Grammomys polionops (Osgood, 1910)

Species: Grammomys polionops (Osgood, 1910)

Synonymy:

Thamnomys surdaster polionops Osgood, 1910

Thamnomys ochraceus G. M. Allen, 1912

Grammomys minnae Hutterer & Dieterlen, 1984

Grammomys brevirostris Kryštufek, 2008

Type locality: Lukenya Mt. , Ulukenia Hills, Kenya .

Distribution: Eastern Arc Mountains (e.g. Udzungwa and a few other hills; not in Usambara), the Gregory Rift in northern Tanzania and southern Kenya, and the southern part of the Great Rift Valley in Ethiopia.

Comments: The name polionops is the oldest available name for populations grouped in the INFOMAP MOTU VII and branch-cutting MOTU 6 ( Figs 3 View Figure 3 , 7D View Figure 7 ). The species inhabits relatively dry forests and woodlands along the Gregory branch of the East African Rift. At one locality (north of Nanyuki, Kenya), the two mtDNA lineages of G. polionops (m7 and m8) were found together with G. ibeanus (mtDNA lineage m4), but the two species were clearly distinguishable by ddRAD data, suggesting a reproductive barrier between these two species. In the Eastern Arc Mountains and Northern Highlands of Tanzania and southern Kenya, the species can be sympatric with G. surdaster , and the mechanisms of their co-occurrence require further studies (e.g. how they differ morphologically and ecologically and whether they can hybridize).

The taxon from the vicinity of Arba Minch in Ethiopia was described as G. minnae , based on karyotype ( Hutterer and Dieterlen 1984), but genomic data were not able to distinguish it from the populations in central and southern Kenya. Both the holotype and the paratype of minnae were clearly classified to the macmillani group by the morphometric analysis. The holotype of brevirostris , described from Loita Plains by Kryštufek (2008), was sequenced at CYTB, and it belongs to the mitochondrial lineage m8, clustering with the genotyped specimens from the nearby Loita Hills (Supporting Information, File S1). The morphologically distinct holotype of brevirostris might represent a typical individual of G. polionops , because no individuals assigned here to G. polionops were included in Kryštufek’s (2008) morphological comparison. The holotype of brevirostris is assigned to the macmillani group (that also includes G. polionops ) with PP = 0.85 ( Table 1 View Table 1 ).

Karyotype: Three very different karyotypes (but all of them with low diploid numbers; Fig. 2 View Figure 2 ) were described for populations that we assign to G. polionops . The role of such different karyotypes in reproductive isolation should be explored further. The specimen from northern Tanzania (a male from Jipe, no. T50485, belonging to mtDNA lineage m7) had 2 n = 20, NFa = 31 ( Corti et al. 2005). Another specimen from northern Tanzania (a female from Ndaleta, ind. no. TZ12, with mtDNA of m8) had 2 n = 27 and NFa = 39 ( Fadda et al. 2001). Finally, the taxon minnae from the Bulcha Forest in Ethiopia was described based on the karyotype 2 n = 32 and NF = 64 (figured by Olert et al. 1978). The same karyotype was found recently in specimens from the Arero forest in southern Ethiopia (L. Lavrenchenko, unpub. obs.) with mtDNA of the lineage m11.