Browsing by Author "Oguge, N."

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    Chromosomal diversity in the genus Arvicanthis (Rodentia, Muridae) from East Africa: a taxonomic and phylogenetic evaluation
    (Blackwell Verlag, Berlin, 2006) Castiglia, R.; Bekele, A.; Makundi, R.; Oguge, N.; Corti, M.
    In this paper we discuss the contribution of cytogenetics to the systematics of Arvicanthis in East Africa, by reviewing all the known chromosomal cytotypes of the genus in the area. We also provide G- and C-banding comparisons for two recently described karyotypes, provisionally named ANI-5 (2n 1⁄4 56, NFa 1⁄4 62) and ANI-6 (2n 1⁄4 60, NFa 1⁄4 72). This, therefore, brings the total number of known cytotypes in this area to 10. Five of these correspond to the species recognized by the latest rodent checklist, i.e. A. nairobae (2n 1⁄4 62, NFa 1⁄4 78), A. neumanni (2n 1⁄4 52–53, NFa 1⁄4 62), A. blicki (2n 1⁄4 48, NFa 1⁄4 62), A. abyssinicus (2n 1⁄4 62, NFa 1⁄4 64) and A. niloticus (2n 1⁄4 62, NFa 1⁄4 60–62). The taxonomic status of the remaining five cytotypes (A. cf. somalicus, 2n 1⁄4 62 NFa 1⁄4 62–63; ANI-5, 2n 1⁄4 56, NFa 1⁄4 62; ANI-6/6a 2n 1⁄4 60, NFa 1⁄4 72/76; ANI-7, 2n 1⁄4 56, NFa 1⁄4 78; and ANI-8, 2n 1⁄4 44, NF 1⁄4 72) is discussed. Finally, we reconstruct the phylogenetic relationships among all the known karyotypes on the basis of banding data available for the genus in Africa and show the occurrence of two main clades, each characterized by different types of chromosomal rearrangements. The times of the cladogenetic events, inferred by a molecular clock, indicate that karyotype evolution has accomplished almost all the dichotomic events from the end of the Miocene to the present day. The discovery of a large chromosomal differentiation between populations showing low genetic distances and intrapopulation chromosomal polymorphism suggests that the process of chromosomal differentiation in Arvicanthis is still ongoing and may possibly be responsible for speciation
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    Mitochondrial phylogeny reveals diVerential modes of chromosomal evolution in the genus Tatera (Rodentia: Gerbillinae) in Africa
    (Elsevier Inc., 2005) Colangelo, P.; Corti, M.; Verheyen, E.; Annesi, F.; Oguge, N.; Makundi, Rhodes H.; Verheyen, W.
    The African gerbils of the genus Tatera are widespread and abundant throughout sub-Saharan Africa. There is still today a certain controversy concerning the taxonomy of these rodents and very few attempts have been made to assess their systematic relationships. The present paper introduces Wndings based on the partial sequences of cytochrome b (495 bp) and the 16S rRNA (469 bp) mitochondrial genes of six (T. robusta, T. nigricauda, T. vicina, T. leucogaster, T. valida, and T. kempi) species together with two additional taxa. We also report the karyotypes of T. vicina and T. leucogaster. We propose that T. vicina should be considered as a valid species and show the monophyly of the robusta species group, with the exclusion of T. leucogaster. Our results show there is a diVerent chromosomal evolutionary pattern within the two major lineages, which is recognizable through molecular phylogenetics. One is characterized by karyotype stability and the other by a considerable number of chromosomal rearrangements. The lineage divergence coincides with the formation of the East African Rift. The processes that led to the origin of the East African species seem to be related to the subsequent climatic changes, which caused cyclic contraction and expansion of the savannah biomes. Furthermore, geological activities that characterized East Africa during Plio-Pleistocene may also have contributed to lineage divergence.