Data from: Extinction of South American sparassodontans (Metatheria): environmental fluctuations or complex ecological processes?

Sparassodontans are a diverse but now extinct group of metatherians that were apex predators in South America during most of the Cenozoic. Studying their decline has been controversial mainly due to the scarcity of the fossil record, and different methodological approaches have led to contradictory hypotheses. In an effort to explore questions about their extinction, we developed a novel multi-model statistical approach to analyse all of the currently available data at a continental scale. Using multiple regression analysis and new advances in beta diversity analysis, we used all currently available fossil data at a continental scale to test four competing hypotheses to account for the decline of sparassodontans: competition with placental carnivorans, competition with avian phorusrhacids, non-competitive ecological interactions, and environmental fluctuations. Our results show that the sparassodontan extinction was a gradual process with species disappearing throughout the Cenozoic. Multiple regression analysis supported non-competitive ecological interactions as the best extinction model. Native South American ungulates, African migrants (caviomorph rodents and platyrrhine primates) and didelphimorphians were the groups with the highest statistical significance. Sparassodontan beta diversity increased between South American Land Mammal Ages after the Paleocene–Eocene boundary. Our results demonstrate that ecological modelling techniques illuminate aspects of extinction processes whilst mitigating the limitations of the fossil record. Our study suggests that non-competitive ecological interactions could have been the main driver for sparassodontan extinction rather than, as commonly assumed, a result of competition and/or abiotic fluctuations.

袋鬣兽类（Sparassodontans）是一类多样性丰富但现已灭绝的后兽类（metatherians），在新生代（Cenozoic）的大部分时期均为南美洲的顶级掠食者。针对其衰退过程的研究始终存在争议，主要原因在于化石记录稀缺，不同的研究方法得出了相互矛盾的假说。为了探究其灭绝相关的问题，我们开发了一种全新的多模型统计方法，用于在大陆尺度下分析当前所有可获取的数据集。我们结合多元回归分析（multiple regression analysis）与β多样性分析（beta diversity analysis）的最新进展，利用大陆尺度下全部现存的化石数据，对解释袋鬣兽类衰退的四项竞争假说进行了检验：胎盘食肉目动物（placental carnivorans）的竞争、骇鸟科鸟类（avian phorusrhacids）的竞争、非竞争性生态相互作用（non-competitive ecological interactions）以及环境波动（environmental fluctuations）。研究结果显示，袋鬣兽类的灭绝是一个渐进过程，其物种在整个新生代时期陆续消失。多元回归分析结果支持非竞争性生态相互作用为最优灭绝模型。其中，南美本土有蹄类、非洲迁徙类群（豚鼠类啮齿动物与阔鼻灵长类）以及负鼠目类群（didelphimorphians）具有最高的统计学显著性。在古新世-始新世边界（Paleocene–Eocene boundary）之后的南美陆生哺乳动物分期（South American Land Mammal Ages）中，袋鬣兽类的β多样性有所上升。我们的研究表明，生态建模技术能够阐明灭绝过程的相关特征，同时缓解化石记录的局限性。本研究提示，非竞争性生态相互作用可能是袋鬣兽类灭绝的主要驱动因素，而非此前普遍认为的竞争和/或非生物环境波动。