Genetic variation in the African rodent subfamily Otomyinae (Muridae)

Abstract

Results of chromosome G- and C-banding studies on 12 specimens of the ice rat, Otomys sloggetti robertsi, from three localities and allozyme analyses of seven individuals from two localities are reported. The subspecies karyotype contains 42, mostly acrocentric, chromosomes. No chromosomal variation was detected among animals from these localities. Allozyme analysis tentatively suggested a limited gene flow between the two populations examined.

When is a species not a species? Uncoupled phenotypic, karyotypic and genotypic divergence in two species of South African laminate‐toothed rats (Murinae: Otomyini)

“…All karyotypes except O. karoensis conformed to previously published work (Robinson & Elder, 1987; Contrafatto et al , 1992 a,b ). Because the karyotype of O. karoensis has never been published, its chromosomes were arranged based on size as done for O. irroratus .…”

“…Vlei rats ( Otomys Cuvier, 1824), Karoo or ice rats ( Myotomys Roberts, 1929) and whistling rats ( Parotomys Thomas, 1918) of the murine tribe Otomyini (‘laminate‐toothed rats’) comprise 23 species that are endemic to sub‐Saharan Africa (mostly to Afromontane habitats) and are characterized by morphological conservatism but karyotypic diversity (Robinson & Elder, 1987; Contrafatto et al , 1992 a,b,c ; Meester et al , 1992; Contrafatto, 1996; Rambau, Elder & Robinson, 2001; Musser & Carleton, 2005).…”

“…Cytotypes are defined by the variable presence of heterochromatic short arms, pericentric inversions, a centric fusion and variable number of B chromosomes (all of which are unlikely to result in reproductive isolation), as well as an important, complex tandem fusion mutation in the A1 cytotype (Contrafatto et al , 1992 c ; Rambau et al , 1997; Engelbrecht et al , 2006), which has been shown to cause infertility of hybrids (Pillay, Willan & Meester, 1995). Cytotypes can be partly distinguished by cranial shape but not by size (Taylor, Kumirai & Contrafatto, 2004 b ), and not by allozymes (Taylor et al , 1992), immuno‐electro‐transfer analysis (Contrafatto et al , 1997) or limited mitochondrial DNA sequences (Maree, 2002). Here we test the taxonomic validity and evolutionary significance of a previously described chromosomal polytypy in O. irroratus based on integrated molecular, cytogenetic and morphometric data.…”

Differences in alarm vocalizations of sympatric populations of the whistling rats, Parotomys brantsii and P. littledalei (Rodentia: Muridae)

“…For the otomyine rodents of southern Africa, the species relationships have not been well resolved. However, approaches using immuno-electrotransfer analysis (Contrafatto, David & Goossens-Le Clerq, 1994) and allozymes (Taylor et al, 1989) suggest that P. brantsii and P. littledalei may be more closely related to other otomyine species (whose vocal repertoire does not include a distinct alarm whistle; Kerley, 1997) than to each other. Thus, the distinction of two otomyine genera, Otomys and Parotomys, the latter distinguished by its in¯ated ear bullae, may be misleading.…”

Strong hybrid viability between two widely divergent chromosomal forms of the pouched mouse

“…Chromosome preparations were obtained from the bone marrow (Contrafatto et al ., 1992), as well as from fibroblast cultures generated from explanted ear pinna biopsies (<5 mm 2 ) and spleen cell suspensions (Contrafatto et al ., 1992) with the following modification. To increase the mitotic yield, fibroblast cultures were incubated for 24 h in culture medium (see Contrafatto et al ., 1992) containing 500 μg mL −1 sodium methotrexate (Sigma, St. Louis, MO, USA) and, thereafter, in a fresh culture medium containing 5 μg mL −1 thymidine (Sigma). Microscope slides carrying metaphase spreads were aged by incubation at 37 °C for 48 h before G‐banding using trypsin digestion (Seabright, 1971).…”