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 as modern fauna communities.

本研究聚焦于第四纪（Quaternary period）栖息于美洲的超大型哺乳动物，以及体型在物种生态学中的核心作用。本研究评估了更新世（Pleistocene）食物网的两大核心特征：体型与①营养级（trophic position）、②被捕食脆弱性（vulnerability to predation）之间的关联。尽管不同物种的体型跨度极大，我们仍发现营养级与体型之间呈现驼峰型关联。同时我们还发现，物种被捕食脆弱性呈负向趋势，这与现代动物群中观测到的规律一致。体型最大的物种生存于能量限制的临界边界附近，因此资源可获得性的任何变动都可能致使这些物种走向灭绝。本研究结果佐证了巨型动物群（megafauna）生态学的多项特征：① 营养级与体型之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突出；② 生存状态接近能量失衡时，物种可能会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））从植食性饮食转向食腐饮食；③ 第四纪巨型动物群群落的种间互动与群落结构，其塑造驱动力与现代动物群群落的驱动力具有相似性。