Ethiopian Vlei Rat

discussion

Discussion: Dieterlen (1968) and Petter (1982) viewed typus as another variant of a highly polymorphic O. irroratus, a conclusion that conflicts with their morphological discrimination as presented elsewhere (e. g., Ansell, 1978; Bohmann, 1952; Kingdon, 1974 b; Misonne, 1974). Nonetheless, the synonyms listed and wide East African distribution as conveyed by the classifications of Bohmann (1952) and Misonne (1974) embrace such immense morphological heterogeneity that diagnosis as a single species is incomprehensible and geographically improbable. In our view, O. typus proper corresponds to those populations with grizzled brown pelage, a moderately vaulted skull, M 3 with 8 - 9 laminae, and two strongly creased grooves on the lower incisors, a morphology endemic to the highlands of Ethiopia. Even so narrowly delineated, the conspecific stature of Ethiopian populations is highly suspect, as suggested by the karyotypic and allozymic diversity reported for Otomys in the Bale Mountains (Lavrenchenko et al., 1997; 2000). Whether the exceptional variation reported by those authors is partly attributable to the presence of the tropicalis elgonis complex (see above) at lower elevations or y

Order Rodentia - Family Muridae

distribution

Distribution: Highlands, ca. 1800 - 4000 m, of NC (Gonder) to SC (Gamo Gofa, N Sidamo, and Bale) Ethiopia (Yalden et al., 1976: Fig. 32).

Order Rodentia - Family Muridae

materials_examined

Holotype: BMNH 2.9. 9.19. Type locality: Gonder Province, Simien Mts .. Taxonomic notes: Otomys typus is a monophyletic genomic clade, sister to O. helleri (Fig. 3). Both species are only weakly differentiated, both at their genomes and skull morphology, but we prefer to keep them as two allopatric species, awaiting further studies of their possible contact zones in central Ethiopia (Fig. 2). Specimens from the Chercher Mts. and Hirna (east of GRV) were assigned to O. typus based on morphometric analysis by Taylor et al. (2011), but they instead represent O. helleri, based on phylogeographic paưerns of other taxa (e. g. Mizerovská et al. 2020). We do not include degeni as a synonym of O. typus [contrary to Taylor et al. (2011) and previous taxonomic revisions]. This taxon was described by Thomas (1902) from Gombitchu (8000 ss = 2438 m a. s. l.) in Shoa, not far from Addis Ababa. The morphological analysis of the holotype was inconclusive (Taylor et al. 2011: fig. 5). Further, the type locality was visited by one of the authors (L. A. L.), and the mid-elevation habitat is very unsuitable for both O. typus and O. helleri. It is also possible that degeni is an available name for O. cf

Genomic diversity, evolutionary history, and species limits of the endemic Ethiopian laminate-toothed rats (genus Otomys, Rodentia: Muridae)

discussion

COMMENTS: Dieterlen (1968) and Petter (1982) viewed typus as another variant of a highly polymorphic O. irroratus, a conclusion which seems at odds with their morphological discrimination as presented elsewhere (e. g., Ansell, 1978; Bohmann, 1952; Kingdon, 1974; Misonne, 1974). The list of synonyms observes the classifications of Bohmann (1952) and Misonne (1974). Their conspecific stature is highly suspect and invites rigorous specimen-based corroboration that also addresses possible relationships to certain forms masquerading under tropicalis. The occurrence of greater species endemism thoughout the isolated East African highlands and volcanoes deserves more serious consideration than it has received to date.

Order Rodentia - Family Muridae