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Accueil du site → Doctorat → Allemagne → 2015 → Systematics and biogeography of the genus Mastomys (Rodentia : Muridae) occurring in Namibia and adjacent countries

Humboldt University of Berlin (2015)

Systematics and biogeography of the genus Mastomys (Rodentia : Muridae) occurring in Namibia and adjacent countries

Eiseb, Seth Johannes

Titre : Systematics and biogeography of the genus Mastomys (Rodentia : Muridae) occurring in Namibia and adjacent countries.

Auteur : Eiseb, Seth Johannes

Université de soutenance : Humboldt University of Berlin

Grade : Doctor rerum naturalium 2015

Résumé
Study aims to summarise the patterns of morphological, cytogenetic and genetic variation of genus Mastomys across the south-west arid region of southern Africa. The methodological approach included skull morphometrics, karyotyping and cytochrome-b gene sequencing. Traditional morphometrics study did not yield clear morphological differences between the three species. Geometric morphometrics analysis was more successful with clear differences, in the shape of the skulls based on landmarks from both the dorsal and ventral views. Results obtained with cytogenetical and molecular methods revealed three forms of Mastomys with different karyotypes and mtDNA clades. These were assigned to M. coucha (2n = 36, aFN = 60/60), M. natalensis (2n = 32, aFN = 57/58) and M. shortridgei (2n = 36, aFN = 51/52). The mtDNA divergence between the species M. coucha and M. shortridgei was relatively low (1.3%), additionally the molecular clock estimated M. shortridgei to be a recent off-shoot of M. coucha (0.71 Mya). It is estimated that the lake Palaeo-Makgadikgadi, in present day Botswana, covered much of the eastern Kalahari basin. It could be that the peripheral ancestral population of M. shortridgei came in contact with the lake Palaeo-Makgadikgadi and was isolated with the shrinking lake Palaeo-Makgadikgadi during the End-Pleistocene to Early Holocene. Over time ancestral populations of M. shortridgei became adapted to the local swampy environmental conditions. M. coucha and M. natalensis have distinct geographical distribution influenced by precipitation. M. coucha mainly occurs in the low rainfall areas of central Namibia, whereas M. natalensis occurs in higher rainfall areas of north-central and north-eastern Namibia, extending into Angola and northern Botswana. The M. shortridgei specimens were only trapped along the Okavango River swamps in northern Botswana and south-eastern Angola.

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