Phylogeny of the African murid tribe Otomyini (Rodentia), based on morphological and allozyme evidence

Abstract

Based on a cladistic analysis of 45 morphological (craniodental) and 46 binary allozyme characters, previous systematic treatments of the African murid tribe, Otomyini (laminate‐toothed rats), are reviewed. Cladistic analysis of the craniodental data, involving eight outgroup taxa, confirmed the monophyly of the Otomyini, and suggested Pelomys to represent the sister genus of the Otomyini. Craniodental synapomorphies provided strong support for certain basal relationships among Otomyini rodents, reinforcing available palaeontological evidence. However, poor statistical (Bremer decay index) support was obtained for terminal relationships. The data presented revealed a ‘mesic clade’ of southern and eastern African species, with Otomys sloggetti basal to this group. The arid‐adapted, southern Africa‐endemic species, Parotomys littledalei, P. brantsii and O. unisulcatus, were all placed basal to the ‘mesic clade’, but did not form a separate ‘arid clade’, as suggested by earlier biochemical studies. Two allozyme synapomorphies supported the existence of the ‘mesic clade’, separate from arid‐adapted southern African species. A strict cladistic interpretation of the present data did not support the existence of two genera in the tribe, and the two species of Parotomys (whistling rats) should be transferred to Otomys. At the species level, specific identity of O. lacustris and O. barbouri, distinct from O. anchietae, was supported by several autapomorphies, and O. tropicalis burtoni was shown to be included in O. angoniensis rather than O. tropicalis, extending the range of the former species into West Africa.