Species
Stenocephalemys albipes
Description
Stenocephalemys albipes (Rüppel, 1842)
Mus albipes Rüppell, 1842
Mus leucopus Fitzinger, 1867 – Eritrea, Massawa (error!)
Mus albipes var. minor Heuglin, 1877 – Eritrea, Modat valley, W of Massawa (error!)
Epimys rufidorsalis alettensis Frick, 1914 – Aletta, Ethiopia
Epimys rufidorsalis ankoberensis Frick, 1914 – Ankober, Ethiopia
Type locality: Massawa, Eritrea (error!).
The type locality of the species (Massawa, Eritrea) is clearly erroneous (see more details in Mizerovská et al. 2020). It is the most widespread of the four named species of the genus. It prefers various forest types at lower elevations, but it is probably more opportunistic, as it was also recorded in deforested areas, fields and even in human settlements. It occurs in sympatry with S. griseicauda in the Arsi Mts. (Kostin et al. 2019), S. ruppi in the Chingawa Forest (Mizerovská et al. 2020) and S. zimai around the camp sites in the Semien Mountains and Choke Mountain (Craig et al. 2020, Kostin et al. 2020), but it can usually be readily recognized by its external morphology. The species is abundant, especially in the forests of southern Ethiopia, where it forms the predominant component of small mammal assemblages., but at most localities it is the only species of the genus. It has a wide elevational distribution range (800-3300 m a.s.l. according to Yalden et al. 1976, 1996). The lowest (genetically confirmed) elevation records are from the humid forests of south-western Ethiopia (Godare forest 1220 m), where many typical species of the Ethiopian Highlands reach their lower elevational limits (Yalden et al. 1976). On the contrary, numerous Ethiopian endemics reach their highest elevation records in the much drier mountains of northern Ethiopia. This is true also for S. albipes which was recorded around the Sankaber camp in the Semien Mts. at an elevation ca. 3250 m a.s.l. A small commensal population (represented by three specimens in Bryja et al. 2018a) was found even higher, at the Chennek camp site (3800 m a.s.l.). Similarly, Müller (1977) found it absent from grassland areas in the Semien Mts. (3700 m a.s.l.), and encountered it there only in buildings. At such high elevation, usually covered by non-forest vegetation, it appears to be replaced by other congenerics (Müller 1977, Rupp 1980, Yalden 1988, Bryja et al. 2018). Bryja et al. (2018) described a profound intraspecific geographical structure of S. albipes in mtDNA, but very low intraspecific divergence at the nuclear markers. This suggests the rapid spread of this species across most Ethiopian Highlands followed by fragmentation of suitable forest habitats during the dry Pleistocene periods and intensive lineage sorting of mtDNA in small fragmented populations. During the expansion of its range in the humid interglacial periods of the Pleistocene, S. albipes encountered other congeners of the genus and occasionally hybridized with them. As a result, Bryja et al. (2018) observed population of S. sokolovi in high elevation of Borena Saynt NP, and S. ruppi in the Chingawa forest in south-western Ethiopia, with introgressed mtDNA of S. albipes. Therefore, caution is needed when using only mitochondrial sequences for identification of Stenocephalemys species. The chromosomal data on S. albipes (Lavrenchenko et al. 1997, 1999, Corti et al. 1999, Bulatova & Lavrenchenko 2005) shows a diploid number 2n = 46 and differ in the autosomal arm number (NFa = 58, 50-53 or 50, respectively). The variation in the number of bi-armed autosomes (from 3 to 7 pairs) may be associated with different degrees of chromosomal contraction carrying very short arms in different studies. To exclude this uncertainty, Bryja et al. (2018) compared NFa counts only for “true” metacentrics and submetacentrics against one-armed groups, which comprised acro- and subacrocentrics. On this basis, the karyotype of S. albipes can be described as 2n = 46, NFa = 50 or 51, which is widespread across Ethiopia (see more details in Bryja et al. 2018).
Taxonomy
Stenocephalemys albipes is a species. It belogs to the Muridae family.
