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Type: Monograph
Published: 2011-09-13
Page range: 1–66
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Specific limits and emerging diversity patterns in East African populations of laminate-toothed rats, genus Otomys (Muridae: Murinae: Otomyini): Revision of the Otomys typus complex

Durban Natural Science Museum, P. O. Box 4085, Durban, 4000, Department of Ecology & Resource Management, University of Venda, Private Bag X5050, Thohoyandou, 0950, and School of Biological and Conservation Sciences, University of KwaZulu Natal, South Africa
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninsky pr., 33, Moscow, 119071, Russia
Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560-0108, US
Vertebrate Department, Royal Belgian Institute of Natural Sciences,Vautiersstraat 29, 1000 Brussels, Belgium
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa
Molecular Ecology and Evolution Programme, Department of Genetics, University of Pretoria, Pretoria, 0002, South Africa
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa Molecular Ecology and Evolution Programme, Department of Genetics, University of Pretoria, Pretoria, 0002, South Africa
Mammalia Otomys geometric morphometrics cytochrome b 12S rRNA microendemism speciation Afromontane

Abstract

We combined evidence from biogeography, craniodental traits, linear and geometric morphometrics (233 skulls), cytogenetics (karyotypes of 18 individuals) and mitochondrial DNA sequences (44 cytochrome b and 21 12S rRNA sequences) to test species limits within Otomys typus s.l. (Muridae: Murinae: Otomyini), a complex that is patchily distributed across alpine zones of Ethiopia and East Africa. Our results confirm the specific validity of O. dartmouthi, O. jacksoni, O. orestes, and O. uzungwensis, forms recently removed from synonymy under typus s.l.; support elevation of four other alpine forms to species (O. fortior, O. helleri, O. thomasi, and O. zinki); identify three additional new species (O. cheesmani sp. nov., O. simiensis sp. nov., O. yaldeni sp. nov.); and enable redefinition of O. typus s.s. as a species restricted to certain mountains west of the Great Rift Valley in Ethiopia (Simien and Guna Mountains in the north, extending to the highlands of the western rim of the Rift Valley). Phylogenetic interpretation of the cytochrome b data clearly demonstrates that the alpine morphotype once united under O. typus s.l. has originated independently at high elevations on several mountain ranges in eastern and northeastern Africa; although generally adapted to high-elevation vegetation, such alpine species are ecologically segregated from one another. Patterns of morphometric, genetic, and ecological differentiation among populations once misassigned to nominal O. tropicalis and O. typus more parsimoniously reflect regional cladogenesis along elevational gradients, rather than multiple, successive colonization by different ancestral forms from southern Africa as earlier supposed. Although incomplete and preliminary, information gathered for O. tropicalis indicates that it too is a species composite; several lines of research are discussed to redress its polyphyletic content. Our results, together with other recent taxonomic studies of Otomys, appreciably elevate the level of endemism within eastern Africa and underscore the significance of Africa's eastern highlands to the continental diversification of Otomyini.

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