Morphological, genetical and ecological discrimination of sympatric Coastal Guinea Mastomys (Mammalia: Rodentia) species (West Africa): implications for health and agriculture

Morphological, genetical and ecological discrimination of sympatric Coastal Guinea Mastomys (Mammalia : Rodentia) species (West Africa) : implications fir health and agriculture. - Cytogenetic and molecular tools have shown the existence of two sibling species of the multimammate rat in Coastal Guinea : M. erythroleucus and M. huberti from Mankoutan locality. Here we present the study of the unique population of M. huberti ever recorded in Guinea, distant from 350 km from the closest locality in Senegal and representing the southernmost point of the species' disjunct distribution. In order to clarify its ecological preferences and define its degree of sympatry with M. erythroleucus, we have searched for morphological and morphometric criteria allowing reliable identification of the species in Coastal Guinea. Discriminant Factorial Analyses (DFA) were performed on external and skull measurements for respectively 108 and 106 previously genetically typed individuals. All discriminant analyses showed that the 100% rate of good classification is never attained. Misclassifications of 55.6 % of the specimens were obtained in the field by using external fur colour and aspect whereas the error score ranged from 4.5 to 8 % by using DFA on external measurements. Furthermore, DFA on skull measurements gave 100 % of correct classification for M. huberti - which is characterized by a smaller size - against 96.97 % for M. erythroleucus. In the same time, we were able to define the local specific habitat of each species. In Mankountan, M. huberti is never found into houses but prefers wet rice fields, while M. erythroleucus is found both in houses and cultures as well as in wet rice fields where it is found in syntopy with M. huberti at the end of the dry season. In Yerende, a hundred kilometres from Mankoutan, we only caught M. etythroleucus both in houses and fields. This study once again highlights the importance of a deep taxonomic knowledge of small mammals' diversity for sanitary and agricultural risks evaluation but also confirms the problems of identification encountered with rodent sibling species living in sympatry.