Invasive rodents have been responsible for the diffusion worldwide of many zoonotic agents, thus representing major threats for public health. Cities are important hubs for people and goods exchange and are thus expected to play a pivotal role in invasive commensal rodent dissemination. Yet, data about urban rodents' ecology, especially invasive vs. native species interactions, are dramatically scarce. Here, we provide results of an extensive survey of urban rodents conducted in Niamey, Niger, depicting the early stages of rodent bioinvasions within a city. We explore the species-specific spatial distributions throughout the city using contrasted approaches, namely field sampling, co-occurrence analysis, occupancy modelling and indicator geostatistics. We show that (i) two species (i.e. rural-like vs. truly commensal) assemblages can be identified, and that (ii) within commensal rodents, invasive (Rattus rattus and Mus musculus) and native (Mastomys natalensis) species are spatially segregated. Moreover, several pieces of arguments tend to suggest that these exclusive distributions reflect an ongoing native-to-invasive species turn over. The underlying processes as well as the possible consequences for humans are discussed.

Based on compiled small mammal trapping data collected over 12 years from Benin and Niger (3701 individual records from 66 sampling sites), located in mainland Africa, we here describe the small mammal community assemblage in urban habitats along the commercial axis connecting the two countries, from the seaport of Cotonou to the Sahelian hinterland, with a particular focus on invasive species. In doing so, we document extant species distributions, which highlight the risks of continuing the range expansion of three synanthropic invasive rodent species, namely black rats (Rattus rattus), brown rats (R. norvegicus), and house mice (Mus musculus). Using various diversity estimates and community ecology approaches, we detect a latitudinal gradient of species richness that significantly decreased Northward. We show that shrews (Crocidura) represent a very important component of micro-mammal fauna in West African towns and villages, especially at lower latitudes. We also demonstrate that invasive and native synanthropic rodents do not distribute randomly in West Africa, which suggests that invasive species dynamics and history differ markedly, and that they involve gradual, as well as human-mediated, long distance dispersal. Patterns of segregation are also observed between native Mastomys natalensis and invasive rats R. rattus and R. norvegicus, suggesting potential native-to-invasive species turn over. Consequences of such processes, especially in terms of public health, are discussed.

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Pericentromeric repeats have been claimed to mediate centric fusions through heterologous recombination of arrays of tandemly repeated and highly homogenized motifs. However, mammalian case studies are essentially restricted to pathologic fusions in human, or to the house mouse Roberstonian (Rb) races. We here provide an example in a wild gerbil rodent, Gerbillus nigeriae, which displays an extensive Rb polymorphism, with 2n ranging between 2n = 60 and 74. The distribution of two closely related repeats, GERB1 and GERB2 that were previously isolated by Volobouev et al. (Chromosoma 104:252-259, 1995) in this African species, were investigated in the genomes of seven individuals with various diploid numbers. Our results clearly show that GERB1 and GERB2 are organized in a non-random manner, with GERB2 and GERB1 being clearly juxtacentromeric and centromeric, respectively. Finally, cloning and sequencing revealed that, unlike GERB2, GERB1 monomers display a more homogeneous organization at both the nucleotide and structural levels. Altogether, our results point toward a pivotal role of GERB1 repeats in the mediation of Rb fusions through heterologous recombination, with some evidence of subsequent loss of repeats after the Rb fusion during the course of evolution of metacentric elements. Moreover, the repeat pattern observed in G. nigeriae closely matches the organization and sequence structure of satellite DNAs described in human acrocentrics. Consequently, G. nigeriae appears as an additional model for the study of repeat evolution and its role in centric fusions and their consequences in mammals.

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Robertsonian (Rb) fusions are one of the most frequent types of chromosomal rearrangements and have greatly contributed to the evolution of mammalian genome architecture. Apart from rare exceptions, investigations at the species level (i.e. polymorphism) are almost exclusively restricted to two mammalian models, namely the house mouse Mus musculus domesticus (2n = 22-40) and the common shrew Sorex araneus (2n = 20-33). Yet, these two species display important but usually locally restricted Rb polymorphisms. Another rodent species, Gerbillus nigeriae, has also been shown to display a wide range of diploid number variation (2n = 60-74) due to Rb polymorphism. However, data about the latter species are rather scarce. We provide here a survey including recapitulation of 137 available karyotypic data that were implemented with 241 new records, thus allowing us to draw the first map of 2n variation throughout the species range. First, truly segregating centric fusions are observed in almost all localities investigated. Moreover, the geographic patterns (from 79 West African localities in total) show that local 2n variations are clearly lower than those observed at a wider scale, thus leading to some spatial structuring that may reflect phylogeographic assemblages. The meiotic study of 13 male specimens allowed us to identify several instances of double and triple Rb heterozygous individuals, and strongly suggested that heterozygosity is more the rule than the exception in the species. From there, it is tempting to speculate that the extraordinary Rb plasticity observed in G. nigeriae may be selectively maintained and confer adaptability to this species, which inhabits unstable Sahelian environments, where it is able to colonize efficiently habitats that undergo rapid human-mediated and/or climatic changes.

The breeding of local chicken is an important source of animal protein and income for the rural populations of Niger, and the improvement of its productivity requires a better knowledge of production practices. Hence, a socio-economic and technical survey was undertaken from July to August 2017 in order to provide necessary information on the practice of family poultry keeping in Niger. For this purpose, two hundred and sixteen (216) producers were interviewed in the different agro-ecological zones of Niger using structured questionnaire. Results from the study revealed that 43.1% of local chicken producers are women. The most production purpose of the chicken in Niger is for selling (38.31%), self-consumption (37.74%) and donation (22.99%). Scavenging is the most dominant feeding system (92.1%). Constraints related to family poultry production as identified by the study are mainly diseases (45%), lack of housing (16%) which favors predation, lack of food (11%) and lack of training (8%). It is clear that the development of the sector necessarily involves strengthening the surveillance of avian diseases, coupled with veterinary monitoring and supervision of producers.

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