Surfaces and spaces: troubleshooting the study of dietary niche space overlap between North American stem primates and rodents
Surfaces and spaces: troubleshooting the study of dietary niche space overlap between North American stem primates and rodents
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表面和空间：解决北美干灵长类动物和啮齿动物之间饮食生态位空间重叠的研究
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发表时间：
2016
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通讯作者：
D. Boyer
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作者：
Kristen A. Prufrock;S. López‐Torres;M. Silcox;D. Boyer
牙齿地形测量提供了有关牙齿三维 (3D) 形状的定量的、具有生物学意义的数据。在这项研究中，使用三种牙齿地形指标（狄利克雷正常能量（DNE）、浮雕指数（RFI）和旋转方向斑块计数（OPCR））来评估北美plesiadapoid灵长类动物（Plesiadapidae、Carpolestidae和Saxonellidae）和早期啮齿动物之间饮食生态位重叠的存在。这些指标的计算需要研究人员通过将牙齿裁剪到感兴趣的区域和/或定向来修改牙齿的 3D 表面模型。因此，当前的研究还检查了裁剪和方向引入的误差，并评估了这些指标对生态位重叠假设的贡献。我们的结果表明，与 DNE 相比，裁剪造成的 RFI 变化明显更大。此外，在 RFI 计算中，方向是比裁剪更大的变异来源。方向不会强烈影响 OPCR 值。然而，这些误差来源都不足以削弱这些指标对利基重叠假设的支持程度。 DNE 和 RFI 结果表明，carpolestids 和 saxonellids 的臼齿形态与早期啮齿类动物非常不同，因此这些群体不适应消耗相同的资源。一些 plesiadapids 表现出与早期啮齿动物相似的咬合曲率、起伏和复杂程度。 plesiadapid Chiromyoides 具有明显的低尖点和弱剪切嵴发育，其臼齿是所有类群中最像啮齿动物的。这表明摇蚊具有与早期啮齿动物重叠的饮食生态位，并且最有可能竞争食物资源。 plesiadapoid-啮齿动物牙齿地形分析的结果强调了 DNE 比 OPCR 更能检测咬合表面形态的细微差异，而 RFI 提供了有关牙齿高冠程度的宝贵数据。
Dental topographic metrics provide quantitative, biologically meaningful data on the three-dimensional (3D) form of teeth. In this study, three dental topographic metrics (Dirichlet normal energy (DNE), relief index (RFI), and orientation patch count rotated (OPCR)) are used to evaluate the presence of dietary niche overlap between North American plesiadapoid primates (Plesiadapidae, Carpolestidae, and Saxonellidae) and early rodents. Calculation of these metrics requires researchers to modify the 3D surface models of the teeth by cropping them to a region of interest and/or orienting them. The current study therefore also examines the error introduced by cropping and orientation, and evaluates the contribution of these metrics to the niche overlap hypothesis. Our results indicate that cropping creates significantly more variation in RFI than DNE. Furthermore, orientation is an even larger source of variation in the calculation of RFI than cropping. Orientation does not strongly influence OPCR values. However, none of these sources of error are significant enough to undermine the extent to which these metrics can speak to the niche overlap hypothesis. The DNE and RFI results suggest that carpolestids and saxonellids had very different molar morphologies from early rodents, and thus these groups were not adapted to consume the same resources. Some plesiadapids show similar levels of occlusal curvature, relief, and complexity to early rodents. The plesiadapid Chiromyoides, which has distinctively low cusps and weak shearing crest development, has molars that are the most rodent-like of all taxa compared. This suggests that Chiromyoides had a dietary niche that overlapped with early rodents and would have been the most likely to be competing over food resources. Results from the plesiadapoid-rodent dental topographic analysis highlight the utility of DNE for detecting more fine-scaled differences in occlusal surface morphology than OPCR, whereas RFI provided valuable data on the degree to which teeth were high crowned.