Biology subjects

Brouat, C.

Publications and source records attributed to Brouat, C..

7 recordsLinked to original sources

bioRxiv2026

Genomic signatures of selection and putative adaptive introgression during the African expansion of the house mouse

How species adapt to novel environments following biological invasion remains a central question in evolutionary biology. The recent human-mediated expansion of the western house mouse (Mus musculus domesticus) across Africa provides an opportunity to investigate the genomic basis of these rapid evolutionary responses. Using whole-genome data from 218 wild mice sampled across Europe and Africa, we combined complementary genome-wide differentiation, genotype-environment association, haplotype-based selection, and localized introgression analyses to investigate genomic signatures of selection and assess the contribution of interspecific gene flow from the native congener Mus spretus to these patterns. Genome-wide differentiation analyses identified candidate regions enriched for immune and epithelial-barrier functions, chemosensory perception, and neural or developmental pathways. Genotype-environment association analyses recovered fewer candidates linked mainly to precipitation, whereas haplotype-based scans highlighted recent selective signals involving sensory, immune, and neural functions. Across analyses, candidate regions were dominated by non-coding variation, supporting a predominantly regulatory and likely polygenic genomic architecture. Although excess allele sharing with M. spretus varied among populations, overlap between introgression and selection candidates was limited but greater than expected by chance. Several overlapping regions were also present in European populations, indicating that introgressed variants likely predated African colonization. Overall, our results suggest that the genomic signatures accompanying the African expansion of house mice were driven mainly by selection on M. m. domesticus variation, whereas introgressed M. spretus alleles contributed to a smaller subset of candidate loci and may have played a role in adaptation in African populations.

evolutionary biology↗

bioRxiv2025

Genetic structure of Rattus rattus populations in an endemic plague focus in Madagascar: implications for rodent surveillance and management

BackgroundPlague remains a major public health concern in Madagascar. In the Central Highlands, where the disease is still endemic, the black rat (Rattus rattus) is the main reservoir of the causative agent Yersinia pestis. Understanding its population dynamics and structure is therefore crucial to inform control strategies, as dispersal may greatly limit the effectiveness of local interventions during outbreaks. In such a context, this study aims at investigating the genetic diversity and temporal structure of R. rattus populations at a fine geographical scale. Methodology/Principal findingsSampling was conducted in six villages of the Ankazobe district, both inside houses and outside villages. A total of 480 individuals, captured in March - May 2019 and 2020, were genotyped at 17 microsatellite loci. Our results show that genetic diversity levels were relatively homogeneous among villages and years. However, subpopulations living outside villages displayed significantly higher genetic diversity and lower genetic differentiation levels than those from inside houses, indicating larger effective population sizes outside villages in the cultivated habitats. These findings suggest more restricted movement among rat subpopulations from the houses, and greater connectivity among subpopulations living outside villages. However, overall genetic differentiation was rather low, suggesting extensive dispersal of rats at the scale of the district, facilitating rapid recolonization after local control efforts. ConclusionAn integrated approach combining flea control within houses together with measures to reduce human-rodent contact would thus appear more appropriate than rodent control only to limit plague transmission.

ecology↗

bioRxiv2025

Aridity shapes adaptive genomic divergence and population connectivity in a Southern African rodent

Elucidating the drivers of evolution in dry environments is central to understanding how organisms respond to climate change. While research on the genomics of adaptation is growing, aridity-driven intraspecific divergence remains poorly quantified. Here, we address this gap by using genomic data from 230 individuals of the arid-adapted four-striped mouse Rhabdomys bechuanae, sampled across an aridity gradient in southern Africa, a region facing increasing aridification. Combining these data with palaeoclimatic reconstructions and present-day aridity indices, we investigate, from a spatio-temporal perspective, how intraspecific genetic variation relates to aridity. Inference of past effective population size revealed a sharp decline in the late Pleistocene, coinciding with regional aridification and potentially reflecting changes in connectivity during dry periods. Current population structure followed a pattern of isolation by distance and mirrored the aridity gradient. Genotype-Environment Association analyses identified SNPs and genes significantly associated with aridity and genetically differentiated among populations, with functions related to water and energy conservation - as expected under arid conditions - as well as neurotransmission. These findings highlight the underappreciated role for neurological processes in coping with water and resource scarcity. More broadly, our integrative genomics approach suggests that aridity shapes population connectivity and adaptation, with implications for climate resilience.

genomics↗

bioRxiv2019

Toxoplasma gondii in house mice Mus musculus domesticus from Dakar, Senegal: clues for oral rather than vertical mode of infection

Toxoplasma gondii is an ubiquitous highly prevalent zoonotic protozoan. Cats are the definitive hosts, while all other warm-blooded animals are intermediate hosts for this parasite. Commensal rodents, being the main preys of cats, are probably the major reservoir for T. gondii. Rodents often develop dormant tissue cysts after ingestion of oocysts shed in the environment by cats in the form of contaminated feces. Experimental evidence that vertical transmission can be sufficient to the perpetuation of transmission between generations of mice has also been found. In natural settings, the relative epidemiological importance of vertical transmission over oral transmission is a matter of debate and raises the question of the possibility of a T. gondii cycle in the absence of cats. In the present study, we took advantage of an extensive survey of commensal rodents in Dakar, Senegal, where the house mouse Mus musculus domesticus is the predominant putative reservoir of T. gondii. Host genotype and spatial location through GPS referencing of all trapping localizations were investigated in relation to T. gondii infection in 12 sites of the city of Dakar and on Goree Island. In each sampled site, the occurrence of over-prevalence zones of T. gondii infection was investigated through Kulldorfs statistic using SaTScan software. For the sites where a possible over-prevalence zone was identified, mice family lines were inferred from Discriminant Analysis of Principal Components (DAPC). In 3 of the 4 identified possible over-prevalence zones, T. gondii infection was not confined to a single family line, which suggested no association between kinship and infection occurrence. This finding rather suggests an environmental source of infection for mice associated with localized putative foci of environmental contamination and supports an oral route of infection for mice from Dakar rather than a cycle based on vertical transmission.

epidemiology↗

bioRxiv2019

Impact of historical and current features of the cityscape on the genetic structure of the house mouse (Mus musculus domesticus) in Dakar (Senegal, West Africa)

AO_SCPLOWBSTRACTC_SCPLOWPopulation genetic approaches may be used to investigate dispersal patterns of species living in highly urbanized environment in order to improve management strategies for biodiversity conservation or pest control. However, in such environment, population genetic structure may reflect both current features of the cityscape and urbanization history. This can be especially relevant when focusing on exotic commensal rodents that have been introduced in numerous primary colonial European settlements. Accounting for spatial and temporal cityscape heterogeneity to determine how past and recent demographic events may interplay to shape current population genetic structure of synanthropic rodents may provide useful insights to manage their populations. In this study, we addressed these issues by focusing on the house mouse, Mus musculus domesticus, in Dakar, Senegal, where the species may have been introduced as soon as Europeans settled in the middle of the nineteenth century. We examined genetic variation at one mitochondrial locus and 15 nuclear microsatellite markers from individuals sampled in 14 sampling sites representing different stages of urbanization history and different socio-economic environments in Dakar. We used various approaches, including model-based genetic clustering and model-free smoothing of pairwise genetic estimates. We further linked observed spatial genetic patterns to historical and current features of Dakar cityscape using random forest and Bayesian conditional autoregressive models. Results are consistent with an introduction of the house mouse at colonial time and the current genetic structure exhibits a gradient-like pattern reflecting the historical process of spatially continuous expansion of the city from the first European settlement. The genetic patterns further suggest that population dynamics of the house mouse is also driven by the spatial heterogeneity of the current cityscape, including socio-economics features, that translate in habitat quality. Our results highlight the potential importance of accounting for past demographic events to understand spatial genetic patterns of nonnative invasive commensal rodents in highly urbanized environment.

ecology↗

bioRxiv2018

Differential immune gene expression associated with contemporary range expansion of two invasive rodents in Senegal

BackgroundBiological invasions are major anthropogenic changes associated with threats to biodiversity and health. What determines the successful establishment of introduced populations still remains unsolved. Here we explore the appealing assertion that invasion success relies on immune phenotypic traits that would be advantageous in recently invaded sites. ResultsWe compared gene expression profiles between anciently and recently established populations of two major invading species, the house mouse Mus musculus domesticus and the black rat Rattus rattus, in Senegal. Transcriptome analyses revealed respectively 364 and 83 differentially expressed genes along the mouse and rat invasion routes. Among them, 20.0% and 10.6% were annotated with functions related to immunity. All immune-related genes detected along the mouse invasion route were over-expressed in recently invaded sites. Genes of the complement activation pathway were over-represented. Results were less straightforward when considering the black rat as no particular immunological process was over-represented. ConclusionsWe revealed changes in transcriptome profiles along invasion routes. Patterns differed between both invasive species. These changes potentially be driven by increased infection risks in recently invaded sites for the house mouse and stochastic events associated with colonization history for the black rat. These results provide a first step in identifying the immune ecoevolutionary processes potentially involved in invasion success.

ecology↗

bioRxiv2017

Biological invasions in rodent communities: from ecological interactions to zoonotic bacterial infection issues

Several hypotheses (such as enemy release, novel weapon, spillback and dilution/density effect) suggest changes in host-parasite ecological interactions during biological invasion events. Such changes can impact both invasion process outcome and the dynamics of exotic and/or endemic zoonotic diseases. To evaluate these predictions, we investigated the ongoing invasions of the house mouse Mus musculus domesticus, and the black rat, Rattus rattus, in Senegal (West Africa). We focused on zoonotic bacterial communities depicted using 16S rRNA amplicon sequencing approach in both invasive and native rodents sampled along two well-defined invasion routes. Overall, this study provided new ecological evidence connecting parasitism and rodent invasion process, with diverse potential roles of zoonotic bacteria in the invasion success. Our results also highlighted the main factors that lie behind bacterial community structure in commensal rodents. Further experimental studies as well as comparative spatio-temporal surveys are necessary to decipher the actual role of zoonotic bacteria in these invasions. Our data also gave new support for the difficulty to predict the direction in which the relationship between biodiversity changes and disease risk could go. These results should be used as a basis for public health prevention services to design reservoir monitoring strategies based on multiple pathogen surveillance.

ecology↗