Infraspeci®c morphometric variation in Aethomys namaquensis (Rodentia: Muridae) from southern Africa C. T. Chimimba Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002 South Africa. (Accepted 2 February 2000) Abstract The Namaqua rock mouse, Aethomys namaquensis (A. Smith, 1834), is a widely distributed species in southern Africa. Analysis of geographic variation among samples of A. namaquensis from southern Africa across a more comprehensive geographical coverage than has hitherto been considered for the species suggests the recognition of four subspecies: A. n. namaquensis (A. Smith, 1834); A. n. lehocla A. Smith, 1836; A. n. alborarius Peters, 1852; and A. n. monticularis Jameson, 1909, which differ both in cranial size and shape. The geographical limits of the proposed subspecies broadly coincide with major phytogeogra- phical zones of southern Africa. This infraspeci®c taxonomic treatment of southern African A. namaquensis reduces the number of previously recognized subspecies or referred taxa from 16 to four. While the subspecies designations in this study are probably valid in terms of their constitution, their boundaries, however, require further re®nement involving other systematic techniques, such as DNA analysis. Key words: Namaqua rock mouse, infraspeci®c variation, morphometrics, cranial morphology, southern Africa INTRODUCTION The Namaqua rock mouse, Aethomys namaquensis (A. Smith, 1834), is widely distributed in southern Africa and shows considerable variation in body size, tail length and pelage colouration among geographical samples (Smithers, 1971; De Graaff, 1981; Meester et al., 1986; Skinner & Smithers, 1990; Musser & Carleton, 1993). This variation led to suggestions that it may re¯ect either a complex of species or subspecies (Smithers, 1971; De Graaff, 1981; Musser & Carleton, 1993). Aethomys namaquensis has, however, recently been shown to be a valid, widely distributed species in southern Africa (Chimimba, 1997; 1998; Chimimba, Dippenaar & Robinson, 1999). This con®rmed earlier reports by Roberts (1951), Ellerman, Morrison-Scott & Hayman (1953) and Meester, Davis & Coetzee (1964), who recognized 16 subspecies: lehocla A. Smith, 1836; alborarius Peters, 1852; auricomis De Winton, 1897; centralis Schwann, 1906; avarillus Thomas & Wroughton, 1908; monticularis Jameson, 1909; albiventer Jentink, 1910; grahami Roberts, 1915; calarius Thomas, 1926; siccatus Thomas, 1926; capensis Roberts, 1926; drakensbergi Roberts, 1926; klaverensis Roberts, 1926; lehochloides Roberts, 1926; waterbergensis Roberts, 1938; and namibensis Roberts, 1946. The infraspeci®c distinctions were made with little or no assessment of patterns of geographic variation over the entire distributional range of the species in southern Africa. Moreover, they were primarily based on non- statistical comparisons of type material and /or small, geographically restricted samples (Smithers, 1971; Smithers & Tello, 1976; Smithers & Wilson, 1979). Major reviews of the genus (Davis, 1975; De Graaff, 1981; Meester et al., 1986; Skinner & Smithers, 1990; Musser & Carleton, 1993) refrained from recognizing subspecies and provisionally regarded all described forms as synonyms of A. namaquensis. To date, the nature and extent of geographic variation in A. nama- quensis still remains virtually unknown. In addition, only a few southern African rodents, such as species of Acomys (Dippenaar & Rautenbach, 1986), Otomys (Taylor, Meester & Kearney, 1993), Saccostomus (Ellison et al., 1993), and Aethomys (Chimimba, Dippenaar & Robinson, 1998; Chimimba, 2000), have been subjected to critical analysis of intra- speci®c variation. The present study, therefore, represents the ®rst analysis of both morphometric and morphological patterns of intraspeci®c variation in A. namaquensis from southern Africa across a more comprehensive geographical coverage than has hitherto been considered for the species. While the analysis of geographic variation, particularly in widely distributed species, may lead to recognizably J. Zool., Lond. (2001) 253, 191±210 # 2001 The Zoological Society of London Printed in the United Kingdom E-mail: ctchimimba@zoology.up.ac.za