Department of Paleontology, GNS Science, 5040 Lower Hutt, New Zealand;
School of Geography, Environment and Earth Sciences, 6140 Wellington, New Zealand.
Proc Natl Acad Sci U S A. 2018 May 29;115(22):5686-5691. doi: 10.1073/pnas.1714342115. Epub 2018 May 14.
Periodic fluctuations in past biodiversity, speciation, and extinction have been proposed, with extremely long periods ranging from 26 to 62 million years, although forcing mechanisms remain speculative. In contrast, well-understood periodic Milankovitch climate forcing represents a viable driver for macroevolutionary fluctuations, although little evidence for such fluctuation exists except during the Late Cenozoic. The reality, magnitude, and drivers of periodic fluctuations in macroevolutionary rates are of interest given long-standing debate surrounding the relative roles of intrinsic biotic interactions vs. extrinsic environmental factors as drivers of biodiversity change. Here, we show that, over a time span of 60 million years, between 9 and 16% of the variance in biological turnover (i.e., speciation probability plus species extinction probability) in a major Early Paleozoic zooplankton group, the graptoloids, can be explained by long-period astronomical cycles (Milankovitch "grand cycles") associated with Earth's orbital eccentricity (2.6 million years) and obliquity (1.3 million years). These grand cycles modulate climate variability, alternating times of relative stability in the environment with times of maximum volatility. We infer that these cycles influenced graptolite speciation and extinction through climate-driven changes to oceanic circulation and structure. Our results confirm the existence of Milankovitch grand cycles in the Early Paleozoic Era and show that known processes related to the mechanics of the Solar System were shaping marine macroevolutionary rates comparatively early in the history of complex life. We present an application of hidden Markov models to macroevolutionary time series and protocols for the evaluation of statistical significance in spectral analysis.
过去的生物多样性、物种形成和灭绝呈现周期性波动，其周期极长，从 2600 万年到 6200 万年不等，尽管推动机制仍存在推测。相比之下，人们对周期性米兰科维奇气候驱动因素有很好的了解，它是宏观进化波动的一个可行驱动因素，尽管除了新生代晚期外，几乎没有证据表明存在这种波动。鉴于长期以来围绕生物内在相互作用与外在环境因素作为驱动生物多样性变化的相对作用的争论，宏观进化率的周期性波动的现实性、幅度和驱动因素引起了人们的兴趣。在这里，我们表明，在 6000 万年的时间跨度内，在前寒武纪至早古生代浮游动物主要类群之一的笔石类中，生物周转率（即物种形成概率加物种灭绝概率）的 9%至 16%的方差可以用与地球轨道偏心率（260 万年）和倾角（130 万年）相关的长周期天文周期（米兰科维奇“大周期”）来解释。这些大周期调节气候变率，使环境的相对稳定期与最大活跃期交替出现。我们推断，这些周期通过气候变化对海洋环流和结构的影响，影响了笔石的物种形成和灭绝。我们的研究结果证实了米兰科维奇大周期在早古生代的存在，并表明与太阳系力学相关的已知过程在复杂生命历史的早期就塑造了海洋宏观进化率。我们提出了一种隐藏马尔可夫模型在宏观进化时间序列中的应用，以及在谱分析中评估统计显著性的协议。
