Dasymys Peters 1875

Dasymys Peters 1875, Monatsb. K. Preuss. Akad. Wiss. Berlin: 12.

Type Species: Dasymys gueinzii Peters 1875

Species and subspecies: 9 species:

Species Dasymys alleni Lawrence and Loveridge 1953

Species Dasymys cabrali W. Verheyen, Hulselmans, Dierckx, Colyn, Leirs, and E. Verheyen 2003

Species Dasymys foxi Thomas 1912

Species Dasymys incomtus (Sundevall 1846)

Species Dasymys montanus Thomas 1906

Species Dasymys nudipes (Peters 1870)

Species Dasymys rufulus Miller 1900

Species Dasymys rwandae W. Verheyen, Hulselmans, Dierckx, Colyn, Leirs, and E. Verheyen 2003

Species Dasymys sua W. Verheyen, Hulselmans, Dierckx, Colyn, Leirs, and E. Verheyen 2003

Discussion: Dasymys Division. Closest phylogenetic allies unidentified. Many pelage, cranial, and dental traits of Dasymys suggest alliance with Aethomys, but Misonne (1969) considered Dasymys to be the most phylogenetically isolated of endemic African murines. In their analysis based on microcomplement fixation of albumin, Watts and Baverstock (1995 a) placed Dasymys as the sister group to their African, Australasian, and Southeast Asian clades. Despite the seemingly isolated position of Dasymys, and its apparent slow rate of albumin evolution, Watts and Baverstock were reluctant to highlight the genus as a separate clade and provisionally included it within their African group. Analyses of combined mtDNA (cytochrome b) and 12S and 16S rRNA gene fragments by Ducroz et al. (2001) placed Dasymys near Hybomys in a clade basal to an arvicanthine clade (containing Lemniscomys, Desmomys, Rhabdomys, Pelomys, Mylomys, and Arvicanthis); an Aethomys chrysophilus / Grammomys dolichurus clade was situated basal to the Dasymys / Hybomys cluster. Ducroz et al.’s (2001) analysis using only cytochrome b sequences placed Dasymys basal to a cluster comprised of Hybomys, otomyines, Grammomys, and Aethomys, a Micaelamys clade, and the arvicanthine cluster. The association with Grammomys, Aethomys, Hybomys, and Arvicanthis is supported by DNA/DNA hybridization (Chevret, 1994). Lecompte’s (2003) phylogenetic analyses of mtDNA cytochrome b and nuclear IRBP sequences identified a clade containing Dasymys, Hybomys, Grammomys, and some arvicanthines ( Arvicanthis, Lemniscomys, and Pelomys). Castiglia et al.’ s (2003 b) phylogenetic analyses of mtDNA cytochrome b sequences revealed two patterns. In one tree Dasymys clustered with Hybomys in a clade that was basal to a clade containing arvicanthines ( Desmomys, Rhabdomys, Pelomys, Mylomys, Arvicanthis, Lemniscomys) and Micaelamys; in another tree, Dasymys is basal to a clade containing otomyines with the arvicanthines basal to the Dasymys and otomyine clusters. Such molecular studies promise insight but generic and species sampling is still limited; until better resolution is achieved we restrict Dasymys to its own division. Chromosomal data summarized by Carleton and Martinez (1991). Sperm morphology similar to that of Australian ‘hydromyines’ (Breed, 1995 a). Measurements, localities with coordinates, and other information listed for holotypes of Dasymys taxa by W. Verheyen et al. (2003:53-54).

Species diversity within Dasymys has shifted from Ellerman’s (1941:121) view, "It appears very unlikely that there is more than one species of this genus...," to the recognition of the nine species covered here, which is still likely an underestimate. Our accounts derive primarily from study of museum specimens and the taxonomic reviews by Carleton and Martinez (1991) and W. Verheyen et al. (2003). Wetland habitats combined with dense ground cover are associated with the presence of Dasymys and, as Carleton and Martinez (1991:429) noted, the "... inherently patchy nature of such wetland environments may account for the interrupted distribution among Dasymys populations..."; past fragmentation of such moist habitats with subsequent genetic isolation of populations may partly explain the species diversity that today characterizes the genus. At least two extinct species have been identified from early Pleistocene beds of South Africa (Avery, 1998, 2000), and the genus is represented by Pleistocene fossils from Namibia (Senut et al., 1992); see review by Denys (1999).