Taxonomy and biogeography of the African Pygmy mice, Subgenus Nannomys (Rodentia, Murinae, Mus) in Ivory Coast and Guinea (West Africa)

Abstract

Recent investigations in Guinea and IvoryCoast showed that Mus (Nannomys) are hosts of new arenaviruses. However, the taxonomy and biogeography of the western pygmy mice are poorly known, as this genus contains many cryptic species. To improve our taxonomic knowledge on this subgenus and its distribution range in West Africa, we performed a molecular, cytogenetical and morphological study of all Mus (Nannomys) species in this part of Africa. This approach allowed us to detect five species in Guinea (Mus mattheyi, M. minutoides, M. setulosus, M. baoulei, M. musculoides) and four (M. minutoides, M. setulosus, M. baoulei, M. musculoides) in Ivory Coast. Our molecular results confirm the validity of M. baoulei and the extended distribution range of M. mattheyi. We also observed a high degree of genetic differentiation between and within these species, especially within the M. setulosus clade which may be a species complex. The canonical analyses on the craniometrical and external morphological features of the sequenced specimens are insufficient to perfectly separate the studied species. Nevertheless, our results confirm that M. setulosus and M. baoulei are the largest Mus species that occur in Guinea and Ivory Coast. M. baoulei can be distinguished by its short tail and M. setulosus by an enlarged and bilobated lower molar (M3). Among the smaller species, M. musculoides is difficult to identify using morphological data alone, but differences in tail length proportions, size of tympanic bullae, the length and shape of the upper dental row allow identification of this species with some confidence. Our results allow us to provide some conclusions about the distribution ranges of the studied Mus (Nannomys) spp. in both countries and to discuss their presence in relation to vegetation, habitat and human settlements.

New data on the taxonomy and distribution of Rodentia (Mammalia) from the western and coastal regions of Guinea West Africa

“…This is the first record of M. mattheyi in Guinea and its distribution could correspond to the so-called Guinean savannas zone. A cytB molecular analysis confirms this attribution (Kan Kouassi et al 2008). …”

“…Among small mammals collected, 139 Mastomys from Mankoutan, Altou, Yerende, Koumbanyi and 8 Mus from Altou, Kandiafara, Boké were treated by DNA sequencing for cytochrome b by two of us (KKS and AL) only for confirmation of morphological and cytogenetic taxonomic identifications following protocols of Lecompte et al (2005b) or following standard procedure in Kan Kouassi et al (2008).…”

Pan-African phylogeny of Mus (subgenus Nannomys) reveals one of the most successful mammal radiations in Africa

“…Specimens from this lineage were found in Guinea and single individuals were sequenced from the eastern Ivory Coast [12] and Ghana [23]. Future more-detailed studies (using more samples, morphology and nuclear markers) are required to resolve whether MOTUs 12 and 13 represent separate species.

The sorella group (Figure 1d):

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Mitochondrial and chromosomal insights into karyotypic evolution of the pygmy mouse, Mus minutoides, in South Africa

“…In a wider biogeographical context, M. minutoides has a vast distribution with a northern limit extending to Kenya in the East and Guinea in the West (Veyrunes et al 2005). Several studies described karyotypes varying from 34 to 22 chromosomes owing to different Rb fusions, but all sharing the diagnostic (X.1) (Y.1) sexautosome fusions (Jotterand-Bellomo 1986;Castiglia et al 2002Castiglia et al , 2006Kan Kouassi et al 2008). None of these autosomal Rb fusions is common to the South African specimens suggesting that the clade 34 is the likely ancestral lineage that colonized South Africa, from which the lineage 18 originated and subsequently diversified.…”