Archaeology Program, Boston University, Boston, MA, USA.
Geography-Anthropology Program, University of Southern Maine, Gorham, ME, USA.
Nat Ecol Evol. 2021 Jul;5(7):995-1002. doi: 10.1038/s41559-021-01455-7. Epub 2021 May 3.
Analysis of enamel stable carbon isotopes (δC) of fossil herbivores is an important tool for making inferences about Plio-Pleistocene vegetation structure in Africa and the environmental context of hominin evolution. Many palaeoecological studies implicitly or explicitly assume that individual variation in C-C plant consumption among fossil herbivores directly reflects the abundance of C (trees, shrubs) or C (low-altitude tropical grasses) vegetation. However, a strong link between δC of herbivores and ecosystem vegetation structure has not been rigorously established. Here we combine δC data from a large dataset (n = 1,643) with multidecadal Landsat estimates of C woody cover across 30 African ecosystems to show that there is little relationship between intrataxonomic variation in δC and vegetation structure. This is especially true when removing forested ecosystems (>80% woody cover)-which numerous lines of evidence suggest are rare in the Plio-Pleistocene fossil record of eastern Africa-from our analyses. Our findings stand in contrast with the common assumption that variation in herbivore δC values reflects changes in the relative abundance of C-C vegetation. We conclude that analyses using herbivore δC data to shed light on the environmental context of hominin evolution should look to explicitly community-level approaches for making vegetation inferences.
分析化石食草动物稳定的碳同位素（δC）是推断非洲上新世-更新世植被结构和人类进化环境背景的重要工具。许多古生态学研究含蓄或明确地假设，化石食草动物之间 C-C 植物消费的个体差异直接反映了 C（树木、灌木）或 C（低海拔热带草）植被的丰度。然而，食草动物的 δC 与生态系统植被结构之间的紧密联系尚未得到严格确立。在这里，我们将来自一个大型数据集（n = 1,643）的 δC 数据与跨越 30 个非洲生态系统的数十年 Landsat 估计的 C 木质覆盖数据相结合，表明种内 δC 变异与植被结构之间几乎没有关系。当我们从分析中去除森林生态系统（木质覆盖> 80%）——大量证据表明它们在东非上新世-更新世化石记录中很少见时，这种情况尤其如此。我们的发现与一个常见的假设相矛盾，即食草动物 δC 值的变化反映了 C-C 植被相对丰度的变化。我们的结论是，使用食草动物 δC 数据来阐明人类进化的环境背景的分析应该寻求明确的群落水平方法来进行植被推断。
