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Accurate knowledge of the biogeographic history and precise characterization of the genetic make-up of a taxon are essential to investigate speciation processes and achieve sound evolutionary comparisons. A case in point is the house mouse Mus musculus and its three parapatric subspecies, which have become a model for such studies. However, although Mus musculus domesticus and Mus musculus musculus constitute genetically well-characterized homogeneous entities, the case of Mus musculus castaneus remains poorly documented. Using mtDNA control region variation in a sample of 402 individuals, covering much of the distribution range of this subspecies, we identify four haplogroups that show largely non-overlapping geographic distributions. They appear to have undergone post-Neolithic expansions, presumably through commensalism with humans, but exhibit a much more ancient divergence. These results point towards a strong past subdivision and a vicariant origin of the different haplogroups, with each retaining a subfraction of the total variability. The genomic consequences of this spatial heterogeneity on the present taxonomic partition will have to be appraised, and may challenge the use of this subspecies as a single entity in evolutionary studies. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••–••.

Two morphological forms of black rats (Rattus cf. rattus) were found living in sympatry in high-altitude dense forests of the Nilgiri Mountains, South India. The 1st one, often brown- or gray-bellied, also is found commensal in lowland settlements and represents Rattus rattus cf. rufescens (Gray 1837), with a diploid number (2N) of 38 chromosomes. The 2nd form, which has most often a pure white belly, has 2N = 42 chromosomes and is referable to Rattus r. satarae Hinton, 1918, based on morphological comparison with the holotype. A multidisciplinary study indicates that these 2 forms are characterized by clear-cut differences in biochemistry (electrophoresis of homologous isozymes), molecular sequences (mitochondrial and nuclear DNA), and chromosomes (detailed banding analysis). All these data, coupled to diagnostic morphological characteristics, support the hypothesis that Rattus satarae and Rattus rattus are separate, sympatric species, with no gene flow between them. Their similar external mor...

A mitochondrial and nuclear gene analysis allowed us to precise the taxonomical position of the two sympatric species of mice known to be present on Cyprus. One of them is the commensal house mouse M. m. domesticus, and the other revealed to be a new taxon that is a sister species of M. spicilegus and M. macedonicus. The new species is equidistant from each of these, the divergence dating around 0.5-1 Myr. Its origin either results from an ancient accidental colonisation of the island or from a recent transportation by the first epipalaeolithic settlers. In this last eventuality, the new species would also exist somewhere else in Asia Minor.

The plague has been present for a century in Madagascar; the only known reservoir is the black rat, which is also the main victim of this disease. Whereas the two plague foci are restricted to an altitude above 800 m, the black rat is distributed over the whole island, the only morphological variation being a within-site variability in belly colour. To resolve these apparent contradictions, an analysis of the different belly colour morphs and of populations living in different habitats and altitudes was undertaken. An allozymic study demonstrated that sympatric white- and grey-bellied rats (N = 26) living within the plague foci, all belonged to the same species: Rattus rattus. This specific assignment was confirmed by a chromosomal analysis which showed that all 90 individuals studied presented the same diploid number, 2n = 38, whatever the habitat and altitude. This study indicates that all specimens investigated in Madagascar could be referred to the same black rat species. Survival of rat populations, despite a century of coexistence with the plague, is most likely related to their high reproductive and recolonization potential, as well as selection of plague resistant genotypes. As the altitudinal limit of the plague foci does not seem to be related to characteristics of the rodent reservoir, investigations concerning the vectors are now essential. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 78, 335–341.

119–127.Molecular, chromosomal and morphometric analyses of wild-caught mice of subgenus Musfrom the central plain of Thailand are presented. These specimens are distinct from all speciespreviously described in the literature. This has led to the characterization of Mus fragilicaudasp. n., a new member of the set of closely related species encompassed by the subgenus . Whilethis species may be considered as a sibling and sympatric species of the Asian M. cervicolor,M. fragilicauda sp. n. is phylogenetically closer to the M. musculus complex of species and tothe other European species of Mus.Jean-Christophe Auffray & Josette Catalan, Institut des Sciences de l’Evolution, UMR 5554CNRS, CC064, Universite Montpellier 2, 34095 Montpellier cedex, France. E-mail:auffray@isem.univ-montp2.fr.Annie Orth, Eric Desmarais & Francois Bonhomme, Laboratoire Genome, Populations, Interactions,UMR 5000 CNRS, CC063, Universite Montpellier 2, 34095 Montpellier cedex 05, France.Jean-Paul Gonzalez, IRD, Research Center for Emerging Viral Diseases, CVD, Institute of Sciencesand Technology for Development, Mahidol University at Salaya, 25/25 Phutthamonthon 4, Nakhon-pathom 73170, Thailand

Background The phylogeography of the house mouse (Mus musculus L.), an emblematic species for genetic and biomedical studies, is only partly understood, essentially because of a sampling bias towards its most peripheral populations in Europe, Asia and the Americas. Moreover, the present-day phylogeographic hypotheses stem mostly from the study of mitochondrial lineages. In this article, we complement the mtDNA studies with a comprehensive survey of nuclear markers (19 microsatellite loci) typed in 963 individuals from 47 population samples, with an emphasis on the putative Middle-Eastern centre of dispersal of the species. Results Based on correspondence analysis, distance and allele-sharing trees, we find a good coherence between geographical origin and genetic make-up of the populations. We thus confirm the clear distinction of the three best described peripheral subspecies, M. m. musculus, M. m. domesticus and M. m. castaneus. A large diversity was found in the Iranian populations, which have had an unclear taxonomic status to date. In addition to samples with clear affiliation to M. m. musculus and M. m. domesticus, we find two genetic groups in Central and South East Iran, which are as distinct from each other as they are from the south-east Asian M. m. castaneus. These groups were previously also found to harbor distinct mitochondrial haplotypes. Conclusion We propose that the Iranian plateau is home to two more taxonomic units displaying complex primary and secondary relationships with their long recognized neighbours. This central region emerges as the area with the highest known diversity of mouse lineages within a restricted geographical area, designating it as the focal place to study the mechanisms of speciation and diversification of this species. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0306-4) contains supplementary material, which is available to authorized users.

A survey of 77 individuals covering the range of Mus macedonicus from Georgia in the East to Greece and Bulgaria in the West and Israel in the South has shown the existence of two deeply divergent mitochondrial clades. The southern clade was until now undetected and characterises mice from Israel. Nuclear genes also show some amount of regional differentiation tending to separate the southern M. macedonicus from the northern ones. These results point towards the fact that the eastern Mediterranean short-tailed mouse, which was seen as a fairly homogeneous monotypic species, has in fact a more complex phylogeographic history than has been suspected, and that it warrants the existence of two subspecies. The reasons for this non-uniformity probably ought to be looked for in the history of faunal movements linked to glacial periods, underlining the possible existence of at least two refugia south of the Caucasus.

Various subspecies of the house mouse (Mus musculus sensu lato) are known to have contributed to its worldwide expansion. However, the origin of mice on some larger islands such as Madagascar has remained unknown, with several sources being possible. In order to classify the Malagasy house mouse, individuals were trapped in 13 different localities distributed throughout the island. For 33 individuals the control region (D-Loop) of the mitochondrial DNA was partially sequenced and 21 males were typed for a Zfy-2 polymorphism of the Y chromosome. Malagasy mt DNA lineages constitute a narrow monophyletic group which suggests a recent and probably single origin, and are very close to the gentilulus mitochondrial lineages from Yemen. This was supported by the fact that all the males have the domesticus type Y chromosome, like gentilulus. From these results, it can be inferred that the Malagasy house mice originate probably from the Arabian peninsula in a single colonisation wave, unlike its human population. Our results provide a better molecular description of the Yemeni-Malagasy mitochondrial clade which clearly belongs to the Mus musculus radiation.

Using protein loci and DNA markers, we show by a multilocus genetic analysis that certain populations of the two sympatric mouse species Mus musculus domesticus and Mus spretus show clear signs of partial introgression. Given the sterility of F1 males and the known partial genetic incompatibilities between the genomes of the two species, our finding does not invalidate the biological species complex, but allows to think that very limited genetic exchanges remain possible even long after the divergence of taxa. This may have some consequences on the dynamics of certain kinds of invasive or advantageous DNAs like transposable elements or pathogen resistance genes.

The house mouse Mus musculus is a polytypic species, distributed worldwide, with three main subspecies: M. m. musculus in the North-East of Eurasia, M. m. castaneus in South-East Asia, and M. m. domesticus in Europe, the Near-East, and Africa. This last subspecies may also be found in Australia and the Americas, where it was brought by European colonization. Previous studies, however, have shown the presence of specific antiviral determinants of Asian origin in a mouse population at Lake Casitas, California. In this study, an analysis of the variability at 35 enzyme loci demonstrates the hybrid nature of this Californian population intermediate between M. m. castaneus and M. m. musculus. Restriction fragment length polymorphisms of two fragments of the mitochondrial DNA also confirm unambiguously the presence of two types of matrilines in comparable frequencies in our sample. Nevertheless, the study of a subspecies-specific Y chromosome microdeletion in the Zfy2 gene reveals only theM. m. domesticus haplotype at Lake Casitas, a phenomenon comparable with the one observed in other hybrid zones of the M. musculus complex. These findings testify once more that genetic exchanges between subspecies inside the broader M. musculus gene pool are still possible.

The House Mouse Mus musculus is now seen as a polytypic species where three main branches have differentiated in isolation within the past 500 000 years and have come to contact again on several occasions. It is almost invariably considered as being constituted of three subspecies, Mus musculus castaneus being considered as more polymorphic, with a larger effective population size and as having retained more ancestral polymorphisms than the other two. Yet, it is the less, well-studied component, and its geographical origin and genetic makeup disserve more careful attention since a recent reappraisal was indeed shown that the House Mouse populations in the region ranging from Middle-East to Southeast Asia classically assigned to M. m. castaneus are indeed much more diverse than previously thought. Since the House Mouse is often taken as a model species, this may have important bearings on our understanding of the context in which genome evolution and speciation occurs.

RésuméLa présente étude porte sur la taille et la forme des dents et sur la morphologie crânienne d'individus en provenance d'Europe sud-occidentale et d'Afrique du Nord caractérisés génétiquement comme appartenant aux espèces Mus spretus et Mus musculus domesticus . Une révision des caractères diagnostiques des dents et du crâne utilisés pour la détermination de l'appartenance spécifique des spécimens a été faite. La révision porte sur 17 caractères métriques et 14 caractères morphologiques. Une application à un matériel fossile inédit d'âge pléistocène supérieur du Maroc a ensuite été tentée. La détermination de ces restes fossiles représentés par des molaires inférieures de souris du gisement de Doukkala II, près de Rabat, permet de conclure à la présence d'une souris très proche de l'actuelle M. spretus . La présence dans le Pléistocène supérieur d'une souris, différente de la souris domestique, est ainsi démontrée dans le nord de l'Afrique, l'arrivée de la souris domestique dans ce secteur restant à préciser.

This study characterises the extent of the susceptibility to parasites (first demonstrated with helminths) of hybrids between Mus musculus domesticus and Mus musculus musculus . Experimental infections with Trypanosoma musculi of M. m . domesticus, M. m. musculus and their natural hybrids have been performed to compare their level of resistance/susceptibility. It appears that contrary to the results with helminths, hybrid mice present the same level of resistance/susceptibility to the trypanosome as M. m. musculus and M. m. domesticus individuals. This result is interpreted in the light of the modalities of host–parasite interactions and leads us to hypothesise on the role of parasitism in the evolution of the house mouse hybrid zone.

Sixteen laboratory and 7 wild-derived strains of mice were infected with the pinworm Aspiculuris tetraptera in order to compare their resistance levels estimated by the intestinal parasite loads. It appears that (i) in 4 strains out of 23, females and males harbour different parasite loads; (ii) wild and laboratory mice display a broad range of infection levels when compared independently; (iii) the laboratory strains are more resistant than the wild ones. We suggest that (i) compared to sex, the strain (i.e. genetic) effect is the main parameter which determines the levels of infection; (ii) resistance was selected in laboratory strains during their breeding because of the parasite pressure present in captivity.

The traditional approach to fluctuating asymmetry (FA) is compared with an application of the Procrustes superposition method. This comparison was performed on wild-derived and random bred strains of two house mouse subspecies, Mus musculus domesticus and M. m. musculus, originated from Denmark, and their hybrids in a controlled experiment. Results obtained with the Procrustes method show a decrease of FA for the hybrid sample, which is consistent with what was expected from previous FA studies on wild populations. However, no trend was detectable using the traditional approach in that specific case. Additionally, the observed levels of FA compared with those found in wild populations of the hybrid zone in Denmark suggest that the latter are under higher environmental stress than are laboratory-reared animals.

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 35 autosomal protein loci and restriction fragment length polymorphisms of three genes of the Vβ 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.