Get access

When is a species not a species? Uncoupled phenotypic, karyotypic and genotypic divergence in two species of South African laminate-toothed rats (Murinae: Otomyini)

Authors

  • P. J. Taylor,

    1. Durban Natural Science Museum, Durban, South Africa
    Search for more papers by this author
  • S. Maree,

    1. Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
    2. Molecular Ecology and Evolution Programme, Department of Genetics, University of Pretoria, Pretoria, South Africa
    Search for more papers by this author
  • J. Van Sandwyk,

    1. Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
    Search for more papers by this author
  • R. Baxter,

    1. Department of Ecology and Resource Management, University of Venda, Thohoyandou, South Africa
    Search for more papers by this author
  • R. V. Rambau

    1. Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
    2. DST-NRF Centre of Excellence for Invasion Biology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
    Search for more papers by this author

  • Editor: Jean-Nicolas Volff

Correspondence
Peter John Taylor, Durban Natural Science Museum, PO Box 4085, Durban 4000, South Africa. Email: taylorpeter@durban.gov.za

Abstract

Chromosomal polytypy, morphological conservatism and absence of data have frustrated the taxonomic revision of two species of southern African-endemic laminate-toothed rats (Otomys irroratus and Otomys saundersiae s.l.). New cytogenetic (G-banding and fluorescence in situ hybridization), DNA sequence [cytochrome b (cyt b) gene] and geometric morphometric data demonstrate the synonymy of O. saundersiae from Grahamstown (Eastern Cape, South Africa) under O. irroratus, and the validity of Otomys karoensis from the Fynbos Biome of the Western Cape. Phenotypic dimorphism in pelage colour and cranial morphology in O. irroratus from the climatically unpredictable Albany Thicket (=Savanna) Biome of the Eastern Cape results from the retention of allometric paedomorphic traits in some adults (saundersiae morph) but not others. The same paedomorphic traits are associated with speciation and karyotypic and genetic differentiation in O. karoensis. Within O. irroratus, two phenotypically and genotypically (cyt b divergence=6.4%) divergent lineages correspond with the Fynbos/Albany Thicket and Grassland biomes. Incipient speciation in O. irroratus seems to be associated with ecology rather than karyotype.

Get access to the full text of this article

Ancillary