Mus Spretus Research Articles

Importance of internal refuges and the external unburnt area in the recovery of rodent populations after wildfire

Rodent populations respond quickly to changes in habitat structure and composition resulting from disturbances such as wildfires. Rodents may recolonise burnt areas from individuals that survived the wildfire in ‘internal refuges’ or from the surrounding unburnt area (i.e. external colonisation). With the aim of assessing the relative role of both hypotheses on rodent abundance and foraging behaviour after fire, four Mediterranean burnt areas were studied using sampling stations at increasing distances from the perimeter of the burnt area. In the first 18 months after fire, the abundance of wood mice (Apodemus sylvaticus) and seed removal activity were highest near the perimeter. This suggests the weight of external sources (i.e. from unburnt areas) in the recolonisation process is higher than that of internal refuges. Algerian mice (Mus spretus) colonised the burnt areas from external sources. Vegetation cover was the most important variable affecting the relative abundance of rodents in recently burnt areas. After some months of vegetation recovery, rodent individuals that had dispersed from the unburnt area were likely to take advantage of sparsely occupied habitat with sufficient resources and, at this time, might use internal refuges. Therefore, understanding recolonisation dynamics is fundamental to anticipate biodiversity patterns and promote adaptive management.

SEMICE: An unbiased and powerful monitoring protocol for small mammals in the Mediterranean Region

Schemes to monitor biodiversity change should detect properly target species without harmful effects on individuals and populations, and be powerful enough to detect expected population trends in the face of global change. Targeting is a key aspect of monitoring schemes since there is no single method able to detect unbiasedly all species of any given community, especially the rarest ones. Here we test whether SEMICE (SEguimiento de MIcromamíferos Comunes de España), a monitoring protocol for small mammal biodiversity in the Mediterranean Region, fulfil these requirements. The protocol aims at monitoring common species easy to catch with the two most widely used commercial live traps (18 Sherman and 18 Longworth traps alternated in position across 6×6 trapping grids spaced 15m, brought into operation for three consecutive nights in spring and fall). We used pilot data from twenty-two plots distributed along wide environmental gradients in Catalonia (NE Spain), sampled from 2008 to 2015. The wood mouse (Apodemus sylvaticus) was dominant throughout the study period (992 individuals, 39.0%), followed by the white-toothed shrew (Crocidura russula, 598 individuals, 23.5%) and the Algerian mouse (Mus spretus, 269 individuals, 10.6%). The two most common rodent species experienced strong population declines during the eight-year period (91% for A. sylvaticus and 83% for M. spretus). Regional community data obtained from diet studies of small mammal predators showed that common keystone prey and seed dispersers were sampled properly. No differences among trap types regarding community parameters and similarity indexes, sampling efficiency, detectability, trap-induced mortality, mean size and sex-ratio were detected, confirming previous results for a smaller pilot study. The method was sensitive enough for detecting expected population changes. We recommended extending the SEMICE protocol to sample common keystone small mammals along wide Mediterranean environmental gradients, since the method was sensitive enough to detect, and even test, expected population trends associated to global change for all them.

Molecular detection of Leishmania infantum and Leishmania tropica in rodent species from endemic cutaneous leishmaniasis areas in Morocco

BackgroundLeishmaniasis remains a major public health problem in African nations, including Morocco, where little is known about the vertebrate reservoirs involved in the causal parasites’ transmission cycles. The present study investigates the role of rodent species as potential reservoirs of Leishmania spp. in central Morocco, where both L. tropica and L. infantum have been reported.MethodsRodents were caught from 22 sites in central Morocco, by using Sherman metal traps, and identified morphologically. For each specimen, genomic DNA was extracted from different tissues using the Speed Tools DNA extraction Kit. Then, samples were PCR-analyzed, targeting the SSU rRNA gene to detect Leishmania spp. DNA, followed by amplification of the internal transcribed spacer 1 (ITS1) and its sequencing to identify the species.ResultsA total of 197 rodents belonging to ten species were captured and identified: Rattus rattus (40.61%), Mus musculus (25.38%), Apodemus sylvaticus (8.63%), Mus spretus (7.11%), Meriones shawi (5.58%), Rattus norvegicus (4.57%), Meriones libycus (3.05%), Mastomys erythroleucus (2.03%), Gerbillus campestris (2.03%) and Lemniscomys barbarus (1.01%). Molecular analysis revealed the presence of Leishmania species in 18 specimens: six R. rattus (out of 80 captured; 7.5%), 11 M. musculus (out of 50 captured; 22%), and one R. norvegicus (out of 9 captured; 11.11%).ConclusionsTo the best of our knowledge, L. infantum and L. tropica were identified in rodent species for the first time in Morocco. These findings suggest that rodent species may be involved in L. infantum and L. tropica transmission cycles in this country but that further studies are needed to confirm their role as reservoirs of Leishmania species in Morocco.

Species-specific movement traits and specialization determine the spatial responses of small mammals towards roads

The barrier effect is a pervasive impact of road networks. For many small mammals individual avoidance responses can be the mechanism behind the barrier effect. However, little attention has been paid to which species and road characteristics modulate road avoidance and mortality risk. We measured the strength of the barrier effect imposed by the road on three rodent species with different body sizes and habitat specializations: Southern water vole (Arvicola sapidus), Mediterranean pine vole (Microtus duodecimcostatus) and Algerian mouse (Mus spretus). We analysed the effect of traffic intensity on use of space and direction of movement and the effect of road type (4-lane highway, 2-lane paved road and 1-lane unpaved road) on crossing rates with simulations of roads bisecting each home range. Finally, we estimated annual mortality risk from collision based on individual speed, crossing rates, body length, traffic volume and road width. Individual mobility and ecological preferences were assumed as two hypotheses to explain species’ responses towards roads. The effects were species-specific, with traffic intensity having a negative influence on the use of space and movement directionality only for water voles and with avoidance of paved roads being evident for the Algerian mouse. Road-kill mortality risk was high in pine voles. Habitat specialization, individual mobility and home-range location were identified as important factors of species’ responses towards roads. This study draws attention to the role of behaviour and ecological requirements as well as road characteristics on the strength of the barrier effect imposed by roads for different species.

Does ungulate disturbance mediate behavioural and physiological stress responses in Algerian mice ( Mus spretus )? A wild exclosure experiment

Ungulate densities increased recently in Mediterranean oak ecosystem where acorn-dispersing small rodents, like the Algerian mouse ( Mus spretus ), are keystone species. Recent work showed important effects of ungulates on the environment (vegetation and soil characteristics) influencing small mammal behaviour and population dynamics, but little is known on the physiological stress responses of small mammals to ungulates. We studied wild ungulate effects on habitat characteristics and whether ungulate pressure influenced both behavioural and physiological stress responses in wild populations of Algerian mice. We manipulated ungulates' presence by large exclosures in Holm oak Quercus ilex open woodland with paired controls, where live trapping of Algerian mice was combined with a detailed evaluation of relevant habitat features for this rodent species such as vegetation height, cover and soil compaction. Further we analysed faecal corticosterone metabolites (FCM) in captured Algerian mice to test whether ungulate presence led to increased glucocorticoids. Fresh faecal samples from 92 different individuals captured with Sherman live traps were collected and analyzed by an enzyme immunoassay. Mouse abundance was higher inside ungulate exclosures due to positive exclosure effects on understory vegetation cover and soil compaction. Mice selected smaller trees with more area covered by resprouts, and this selection was stronger outside than inside exclosures. FCM levels were higher in females than in males. FCM levels were positively correlated with soil compaction and inversely with tree canopy size; however, individuals showed higher FCM levels inside than outside exclosures probably due to the higher local mouse abundance inside exclosures. Mouse behaviour varied in relation to direct effects of wild ungulates on key habitat traits whereas physiological stress responses seemed to be mediated by the increased intraspecific competition, an indirect effect of wild ungulates.

Enhanced Macrophage M1 Polarization and Resistance to Apoptosis Enable Resistance to Plague.

Susceptibility to infection is in part genetically driven, and C57BL/6 mice resist various pathogens through the proinflammatory response of their M1 macrophages (MPs). However, they are susceptible to plague. It has been reported elsewhere that Mus spretus SEG mice resist plague and develop an immune response characterized by a strong recruitment of MPs. The responses of C57BL/6 and SEG MPs exposed to Yersinia pestis in vitro were examined. SEG MPs exhibit a stronger bactericidal activity with higher nitric oxide production, a more proinflammatory polarized cytokine response, and a higher resistance to Y. pestis-induced apoptosis. This response was not specific to Y. pestis and involved a reduced sensitivity to M2 polarization/signal transducer and activator of transcription 6 activation and inhibition of caspase 8. The enhanced M1 profile was inducible in C57BL/6 MPs in vitro, and when transferred to susceptible C57BL/6 mice, these MPs significantly increased survival of bubonic plague. MPs can develop an enhanced functional profile beyond the prototypic M1, characterized by an even more potent proinflammatory response coordinated with resistance to killing. This programming plays a key role in the plague-resistance phenotype and may be similarly significant in other highly lethal infections, suggesting that orienting the MP response may represent a new therapeutic approach.

Context dependence of acorn handling by the Algerian mouse (Mus spretus)

Perceived predation risk and competition for acorns are expected to affect scatter-hoarding decisions by Algerian mice (Mus spretus). We manipulated both factors by means of predator fecal scents and ungulate exclosures. We hypothesized that high-risk perception and ungulate presence would promote acorn dispersal. In the former case, it would stimulate acorn mobilization to safe microhabitats rather than in situ consumption. In the latter, increased competition for acorns would promote their storage for later consumption. We also expected that mice would adapt their foraging behavior to previous experience modulating the strength of these effects.In the presence of ungulates, mice focused their foraging activities on food acquisition at the expenses of vigilant behaviors. However, a more efficient foraging did not entail enhanced dispersal services. Lack of anti-predatory cover in tree surroundings may have deterred mice from transporting seeds outside canopies. Increased risk interacted with previous experience. In control trees (no predator odor), mice confidence increased throughout the night resulting in decreased vigilance and enhanced acorn mobilization rates. In contrast, in risky conditions (trees with predator odor) mice maintained a base-line vigilant behavior. Contrary to our expectations, increased risk did not result in higher acorn mobilization, but the opposite. Again, the scarcity of safe microhabitats for mobilization may have been the underlying cause of this behavior.Our results show that successful acorn dispersal depends, at least partly, on plant-animal relationships that are beyond the oak-rodent mutualism. Thus, any conservation policy aimed at restoring natural regeneration of oaks should take into account the interaction network in which oak-rodent encounters are embedded. In addition, they suggest that mice incorporate direct and indirect cues of risks (habitat structure) through recent experience. A better understanding of this process will improve our ability to incorporate such temporal and spatial variability in models of acorn dispersal.

Validation of commercial real-time PCR-arrays for environmental risk assessment: Application to the study of p,p´-DDE toxicity in Mus spretus mice liver

Data on gene transcription profiles provide a comprehensive assessment of the toxic and defensive mechanisms that are triggered by pollutants. PCR-arrays have emerged as a reliable tool for analyzing the expression of a panel of relevant, pathway- or disease-focused genes under uniform cycling conditions. By using SYBR Green-optimized primer assays, it is possible to simultaneously amplify a sample with high specificity and amplification efficiencies. However, commercial PCR-arrays target a limited group of organisms, excluding most of those with environmental relevance, as is the case with Mus spretus mice. Our previous works with M. spretus showed a high sequence similarity between M. spretus and the model organism M. musculus allowing the use of commercial platforms with M. spretus. This work demonstrates the successful application of a commercial PCR-array designed for the model organism M. musculus to assess the biological effects caused by the organochlorine pesticide p,p´-DDE in a focused panel of stress-related genes in M. spretus mice. This cost-effective, easy-to-use platform detected quantitative gene profiling differences between M. spretus hepatic RNA samples and generated data highly concordant with those obtained by absolute qRT-PCR, the most sensitive method to quantify transcripts. This platform is also suitable for use in field studies with free-living M. spretus mice for routine environmental risk assessment. Our results provide a broad impression of the biological consequences of p,p´-DDE on the hepatic health of mice.

Analysis of Copy Number Variation in the Abp Gene Regions of Two House Mouse Subspecies Suggests Divergence during the Gene Family Expansions.

The Androgen-binding protein (Abp) gene region of the mouse genome contains 64 genes, some encoding pheromones that influence assortative mating between mice from different subspecies. Using CNVnator and quantitative PCR, we explored copy number variation in this gene family in natural populations of Mus musculus domesticus (Mmd) and Mus musculus musculus (Mmm), two subspecies of house mice that form a narrow hybrid zone in Central Europe. We found that copy number variation in the center of the Abp gene region is very common in wild Mmd, primarily representing the presence/absence of the final duplications described for the mouse genome. Clustering of Mmd individuals based on this variation did not reflect their geographical origin, suggesting no population divergence in the Abp gene cluster. However, copy number variation patterns differ substantially between Mmd and other mouse taxa. Large blocks of Abp genes are absent in Mmm, Mus musculus castaneus and an outgroup, Mus spretus, although with differences in variation and breakpoint locations. Our analysis calls into question the reliance on a reference genome for interpreting the detailed organization of genes in taxa more distant from the Mmd reference genome. The polymorphic nature of the gene family expansion in all four taxa suggests that the number of Abp genes, especially in the central gene region, is not critical to the survival and reproduction of the mouse. However, Abp haplotypes of variable length may serve as a source of raw genetic material for new signals influencing reproductive communication and thus speciation of mice.

Redox proteomics reveals the hepatoprotective effect of must from Pedro Ximénez dried grapes in aged Mus spretus mice

Aged mice consumed water supplemented with Pedro Ximénez must (PXM). After 20weeks, histological analyses showed that PXM consumption highly alleviated the age-related hepatic damage observed in control mice, restoring the cytoplasmic appearance and normal arrangement of hepatic cords of young mice. Bidimensional electrophoresis of 5-IAF labeled hepatic proteins showed changes in the reversibly oxidized thiol status of 42 protein spots. Fourteen proteins were identified. Seven (FAM210B, RPE, SRSF1, KRT1, ATF1, ZEB1, IgM) resulted reduced and other seven (RPL29, GABPB1, ACTB, DDC, INA, PRKAR1B, ZFP738) oxidized. For 6 proteins (ATF1, RPE, ZEB1, IGM, PRKAR1B and ZFP738) the susceptibility of a particular Cys to reversible oxidation was analyze. The histological changes, the variations in the oxidation status of protein thiolic groups and the identification of specific Cys residues affected, indicated that the PXM must is acting as an antioxidant but also a pro-oxidant that might help the elderly liver to regenerate.

Establishment of a heteroplasmic mouse strain with interspecific mitochondrial DNA haplotypes and improvement of a PCR-RFLP-based measurement system for estimation of mitochondrial DNA heteroplasmy.

Mitochondrial DNA segregation is one of the characteristic modes of mitochondrial inheritance in which the heteroplasmic state of mitochondrial DNA is transmitted to the next generation in variable proportions. To analyze mitochondrial DNA segregation, we produced a heteroplasmic mouse strain with interspecific mitochondrial DNA haplotypes, which contains two types of mitochondrial DNA derived from C57BL/6J and Mus spretus strains. The strain was produced on a C57BL/6J nuclear genomic background by microinjection of donor cytoplasm into fertilized eggs. The PCR-RFLP semi-quantitative analysis method, which was improved to reduce the effect of heteroduplex formation, was used to measure the proportion of heteroplasmic mitochondrial DNA in tissues. Founder mice contained up to approximately 14% of exogenous Mus spretus mitochondrial DNA molecules in their tails, and the detected proportions differed among tissues of the same individual. Heteroplasmic mitochondrial DNA is transmitted to the next generation in varying proportions under the maternal inheritance mode. This mitochondrial heteroplasmic mouse strain and the improved PCR-RFLP measurement system enable analysis of the transmission of heteroplasmic mitochondrial DNA variants between tissues and generations.

Pérdida de diversidad en la comunidad de micromamíferos del Parque Nacional de Doñana durante las últimas cuatro décadas

In this study, we analyze the changes occurred since 1978 in the community of small mammals of Doñana and the relationship with local climatic changes. Capture-mark-recapture methods were carried out for a total of 16 years, distributed over the last four decades. The results clearly reflect a significant loss of diversity and decline of the community of small mammals, with the virtual disappearance of Eliomys quercinus and Rattus rattus, the sharp decline of Apodemus sylvaticus and the progressive domination of Mus spretus, which is a worrying process because the small mammals are, after the rabbit, the most commonly group of prey consumed by carnivores and raptors in Doñana. The detected changes could have a certain causal relationship with the progressive increase in temperature detected during the study period in Doñana, which would be supported by the fact that species in clear regression are those of eurasian origin and northern distribution E. quercinus and R. rattus, while the current dominant species, M. spretus, has a North African origin and a Mediterranean distribution. Another possibility, not exclusive, is that extreme rarefaction of rabbit may have caused changes in interspecific relationships of the community of vertebrates, and that the impact caused by carnivores and raptors could deviate progressively towards smaller species (from rabbits, to rats and dormice) determining a gradual decline in their abundance.

Experimental transmission of rabbit haemorrhagic disease virus (RHDV) from rabbit to wild mice (Mus spretus and Apodemus sylvaticus) under laboratory conditions

Rabbit haemorrhagic disease (RHD) is a highly lethal and contagious viral disease that produces haemorrhagic lesions in liver and lungs of domestic and wild rabbits (Oryctolagus cuniculus). This study investigates the transmission of RHDV from infected rabbits to mice, based on the detection of viral RNA. Sixteen wild mice (Mus spretus, n=12 and Apodemus sylvaticus, n=4) were put in contact with nine rabbits inoculated with RHDV. No mice died following exposure to RHDV-infected rabbits or developed macroscopic haemorrhagic lesions. On the fourth day of contact, RHDV was detected by RT-PCR in the faeces of three of the four mice killed and in the livers of two of them. Three days after contact period with the inoculated rabbits (7th day of the experiment), RHDV was detected by RT-PCR in 100% (n=4) of the faeces and 50% (n=2) of the livers of euthanized animals. Ten days after contact period (14th day of the experiment), RHDV was not detected in the faeces or liver from any of the mice euthanized. However, 64days after contact period, RHDV was detected in the faeces of one mouse (1 of 4). We demonstrate cross-species transmission of RHDV-RNA from rabbit to rodent and the capability of RHDV-RNA to persist in mice for at least 10days after contact, and potentially up to two months, although viral replication within the rodent and/or infectivity was not evaluated in the present study.

Long-term data from a small mammal community reveal loss of diversity and potential effects of local climate change.

Climate change affects distribution and persistence of species. However, forecasting species’ responses to these changes requires long-term data series that are often lacking in ecological studies. We used 15 years of small mammal trapping data collected between 1978 and 2015 in 3 areas at Doñana National Park (southwest Spain) to (i) describe changes in species composition and (ii) test the association between local climate conditions and size of small mammal populations. Overall, 5 species were captured: wood mouse Apodemus sylvaticus, algerian mouse Mus spretus, greater white-toothed shrew Crocidura russula, garden dormouse Eliomys quercinus, and black rat Rattus rattus. The temporal pattern in the proportion of captures of each species suggests that the small mammal diversity declined with time. Although the larger species (e.g., E. quercinus), better adapted to colder climate, have disappeared from our trapping records, M. spretus, a small species inhabiting southwest Europe and the Mediterranean coast of Africa, currently is almost the only trapped species. We used 2-level hierarchical models to separate changes in abundance from changes in probability of capture using records of A. sylvaticus in all 3 areas and of M. spretus in 1. We found that heavy rainfall and low temperatures were positively related to abundance of A. sylvaticus, and that the number of extremely hot days was negatively related to abundance of M. spretus. Despite other mechanisms are likely to be involved, our findings support the importance of climate for the distribution and persistence of these species and raise conservation concerns about potential cascading effects in the Doñana ecosystem.

Genomic resources for wild populations of the house mouse, Mus musculus and its close relative Mus spretus.

Wild populations of the house mouse (Mus musculus) represent the raw genetic material for the classical inbred strains in biomedical research and are a major model system for evolutionary biology. We provide whole genome sequencing data of individuals representing natural populations of M. m. domesticus (24 individuals from 3 populations), M. m. helgolandicus (3 individuals), M. m. musculus (22 individuals from 3 populations) and M. spretus (8 individuals from one population). We use a single pipeline to map and call variants for these individuals and also include 10 additional individuals of M. m. castaneus for which genomic data are publically available. In addition, RNAseq data were obtained from 10 tissues of up to eight adult individuals from each of the three M. m. domesticus populations for which genomic data were collected. Data and analyses are presented via tracks viewable in the UCSC or IGV genome browsers. We also provide information on available outbred stocks and instructions on how to keep them in the laboratory.

Panx3 links body mass index and tumorigenesis in a genetically heterogeneous mouse model of carcinogen-induced cancer.

BackgroundBody mass index (BMI) has been implicated as a primary factor influencing cancer development. However, understanding the relationship between these two complex traits has been confounded by both environmental and genetic heterogeneity.MethodsIn order to gain insight into the genetic factors linking BMI and cancer, we performed chemical carcinogenesis on a genetically heterogeneous cohort of interspecific backcross mice ((Mus Spretus × FVB/N) F1 × FVB/N). Using this cohort, we performed quantitative trait loci (QTL) analysis to identify regions linked to BMI. We then performed an integrated analysis incorporating gene expression, sequence comparison between strains, and gene expression network analysis to identify candidate genes influencing both tumor development and BMI.ResultsAnalysis of QTL linked to tumorigenesis and BMI identified several loci associated with both phenotypes. Exploring these loci in greater detail revealed a novel relationship between the Pannexin 3 gene (Panx3) and both BMI and tumorigenesis. Panx3 is positively associated with BMI and is strongly tied to a lipid metabolism gene expression network. Pre-treatment Panx3 gene expression levels in normal skin are associated with tumor susceptibility and inhibition of Panx function strongly influences inflammation.ConclusionsThese studies have identified several genetic loci that influence both BMI and carcinogenesis and implicate Panx3 as a candidate gene that links these phenotypes through its effects on inflammation and lipid metabolism.Electronic supplementary materialThe online version of this article (doi:10.1186/s13073-016-0334-8) contains supplementary material, which is available to authorized users.

Study of the efficiency of anticoagulant rodenticides to control Mus musculus domesticus introgressed with Mus spretus Vkorc1.

Antivitamin K anticoagulant (AVK) rodenticides are commonly used to control rodent pests worldwide. They specifically inhibit the VKORC1 enzyme essential for the recycling of vitamin K, and thus prevent blood clotting and cause death by haemorrhage. Numerous mutations or polymorphisms of the Vkorc1 gene were reported in rodents, and some led to resistance to rodenticides. In house mice (Mus musculus domesticus), adaptive introgression of the Vkorc1 gene from the Algerian mouse (Mus spretus) was reported. This adaptive introgression causes the substitution of four amino acids in M. musculus domesticus. The consequences of introgression were assessed by (i) the characterisation of the in vivo resistant phenotype of adaptive Vkorc1spr -introgressed mice, (ii) the characterisation of the ex vivo resistance phenotype of the liver VKOR activity and (iii) the comparison of these results with the properties of recombinant VKORC1spr protein expressed in yeast. The resistance factor (from 1 to 120) induced by the four introgressed polymorphisms obtained using these three approaches was dependent on the AVKs used but were highly correlated among the three approaches. The four introgressed polymorphisms were clearly the cause of the strong resistant phenotype observed in the field. In the context of strong selection pressure due to the extensive use of AVKs, this resistant phenotype may explain the widespread distribution of this genotype from Spain to Germany. © 2016 Society of Chemical Industry.

Heterogeneous road networks have no apparent effect on the genetic structure of small mammal populations

Roads are widely recognized to represent a barrier to individual movements and, conversely, verges can act as potential corridors for the dispersal of many small mammals. Both barrier and corridor effects should generate a clear spatial pattern in genetic structure. Nevertheless, the effect of roads on the genetic structure of small mammal populations still remains unclear. In this study, we examine the barrier effect that different road types (4-lane highway, 2-lane roads and single-lane unpaved roads) may have on the population genetic structure of three species differing in relevant life history traits: southern water vole Arvicola sapidus, the Mediterranean pine vole Microtus duodecimcostatus and the Algerian mouse Mus spretus. We also examine the corridor effect of highway verges on the Mediterranean pine vole and the Algerian mouse. We analysed the population structure through pairwise estimates of FST among subpopulations bisected by roads, identified genetic clusters through Bayesian assignment approaches, and used simple and partial Mantel tests to evaluate the relative barrier or corridor effect of roads. No strong evidences were found for an effect of roads on population structure of these three species. The barrier effect of roads seems to be site-specific and no corridor effect of verges was found for the pine vole and Algerian mouse populations. The lack of consistent results among species and for each road type lead us to believe that the ability of individual dispersers to use those crossing structures or the habitat quality in the highway verges may have a relatively higher influence on gene flow among populations than the presence of crossing structures per se. Further research should include microhabitat analysis and the estimates of species abundance to understand the mechanisms that underlie the genetic structure observed at some sites.

Efficient analysis of mouse genome sequences reveal many nonsense variants

Genetic polymorphisms in coding genes play an important role when using mouse inbred strains as research models. They have been shown to influence research results, explain phenotypical differences between inbred strains, and increase the amount of interesting gene variants present in the many available inbred lines. SPRET/Ei is an inbred strain derived from Mus spretus that has ∼1% sequence difference with the C57BL/6J reference genome. We obtained a listing of all SNPs and insertions/deletions (indels) present in SPRET/Ei from the Mouse Genomes Project (Wellcome Trust Sanger Institute) and processed these data to obtain an overview of all transcripts having nonsynonymous coding sequence variants. We identified 8,883 unique variants affecting 10,096 different transcripts from 6,328 protein-coding genes, which is about 28% of all coding genes. Because only a subset of these variants results in drastic changes in proteins, we focused on variations that are nonsense mutations that ultimately resulted in a gain of a stop codon. These genes were identified by in silico changing the C57BL/6J coding sequences to the SPRET/Ei sequences, converting them to amino acid (AA) sequences, and comparing the AA sequences. All variants and transcripts affected were also stored in a database, which can be browsed using a SPRET/Ei M. spretus variants web tool (www.spretus.org), including a manual. We validated the tool by demonstrating the loss of function of three proteins predicted to be severely truncated, namely Fas, IRAK2, and IFNγR1.

Differences in the ectoparasite fauna between micromammals captured in natural and adjacent residential areas are better explained by sex and season than by type of habitat

We compared the ectoparasite fauna in 608 micromammals (chiefly 472 wood mice Apodemus sylvaticus, 63 Algerian mice Mus spretus, and 51 greater white-toothed shrews Crocidura russula) captured in natural and adjacent residential areas in spring and autumn during three consecutive years in four areas in periurban Barcelona (NE Spain). We found little support for an association of urbanization with differences in infestation by ectoparasites. Prevalence of Rhipicephalus sp. tick in wood mice and shrews was significantly higher in residential than in natural habitats, and the opposite was found for the flea Ctenophtalmus andorrensis catalanensis in shrews. Marked differences in the prevalence of the flea Leptopsylla taschenbergi amitina in wood mice between seasons were observed in natural but not in residential habitats, probably due to enhanced flea survival probabilities in the latter. However, as a rule, males were more frequently and heavily infested than females, and the prevalence was higher in autumn than in spring. Our results suggest that the ectoparasite fauna of periurban micromammals is shaped more by other factors than by habitat modification. People living in residential areas are at risk of contact with the arthropods borne by non-commensal micromammals and the pathogens transmitted by them.