Data from: Exceptional body sizes but typical trophic structure in a Pleistocene food web

In this study, we focused on the exceptionally large mammals inhabiting the Americas during the Quaternary period and the paramount role of body size in species ecology. We evaluated two main features of Pleistocene food webs: the relationship between body size and (i) trophic position and (ii) vulnerability to predation. Despite the large range of species sizes, we found a hump-shaped relationship between trophic position and body size. We also found a negative trend in species vulnerability similar to that observed in modern faunas. The largest species lived near the boundary of energetic constraints, such that any shift in resource availability could drive these species to extinction. Our results reinforce several features of megafauna ecology: (i) the negative relationship between trophic position and body size implies that large-sized species were particularly vulnerable to changes in energetic support; (ii) living close to energetic imbalance could favour the incorporation of additional energy sources, for example, a transition from a herbivorous to a scavenging diet in the largest species (e.g. Megatherium) and (iii) the interactions and structure of Quaternary megafauna communities were shaped by similar forces to those shaping modern fauna communities.本研究聚焦于第四纪（Quaternary）时期栖息于美洲的特大型哺乳动物，以及体型在物种生态学中的核心作用。我们评估了更新世（Pleistocene）食物网的两大核心特征：体型与（i）营养级（trophic position）、（ii）被捕食脆弱性之间的关联。尽管物种体型跨度极大，我们仍发现营养级与体型间呈现驼峰型相关关系。我们还发现，物种的被捕食脆弱性呈负向趋势，这与现代动物群中的观测结果一致。体型最大的物种生存于能量约束的临界边界，资源可获得性的任何波动都可能引发这些物种的灭绝。本研究结果进一步印证了巨型动物群（megafauna）生态学的若干核心特征：（i）营养级与体型间的负相关关系表明，大型物种对能量供给变动的脆弱性尤为显著；（ii）处于能量失衡临界状态的物种，更倾向于纳入额外的能量来源，例如体型最大的物种（如大地懒（Megatherium））从植食性食谱转向食腐性食谱；（iii）第四纪巨型动物群落的相互作用与结构，其塑造驱动力与现代动物群落的塑造驱动力高度一致。