Dasymys incomtus (Sundevall 1846)

[Dasymys] incomtus (Sundevall 1846), Ofv. K. Svenska Vet.-Akad. Forhandl. Stockholm, Vol. 1846, 3: 120.

Type Locality: South Africa, "Caffraria prope Portum Natal," (= Durban, KwaZulu-Natal); 29°15’S, 31°01’E (W. Verheyen et al., 2003).

Vernacular Names: Common Dasymys.

Synonyms: Dasymys bentleyae (Thomas 1892); Dasymys capensis Roberts 1936; Dasymys edsoni Hatt 1934; Dasymys fuscus De Winton 1897; Dasymys griseifrons Osgood 1936; Dasymys gueinzii Peters 1875; Dasymys helukus Heller 1910; Dasymys longipilosus Eisentraut 1963; Dasymys medius Thomas 1906; Dasymys nigridius Hollister 1916; Dasymys orthos Heller 1911; Dasymys palustris Setzer 1956; Dasymys savannus Heller 1911; Dasymys shawi Kershaw 1924 .

Distribution: South Africa (de Graaff, 1997 g; Skinner and Smithers, 1990; Taylor, 1998), Malawi (Ansell and Dowsett, 1988), Zambia (Ansell, 1978), Zimbabwe (Smithers and Wilson, 1979), C and S Mozambique (Smithers and Lobao Tello, 1976), Angola (Crawford-Cabral, 1998), Dem. Rep. Congo, Uganda (Delaney, 1975), Kenya (Hollister, 1919), Tanzania (Swynnerton and Hayman, 1951), Ethiopia, S Sudan (Setzer, 1956); limits unknown. Also recorded from N Botswana (Smithers, 1971), but unclear whether these records represent D. incomtus, D. cabrali, or both species.

Conservation: IUCN – Data Deficient.

Discussion: Despite recent attempts at systematic revision (e. g., W. Verheyen et al., 2003), morphological and geographic definition of D. incomtus remains intractable and probably a complex of several species. W. Verheyen et al. (2003), for example, considered bentleyae to be one of the synonyms of D. incomtus in one part of their report (p. 36) but elsewhere treated it as a separate species with an expansive range "... consisting mainly of the fringes of the lowland rain forest between the Atlantic coast and the western rift...," and "... in the fringes of the western forest block and in the region adjacent to the highlands of the western flank of Lake Malawi " (p. 48). Dasymys incomtus, according to W. Verheyen et al. (2003:48), has the widest range, covering "... the moist woodlands of western, northcentral and northeastern Africa,... the moist woodlands of the north western and eastern part of southern Africa and... approximately the western half of the inland of Kenya and Tanzania ...." Chromosomal variation from South African specimens reported by Gordon (1991:413) who noted it "is equivocal whether the different chromosomal forms represent distinct species characterized by fixed rearrangements or a chromosomally polymorphic species." Allozymic and cranial differences are also concordant with the chromosomal distinctions (2n = 38, FN = 44 from KwaZulu-Natal; 2n = 46, FN = 44 from Northern Province) between the populations (Mullin et al., 2002). Non-geographic morphometric variation in samples from Southern Africa subregion reported by Mullin et al. (2001). Spermatozoon morphology documented by Breed (1995 a) and Breed and Pillay (1999). A morphometric analysis by Crawford-Cabral and Pacheco (1989) suggested that Angolan bentleyae is a separate species, but later Crawford-Cabral (1998) listed it as a subspecies of D. incomtus and noted the wide gap in geographic range between the Angolan populations and those of typical D. incomtus .

Recorded from fynbos, grassland, and savanna woodlands biomes in Southern African Subregion (Mugo et al., 1995); those populations reviewed by Skinner and Smithers (1990) and de Graaff (1997 g). Documented from the isolated Harenna Forest of S Ethiopia by Lavrenchenko (2000) who claimed it was a new record for the entire region of the Ethiopian Rift Valley, but Yalden et al. (1996) had already recorded collections from the Didessa River valley and the Jimma region in S Ethiopia. Habitat and altitudinal distribution on Ugandan slopes of Mt Elgon reported by Clausnitzer and Kityo (2001), and in SW Uganda by Lunde and Sarmiento (2002).