Shapiro Amy E, Venkataraman Vivek V, Nguyen Nga, Fashing Peter J
School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA.
Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
J Hum Evol. 2016 Oct;99:1-9. doi: 10.1016/j.jhevol.2016.05.010. Epub 2016 Jul 26.
As the only extant graminivorous primate, gelada monkeys (Theropithecus gelada) offer unique insights into how hominins and other extinct primates with strong C4 isotopic signatures may have subsisted on graminoid-rich diets. Fossil Theropithecus species sharing a strong C4 signal (i.e., Theropithecus brumpti, Theropithecus darti, and Theropithecus oswaldi) have been reconstructed as predominantly graminivorous and potentially in ecological competition with contemporaneous hominins. However, inferring the breadth and variation of diet in these species (and therefore hominins) has proven problematic. Understanding how ecological variation within extant geladas impacts microwear and isotopic signatures may contribute to reconstructions of diet in fossil Theropithecus. Here, we build on a recent study at an ecologically intact tall grass ecosystem (Guassa, Ethiopia) that expanded the known diversity of gelada diets by demonstrating lower reliance on graminoids, greater consumption of forbs, and greater dietary species richness than previously described at disturbed sites. We used dental microwear texture analysis to explore how dietary variation among extant geladas may inform our understanding of the diets of fossil Theropithecus. First, we compared the dental microwear textures of geladas at Guassa to those of geladas from other sites. The microwear textures of geladas at Guassa exhibited more complexity, less anisotropy, and more variance in anisotropy and heterogeneity, reflecting the greater dietary diversity of Guassa geladas. Comparing microwear texture variables among this expanded gelada sample to those for T. brumpti, T. oswaldi, and T. darti yielded no significant differences. These results raise the intriguing possibility that data on how ecological variation and diet impact dental microwear and (possibly) isotopic signatures in extant geladas can be used to reconstruct the diets of extinct theropiths and, more broadly, hominins with strong C4 isotopic signatures. We conclude that extant gelada populations offer a powerful analog for inferring dietary variation among predominantly graminivorous fossil primates.
作为现存唯一的食草灵长类动物，狮尾狒（Theropithecus gelada）为研究古人类以及其他具有强烈C4同位素特征的已灭绝灵长类动物如何以富含禾本科植物的食物为生提供了独特视角。具有强烈C4信号的化石狮尾狒物种（即布鲁姆氏狮尾狒、达蒂氏狮尾狒和奥斯瓦尔德氏狮尾狒）已被推断主要以食草为主，并且可能与同时期的古人类存在生态竞争。然而，推断这些物种（以及古人类）饮食的广度和变化已被证明存在问题。了解现存狮尾狒内部的生态变化如何影响微磨损和同位素特征，可能有助于重建化石狮尾狒的饮食。在此，我们基于最近在一个生态完整的高草生态系统（埃塞俄比亚瓜萨）进行的一项研究，该研究通过证明狮尾狒对禾本科植物的依赖较低、对草本植物的消耗量更大以及饮食物种丰富度高于之前在受干扰地点所描述的情况，扩展了已知的狮尾狒饮食多样性。我们使用牙齿微磨损纹理分析来探究现存狮尾狒之间的饮食差异如何增进我们对化石狮尾狒饮食的理解。首先，我们将瓜萨地区狮尾狒的牙齿微磨损纹理与其他地区狮尾狒的进行了比较。瓜萨地区狮尾狒的微磨损纹理表现出更多的复杂性、更低的各向异性以及各向异性和非均质性方面更大的变化，这反映了瓜萨地区狮尾狒饮食多样性更高。将这个扩展后的狮尾狒样本的微磨损纹理变量与布鲁姆氏狮尾狒、奥斯瓦尔德氏狮尾狒和达蒂氏狮尾狒的进行比较，未发现显著差异。这些结果提出了一个有趣的可能性，即关于生态变化和饮食如何影响现存狮尾狒牙齿微磨损和（可能的）同位素特征的数据，可用于重建已灭绝的恐狒以及更广泛地说具有强烈C4同位素特征的古人类的饮食。我们得出结论，现存的狮尾狒种群为推断主要以食草为主的化石灵长类动物的饮食差异提供了一个有力的类比。
