Carlson Bryce A, Kingston John D
Department of Anthropology, Purdue University, 700 W State St, West Lafayette, IN 47907, USA.
Department of Anthropology, University of Michigan, 1085 S University Ave, Ann Arbor, MI 48109, USA.
J Hum Evol. 2014 Nov;76:107-15. doi: 10.1016/j.jhevol.2014.06.001. Epub 2014 Jul 1.
The most significant hominin adaptations, including features used to distinguish and/or classify taxa, are critically tied to the dietary environment. Stable isotopic analyses of tooth enamel from hominin fossils have provided intriguing evidence for significant C4/CAM (crassulacean acid metabolism) resource consumption in a number of Plio-Pleistocene hominin taxa. Relating isotopic tooth signatures to specific dietary items or proportions of C3 versus C4/CAM plants, however, remains difficult as there is an ongoing need to document and quantify isotopic variability in modern ecosystems. This study investigates the ecological variables responsible for carbon isotopic discrimination and variability within the C3-dominated dietary niche of a closed canopy East African hominoid, Pan troglodytes, from Ngogo, Kibale National Park, Uganda. δ(13)C values among C3 resources utilized by Ngogo chimpanzees were highly variable, ranging over 13‰. Infrequent foraging on papyrus (the only C4 plant consumed by chimpanzees at the site) further extended this isotopic range. Variation was ultimately most attributable to mode of photosynthesis (C3 versus C4), food type, and elevation, which together accounted for approximately 78% of the total sample variation. Among C3 food types, bulk carbon values ranged from -24.2‰ to -31.1‰ with intra-plant variability up to 12.1‰. Pith and sapling leaves were statistically more (13)C depleted than pulp, seeds, flowers, cambium, roots, leaf buds, and leaves from mature trees. The effect of elevation on carbon variation was highly significant and equivalent to an approximately 1‰ increase in δ(13)C for every 150 m of elevation gain, likely reflecting habitat variability associated with topography. These results indicate significant δ(13)C variation attributable to food type and elevation among C3 resources and provide important data for hominin dietary interpretations based on carbon isotopic analyses.
最显著的古人类适应性变化，包括用于区分和/或分类分类单元的特征，都与饮食环境密切相关。对古人类化石牙釉质的稳定同位素分析提供了有趣的证据，表明在一些上新世-更新世古人类分类单元中大量消耗了C4/CAM（景天酸代谢）资源。然而，将同位素牙齿特征与特定饮食项目或C3与C4/CAM植物的比例联系起来仍然很困难，因为目前仍需要记录和量化现代生态系统中的同位素变异性。本研究调查了乌干达基巴莱国家公园恩戈戈地区一种封闭树冠东非类人猿——黑猩猩（Pan troglodytes）在以C3为主的饮食生态位中导致碳同位素分馏和变异的生态变量。恩戈戈黑猩猩所利用的C3资源中的δ(13)C值变化很大，范围超过13‰。对纸莎草（该地点黑猩猩食用的唯一C4植物）的不频繁觅食进一步扩大了这个同位素范围。变异最终主要归因于光合作用模式（C3与C4）、食物类型和海拔高度，它们共同占总样本变异的约78%。在C3食物类型中，总碳值范围为-24.2‰至-31.1‰，植物内部变异性高达12.1‰。髓和幼树叶在统计学上比果肉、种子、花朵形成层、根、叶芽和成熟树的叶子的(13)C含量更低。海拔高度对碳变异的影响非常显著，相当于海拔每升高150米，δ(13)C大约增加1‰，这可能反映了与地形相关的栖息地变异性。这些结果表明，C3资源中食物类型和海拔高度导致了显著的δ(13)C变异，并为基于碳同位素分析的古人类饮食解释提供了重要数据。
