Testing UV-B radiation as a proposed driver behind the end-Permian biotic crisis

臭氧层在拦截到达地球表面的有害太阳紫外线-B辐射(UV-B)方面发挥着至关重要的作用。然而，它的有效性在过去一直起伏不定，对臭氧层变薄对植被的影响知之甚少。预测未来的潜在后果取决于对过去紫外线胁迫加剧的时间间隔的了解。二叠纪末期(约2.52亿年前)历史上最大规模的物种灭绝可能就是这些时间间隔之一。这场危机中的植物化石记录显示了全球范围内的两个奇怪特征。消失的林地种子植物产生的许多花粉粒都是畸形的，而不断繁殖的草本植物(石松属)的孢子经常以四个独立的丛生形式传播。紫外线暴露的增加被认为是导致这些异常的原因。历史上最大的火山省西伯利亚陷阱产生的化合物可能会导致臭氧层长期或频繁地恶化。在这项研究中，研究人员将测试高UV-B辐射水平是否真的可以解释在二叠纪末生物危机期间观察到的植物的异常和灭绝模式。这项研究对社会很重要，因为它将评估未来削弱臭氧层的活动是否会通过经济上重要的植物种群的繁殖失败而破坏森林生态系统的稳定。通过这项工作的推广将通过开发一个关于生态系统和古生代Era灭绝的公众可访问的教育展览和网络模块来提高公众对过去环境变化的认识。利用生长室和萌发实验，研究人员将确定增加的UV-B暴露是否会引发化石记录中观察到的类似的花粉和孢子畸形，以及这是否可能导致受危机影响的植物群体的测试在世亲属之间的生殖成功对比。他们假设高水平的UV-B将对针叶树的繁殖产生负面影响，但不会严重影响石松的繁殖力。此外，他们还将调查紫外线诱导的发育反应是否出现在活火山活动的源头。为此，他们将从西伯利亚圈闭内的沉积物中分析二叠纪末化石的花粉和孢子组合。将观察与当代生态学实验方法相结合是一种新的方法，它将检验古生态学中的一个重要假说，并可能深入了解当代非生物应激源下的物种反应。

The ozone layer plays a vital role in intercepting harmful solar ultraviolet-B radiation (UV-B) from reaching Earth's surface. However, its effectiveness in doing so has fluctuated in the past and little is known of the impacts of a thinning ozone layer on vegetation. Anticipating potential consequences in the future depends on understanding time intervals with heightened UV stress in the past. The largest mass extinction in history at the end of the Permian Period (~252 million years ago) may have been one of these time intervals. Plant fossil records from this crisis show two odd features worldwide. Many pollen grains produced by vanishing woodland seed plants were malformed, and proliferating herbaceous plants (lycopsids) spread their spores frequently as unseparated clusters of four. Heightened UV exposure is hypothesized to have caused these abnormalities. Compounds produced by the largest volcanic province in history, the Siberian Traps, likely caused prolonged or frequent deterioration of the ozone shield. In this study researchers will test if high UV-B radiation levels could indeed explain the abnormalities and extinction patterns in plants observed during the end-Permian biotic crisis. This research is important to society because it will assess whether future activities weakening the ozone layer could destabilize forest ecosystems through reproductive failure of economically important groups of plants. Outreach from this work will raise public awareness of environmental changes in the past through developing a publicly accessible educational exhibit and web-module on ecosystems and extinctions of the Paleozoic Era.Using growth chamber and germination experiments, the researchers will determine whether elevated UV-B exposure triggers similar malformations in pollen and spores as observed in the fossil record, and whether this may lead to contrasting reproductive success between the tested living relatives of plant groups impacted by the crisis. They hypothesize high levels of UV-B will have a negative effect on conifer reproduction, but not severely affect fertility in lycopsids. In addition, they will also investigate whether UV-induced developmental responses appeared during times of active volcanism at its very source. For this, they will analyze end-Permian fossil pollen and spore assemblages from sediments within the Siberian Traps. Using observations in combination with a contemporary ecological experimental approach is a novel approach which will test an important hypothesis in paleoecology and may lend insight into species response under contemporary abiotic stressors.