CHARACTERS AND DISTRIBUTION OF 3 ACOMYS P HENOTPPES (RODENTIA, MURIDAE) FROM BURKINA-FASO

Among specimens of recently collected Acomys from Burkina Faso, three types of dorsal pigmentation can be distinguished: brown, red and grey . Based upon dental morphology, these specimens belong to the widely d istributed Acomys cahirinus group. These forms are not syntopic. The b igger brownish form can be distinguished immediately from the two othe rs by its pelage colour, large size and large teeth (very broad molars with a prominent pre-lobe). The greyish and reddish Acomys are less d ifferentiated from each other: the greyish form has a pale bluish-grey pelage, and almost no t(3) on M(3), whereas the reddish form has a ri ch fulvous pelage and a noticeable t(3) on M(3). All three forms have a standard karyotype which shows only small amounts of variability, wi th 2N = 66 or 68, and NF = 68 to 74; all or most of the autosomes are acrocentric. Both geographically and morphologically, these Acomys see m close to Acomys johannis Thomas, 1912 described from northeastern Ni geria. Only the brownish form occupies the sandstone cliffs called <<F alaise de Banfora>> in southwestern Burkina Faso. The greyish and redd ish forms are sympatric, but not syntopic, in central and eastern Burk ina Faso. When the greyish and reddish forms share the same rocky area s, a minimum distance of 850 m separates their respective populations; in such regions, the greyish form seems more frequent than the reddis h one. The <<insularity>> of these three Acomys depends on the isolati on of inselbergs and cliffs, and the nature of the soil. The brownish form has probably been isolated long ago from the two others on a homo genous substrate by permanent rivers and reckless soils, that probably constitute efficient barriers. We think that speciation is at work on these three Acomys, with two different levels of differenciation.