Cyclic evolution of phytoplankton forced by changes in tropical seasonality
Cyclic evolution of phytoplankton forced by changes in tropical seasonality
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DOI：
10.1038/s41586-021-04195-7
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发表时间：
2021-12-01
期刊：
影响因子：
64.8
通讯作者：
Tetard, Martin
中科院分区：
文献类型：
--
作者：
Beaufort, Luc;Bolton, Clara T.;Tetard, Martin
尽管人们早已认识到地球轨道变化在驱动全球气候循环中的作用，但它们对进化的影响迄今尚不清楚。颗石藻是一种重要的钙化浮游植物群，其化石遗骸能够详细评估循环轨道尺度气候变化对进化的影响，因为它们在海洋沉积物中含量丰富，并且保留了它们对不断变化的环境的形态适应性(1,2)。进化遗传分析将更新世化石球石形态的广泛变化与物种辐射事件联系起来(3)。在这里，我们利用高分辨率颗石数据表明，在过去 280 万年中，颗石藻的形态演化受到地球轨道偏心率的影响，其节奏约为 100,000 年和 405,000 年，这是与同时期全球气候周期不同的光谱特征 (4)。地球系统模型（5）与海洋生物地球化学模型（6）相结合的模拟显示了季节周期的强烈偏心率调节，我们认为这直接影响热带海洋年度周期中发生的生态位的多样性。表层海洋条件的季节性减弱有利于中等大小的颗石藻物种，从而增加了颗石碳酸盐的出口和埋藏；而增强的季节性有利于更大范围的颗石石尺寸并减少碳酸盐出口。我们假设浮游植物进化的偏心率导致了全球碳循环记录中所见的 405,000 年的强烈周期性。
Although the role of Earth's orbital variations in driving global climate cycles has long been recognized, their effect on evolution is hitherto unknown. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable a detailed assessment of the effect of cyclic orbital-scale climate changes on evolution because of their abundance in marine sediments and the preservation of their morphological adaptation to the changing environment(1,2). Evolutionary genetic analyses have linked broad changes in Pleistocene fossil coccolith morphology to species radiation events(3). Here, using high-resolution coccolith data, we show that during the last 2.8 million years the morphological evolution of coccolithophores was forced by Earth's orbital eccentricity with rhythms of around 100,000 years and 405,000 years-a distinct spectral signature to that of coeval global climate cycles(4). Simulations with an Earth System Model(5) coupled with an ocean biogeochemical model(6) show a strong eccentricity modulation of the seasonal cycle, which we suggest directly affects the diversity of ecological niches that occur over the annual cycle in the tropical ocean. Reduced seasonality in surface ocean conditions favours species with mid-size coccoliths, increasing coccolith carbonate export and burial; whereas enhanced seasonality favours a larger range of coccolith sizes and reduced carbonate export. We posit that eccentricity pacing of phytoplankton evolution contributed to the strong 405,000-year cyclicity that is seen in global carbon cycle records.