Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
Evolution. 2021 Mar;75(3):656-671. doi: 10.1111/evo.14177. Epub 2021 Feb 2.
The "law of constant extinction," proposed by Van Valen, states that long and short-lived taxa have equal chances of going extinct. This pattern of age-independent extinction was originally inferred using the fossil record of several different taxa and relied on survivorship curves built from the literal reading of the fossil record. Van Valen's seminal work was mostly done at higher taxonomic levels, hence its prevalence at the species level could not be directly inferred. The surprisingly few subsequent studies done at the species level have challenged the prevalence of age-independent extinction, but those have, for the most part, failed to explicitly incorporate inherent biases of the fossil record. Using a recent Bayesian framework that accounts for several of those biases, including the fact that very short-living lineages might never make to the record itself, we showed that Ruminantia species present age-dependent extinction, where extinction probability decreases with species age. An analysis at the genus level suggested age-independent extinction but further examination suggested that the pattern might be more complex than previously reported by Van Valen. Our results indicate that different taxonomic levels may present different extinction regimes, which could justify the development of new macroevolutionary theory and methods.
范瓦伦提出的“灭绝定律”指出，长寿命和短寿命的分类群灭绝的几率相等。这种与年龄无关的灭绝模式最初是根据几种不同分类群的化石记录推断出来的，并且依赖于从化石记录的字面解读构建的存活曲线。范瓦伦的开创性工作主要是在更高的分类学水平上完成的，因此不能直接推断其在物种水平上的普遍性。此后在物种水平上进行的为数不多的后续研究对与年龄无关的灭绝的普遍性提出了挑战，但这些研究在很大程度上未能明确纳入化石记录固有的偏见。我们使用了一种新的贝叶斯框架，该框架考虑了其中的几个偏见，包括事实上，寿命极短的谱系可能根本无法进入记录本身，结果表明反刍动物的物种存在与年龄相关的灭绝，即灭绝概率随物种年龄的增加而降低。在属的水平上的分析表明存在与年龄无关的灭绝，但进一步的研究表明，这种模式可能比范瓦伦之前报道的更为复杂。我们的研究结果表明，不同的分类学水平可能呈现出不同的灭绝模式，这可以为新的宏观进化理论和方法的发展提供依据。
