House Mice Mus Musculus Research Articles

Social dominance and wheel running in females of Djungarian hamster (Phodopus sungorus)

AbstractWheel running is a behaviour that has a rewarding effect on animals. There are not numerous papers investigating potential relationships between social rank and wheel running in mammals kept in groups, and the majority of published researches were conducted on male house mice (Mus musculus). The aim of our study was to investigate if social dominance and wheel running are related in female Djungarian hamsters (Phodopus sungorus). Hamsters were kept in groups, and social position of every animal was expressed as dominance index calculated on the basis of agonistic behaviour. We found significant positive correlation between dominance index and wheel running (rs = 0.809, n = 18, P < 0.0001), thus dominants used wheel more often than subordinates. Our results are consistent with those published on male mice. In conclusion, we claim that in majority of mammals (independent of their sex) kept in groups with restricted possibility of wheel running, dominants use wheel more often (or in optimal time) than subordinates, what is consistent with the fact that dominants have priority of access to resources.

Altered serotonergic and GABAergic neurotransmission in a mice model of obsessive-compulsive disorder

There is ample evidence that obsessive-compulsive disorder (OCD) is based on reduced serotonergic function. Replicated bidirectional selection for thermoregulatory nest-building behavior in the laboratory house mouse (Mus musculus) resulted in compulsive-like, non-compulsive-like and randomly bred control mice that represent a non-induced animal model of OCD. The present study aimed at investigating the neurochemical patterns in specific brain regions of compulsive-like (HA) versus non-compulsive-like (LA) and normal (CA) mice. The neurochemical investigation of several brain regions of the corticostriato-thalamocortical circuity, i.e., nucleus caudatus (CPU), nucleus accumbens (NAc), globus pallidus (GP), hippocampus (HPC), amygdala (AM), ventral tegmental area (VTA) and substantia nigra (SN) was performed by electrochemical (serotonin and dopamine) and fluorescence (glutamate and GABA) HPLC detection. HA mice displayed significantly decreased 5-HT concentrations in the mPFC and LA mice displayed a significant increase in GABA concentrations in the mPFC. This supports the pathophysiological relevance of serotonin in the manifestation of OCD and adding to the construct validity of the non-induced mouse model of OCD.

Peptides (Epigenetic Regulators) in the Structure of Rodents with a Long and Short Lifespan.

We have discovered motives of short-chain epigenetically active peptides in some proteins of long-lived African mole rat Heterocephalus glaber. These epigenetic regulators are located in the protein structure between lysine and arginine residues, thus facilitating their release in limited proteolysis. Some of these epigenetic regulators are not found in the proteins of short-lived species - Norway rat Rattus norvegicus and house mouse Mus musculus.

Like or dislike: Response of rodents to the odor of plant secondary metabolites.

Rodents, including common voles (Microtus arvalis) and house mice (Mus musculus) cause immense pre-harvest and post-harvest losses. Therefore, developing methods that mitigate these losses while maintaining their role in ecosystems is a priority. Several plant secondary metabolites (PSM) which significantly reduce food intake of both species under laboratory conditions have been identified. However, before these can be used in rodent pest management, they must be tested under more natural conditions where other food sources are available. In this study, the odors of 4 PSMs were evaluated for their repellent effects in experiments conducted in semi-natural enclosures. Soil treated with PSMs or untreated soil (experimental control) was placed in an underground box containing food (rolled oats). We quantified the number of visits to each box and could demonstrate that all 4 PSMs reduced the number of visits to treatment boxes in both rodent species. For common voles the combination of methyl nonyl ketone + black pepper oil was the most repellent PSM. House mice made fewer visits to all PSM boxes; boxes with the anthraquinone were visited least. Furthermore, house mice consumed less food from boxes containing soil treated with all 4 PSMs. Our results suggest that PSMs are repellent in murid and microtine rodents under semi-field conditions. In addition, the future use of PSM odors for repelling both pest species, especially house mice, seems promising. Further investigations with other PSMs, different concentrations as well as alternative application methods are needed to repel common voles from attractive crops.

Epidemiological Study of dwarf tapeworm Hymenolepis nana in Najaf province / Iraq

The infection rate with Hymenolepis nana in Najaf province was 446 (1.79%) from the results of about 24.800 stool samples from different parts of Najaf province were examined by direct wet mount methodin Al-Sadder Medical City, Al-Hakeem Hospital, Al-Zahraa children and Maternity Hospital, Al-Menathera Hospital and Al-Sajad Hospital, in addition to medical centers and private clinics in province . This study was conducted during September 2013 to September 2014 . A questionnaire sheet, shown in appendix was filled for each individual studies . There was no significant difference (p< 0.05 )in the rate of infection between male and female and there was a significant difference (p<0.05) between infected patients (6-12 years) in comparison with other age distribution . It was found that 20% of 150 house mouse Mus musculus were infected with H.nana . The highest rate of the total infection was 7.34% in grain stores and the lowest rate (4%) in restaurants .

Heterogeneous genetic make-up of Japanese house mice (Mus musculus) created by multiple independent introductions and spatio-temporally diverse hybridization processes

In this study, phylogenetic analysis of relatively long sequences of mitochondrial DNA (4225 bp) in the Japanese house mouse Mus musculus provides the first evidence that both southern Asian subspecies of Mus musculus castaneus (CAS) and northern Asian subspecies of Mus musculus musculus (MUS) arrived in Japan through rapid population expansion events, from Southern China ~4000 years ago and the Korean Peninsula ~2000 years ago, respectively. Nuclear DNA haplotype structure analyses targeting a chromosome region with two different tract sizes, 1 and 5 Mb, consisting of nine and six tandemly arranged markers, respectively, yielded a possible average fragment length of 170 kb of CAS haplotypes in the MUS background genome in northern Japan, providing a rough estimate of its elapsed time of 815 generations under an assumption of continued backcrossing. Less frequent and shortened CAS-like haplotypes specific to Japan were detected, suggesting ancient introduction prior to the appearance of the South Chinese CAS in Japan. Our analyses also showed sporadic appearance of long fragments (2–5 Mb) from the west European subspecies Mus musculus domesticus, indicating contemporary stowaway introduction. Overall, multiple overseas introductions, and the time-lagged inter-subspecies genetic admixture, probably resulted in the heterogeneous state of Japanese wild mice.

Genetics of Genome-Wide Recombination Rate Evolution in Mice from an Isolated Island.

Recombination rate is a heritable quantitative trait that evolves despite the fundamentally conserved role that recombination plays in meiosis. Differences in recombination rate can alter the landscape of the genome and the genetic diversity of populations. Yet our understanding of the genetic basis of recombination rate evolution in nature remains limited. We used wild house mice (Mus musculus domesticus) from Gough Island (GI), which diverged recently from their mainland counterparts, to characterize the genetics of recombination rate evolution. We quantified genome-wide autosomal recombination rates by immunofluorescence cytology in spermatocytes from 240 F2 males generated from intercrosses between GI-derived mice and the wild-derived inbred strain WSB/EiJ. We identified four quantitative trait loci (QTL) responsible for inter-F2 variation in this trait, the strongest of which had effects that opposed the direction of the parental trait differences. Candidate genes and mutations for these QTL were identified by overlapping the detected intervals with whole-genome sequencing data and publicly available transcriptomic profiles from spermatocytes. Combined with existing studies, our findings suggest that genome-wide recombination rate divergence is not directional and its evolution within and between subspecies proceeds from distinct genetic loci.

No speed dating please! Patterns of social preference in male and female house mice

BackgroundIn many animal species, interactions between individuals of different sex often occur in the context of courtship and mating. During these interactions, a specific mating partner can be chosen. By discriminating potential mates according to specific characteristics, individuals can increase their evolutionary fitness in terms of reproduction and offspring survival. In this study, we monitored the partner preference behaviour of female and male wild house mice (Mus musculus domesticus) from populations in Germany (G) and France (F) in a controlled cage setup for 5 days and six nights. We analysed the effects of individual factors (e.g. population origin and sex) on the strength of preference (selectivity), as well as dyadic factors (e.g. neutral genetic distance and major histocompatibility complex (MHC) dissimilarity) that direct partner preferences.ResultsSelectivity was stronger in mice with a pure population background than mixed individuals. Furthermore, female mice with a father from the German population had stronger selectivity than other mice. In this group, we found a preference for partners with a larger dissimilarity of their father’s and their partner’s MHC, as assessed by sequencing the H2-Eß locus. In all mice, selectivity followed a clear temporal pattern: it was low in the beginning and reached its maximum only after a whole day in the experiment. After two days, mice seemed to have chosen their preferred partner, as this choice was stable for the remaining four days in the experiment.ConclusionsOur study supports earlier findings that mate choice behaviour in wild mice can be paternally influenced. In our study, preference seems to be potentially associated with paternal MHC distance. To explain this, we propose familial imprinting as the most probable process for information transfer from father to offspring during the offspring’s early phase of life, which possibly influences its future partner preferences. Furthermore, our experiments show that preferences can change after the first day of encounter, which implies that extended observation times might be required to obtain results that allow a valid ecological interpretation.

Automatic mouse ultrasound detector (A-MUD): A new tool for processing rodent vocalizations.

House mice (Mus musculus) emit complex ultrasonic vocalizations (USVs) during social and sexual interactions, which have features similar to bird song (i.e., they are composed of several different types of syllables, uttered in succession over time to form a pattern of sequences). Manually processing complex vocalization data is time-consuming and potentially subjective, and therefore, we developed an algorithm that automatically detects mouse ultrasonic vocalizations (Automatic Mouse Ultrasound Detector or A-MUD). A-MUD is a script that runs on STx acoustic software (S_TOOLS-STx version 4.2.2), which is free for scientific use. This algorithm improved the efficiency of processing USV files, as it was 4–12 times faster than manual segmentation, depending upon the size of the file. We evaluated A-MUD error rates using manually segmented sound files as a ‘gold standard’ reference, and compared them to a commercially available program. A-MUD had lower error rates than the commercial software, as it detected significantly more correct positives, and fewer false positives and false negatives. The errors generated by A-MUD were mainly false negatives, rather than false positives. This study is the first to systematically compare error rates for automatic ultrasonic vocalization detection methods, and A-MUD and subsequent versions will be made available for the scientific community.

A survey of zoonotic pathogens carried by house mouse and black rat populations in Yucatan, Mexico.

The house mouse (Mus musculus) and the black rat (Rattus rattus) are reservoir hosts for zoonotic pathogens, several of which cause neglected tropical diseases (NTDs). Studies of the prevalence of these NTD-causing zoonotic pathogens, in house mice and black rats from tropical residential areas are scarce. Three hundred and two house mice and 161 black rats were trapped in 2013 from two urban neighbourhoods and a rural village in Yucatan, Mexico, and subsequently tested for Trypanosoma cruzi, Hymenolepis diminuta and Leptospira interrogans. Using the polymerase chain reaction we detected T. cruzi DNA in the hearts of 4·9% (8/165) and 6·2% (7/113) of house mice and black rats, respectively. We applied the sedimentation technique to detect eggs of H. diminuta in 0·5% (1/182) and 14·2% (15/106) of house mice and black rats, respectively. Through the immunofluorescent imprint method, L. interrogans was identified in 0·9% (1/106) of rat kidney impressions. Our results suggest that the black rat could be an important reservoir for T. cruzi and H. diminuta in the studied sites. Further studies examining seasonal and geographical patterns could increase our knowledge on the epidemiology of these pathogens in Mexico and the risk to public health posed by rodents.

The role of rodents in the transmission of Leptospira spp. in swine farms

Different species of rodents are potential transmitters of multiple zoonotic agents such as Leptospira spp., a spirochete that causes leptospirosis. This is an infectious disease that has a negative impact on pig production because it generates large productive, reproductive and economic losses. In swine farms, the most common rodent species are house mice (Mus musculus), brown rats (Rattus norvegicus) and black rats (Rattus rattus), which act as maintenance hosts for different serovars of Leptospira, contaminating the environment, food and water through urine, and putting human and animal health at risk. For this reason, the objective of this article is to describe the role of rodents in the transmission of Leptospira in swine farms. For this purpose, a bibliographic search was carried out in different databases such as Science Direct, Scopus, Redalyc, PubMed and SciELO. The results of the literature review show that there are few studies that report the importance of rodents in the transmission of Leptospira in swine farms. The onset of the disease depends to a large extent on the presence, contact and control of rodents in farms, although environmental factors, agent survival and hygiene, among others, must also be considered.

Suppression of food intake by house mouse (Mus musculus) following ingestion of brodifacoum-based rodenticide bait

Rodenticides are evaluated mainly with regard to mortality, with less attention to prevention of stored-commodity losses. We quantified the extent and speed of suppression of food intake in wild house mice (Mus musculus Linnaeus, 1758) after consumption of brodifacoum-based bait. We found that although there was a significant delay in mouse mortality (LT50 = 6.4 days, max. survival = 14 days), suppression of food consumption occurred sooner: time to consume 50% of the food was 2.1 days. Food consumption was continual in control mice, while treated mice increased consumption during the first 3 days and then showed a sharp decline, approaching zero consumption by the 10th day. Although practitioners may worry that extensive damage to expensive commodities (e.g., seed packages) continues long after bait consumption due to the delayed mortality associated with anticoagulants, our study demonstrates that brodifacoum bait has high potential to substantially decrease food losses (by 75%) shortly after administration.

No evidence for punishment in communally nursing female house mice (Mus musculus domesticus).

Punishment is claimed as an important mechanism to stabilise costly cooperation in humans, but its importance in social animals has been questioned recently due to both conceptual considerations and a lack of empirical evidence (only few published studies). We empirically tested whether there is evidence for punishment in communally nursing house mice (Mus musculus domesticus, direct descendants of “wild” animals). Communally breeding females pool their litters and raise all offspring together, indiscriminately caring for own and other offspring. Such a situation resembles a public good and provides scope for exploitation if females vary in their relative contributions to the joint nest (offspring number). We allowed two females to communally breed and conducted removal experiments both in the presence and absence of pups. We aimed to test whether reduced investment by one of the females (induced through separation from the partner and their combined offspring for 4 or 12 hours) leads to increased aggression by the other female after the reunion. We found no evidence for punishment, on the contrary, females increased socio-positive behaviours. The costs of losing a partner in a communally breeding species might be too high and hinder the evolution of punishment. Our findings add to a growing list of examples questioning the role of punishment in cooperating non-human animals and emphasise the importance of empirical testing of its assumptions and predictions.

Low-basal area treatment and prescribed fire to restore oak-pine savannas alter small mammal communities

Following decades of fire suppression many oak-pine savanna ecosystems have shifted to closed-canopied forests. Restoration of these ecosystems to their savanna condition is seen as a way to reduce woody species encroachment and dangerous fuel loads, and restore community species composition. The management practices to achieve these goals typically involve thinning and prescribed fire. We assessed how thinning to reduce basal area combined with frequent prescribed fire influenced small mammal communities and their habitat. We focused on six habitat variables that can influence small mammal abundance and species composition: stand basal area of live trees and snags, volume of coarse woody debris, percent ground cover, forest floor depth, and distance of vulnerability, a measure of understory vegetation structure and animal vulnerability to predators. Although savanna restoration reduced basal area by 80%, there was no change in snag density or coarse woody debris volume. Savanna restoration significantly increased the ground cover of graminoids, forbs, bare ground, and down woody debris and reduced forest floor depth and distance of vulnerability. These habitat changes likely contributed to the significant differences between small mammal communities in restored and non-restored stands. Restoration treatments caused a large increase in abundance of White-footed Mouse (Peromyscus leucopus) and important changes in community assemblages. Least Shrew (Cryptotis parva), Fulvous Harvest Mouse (Reithrodontomys fulvescens), Eastern Harvest Mouse (R. humulis), and Hispid Cotton Rat (Sigmodon hispidus) were caught only in restored stands, while House Mouse (Mus musculus), Plains Harvest Mouse (R. montanus), and Texas Mouse (P. attwateri) were caught only in non-restored stands.

Sarcocystis pantherophisi n. sp., from Eastern Rat Snakes (Pantherophis alleghaniensis) as Definitive Hosts and Interferon Gamma Gene Knockout Mice as Experimental Intermediate Hosts.

Here, we report a new species, Sarcocystis pantherophisi n. sp., with the Eastern rat snake (Pantherophis alleghaniensis) as natural definitive host and the interferon gamma gene knockout (KO) mouse as the experimental intermediate host. Sporocysts (n = 15) from intestinal contents of the snake were 10.8 × 8.9 μm. Sporocysts were orally infective to KO mice but not to laboratory-raised albino outbred house mice (Mus musculus). The interferon gamma KO mice developed schizont-associated neurological signs, and schizonts were cultivated in vitro from the brain. Mature sarcocysts were found in skeletal muscles of KO mice examined 41 days postinoculation (PI). Sarcocysts were slender, up to 70 μm wide and up to 3.5 mm long. By light microscopy, sarcocysts appeared thin-walled (<1 μm) without projections. By transmission electron microscopy, the sarcocyst wall was a variant of "type 1" (type 1i, new designation). The parasitophorous vacuolar membrane (pvm) had approximately 100-nm-wide × 100-nm-long bleb-like evaginations interspersed with 100-nm-wide × 650-nm-long elongated protrusions at irregular distances, and invaginations into the ground substance layer (gs) for a very short distance (6 nm). The gs was smooth, up to 500 nm thick, without tubules, and contained a few vesicles. Longitudinally cut bradyzoites at 54 days PI were banana-shaped, 7.8 × 2.2 μm (n = 5). Molecular characterization using 18S rRNA, 28S rRNA, ITS-1, and cox1 genes indicated a close relationship with other Sarcocystis parasites that have snake-rodent life cycles. The parasite in the present study was molecularly and biologically similar to a previously reported isolate (designated earlier as Sarcocystis sp. ex Pantherophis alleghaniensis) from P. alleghaniensis, and it was structurally different from other Sarcocystis species so far described.

Does chromosomal change restrict gene flow between house mouse populations (Mus musculus domesticus)? Evidence from microsatellite polymorphisms

Chromosomal change is recognized as an important force in speciation-with-gene-flow models. Although Robertsonian (Rb) translocations contribute to hybrid unfitness and modify recombination patterns, they are generally not considered as efficient as inversions in reducing gene flow. The present study analyses two hybridizing chromosomal races of the house mouse (Mus musculus domesticus), one carrying nine Rb fusions (2n = 22) and the other carrying the ancestral karyotype (2n = 40). Chromosomal heterozygosity involves simple meiotic configurations, the underdominance of which is not as efficient in promoting speciation as more complex chromosomal differences. The pattern of divergence between these races was investigated using 32 microsatellite loci distributed over all autosomes. The results highlighted a relatively large differentiation between the two chromosomal races. The contribution of variation in recombination patterns to this differentiation was supported by the contrasting levels of divergence between proximal vs. non-proximal microsatellite loci. Clinal analyses of the Rb fusions through the hybrid zone uncovered differences in steepness between metacentrics, suggesting associated differences in selection which did not involve linked genic incompatibilities. This study illustrates the significant role of Rb-associated changes in recombination in promoting or maintaining divergence between chromosomal races of the house mouse.

0199 CHARACTERIZING SLEEP, CIRCADIAN RHYTHMS, AND EYE CLOSURE IN ACOMYS CAHIRINUS (CAIRO SPINY MOUSE)

In order to better understand the functions and origins of sleep, sleep should be studied across a variety of species. We aim to characterize sleep and wake in Acomys cahirinus, the Cairo spiny mouse. Few studies on the circadian activity of this species are available and nothing is known of their sleep behavior. Therefore, we have begun to characterize sleep, circadian rhythms, and eye closure for this species (A. cahirinus) in greater detail and alongside the well-studied house mouse (Mus musculus). Sleep and wake states were determined using a piezoelectric system for individually housed mice for 7 days under 12:12 LD condition. Four infrared cameras were set up around the cage to monitor activity patterns of A. cahirinus in light and dark conditions. Starting with one mouse, two more were added to the cage every four days ending with a total of five to study the effect of group housing on activity. Then, mice were surgically instrumented for tethered electroencephalogram (EEG) recording. To research eye closure of A. cahirinus, we set up a light flashing experiment to challenge the eye. We found A. cahirinus and M. musculus to be primarily nocturnal, but with distinct behavioral patterns. The activity of A. cahirinus sharply increases at dark onset, but surprisingly, decreases sharply just one hour later. A. cahirinus is more active in the first half of the night than the second half in both single and group housing. Based on EEG analysis, A. cahirinus sleeps more than Mus during both day and night. The proportion of REM is significantly higher (nearly tripled). The proportion of wakefulness is more in the first half of the night. We also found that A. cahirinus do not close their eyes during sleep periods of the day or night, even with lights flashing. A. cahirinus has different sleep and circadian behavior than the standard laboratory nocturnal mouse. They sleep more than Mus during both daytime and night time. REM percentage is significantly higher. NSF and OISE (IOS-1353713), NIH grant NS083218, Kentucky Cabinet for Economic Development.

Morphometric variations at an ecological scale: Seasonal and local variations in feral and commensal house mice

The time scales of evolutionary and ecological studies tend to converge, as shown by evidences that contemporary evolution can occur as fast as ecological processes. This opens new questions regarding variation of characters usually considered to change mostly along an evolutionary time scale, such as morphometric traits, including osteological and dental features such as mandibles and teeth of mammals. Using two-dimensional geometric morphometric approach, we questioned whether such features can change on a seasonal and local basis, in relation to the ecological dynamics of the populations. Our model comprised populations of house mice (Mus musculus domesticus) in two contrasted situations in mainland Western Europe: a feral population vs. two close commensal populations. Mitochondrial DNA (D-loop) provided insight into the diversity and dynamics of the populations.The feral population appeared as genetically highly diversified, suggesting a possible functioning as a sink in relation to the surrounding commensal populations. In contrast, commensal populations were highly homogeneous from a genetic point of view, suggesting each population to be isolated. This triggered morphological differentiation between neighboring farms. Seasonal differences in morphometric traits (mandible size and shape and molar size and shape) were significant in both settings, although seasonal variations were greater in the feral than in the commensal population. Seasonal variations in molar size and shape could be attributed to differential wear in young or overwintered populations. Differences in mandible shape could be related to aging in overwintered animals, but also possibly to differing growth conditions depending on the season. The impact of these ecological processes on morphometric traits is moderate compared to divergence over a large biogeographic scale, but their significance nevertheless underlines that even morphological characters may trace populations dynamics at small scale in time and space.

DNA Methylation Divergence and Tissue Specialization in the Developing Mouse Placenta.

The placental epigenome plays a vital role in regulating mammalian growth and development. Aberrations in placental DNA methylation are linked to several disease states, including intrauterine growth restriction and preeclampsia. Studying the evolution and development of the placental epigenome is critical to understanding the origin and progression of such diseases. Although high-resolution studies have found substantial variation between placental methylomes of different species, the nature of methylome variation has yet to be characterized within any individual species. We conducted a study of placental DNA methylation at high resolution in multiple strains and closely related species of house mice (Mus musculus musculus, Mus m. domesticus, and M. spretus), across developmental timepoints (embryonic days 15-18), and between two distinct layers (labyrinthine transport and junctional endocrine). We observed substantial genome-wide methylation heterogeneity in mouse placenta compared with other differentiated tissues. Species-specific methylation profiles were concentrated in retrotransposon subfamilies, specifically RLTR10 and RLTR20 subfamilies. Regulatory regions such as gene promoters and CpG islands displayed cross-species conservation, but showed strong differences between layers and developmental timepoints. Partially methylated domains exist in the mouse placenta and widen during development. Taken together, our results characterize the mouse placental methylome as a highly heterogeneous and deregulated landscape globally, intermixed with actively regulated promoter and retrotransposon sequences.

Genetic structure and invasion history of the house mouse (Mus musculus domesticus) in Senegal, West Africa: a legacy of colonial and contemporary times

Knowledge of the genetic make-up and demographic history of invasive populations is critical to understand invasion mechanisms. Commensal rodents are ideal models to study whether complex invasion histories are typical of introductions involving human activities. The house mouse Mus musculus domesticus is a major invasive synanthropic rodent originating from South-West Asia. It has been largely studied in Europe and on several remote islands, but the genetic structure and invasion history of this taxon have been little investigated in several continental areas, including West Africa. In this study, we focussed on invasive populations of M. m. domesticus in Senegal. In this focal area for European settlers, the distribution area and invasion spread of the house mouse is documented by decades of data on commensal rodent communities. Genetic variation at one mitochondrial locus and 16 nuclear microsatellite markers was analysed from individuals sampled in 36 sites distributed across the country. A combination of phylogeographic and population genetics methods showed that there was a single introduction event on the northern coast of Senegal, from an exogenous (probably West European) source, followed by a secondary introduction from northern Senegal into a coastal site further south. The geographic locations of these introduction sites were consistent with the colonial history of Senegal. Overall, the marked microsatellite genetic structure observed in Senegal, even between sites located close together, revealed a complex interplay of different demographic processes occurring during house mouse spatial expansion, including sequential founder effects and stratified dispersal due to human transport along major roads.