Chromosomal and Protein Evolution in Morphologically Similar Species of Praomys sensu lato (Rodentia, Muridae)

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Abstract
Evidence of extensive chromosomal evolution in a biologically and economically important group of African murids of the Praomys/Mastomys complex was provided by examination of G- and C-band chromosomal data on P. coucha (2n = 32), p. fumatus (2n = 38), P. hildebrandti (2n = 32), P. jacksoni (2n = 28), P. misonnei (2n = 36), and P. cf. tulibergi (2n = 35). A coding system was developed for the chromosomal characters, and analyses were performed by a computer program to find the shortest tree with a minimum of 35 autosomal rearrangements (pericentric inversions, complex translocations, centric fusions, centric fissions, tandem fusions, euchromatic additions, and heterochromatic additions). The resulting phylogenetic hypothesis differs from traditionally accepted hypotheses regarding this complex group of rodents. The cytogenetic data show that 1) there is no support for the dichotomy of Mastomys/Praomys previously based on morphology, 2) the 2n = 32 species from eastern Africa (P. hlldebrandti) is distinct from the 2n = 32 species from southern Africa (P. natalensis), and 3) there is a close association between P. Jacksoni and P. cf. tullbergi. Polyacrylamide gel electrophoresis of liver membrane proteins demonstrated few differences in protein mobilities between species and even fewer between individuals of the same species taken from different habitats and localities in Kenya. Monocional antibodies produced against liver proteins of one species and tested for reactivity to other species confirmed the evolutionary similarity of species of this complex. This immunologic approach may provide a robust data set for future phylogenetic studies of muroid rodents. Species identification and evaluation of the relationships among these African murids should be easier to elucidate by using a combination of data sets such as morphology, chromosomes, and immunology.