Geometric morphometric analysis of adaptive cranial evolution in southern African laminate-toothed rats (Family: Muridae, Tribe: Otomyini)

Taylor, P.J., Kumirai, A., Contrafatto, G.-C. 2004. Geometric morphometric analysis of adaptive cranial evolution in southern African laminate-toothed rats (Family: Muridae, Tribe: Otomyini). Durban Museum Novitates 29: 110-122. Geometric morphometric analysis of cranial shape and size variation was carried out on laminate-toothed rats (Rodentia: Muridae: Otomyini) from southern Africa, to investigate adaptive evolution and morphometric relationships in eight species, and in cytotype-specific populations within one species, Otomys irroratus. Cranial size and shape variation between species could be explained by climate, habitat, phylogeny and burrowing behaviour. In dorsal shape, Otomys sloggetti (from montane and alpine habitats) and O. unisulcatus (from semi-arid habitats) were morphologically intermediate between arid-adapted (Paromys spp.) and mesic-adapted (O. irroratus, O. angoniensis, O. laminatus, O. tropicalis) lineages, consistent with an independently derived phylogeny. However, in ventral cranial shape and mandibular shape, Parotomys and Otomys were distinct from each other, and O. sloggetti (but not O. unisulcatus) was distinct from its congeners. Species from arid, semi-arid and Mountain Fynbos habitats were significantly smaller in size than remaining mesic-adapted species. Significant correlations were obtained between centroid size and both affine and non-affine components of skull shape in dorsal and ventral (but not mandibular) views. Subtle, but significant shape (but not size) differences were shown to distinguish the South African O. irroratus cytotypes (A, A1, A2, B and C) from the allopatric eastern Zimbabwe B cytotype population of O. irroratus.