Department of Anthropology, The Ohio State University, 174 West 18th Ave, Columbus, OH, 43210, USA; School of Anthropology and Conservation, University of Kent, Canterbury, Kent, CT2 7NR, UK.
Institute of Human Origins & School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, 85287, USA.
J Hum Evol. 2023 Jul;180:103384. doi: 10.1016/j.jhevol.2023.103384. Epub 2023 May 16.
This study investigates aspects of molar form in three African colobine species: Colobus polykomos, Colobus angolensis, and Piliocolobus badius. Our samples of C. polykomos and P. badius are from the Taï Forest, Ivory Coast; our sample of C. angolensis is from Diani, Kenya. To the extent that protective layers surrounding seeds are hard, we predicted that molar features related to hard-object feeding would be more pronounced in Colobus than they are Piliocolobus, as seed-eating generally occurs at higher frequencies in species of the former. We further predicted that among the colobines we studied, these features would be most pronounced in Taï Forest C. polykomos, which feeds on Pentaclethra macrophylla seeds encased within hard and tough seed pods. We compared overall enamel thickness, enamel thickness distribution, absolute crown strength, cusp tip geometry, and flare among molar samples. Sample sizes per species and molar type varied per comparison. We predicted differences in all variables except overall enamel thickness, which we expected would be invariant among colobines as a result of selection for thin enamel in these folivorous species. Of the variables we examined, only molar flare differed significantly between Colobus and Piliocolobus. Our findings suggest that molar flare, an ancient feature of cercopithecoid molars, was retained in Colobus but not in Piliocolobus, perhaps as a result of differences in the seed-eating proclivities of the two genera. Contrary to predictions, none of the aspects of molar form we investigated tracked current dietary differences in seed-eating between the two Colobus species. Finally, we explored the possibility that molar flare and absolute crown strength, when analyzed together, might afford greater differentiation among these colobine species. A multivariate t test of molar flare and absolute crown strength differentiated C. polykomos and P. badius, possibly reflecting known niche divergence between these two sympatric Taï Forest species.
本研究调查了三种非洲长尾猴物种（Colobus polykomos、Colobus angolensis 和 Piliocolobus badius）的臼齿形态。我们的 C. polykomos 和 P. badius 样本来自科特迪瓦的泰莱森林；我们的 C. angolensis 样本来自肯尼亚的迪尼亚。在种子周围的保护层是硬的情况下，我们预测与硬物体取食相关的臼齿特征在 Colobus 中会比在 Piliocolobus 中更为明显，因为食种子的行为通常在前者的物种中发生的频率更高。我们进一步预测，在所研究的长尾猴中，这些特征在泰莱森林中的 C. polykomos 中最为明显，它以包裹在坚硬和坚韧种子荚中的 Pentaclethra macrophylla 种子为食。我们比较了臼齿样本的整体牙釉质厚度、牙釉质厚度分布、绝对冠强度、尖顶几何形状和牙尖扩张。每种物种和每种臼齿类型的样本量因比较而异。我们预测除了整体牙釉质厚度之外，所有变量都会有所不同，我们预计由于这些食叶动物物种对薄牙釉质的选择，牙釉质厚度在长尾猴中是不变的。在所检查的变量中，只有臼齿扩张在 Colobus 和 Piliocolobus 之间存在显著差异。我们的研究结果表明，臼齿扩张是一种古老的类人猿臼齿特征，在 Colobus 中得以保留，但在 Piliocolobus 中却没有，这可能是由于这两个属的食果倾向不同所致。与预测相反，我们研究的臼齿形态的各个方面都没有追踪到这两个 Colobus 物种在食果方面的当前差异。最后，我们探讨了臼齿扩张和绝对冠强度结合分析是否可以更好地区分这些长尾猴物种。臼齿扩张和绝对冠强度的多元 t 检验可以区分 C. polykomos 和 P. badius，这可能反映了这两个泰莱森林共生物种之间已知的生态位分化。
