Systematics and phylogeny of the genus Stenocephalemys Frick, 1914 (Rodentia, Muridae):: a multidisciplinary approach

Morphological (multivariate craniometry and phallic structure), genetic (allozymes) and cytogenetic (G-banding) analyses were performed to clarify systematics and phylogenetic relationships within the presumably monophyletic group of Ethiopian endemic murines (Stenocephalemys species and Praomys albipes). Results of these analyses suggest full species rank for S. griseicauda and S. albocaudata. Nevertheless, karyotypes of these two species (2n = 54, NFa = 58, and 2n = 54, NFa = 62; respectively) demonstrate intraspecific variability sharing two types of X-chromosomes (submetacentric and metacentric). Besides that, marked intraspecific allozymic differentiation within each of the two Stenocephalemys species contrasts with morphological homogeneity within both S. albocaudata and S. griseicauda. On the other hand, the genetic distance between P. albipes and some populations of S. griseicauda (Nei's D = 0.061-0.126) corresponds to genetic differentiation usually recorded for rodent subspecies or closely related species. Furthermore, analysis of G-banding patterns reveals that the P. albipes karyotype (2n = 46, NFa = 58) differs from those of Stenocephalemys spp. mainly by four simple structural rearrangements (two Robertsonian fusions and two centromere-telomere translocations) only. These results suppose that P. albipes and Stenocephalemys species are congeners. Phylogenetic analysis of allozyme data indicates an early origin of S. albocaudata and a recent descendence of P. albipes which is the sister taxon to S. griseicauda. P. albipes diverges significantly from Stenocephalemys in a number of penial traits which suggests an accelerated rate of morphological evolution. Superficial resemblance of P. albipes with some forest Praomys and Myomys species may be a result of convergent evolution in similar environments.