MOLECULAR EVIDENCE THAT THE SPINY MOUSE (ACOMYS) IS MORE CLOSELY RELATED TO GERBILS (GERBILLINAE) THAN TO TRUE MICE (MURINAE)

Spiny mice of the genus Acomys traditionally have been classified as m embers of the Murinae, a subfamily of rodents that also includes rats and mice with which spiny mice share a complex set of morphological ch aracters, including a unique molar pattern. The origin and evolution o f this molar pattern, documented by many fossils from Southern Asia, s upport the hypothesis of the monophyly of Acomys and all other Murinae . This view has been challenged by immunological studies that have sug gested that Acomys is as distantly related to mice (Mus) as are other subfamilies (e.g., hamsters: Cricetinae) of the muroid rodents. We pre sent molecular evidence derived from DNA-DNA hybridization data that i ndicate that the spiny mouse Acomys and two African genera of Murinae, Uranomys and Lophuromys, constitute a monophyletic clade, a view that was recently suggested on the basis of dental characters. However, ou r DNA.DNA hybridization data also indicate that the spiny mice (Acomys ) are more closely related to gerbils (Gerbillinae) than to the true m ice and rats (Murinae) with which they have been classified. Because A comys and the brush-furred mice Uranomys and Lophuromys share no deriv ed morphological characters with the Gerbillinae, their murine morphol ogy must have evolved by convergence, including the molar pattern prev iously considered to support the monophyly of the Murinae.