Grammomys ibeanus (Osgood, 1910)

Species: Grammomys ibeanus (Osgood, 1910) View in CoL

Synonymy:

Thamnomys ibeanus Osgood, 1910

Thamnomys surdaster lutosus Dollman, 1911

Thamnomys gigas Dollman, 1911

Type locality: Kenya, Molo .

Distribution: Montane forests in Kenyan Highlands, eastern Uganda, South Sudan, south-western Ethiopia, and Mt. Kilimanjaro.

Comments: Hutterer and Dieterlen (1984) treated ibeanus as a form of G. cometes (both taxa are relatively large-bodied), but the striking morphological distinctions between samples of ibeanus and the type series of cometes analysed by Musser and Carleton (2005) prompted specific ranking of ibeanus . We include in G. ibeanus two INFOMAP gene pools: MOTU IV from montane forests in Kenyan Highlands, eastern Uganda (Mt. Elgon and Mt. Morungole), the Imatong Mountains in South Sudan, highlands in the Ilemi Triangle, and forests of south-western Ethiopia, and MOTU V from Mt. Kilimanjaro. Both MOTUs are sister clades in both mitochondrial and genomic trees (albeit in the former with only weak support; Fig. 2 View Figure 2 ). The species can be sympatric with G. macmillani (Imatong Mountains, north-eastern Uganda, and western Kenya) and G. polionops (Nanyuki, Kenya), but the sympatric populations are genetically well distinguishable in both mtDNA and nuDNA ( Fig. 7 View Figure 7 ), supporting their reproductive isolation. The ecological differences, e.g. the preference for different types of habitats and elevation, are worth further studies. The population from Mt. Kilimanjaro (MOTU V) is highly distinct genetically ( Fig. 3 View Figure 3 ) and separated geographically from all other populations of G. ibeanus . More detailed morphological and ecological studies in the future might possibly lead to its full species status (and proposal of a new name, given that no Grammomys was described from Mt. Kilimanjaro).

The specimens in FMNH identified as G. ibeanus from the Eastern Arc Mountains in Tanzania, from Malawi, and from Mozambique belong genetically to the cometes group (sensu Bryja et al. 2017) and represent G. cometes (as defined in this study; see above). The taxon lutosus (from Mt. Nyiro in Kenya) was listed as a subspecies of G. ibeanus by Allen (1939). In our morphological analysis, it was classified into the surdaster group (PP = 0.67), but the holotype is a sub-adult specimen with a broken skull, and the analysis was based on only a subset of landmarks. Geographically, it might belong to G. ibeanus , hence we keep it as its younger synonym. The holotype of T. gigas from Mt. Kenya in our opinion simply represents an extremely large individual of G. ibeanus (see also Musser and Carleton 2005, Denys et al. 2011). All recently genotyped specimens from Mt. Kenya (collected by K. Onditi and colleagues) have mtDNA of the lineage m4 (Supporting Information, File S1), supporting this conclusion. The holotype of gigas was classified as a member of the cometes group (with PP = 0.95; Table 1 View Table 1 ), which is attributable to its large size. When only shape is considered, it fits in the macmillani group (PP = 0.90).

Karyotype: Not known.