. m. musculus, we show that this is due to a locus on chromosome 11 that includes the genes that encode the interferon gamma (IFNG)-inducible immunity-related GTPases (Irgs) that can kill the parasite by localising and subsequently vesiculating the parasitophorous vacuole membrane. However, despite the localization of known effector Irgs to the Toxoplasma parasitophorous vacuole membrane, we observed that some atypical Toxoplasma strains are virulent in all the mouse strains tested. The virulence of these atypical strains in M. m. musculus could not be attributed to individual rhoptry protein 5 (ROP5) alleles, a secreted parasite pseudokinase that antagonises the canonical effector Irgs and is indispensable for parasite virulence in laboratory inbred mice (M. m. domesticus). We conclude that murine resistance to Toxoplasma is modulated by complex interactions between host and parasite genotypes and may be independent of known effector Irgs on murine chromosome 11.     

Location of a contact zone between Mus musculus domesticus and M. m. domesticus with M. m. castaneus mtDNA in southern New Zealand

The house mouse, Mus musculus, was first introduced into New Zealand in significant numbers in the early to mid nineteenth century, with genomic components from different sources of the three subspecies M. m. domesticus, M. m. musculus and M. m. castaneus. M. m. domesticus is now widely distributed in New Zealand, with genomic and morphological evidence of M. m. musculus in a few scattered locations. M. m. domesticus/M. m. castaneus hybrids are dominant in the southern third of the South Island. We anticipated that there should be a definable southern contact zone between pure M. m. domesticus and M. m. domesticus/M. m. castaneus hybrids. We tested this hypothesis by screening 170 DNA samples from mice collected in the southern South Island, using a PCR technique which rapidly distinguishes the mitochondrial genomes of the three subspecies.All mice sampled from in or north of Lincoln (43.63° S) had only M. m. domesticus mtDNA, whereas all those from or further south than Hook (44.68° S) had M. m. castaneus mtDNA. Between the two sites, mice carrying mtDNA of both subspecies were found, sometimes in the same building. On present data, this contact zone extends approximately 50 km north to south and some 30 km inland. Classical tests with three nuclear DNA markers confirmed earlier work showing that the nuclear genomes of all mice appeared to be predominantly domesticus-like.We conclude that if purebred M. m. castaneus mice did originally reach New Zealand, extensive backcrossing with M. m. domesticus has made the castaneus nuclear genome virtually undetectable with the tests that we employ.     

Genetic analysis of protein variations in Mus musculus using two-dimensional electrophoresis

We have investigated the variation of proteins from crude homogenates of mouse kidneys in several strains of Mus musculus by means of two-dimensional electrophoresis. In this study, we have used the strains C57BL/6J, DBA/2J, CD-1, M. m. castaneus, and M. m. molossinus, as well as offspring from crosses among these strains. Out of the 100 loci screened, we have found nine loci showing interstrain differences. We have been able to identify three proteins as Id-1, Car-2, and Sep-1. The remaining variants are probably new loci in the mouse. Most of the variants (seven) can be mapped to a chromosome. We have found also that differences in the protein pattern as seen on two-dimensional gels are small among subspecies of Mus musculus.     

Gene flow of unique sequences between Mus musculus domesticus and Mus spretus

Allelic diversity has been examined from a variety of Mus musculus subspecies and Mus spretus strains by sequencing at a 453-bp unique sequence locus. One M. m. domesticus classic inbred strain, C57BL/KsJ, contained a sequence identical to that in the M. spretus wild-derived inbred strain SEG, and other wild M. spretus isolates. Such a result should have been precluded by the expected divergence between the species unless there has been interspecies gene flow. Examination of C57BL/KsJ for M. spretus-specific repetitive sequences shows that it is neither a mis-identified spretus strain nor a domesticus/spretus hybrid. Thus, in addition to the previously reported presence of small amounts of Mus spretus-specific repetitive DNA in M. m. domesticus, there is a detectable flow of unique sequence between the two species. There was also ancestral polymorphism observed among the spretus alleles. The difficulty of distinguishing ancestral polymorphism from horizontal transfer is discussed. Received: 14 May 1999 / Accepted: 5 November 1999     

Detection of recombinant haplotypes in wild mice (Mus musculus) provides new insights into the origin of Japanese mice

Japanese house mice (Mus musculus molossinus) are thought to be a hybrid lineage derived from two prehistoric immigrants, the subspecies M. m. musculus of northern Eurasia and M. m. castaneus of South Asia. Mice of the western European subspecies M. m. domesticus have been detected in Japanese ports and airports only. We examined haplotype structuring of a 200 kb stretch on chromosome 8 for 59 mice from throughout Eurasia, determining short segments (≈ 370–600 bp) of eight nuclear genes (Fanca, Spire2, Tcf25, Mc1r, Tubb3, Def8, Afg3l1 and Dbndd1) which are intermittently arranged in this order. Where possible we identified the subspecies origin for individual gene alleles and then designated haplotypes for concatenated alleles. We recovered 11 haplotypes among 19 Japanese mice examined, identified either as ‘intact’ haplotypes derived from the subspecies musculus (57.9%), domesticus (7.9%), and castaneus (2.6%), or as ‘recombinant’ haplotypes (31.6%). We also detected recombinant haplotypes unique to Sakhalin. The complex nature of the recombinant haplotypes suggests ancient introduction of all three subspecies components into the peripheral part of Eurasia or complicated genomic admixture before the movement from source areas. ‘Intact’domesticus and castaneus haplotypes in other Japanese wild mice imply ongoing stowaway introductions. The method has general utility for assessing the history of genetic admixture and for disclosing ongoing genetic contamination.     

Phylogeography of Chinese house mice (Mus musculus musculus/castaneus): distribution,routes of colonization and geographic regions of hybridization

House mice (Mus musculus) are human commensals and have served as a primary model in biomedical, ecological and evolutionary research. Although there is detailed knowledge of the biogeography of house mice in Europe, little is known of the history of house mice in China, despite the fact that China encompasses an enormous portion of their range. In the present study, 535 house mice caught from 29 localities in China were studied by sequencing the mitochondrial D‐loop and genotyping 10 nuclear microsatellite markers distributed on 10 chromosomes. Phylogenetic analyses revealed two evolutionary lineages corresponding to Mus musculus castaneus and Mus musculus musculus in the south and north, respectively, with the Yangtze River approximately representing the boundary. More detailed analyses combining published sequence data from mice sampled in neighbouring countries revealed the migration routes of the two subspecies into China: M. m. castaneus appeared to have migrated through a southern route (Yunnan and Guangxi), whereas M. m. musculus entered China from Kazakhstan through the north‐west border (Xinjiang). Bayesian analysis of mitochondrial sequences indicated rapid population expansions in both subspecies, approximately 4650–9300 and 7150–14 300 years ago for M. m. castaneus and M. m. musculus, respectively. Interestingly, the migration routes of Chinese house mice coincide with the colonization routes of modern humans into China, and the expansion times of house mice are consistent with the development of agriculture in southern and northern China, respectively. Finally, our study confirmed the existence of a hybrid zone between M. m. castaneus and M. m. musculus in China. Further study of this hybrid zone will provide a useful counterpart to the well‐studied hybrid zone between M. m. musculus and Mus musculus domesticus in central Europe.     

Variation in mandible shape and body size of house mice Mus musculus in five separate New Zealand forest habitats

This study investigates variation in house mouse Mus musculus body size and mandible shape across New Zealand, using geometric morphometrics and biomechanical advantage analyses. The Mus phylogroups currently known in New Zealand include Mus musculus domesticus, M. m. musculus and M. m. castaneus. We examined samples of house mice inhabiting five different podocarp and beech forest environments across the North and South Islands (Pureora Forest, Zealandia Wildlife Sanctuary, Craigieburn Forest Park, Eglinton Valley and Hollyford Valley). Significant variation in mandible shape and body size was found between all five forest populations. South Island mice had larger bodies and greater mechanical advantage in the temporalis muscle compared with their North Island counterparts. Zealandia Sanctuary mouse mandibles were broader and shorter than South Island mouse mandibles, and had greater masseter muscle advantage. Centroid size and body weight, but not head-body length, varied significantly with two distinct genetic haplotypes. Finally, annual rainfall was the most significant covariate with mandible shape. Higher rainfall locations were generally associated with soft-food related mandible shapes, while lower rainfall correlated with hard-food mandible shapes. This preliminary investigation provides the framework for further research into mandible shape and body size variation in New Zealand house mice.     

Origin and radiation of the house mouse: mitochondrial DNA phylogeny

On the basis of patterns of allele frequency variation in nuclear genes (Din et al., in press) it has been proposed that the house mouse M. musculus originated in the northern Indian subcontinent, from where it radiated in several directions to form the well-described peripheral subspecies (M. m. domesticus, M. m. musculus and M. m. castaneus). Here we use a mitochondrial DNA (mtDNA) phylogeny to test this hypothesis and to analyse the historical and demographic events that have accompanied this differentiation. This marker also provides a powerful means to check for genetic continuity between the central and peripheral populations. We studied restriction site polymorphism of samples from India and the Middle East as well as samples from the rest of Eurasia and northern Africa. M. m. domesticus and M. m. musculus are both monophyletic for mtDNA and belong to the subspecies-specific mtDNA lineages that have been described previously. Average nucleotide diversity is low in M. m. musculus (0.2–5%). It is not only higher in M. m. domesticus (0.7–0.9%) but the distribution of pairwise divergence is wider, and the rate of evolution in this branch appears to be higher than in M. m. musculus. The nucleotide diversity found in M. m. castaneus (0.4%) is due to the existence of two rather divergent linages with little intralineage variation. These two lineages are part of a diversified bush of the phylogenetic tree that also comprises several previously undescribed branches and includes all samples from the northern Indian subcontinent and Iran. The degree of diversity found in each of the samples from this region is high (1.2–2.4%) although they come from small geographic areas. This agrees well with the idea that the origin of the radiation was in the northern Indian subcontinent. However, as neither haplotypes on the M. m. domesticus nor on the M. m. musculus branches were found in this region, there appear to be important phylogeographic discontinuities between this central region and these peripherial subspecies. On the basis of the present result and the nuclear data (Din et al., in press), we propose that M. musculus originated in the north of the indian subcontinent. Our calibration of the evolutionary rate of mtDNA in mice suggests that the mouse settlement in this region could be as old as 900 000 years. Possibly from there, a first radiation could have reach the Middle East and the Caspian Sea, where the M. m. domesticus and M. m. musculus lineages, respectively, would have started to differentiate a few hundred thousand years ago, and from where they could have colonised the peripheral part of their ranges only recently.M. m. castaneus appears from its mtDNA to be recent offshoot of the northern Indian population. This multiple and gradual radiation ultimately led to recent peripheral secondary contacts, such as the well-known European hybrid zone.     

Patterns of morphological evolution in the mandible of the house mouse Mus musculus (Rodentia: Muridae)

The worldwide distributed house mouse, Mus musculus, is subdivided into at least three lineages, Mus musculus musculus, Mus musculus domesticus, and Mus musculus castaneus. The subspecies occur parapatrically in a region considered to be the cradle of the species in Southern Asia (‘central region’), as well as in the rest of the world (‘peripheral region’). The morphological evolution of this species in a phylogeographical context is studied using a landmark‐based approach on mandible morphology of different populations of the three lineages. The morphological variation increases from central to peripheral regions at the population and subspecific levels, confirming a centrifugal sub‐speciation within this species. Furthermore, the outgroup comparison with sister species suggests that M. musculus musculus and populations of all subspecies inhabiting the Iranian plateau have retained a more ancestral mandible morphology, suggesting that this region may represent one of the relevant places of the origin of the species. Mus musculus castaneus, both from central and peripheral regions, is morphologically the most variable and divergent subspecies. Finally, the results obtained in the present study suggest that the independent evolution to commensalism in the three lineages is not accompanied by a convergence detectable on jaw morphology. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 635–647.     

Ultrasonic Vocalizations of Male Mice Differ among Species and Females Show Assortative Preferences for Male Calls

Male house mice (Mus musculus) emit ultrasonic vocalizations (USVs) during courtship, which attract females, and we aimed to test whether females use these vocalizations for species or subspecies recognition of potential mates. We recorded courtship USVs of males from different Mus species, Mus musculus subspecies, and populations (F1 offspring of wild-caught Mus musculus musculus, Mus musculus domesticus (and F1 hybrid crosses), and Mus spicilegus), and we conducted playback experiments to measure female preferences for male USVs. Male vocalizations contained at least seven distinct syllable types, whose frequency of occurrence varied among species, subspecies, and populations. Detailed analyses of multiple common syllable types indicated that Mus musculus and Mus spicilegus could be discriminated based on spectral and temporal characteristics of their vocalizations, and populations of Mus musculus were also distinctive regardless of the classification model used. Females were able to discriminate USVs from different species, and showed assortative preferences for conspecific males. We found no evidence that females discriminate USVs of males from a different subspecies or separate populations of the same species, even though our spectral analyses identified acoustic features that differ between species, subspecies, and populations of the same species. Our results provide the first comparison of USVs between Mus species or between Mus musculus subspecies, and the first evidence that male USVs potentially facilitate species recognition.     

Restriction fragment length polymorphism and chromosome mapping of a mouse homeo box gene,Hox-2.1

Restriction endonuclease fragment length polymorphisms (RFLPs) were found using the cDNA probe Hox-2.1 for the homeo box-2.1 gene in the mouse. Polymorphism was detected in restriction patterns generated by fragments fromHindIII digestion. The great majority of laboratory strains of mice carries theHox-2.1 ^a allele. Only two laboratory strains carry theHox-2.1 ^b allele. Among strains of wild origin, the European subspecies (Mus m. domesticus, M. m. brevirostris, andM. m. musculus) and some Asian subspecies (M. m. castaneus) carry theHox-2.1 ^a allele. The subspecies from Far Eastern countries (M. m. molossinus, Chinese mice of wild origin, andM. m. yamashinai) carry theHox-2.1 ^ballele. Using the RFLP, theHox-2.1 gene was mapped on chromosome 11. Three-point cross test data showed that the recombination frequency is 29.6% between theHba and theHox-2.1 genes and 23.5% between theHox-2.1 and theEs-3 genes. The gene order ofHba-Hox-2.1-Es-3 has been confirmed.     

Fine-Scale Phylogenetic Discordance across the House Mouse Genome

Population genetic theory predicts discordance in the true phylogeny of different genomic regions when studying recently diverged species. Despite this expectation, genome-wide discordance in young species groups has rarely been statistically quantified. The house mouse subspecies group provides a model system for examining phylogenetic discordance. House mouse subspecies are recently derived, suggesting that even if there has been a simple tree-like population history, gene trees could disagree with the population history due to incomplete lineage sorting. Subspecies of house mice also hybridize in nature, raising the possibility that recent introgression might lead to additional phylogenetic discordance. Single-locus approaches have revealed support for conflicting topologies, resulting in a subspecies tree often summarized as a polytomy. To analyze phylogenetic histories on a genomic scale, we applied a recently developed method, Bayesian concordance analysis, to dense SNP data from three closely related subspecies of house mice: Mus musculus musculus, M. m. castaneus, and M. m. domesticus. We documented substantial variation in phylogenetic history across the genome. Although each of the three possible topologies was strongly supported by a large number of loci, there was statistical evidence for a primary phylogenetic history in which M. m. musculus and M. m. castaneus are sister subspecies. These results underscore the importance of measuring phylogenetic discordance in other recently diverged groups using methods such as Bayesian concordance analysis, which are designed for this purpose.     

Phylogenetic relationships among laboratory and wild-origin Mus musculus strains on the basis of genomic DNA RFLPs

Genetic distance measures between the laboratory mouse strains C57BL/6J and RF/J and the wild-origin Mus musculus mouse strains CAST/Ei, MOLF/Ei, POSCH I, and CZECH II were estimated by allelic patterns revealed by RFLP analysis. These results suggest phylogenetic relationships indicating that the mouse strains related to the subspecies M.m. domesticus (RF/J, POSCH I and C57BL/6J) are more closely related to the CAST/Ei strain (derived from M.m. castaneus) than to the strains CZECH II (M.m. musculus) and MOLF/Ei (M.m. molossinus). Furthermore, the hybrid strain C57BL/6J is more closely related to POSCH I (M.m. poschiavinus) than to RF/J as calculated by the method distance measures of Cavalli-Sforza and Edwards (Evolution 21,550, 1967), Nei's minimum (Am. Natural. 106,283, 1972) and unbiased minimum (Genetics 89,583, 1978), Edwards (Biometrics 27,873, 1971; Genetic Distance, p. 41, 1974) and Rogers modified (1986).     

A molecular characterization of the charismatic Faroe house mouse

Faroe house mice are a ‘classic’ system of rapid and dramatic morphological divergence highlighted by J. S. Huxley during the development of the Modern Synthesis. In the present study, we characterize these charismatic mice using modern molecular techniques, examining specimens from all Faroe islands occupied by mice. The aims were to classify the mice within the modern house mouse taxonomy (i.e. as either Mus musculus domesticus or Mus musculus musculus) using four molecular markers and a morphological feature, and to examine the genetic diversity and possible routes of colonization using mitochondrial (mt) control region DNA sequences and microsatellite data (15 loci). Mice on the most remote islands were characterized as M. m. domesticus and exhibited exceptionally low genetic diversity, whereas those on better connected islands were more genetically diverse and had both M. m. musculus and M. m. domesticus genetic elements, including one population which was morphologically M. m. musculus‐like. The mtDNA data indicate that the majority of the mice had their origins in south‐western Norway (or possibly southern Denmark/northern Germany), and probably arrived with the Vikings, earlier than suggested by Huxley. The M. m. musculus genetic component appears to derive from recent mouse immigration from Denmark. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 471–482.