Geographic variation in gorilla limb bones Rebecca S. Jabbour * , Tessa L. Pearman Department of Biology, Saint Mary's College of California, 1928 Saint Mary's Road, Moraga, CA 94575, USA article info Article history: Received 26 August 2013 Accepted 15 March 2016 Available online 7 May 2016 Keywords: African ape Taxonomy Skeleton Hand Foot Altitude abstract Gorilla systematics has received increased attention over recent decades from primatologists, conser- vationists, and paleontologists. Studies of geographic variation in DNA, skulls, and teeth have led to new taxonomic proposals, such as recognition of two gorilla species, Gorilla gorilla (western gorilla) and Gorilla beringei (eastern gorilla). Postcranial differences between mountain gorillas (G. beringei beringei) and western lowland gorillas (G. g. gorilla) have a long history of study, but differences between the limb bones of the eastern and western species have not yet been examined with an emphasis on geographic variation within each species. In addition, proposals for recognition of the Cross River gorilla as Gorilla gorilla diehli and gorillas from Tshiaberimu and Kahuzi as G. b. rex-pymaeorum have not been evaluated in the context of geographic variation in the forelimb and hindlimb skeletons. Forty-three linear measurements were collected from limb bones of 266 adult gorillas representing populations of G. b. beringei, Gorilla beringei graueri, G. g. gorilla, and G. g. diehli in order to investigate geographic diversity. Skeletal elements included the humerus, radius, third metacarpal, third proximal hand phalanx, femur, tibia, calcaneus, first metatarsal, third metatarsal, and third proximal foot phalanx. Comparisons of means and principal components analyses clearly differentiate eastern and western gorillas, indicating that eastern gorillas have absolutely and relatively smaller hands and feet, among other differences. Gorilla subspecies and populations cluster consistently by species, although G. g. diehli may be similar to the eastern gorillas in having small hands and feet. The subspecies of G. beringei are distinguished less strongly and by different variables than the two gorilla species. Populations of G. b. graueri are variable, and Kahuzi and Tshiaberimu specimens do not cluster together. Results support the possible influence of higher-altitude Pleistocene refugia on patterns of geographic variation in gorillas. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Differences between the gorillas of eastern and western Africa have long been recognized on the basis of external and skeletal features (e.g., Coolidge, 1929; Schultz, 1934). In the past two de- cades, studies of gorilla DNA have also supported a deep evolu- tionary split between eastern and western gorillas (Ruvolo et al., 1994; Garner and Ryder, 1996; Gagneux et al., 1999; Scally et al., 2012, 2013; Prado-Martinez et al., 2013). A species-level distinc- tion between eastern gorillas (Gorilla beringei) and western gorillas (Gorilla gorilla) has been suggested (Groves, 2001) and widely adopted, and studies have increasingly examined variation below the species level. Research on geographic variation in skulls and teeth has shown that differences between the two species are greater than differences among subspecies and populations within each species (Uchida, 1998; Stumpf et al., 2003; Taylor and Groves, 2003; Pilbrow, 2006, 2010), but differences between eastern and western gorillas in the limb bones have not yet been studied with a focus on geographic diversity within each species. Differences among Gorilla subspecies have been identified using their skulls, teeth, and postcrania (e.g., Groves, 1970, 2001; Sarmiento, 1994; Uchida, 1998), but mountain gorillas (G. beringei beringei) and western lowland gorillas (G. g. gorilla) have received more attention than eastern lowland gorillas (G. b. graueri) and Cross River gorillas (Gorilla. gorilla diehli). Since the proposal by Sarmiento and Oates (2000) that the Cross River gorillas, long included in G. g. gorilla, be recognized as the subspecies G. g. diehli, research on Cross River gorilla morphology has increased. A few large multivariate studies of skulls and teeth have indicated that all four subspecies can be distinguished from one another (Stumpf et al., 2003; Pilbrow, 2010), but comparable studies have not been conducted using postcrania. Gorillas from the G. beringei pop- ulations of Tshiaberimu and Kahuzi have unusual combinations of * Corresponding author. E-mail address: rsj2@stmarys-ca.edu (R.S. Jabbour). Contents lists available at ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol http://dx.doi.org/10.1016/j.jhevol.2016.03.008 0047-2484/© 2016 Elsevier Ltd. All rights reserved. Journal of Human Evolution 95 (2016) 68e79