The Spatial Distribution of the House Mouse, Mus musculus domesticus, in Multi-Family Dwellings

The house mouse, Mus musculus domesticus, creates significant public health risks for residents in low-income multi-family dwellings (MFDs). This study was designed to evaluate the spatial distribution of house mice in MFDs. Four low-income high-rise apartment buildings in three cities in New Jersey were selected for building-wide monitoring on two occasions with approximately one year between the monitoring events. The presence of a house mouse infestation was determined by placing mouse bait stations with three different non-toxic baits for a one-week period in all accessible units as well as common areas. Permutation tests were conducted to evaluate house mouse infestation spatial patterns. All four analyzed buildings exhibited a significant correlation between apartments with house mouse infestations and whether they share a common wall or ceiling/floor at both sampling periods except one building during the second inspection, which contained a high number of isolated apartments. Foraging ranges, speed of locomotion, and dispersal behavior of house mice are relatively larger, faster, and more common, respectively, compared to common urban arthropod pests. This could lead to the conclusion that house mice are as likely to infest non-neighboring apartments as those that share a wall or floor/ceiling. However, these results demonstrate that house mouse infestations tend to occur among apartments that share common walls or ceilings/floors. This spatial distribution pattern can be utilized in rodent management plans to improve the efficiency of house mouse management programs in MFDs.

Synanthropic rodent fauna of Eastern Transbaikalia in the early 21st century

The article provides information on the synanthropic rodent fauna of Eastern Transbaikalia. In 2017–2020 the city of Chita, the town of Baley and small settlements of Zabaykalsky krai were surveyed. True synanthropes: the house mouse and the brown rat are most abundant in residential landscapes. Natural populations of the house mouse are typical for coastal biotopes of the steppe zone, and the brown rat is typical for forest-steppe zone of Zabaykalsky krai. In Chita (administrative centre of Zabaykalsky krai) the share of the brown rat in rodent communities has considerably increased in recent decades. There is an extension of the brown rat’s habitat in the area of Baikal-Amur Mainline. Optional synanthropes: striped field mouse, striped dwarf hamster, Maximowicz’s vole, and narrow-headed vole are less important in residential landscapes of the region. In the beginning of the 21st century the field mouse is extending its habitat to the disjunct zone to the west of Transbaikalia: it is now common in the residential area of the town of Baley. Penetration of another optional synanthropic species recorded in the neighbouring Siberian regions – the East European vole – has not been detected.

Copy number variation of the putative speciation genes in the European house mouse hybrid zone

Hybrid zones have long been described as "windows on the evolutionary process", and studying them has become even more important since the advance in the genome analysis tools. The hybrid zone between two subspecies of the house mouse (Mus musculus musculus and Mus m. domesticus) is a unique model speciation system to study fine scale interactions of recently diverged genomes. Here, we explore the role of gene Copy Number Variation in shaping the barrier to introgression in the hybrid zone within a previously established transect in Central Europe. The CNV of seven pre-selected candidate genes was determined via droplet-digital PCR and analyzed in the context of ~500k SNPs, with the ancestral population (i.e. musculus or domesticus) of every SNP allele previously inferred in the admixed individuals (Baird et al., in prep.). The copy numbers of five genes were clearly associated with the prevalence of either musculus or domesticus genomes across the hybrid zone. In three cases, the highest and/or outlying levels of association were observed at or very close to the annotated positions of the respective gene amplicons, demonstrating the power of our approach in confirming the reference locations of copy number variants. Notably, several other reference locations were recognized as positive outliers in the association with particular CNV genes, possibly representing the extra gene copies and/or their epistatic interaction sites.

Estimating the rates of crossover and gene conversion from individual genomes

Recombination can occur either as a result of crossover or gene conversion events. Population genetic methods for inferring the rate of recombination from patterns of linkage disequilibrium generally assume a simple model of recombination that only involves crossover events and ignore gene conversion. However, distinguishing the two processes is not only necessary for a complete description of recombination, but also essential for understanding the evolutionary consequences of inversions and other genomic partitions in which crossover (but not gene conversion) is reduced. We present heRho, a simple composite likelihood scheme for co-estimating the rate of crossover and gene conversion from individual diploid genomes. The method is based on analytic results for the distance-dependent probability of heterozygous and homozygous states at two loci. We apply heRho to simulations and data from the house mouse Mus musculus castaneus, a well studied model. Our analyses show i) that the rates of crossover and gene conversion can be accurately co-estimated at the level of individual chromosomes and ii) that previous estimates of the population scaled rate of recombination ρ = 4Ner under a pure crossover model are likely biased

The Influence of Ship Rats (Rattus Rattus) on the Habitat Preferences of the House Mouse (Mus Musculus)

<p>As methods and successes of Rattus rattus (ship rat) control progress, particularly in island environments, the importance of managing Mus musculus (house mouse) increases. M. musculus can negatively impact on a variety of native fauna and flora, potentially creating long term cascading effects. M. musculus populations benefit with the reduction in R. rattus abundance and recover sooner from pest control programs. This three-part study investigated the habitat utilisation of M. musculus and how their relationship with R. rattus influences their habitat preferences. Firstly, hypotheses about the habitat preferences of M. musculus were tested over a landscape scale to determine the features of the environment most important to their distribution. Then the direct effect of R. rattus presence on M. musculus habitat-use was investigated in arena trials. Lastly, in the same arenas, canopy cover was tested as an indirect cue for M. musculus to evaluate the presence of R. rattus. Across 32 sites, M. musculus were the most abundant in warm dry habitats. North facing slopes and rank grass cover were the features of the environment that had the strongest relationship with abundance. In arenas M. musculus foraging activity was 52% lower in patches of short grass when R. rattus scent was present but foraging in rank grass and bare ground was not altered, suggesting activity was suppressed not competitive displacement. There were no significant changes in M. musculus foraging behaviour between different canopy treatments. Although a trend of nocturnal foraging activity dropping 26% when high canopy cover was over short grass compared to short grass patches with lower or no canopy treatments may indicate a risky habitat. M. musculus use of dense ground cover was common theme in this study and in the literature. R. rattus do influence the habitat selection of M. musculus though this was with direct presence more than indirect cues.</p>

The Influence of Ship Rats (Rattus Rattus) on the Habitat Preferences of the House Mouse (Mus Musculus)

<p>As methods and successes of Rattus rattus (ship rat) control progress, particularly in island environments, the importance of managing Mus musculus (house mouse) increases. M. musculus can negatively impact on a variety of native fauna and flora, potentially creating long term cascading effects. M. musculus populations benefit with the reduction in R. rattus abundance and recover sooner from pest control programs. This three-part study investigated the habitat utilisation of M. musculus and how their relationship with R. rattus influences their habitat preferences. Firstly, hypotheses about the habitat preferences of M. musculus were tested over a landscape scale to determine the features of the environment most important to their distribution. Then the direct effect of R. rattus presence on M. musculus habitat-use was investigated in arena trials. Lastly, in the same arenas, canopy cover was tested as an indirect cue for M. musculus to evaluate the presence of R. rattus. Across 32 sites, M. musculus were the most abundant in warm dry habitats. North facing slopes and rank grass cover were the features of the environment that had the strongest relationship with abundance. In arenas M. musculus foraging activity was 52% lower in patches of short grass when R. rattus scent was present but foraging in rank grass and bare ground was not altered, suggesting activity was suppressed not competitive displacement. There were no significant changes in M. musculus foraging behaviour between different canopy treatments. Although a trend of nocturnal foraging activity dropping 26% when high canopy cover was over short grass compared to short grass patches with lower or no canopy treatments may indicate a risky habitat. M. musculus use of dense ground cover was common theme in this study and in the literature. R. rattus do influence the habitat selection of M. musculus though this was with direct presence more than indirect cues.</p>

Same Invasion, Different Routes: Helminth Assemblages May Favor the Invasion Success of the House Mouse in Senegal

Previous field-based studies have evidenced patterns in gastrointestinal helminth (GIH) assemblages of rodent communities that are consistent with “enemy release” and “spill-back” hypotheses, suggesting a role of parasites in the ongoing invasion success of the exotic house mouse (Mus musculus domesticus) in Senegal (West Africa). However, these findings came from a single invasion route, thus preventing to ascertain that they did not result from stochastic and/or selective processes that could differ across invasion pathways. In the present study, we investigated the distribution of rodent communities and their GIH assemblages in three distinct zones of Northern Senegal, which corresponded to independent house mouse invasion fronts. Our findings first showed an unexpectedly rapid spread of the house mouse, which reached even remote areas where native species would have been expected to dominate the rodent communities. They also strengthened previous insights suggesting a role of helminths in the invasion success of the house mouse, such as: (i) low infestation rates of invading mice by the exotic nematode Aspiculuris tetraptera at invasion fronts—except in a single zone where the establishment of the house mouse could be older than initially thought, which was consistent with the “enemy release” hypothesis; and (ii) higher infection rates by the local cestode Mathevotaenia symmetrica in native rodents with long co-existence history with invasive mice, bringing support to the “spill-back” hypothesis. Therefore, “enemy release” and “spill-back” mechanisms should be seriously considered when explaining the invasion success of the house mouse—provided further experimental works demonstrate that involved GIHs affect rodent fitness or exert selective pressures. Next steps should also include evolutionary, immunological, and behavioral perspectives to fully capture the complexity, causes and consequences of GIH variations along these invasion routes.

How the naked mole-rat resists senescence: a constraints-based theory

Here, I present a theory describing how the stabilization of constraints imposed on chromatin dynamics by the naked mole-rat's histone H1.0 protein—which in terminally differentiated cells constrains the accessibility of the nucleosome core particle for histone-modifying enzymes and chromatin remodeling factors—explains its resistance to both senescence and cancer. Further, this theory predicts that a mutant house mouse displaying such stabilization will be similarly resistant to both senescence and cancer. A proof-of-concept computational analysis is presented and two predictions for the direct testing of the theory are provided. These experiments comprise, as test subjects, mutant naked mole-rats synthesizing a house mouse (Mus musculus)-like histone H1.0, and mutant house mice synthesizing a naked mole-rat-like histone H1.0. The predictions are that the constraints on chromatin dynamics embodied by the respective mutant histone H1.0 proteins will negate the otherwise significant resistance to both senescence and cancer of the naked mole-rats and, conversely, confer such resistance to the house mice. A verification of these predictions will imply that constraints on chromatin dynamics embodied by naked mole-rat-like histone H1.0 proteins may confer significant resistance to both senescence and age-related cancer to otherwise senescence-prone and/or cancer-susceptible multicellular species, including humans.

Whole-genome sequencing analysis reveals the population history of Mus musculus in Madagascar

In Madagascar, the house mouse (Mus musculus) is thought to have colonized along with humans and is now one of the most successfully colonized rodents on the island. In this study, we determined the whole-genome sequences of the Madagascar house mouse captured from the wild. We examined the evolutionary history of its population regarding the mitochondrial and autosomal genomes. We confirmed that in the mitochondrial genomes of Madagascar house mice, a monophyletic clade forms a basal origin within the species. An analysis of autosomal genomic sequences indicates that the Madagascar house mouse population is genetically a member of M. m. castaneus (CAS). It also contains genetic elements of M. m. domesticus (DOM) resulting from ancient hybridization. The signature of a strong population bottleneck 1000–3000 years ago was observed in the mitochondrial and autosomal genomic data. We also show that the divergence of the Madagascar population from the CAS population occurred approximately 50,000–99,000 years ago. Madagascar house mice show strong genetic affinity to many CAS samples across a wide range of Indian Ocean coastal regions. However, our results suggest that they would not have originated directly from the Indonesian islands, where Austronesian-speaking people in Madagascar originated. Because the ancient hybridization signature with DOM did not appear in the Indonesian and other CAS samples, we propose that Madagascar house mice were not directly brought by Austronesian-speaking people but came from somewhere around the Middle East or South Asia soon after the colonization of initial farmers.

Mice of the genus Mus in the Crimea: species diagnostics, distribution, and ecology

The paper presents the first detailed summary of the current state of mice of the genus Mus in the Crimea, namely of the house mouse (Mus musculus Linnaeus, 1758) and steppe mouse (Mus spicilegus Petenyi, 1882). Morphological structures of the house mouse and steppe mouse are characterized and external and craniometrical features important for species diagnostics are presented. Most of the morphological characters tend to vary within the entire geographic range of both species. Body length of house mice is significantly greater compared to that of steppe mice. Tail length in house mice is greater than in steppe mice, but the tail index is greater in the latter. Therefore, house mice look more ‘short-tailed’, and this feature can be used as an additional diagnostic character. In steppe mice, the tail becomes thinner gradually from base to tip and thus it is awl-shaped. The tail of fit house mice, especially of autumn-winter generations, often has a thickened base, which increases the visual effect of a short tail. Among internal characters, the most significant are the differences between testicles size of mature males. For species diagnostics of mice of the genus Mus, the size and shape of the following cranial structures can be used: location of the root and frontal wall of the crown of the first upper molar (M1) in relation to the diastema; zygomatic process of the maxilla and zygomatic arch; palatine foramens foramina palatinum, and others. These are reliable characters for morphological identification of M. musculus and M. spicilegus in the territory of the Crimea, in the zone of their sympatry. Reliable diagnostic characters are the dimensions of palatine foramens. In general, the entire complex of characters analysed in this study should be used for correct morphological diagnostics of these species. Features of distribution and population dynamics of the house mouse and steppe mouse in the Crimea are studied. It has been revealed that both the house mouse and the steppe mouse are distributed mainly in the lowland part of the Crimea and the forest-steppe belt of the foothills. Data on the ecology of species are presented, including specifics of reproduction and habitat preferences. The place and role of house mice in small-mammal assemblages of various landscape and ecological zones are estimated.