Southern African Vlei Rat

discussion

Discussion: Bohmann (1952) established a broad, improbably polymorphic definition of O. irroratus, including some 23 subspecies, a concept further enlarged by Dieterlen (1968) and Petter (1982) and collectively enveloping the following forms here (and elsewhere) treated as separate species (see individual accounts): O. anchietae, O. angoniensis, O. barbouri, O. burtoni, O. cuanzensis, O. dollmani, O. jacksoni, O. laminatus, O. maximus, O. orestes, O. tropicalis, O. typus, and O. uzungwensis. Although followed to a greater or lesser extent (e. g., Delany, 1975; Honacki et al., 1982; Kingdon, 1974 b), such an inclusive species construct has been refuted by others who identify O. irroratus proper as a species indigenous to southern Africa, south of the Zambezi River (e. g., De Graaff, 1981; Meester et al., 1986; Misonne, 1974; Taylor and Kumirai, 2001). Morphometrically distinguishable from East African forms, such as O. typus and O. tropicalis, and M 3 characteristically possessing 6 laminae compared with 7 - 8 in those forms (Dollman, 1915; Thomas, 1918 b; Taylor and Kumirai, 2001). A subject of intensive investigation of intraspecific patterns of differentiation, O. irroratus sensu

Order Rodentia - Family Muridae

distribution

Distribution: Mesic savannah and grasslands of southern Africa — S Western Cape Province to Limpopo Province, South Africa; disjunct populations in W South Africa and in E Zimbabwe and contiguous Mozambique (De Graaff, 1981: 146).

Order Rodentia - Family Muridae

materials_examined

Type Locality: South Africa, Western Cape Province, Cape Town district, near Constantia (fixed by A. Smith, 1834: 149, in supplying replacement name typicus; see Meester et al., 1986: 250).

Order Rodentia - Family Muridae

discussion

COMMENTS: Bohmann (1952) established a broad, highly polymorphic definition of O. irroratus, then including among his 23 subspecies angoniensis and maximus (see those accounts). Presumably excepting angoniensis and maximus, Dieterlen (1968) and Petter (1982) further enlarged Bohmann's concept of irroratus to subsume the following forms here (and elsewhere) treated as separate species (see individual accounts): anchietae, laminatus, tropicalis, and typus. Although followed to a greater or lesser extent (e. g., Delany, 1975; Kingdon, 1974), such an inclusive species construct is disputed by others who restrict O. irroratus proper to southern Africa (e. g., Meester et al., 1986; Misonne, 1974). G-banded comparisons reveal a karyotype that is highly derived (Robinson and Elder, 1987). Cytogenetic variation extensive among South African population samples (Contrafatto et al., 1992 a). See Bronner et al. (1988, Mammalian Species, 308).

Order Rodentia - Family Muridae