Hylomyscus denniae (Thomas 1906)

[Mus] denniae Thomas 1906, Ann. Mag. Nat. Hist., ser. 7, 18: 144.

Type Locality: Uganda, Mubuku Valley, Ruwenzori East, 7000 ft (2134 m).

Vernacular Names: Montane Hylomyscus.

Synonyms: Hylomyscus anselli Bishop 1979; Hylomyscus endorobae (Heller 1910); Hylomyscus vulcanorum (Lönnberg and Gyldenstolpe 1925) .

Distribution: Montane forest islands in WC Angola, extreme E Dem. Rep. Congo, Uganda, W Rwanda, and Kenya through Tanzania to NE Zambia.

Conservation: IUCN – Lower Risk (lc).

Discussion: The species was superficially reviewed by Hatt (1940 a) and somewhat more thoroughly by Bishop (1979). The records of H. carillus from Chitau and Hanha in WC Angola (Hill and Carter, 1941:98) are based upon examples of what we identify here as H. denniae; additional samples (in FMNH) were collected in the same region on Mt Moco and Mt Soque. Although far west from the nearest records of H. denniae, most morphological characteristics of the Angolan series fall within the range of variation among samples now defined as that species. That variation, however, is appreciable, especially in body size, and its significance in determining whether one or more species is present in what is now regarded as H. denniae has to be assessed by systematic revision; certainly more than one species is represented. The distribution of H. denniae like populations in afromontane habitats of East Africa and the Angolan plateau parallels the pattern seen in Rhabdomys dilectus (see account). Stanley et al. (1998) discussed distribution in the Eastern Arc Mtns of Tanzania. Altitudinal distribution of H. denniae on Ugandan slopes of Ruwenzori Mtns reviewed by Kerbis Peterhans et al. (1998), who regarded true H. denniae as a Ruwenzori endemic. Habitat and altitudinal distribution on Ugandan slopes of Mt Elgon documented by Clausnitzer and Kityo (2001).

In their principle components analysis of holotypes, Van der Straeten and Robbins (1997) interpreted the score for the holotype of endorobae as falling within the Praomys cluster. But that specimen is part of a large series used by Heller to describe endorobae and in a preliminary multivariate analysis generated by Carleton, the entire series forms a swarm overlapping the cluster of denniae from Ruwenzori. The holotype is a large individual and it is not surprising that in a principle components analysis of holotypes alone it would fall near or among small holotypes of Praomys . The holotype of endorobae also has all the qualitative traits we associate with Hylomyscus and not Praomys: scarcely expressed cusps t3 and t9 (the latter just a slight spur off cusp t8), zygomatic plate relatively narrow and the notch shallow, and digit 5 of hindfoot about as long as digits 2-4.