Rachel H. Dunn and Matthew W. Tocheri contributed equally to this work.
Ecological divergence and talar morphology in gorillas
Article first published online: 21 DEC 2013
Copyright © 2013 Wiley Periodicals, Inc.
American Journal of Physical Anthropology
Volume 153, Issue 4, pages 526–541, April 2014
How to Cite
Dunn, R. H., Tocheri, M. W., Orr, C. M. and Jungers, W. L. (2014), Ecological divergence and talar morphology in gorillas. Am. J. Phys. Anthropol., 153: 526–541. doi: 10.1002/ajpa.22451
- Issue published online: 7 MAR 2014
- Article first published online: 21 DEC 2013
- Manuscript Accepted: 2 DEC 2013
- Manuscript Revised: 1 DEC 2013
- Manuscript Received: 16 MAY 2013
- Wenner-Gren Foundation post-PhD award to MWT. Grant Number: 7822
Gorillas occupy a variety of habitats from the west coast to eastern central Africa. These habitats differ considerably in altitude, which has a pronounced effect on forest ecology. Although all gorillas are obligate terrestrial knuckle-walking quadrupeds, those that live in lowland habitats eat fruits and climb more often than do those living in highland habitats. Here we test the hypothesis that gorilla talus morphology falls along a morphocline that tracks locomotor function related to a more inverted or everted foot set. This proposed morphocline predicts that gorillas living in lowland habitats may have a talocrural joint configured to facilitate a more medially oriented foot during climbing, suggesting that they may be more adaptively committed to arboreality than gorillas living in highland habitats. To quantify the relative set of the foot in gorillas, we chose two three-dimensional measurements of the talocrural joint: mediolateral curvature of the trochlea and relative surface area of the lateral malleolus. Our results show that, in comparison to their eastern counterparts, western gorillas have talar features that reflect a more medially directed sole of the foot. This morphology likely facilitates foot placement in a wider range of positions and minimization of shearing stresses across the joint when the foot is loaded on more curved or vertically oriented substrates as occurs during climbing and other arboreal behaviors. In contrast, eastern gorilla talar morphology is consistent with habitual placement of the foot with the sole directed more inferiorly, suggesting more effective loading during plantigrade push-off on terrestrial substrates. Am J Phys Anthropol 153:526–541, 2014. © 2013 Wiley Periodicals, Inc.