Human Origins Program, Department of Anthropology, National Museum of Natural History, Smithsonian Institution, 10th and Constitution Avenue NW, Washington, DC 20013-7012, USA.
J Hum Evol. 2011 Feb;60(2):171-84. doi: 10.1016/j.jhevol.2010.09.002. Epub 2010 Nov 19.
Gorillas are more closely related to each other than to any other extant primate and are all terrestrial knuckle-walkers, but taxa differ along a gradient of dietary strategies and the frequency of arboreality in their behavioral repertoire. In this study, we test the hypothesis that medial cuneiform morphology falls on a morphocline in gorillas that tracks function related to hallucial abduction ability and relative frequency of arboreality. This morphocline predicts that western gorillas, being the most arboreal, should display a medial cuneiform anatomy that reflects the greatest hallucial abduction ability, followed by grauer gorillas, and then by mountain gorillas. Using a three-dimensional methodology to measure angles between articular surfaces, relative articular and nonarticular areas, and the curvatures of the hallucial articular surface, the functional predictions are partially confirmed in separating western gorillas from both eastern gorillas. Western gorillas are characterized by a more medially oriented, proportionately larger, and more mediolaterally curved hallucial facet than are eastern gorillas. These characteristics follow the predictions for a more prehensile hallux in western gorillas relative to a more stable, plantigrade hallux in eastern gorillas. The characteristics that distinguish eastern gorilla taxa from one another appear unrelated to hallucial abduction ability or frequency of arboreality. In total, this reexamination of medial cuneiform morphology suggests differentiation between eastern and western gorillas due to a longstanding ecological divergence and more recent and possibly non-adaptive differences between eastern taxa.
大猩猩彼此之间的亲缘关系比任何其他现存的灵长类动物都要密切，都是在地面上用指关节行走的动物，但在饮食策略和行为谱中树栖行为的频率方面，各分类群存在差异。在这项研究中，我们检验了这样一个假设，即内侧楔骨形态沿着一个形态渐变线在大猩猩中变化，该渐变线与与趾骨外展能力和树栖行为频率相关的功能有关。这个形态渐变线预测，最具树栖性的西部大猩猩应该具有反映出最大趾骨外展能力的内侧楔骨解剖结构，其次是格雷尔大猩猩，然后是山地大猩猩。通过使用三维方法来测量关节表面之间的角度、相对关节和非关节区域以及趾骨关节表面的曲率，在将西部大猩猩与东部大猩猩区分开来时，这些功能预测得到了部分证实。西部大猩猩的特点是内侧方向更明显、比例更大、横向更弯曲的趾骨关节面，与东部大猩猩相比，其趾骨具有更强的抓握能力。这些特征符合在西部大猩猩中相对稳定的、跖行的趾骨而言，其更具可操作性的大脚趾的预测。区分东部大猩猩分类群彼此之间的特征似乎与趾骨外展能力或树栖行为频率无关。总的来说，对内侧楔骨形态的重新检查表明，由于长期的生态分化以及东部分类群之间最近的、可能是非适应性的差异，东部和西部大猩猩之间存在分化。
