Otomys yaldeni Taylor et al. 2011

Yalden’s Vei Rat

Otomys sp. A: Lavrenchenko et al., (1997).

Otomys typus A: Aniskin et al. (1998).

Holotype: ZMMU 162594; adult male, dry skin and skull, collector’s number 132; collected by L.A. Lavrenchenko, 17 February 1995.

Type locality: Ethiopia, vicinity of Dinsho, Bale Mountains, 3170 m a.s.l..

Taxonomicnotes: ThesmallestrepresentativeofEthiopian Otomys, reported only from the Bale Mts., differing from O. simiensis by its smaller size and karyotype (Taylor et al. 2011). There are no DNA sequences of this species, and its phylogenetic position is unresolved. We assigned the animals of the SIMIENSIS group from Ankober to O. cf. yaldeni. The possible conspecificity of Ankober and Bale populations was further supported by morphological analysis that included the type material of O. yaldeni (Fig. 7). The population in Ankober represents the first record of O. yaldeni west of GRV, but future studies should confirm it by the sequencing of O. yaldeni from Bale (from where only old museum material is now available). The biogeographical link between Bale-Arsi (east of GRV) and DebreSina-Ankober-Guwasa (west of GRV) has been observed in various vertebrate taxa, including rodents (e.g. Stenocephalemys — Bryja et al. 2018; Arvicanthis — Bryja et al. 2019b). An alternative taxonomic solution could be the conspecificity of O. yaldeni and O. simiensis, which is the solution proposed by InfoMap, and the records from Ankober just fill the gap between previously very distant known (and type) localities of both species (see also the discussion about the possible hybrid origin of the population in the Borena Saynt NP above).

Ecological notes: Specimens of O. yaldeni in the Bale Mts. were collected in a mosaic habitat of forest (Juniperus procera, Hypericum revolutum, and Rosa abyssinica), open grassy patches (including: Euphorbia dumalis, Festuca abyssinica, etc.), Afromontane forest, moorland with Erica trimera, open woodland, or bamboo patches. In Ankober, the population was found in a dense Erica growth.

Distribution: The distribution of this species was restricted to the northern (Dinsho and Goba areas, from 3170 to 3800 m a.s.l.) and southern (70 km NW Kebre Mengist, 2650 m) slopes of the Bale Mts. (Taylor et al. 2011, Kostin et al. 2019). Here we documented a conspecific population from Ankober, west of GRV, at elevation 3194 m a.s.l. Morphologically and genetically similar specimens were also found in the Borena Saynt NP, leaving the taxonomic assignment of this population open (see O. simiensis account).

The TYPUS group

There are three species formally described in this Ethiopian clade (Taylor et al. 2011). Genomic data suggest that all of them are very similar and diverged very recently. InfoMap solution proposes only a single gene pool (i.e. genetic species), although relatively strongly structured geographically. Morphological analysis (bgPCA; Fig. 8) confirmed slight differences in the skull morphology between three species, and we suggest following the taxonomic arrangement proposed by Taylor et al. (2011). Here we provide numerous new records of all three species and significantly modify their known distribution.