Molecular identification of four cryptic species of Mastomys (Rodentia, Murinae)

Multimammate rats (genus Mastomys) are abundant in many regions throughout sub-Saharan Africa, and are of high economical and sanitary importance as agricultural pests as well as reservoir/vectors of human diseases. In pest management and in epidemiological studies, unequivocal species identification of individuals collected in the field is crucial. However, the discrimination among most of the Mastomys species is often difficult, if not impossible, on the basis of external characters. Karyology provides unambiguous specific assignations, but is not suitable for population studies involving large numbers of individuals because it requires fresh material and/or quick transfer from the field to the laboratory. The purpose of this study was to search for molecular markers allowing a clear discrimination of field collected individuals on the basis of ethanol-preserved samples. Using sequences of the cytochrome b region of mitochondrial DNA, two molecular tests based on species-specific primers (test 1) and restriction sites generating species-specific profiles (test 2), were designed and evaluated for species identification on a large number of karyotypically or electrophoretically unambiguously determined individuals. The tests clearly discriminate the four most widespread species. They are easy to perform on a small piece of ear or tail taken from live animals, and can probably be adapted to identify museum specimens.