Abstract Multi‐mammate rats (Muridae, Murinae, Mastomys spp.) are Sub‐Saharan pest rodents, the systematics of which has long remained confused due to poor morphologic differentiation. Cytotaxonomy and DNA sequencing have provided excellent diagnostic markers for species identification, thus improving the assessment of taxonomic diversity within the genus. In West and Central Africa, three species have been unambiguously identified and are now well documented: Mastomys erythroleucus, Mastomys natalensis and Mastomys huberti . However, recent studies suggest the existence of two other taxa on the basis of morphology, DNA sequencing ( Mastomys verheyeni , from Nigeria and Northern Cameroon) or karyotypes ( Mastomys cf. kollmannspergeri , from Northern Niger and Chad). In order to clarify the systematic status of the latter taxa, we collected all the available cytotaxonomic as well as cytochrome b sequencing data to which were added results obtained from recently trapped specimens in Northern Cameroon. Our combined molecular and cytogenetic analyses unambiguously confirm the presence of another Mastomys species inhabiting various habitats in Niger, Nigeria, Cameroon, Chad and Sudan. This taxon is clearly differentiated from M. erythroleucus, M. huberti and M. natalensis . Furthermore, the inclusion in our analysis of two M. verheyeni paratypes as well as individuals trapped in close vicinity to the type locality of M. kollmannspergeri supports the assignation of all specimens to M. kollmanspergeri , thus making M. verheyeni its junior synonym. Our study once again highlights the reliability of DNA‐ and karyotype‐based methods to accurately assess specific diversity in African rodents, particularly in the Mastomys genus, which shelters several species of agricultural and epidemiological importance.
Abstract An understanding of the evolutionary history and dynamics of invasive species is required for the construction of predictive models of future spread and the design of biological management measures. The black rat ( Rattus rattus ) is a major vertebrate invader with a worldwide distribution. Despite the severe ecological, economic and health impacts of this species, its evolutionary history has been little studied. We carried out extensive specimen sampling in Senegal, West Africa, and used microsatellite markers to describe the pattern and processes of invasion in this large continental area. The genetic data obtained were combined with historical knowledge concerning the presence of this species in Senegal. Data were analysed by a combination of Bayesian clustering and approximate Bayesian computation methods. The invasion pathways closely paralleled the history of human trade routes in Senegal. In several places, we detected the occurrence of multiple introductions from genetically different sources. Long‐distance migration between towns and villages was also observed. Our findings suggest that genetic bottlenecks and admixture have played a major role in shaping the genetics of invasive black rats. These two processes may generate genetic novelty and favour rapid evolution along the invasion pathways.
Des populations du genre mastomys sont etudiees au Senegal sous les aspects suivants: caryologie, electrophorese, biometrie, reproduction, croissance et rythmes d'activite. L'existence de trois especes sympatriques est etablie, au lieu de deux precedemment reconnues. Leurs relations phylogenetiques sont discutees. La variabilite intra specifique de chaque espece est observee pour les differents parametres cites ci-dessus. Le cas des populations insulaires est plus particulierement developpe. La repartition biogeographique et ecologique des differentes especes est determinee a partir des criteres systematiques
Abstract More than 2000 animals belonging to six different rodent species and one insectivore species were examined for infection with schistosomes in the region of Richard-Toll, Senegal. Two murid rodents, Arvicanthis niloticus and Mastomys huberti , were found infected with Schistosoma mansoni . Prevalences were about 5% for both rodent species with a mean worm burden of about 20 worms per host. The sex-ratios of S. mansoni worms were always biased towards males. Prevalences and worm burdens, although similar in both male and female rodents, increased significantly with age. The highest prevalences and worm burdens were found near habitations and decreased significantly with the distance from the town of Richard-Toll. Eggs were also observed in the liver and faeces of the two naturally infected rodent species. The results suggest that rodents participate in the transmission of intestinal schistosomiasis in Richard-Toll but the human population is the main source of infection. The genetic resemblance between human and murine isolates of S. mansoni suggests that further epidemiological studies are needed in this region of Senegal.
Abstract Studies on human and murine isolates of Schistosoma mansoni , from Richard-Toll, Senegal, were carried out by isoelectric focusing in polyacrylamide gels. Seven enzyme systems; lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PD), acid phosphatase (AcP), hexokinase (HK), glucose phosphate isomerase (GPI), and phosphoglucomutase (PGM), were used to compare the two isolates. All systems tested, apart from LDH, were found to be polymorphic for both isolates. Interestingly, one phenotype is more frequent than the remainder. The results show that there is no significant genetic variation between the S. mansoni isolates from man and the rodents, Arvicanthis niloticus and Mastomys huberti .
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