Nature, 27 February 2025, Volume 638 Issue 8052
《自然》2025年2月27日，第638卷，8052期
化學Chemistry
Total synthesis of 25 picrotoxanes by virtual library selection
通過虛擬庫篩選實現25種木防己苦毒素化合物的全合成
▲ 作者：Chunyu Li (李春雨) & Ryan A. Shenvi
▲ 鏈接：https://www.nature.com/articles/s41586-024-08538-y
▲摘要：為了解決問題且避免繁瑣的試錯實驗，我們構建了一個虛擬庫，其中包含難以捉摸的后期中間體類似物，這些類似物通過反應性進行篩選并改變了合成路徑。該方法的效率促成了25種天然木防己苦毒素化合物的簡化合成路線。
昂貴的密度泛函理論過渡態計算被更快的反應物參數化所取代，從而提高了可擴展性，并在本研究中揭示了反應機制。這種方法可以作為人類或計算機輔助合成規劃的附加搜索工具，適用于高復雜性目標化合物和/或文獻或反應數據庫中代表性不足的步驟。
▲ Abstract：Here, to solve this problem but avoid tedious guess-and-check experimentation, we built a virtual library of elusive late-stage intermediate analogues that were triaged by reactivity and altered the synthesis pathway. The efficiency of this method led to concise routes to 25 naturally occurring picrotoxanes. Costly density-functional-theory transition-state calculations were replaced with faster reactant parameterizations to increase scalability and, in this case, inform the mechanism. This approach can serve as an add-on search to human or computer-assisted synthesis planning applicable to high-complexity targets and/or steps with little representation in the literature or reaction databases.
古人類學Paleoanthropology
Ancient DNA reveals reproductive barrier despite shared Avar-period culture
古代DNA揭示阿瓦爾時期存在生殖隔離
▲ 作者：Ke Wang, Bendeguz Tobias et al.
▲ 鏈接：https://www.nature.com/articles/s41586-024-08418-5
▲摘要：公元567至568年，具有東亞血統的阿瓦爾人經過長途遷徙抵達了東中歐，并與具有歐洲血統的群體相遇。我們利用722個個體的古代全基因組數據，并結合對維也納南部兩處大型七至八世紀相鄰墓地的精細跨學科分析，探討這一相遇在數百年間的影響。
我們發現，即使在200年后，一處遺址（萊奧貝斯多夫）的血統仍以東亞為主，而另一處遺址（默德林）則顯示出本地歐洲血統。盡管這兩處相鄰遺址共享獨特的晚期阿瓦爾文化，但它們之間的生物學親緣關系卻非常有限。我們重建了兩處遺址的六代家譜，涵蓋多達450名近親個體，從而對社區進行逐代人口統計分析。
盡管血統不同，但這些家譜以及廣泛的遠親關系網絡顯示，近親繁殖現象不存在，父系模式與女性外婚制并存，存在多重生殖伙伴關系（如娶寡嫂制），并且生物學連通性與社會地位的考古標記直接相關。這種代際遺傳屏障的維持，是通過系統性地選擇來自阿瓦爾領域內其他遺址的具有相似血統的伴侶實現的。
萊奧貝斯多夫與阿瓦爾核心地區的生物學聯系比與默德林更為緊密，而默德林則與維也納盆地的另一處具有歐洲血統的遺址相關聯。遺址之間的流動性主要源于女性外婚制，表明不同的婚姻網絡是維持遺傳屏障的主要驅動力。
▲ Abstract：After a long-distance migration, Avars with Eastern Asian ancestry arrived in Eastern Central Europe in 567 to 568 CE and encountered groups with very different European ancestry. We used ancient genome-wide data of 722 individuals and fine-grained interdisciplinary analysis of large seventh- to eighth-century CE neighbouring cemeteries south of Vienna (Austria) to address the centuries-long impact of this encounter. We found that even 200?years after immigration, the ancestry at one site (Leobersdorf) remained dominantly East Asian-like, whereas the other site (M?dling) shows local, European-like ancestry. These two nearby sites show little biological relatedness, despite sharing a distinctive late-Avar culture. We reconstructed six-generation pedigrees at both sites including up to 450 closely related individuals, allowing per-generation demographic profiling of the communities. Despite different ancestry, these pedigrees together with large networks of distant relatedness show absence of consanguinity, patrilineal pattern with female exogamy, multiple reproductive partnerships (for example, levirate) and direct correlation of biological connectivity with archaeological markers of social status. The generation-long genetic barrier was maintained by systematically choosing partners with similar ancestry from other sites in the Avar realm. Leobersdorf had more biological connections with the Avar heartlands than with M?dling, which is instead linked to another site from the Vienna Basin with European-like ancestry. Mobility between sites was mostly due to female exogamy pointing to different marriage networks as the main driver of the maintenance of the genetic barrier.
地球科學Earth Science
Continued Atlantic overturning circulation even under climate extremes
大西洋經向翻轉環流在極端氣候下仍然持續
▲ 作者：J. A. Baker, M. J. Bell et al.
▲ 鏈接：https://www.nature.com/articles/s41586-024-08544-0
▲ 摘要：我們展示了大西洋經向翻轉環流（AMOC）在34個氣候模型中對極端溫室氣體和北大西洋淡水強迫表現出適應性。由持續的南大洋風驅動的南大洋上升流維持了AMOC的減弱狀態，防止其完全崩潰。
由于南大洋上升流必須通過大西洋或太平洋的下沉流來平衡，因此只有在補償性的太平洋經向翻轉環流（PMOC）發展時，AMOC才可能崩潰。值得注意的是，幾乎所有模型中都出現了PMOC，但其強度不足以平衡所有南大洋上升流，這表明本世紀AMOC崩潰的可能性較低。
我們的研究揭示了AMOC的穩定機制，這些機制對過去和未來的AMOC變化具有重要意義，進而對生態系統和海洋生物地球化學產生影響。
研究還表明，迫切需要更好地理解和評估南大洋和印度—太平洋環流，以準確預測未來AMOC的變化。
▲ Abstract：Here we show that the The Atlantic Meridional Overturning Circulation (AMOC) is resilient to extreme greenhouse gas and North Atlantic freshwater forcings across 34 climate models. Upwelling in the Southern Ocean, driven by persistent Southern Ocean winds, sustains a weakened AMOC in all cases, preventing its complete collapse. As Southern Ocean upwelling must be balanced by downwelling in the Atlantic or Pacific, the AMOC can only collapse if a compensating Pacific Meridional Overturning Circulation (PMOC) develops. Remarkably, a PMOC does emerge in almost all models, but it is too weak to balance all of the Southern Ocean upwelling, suggesting that an AMOC collapse is unlikely this century. Our findings reveal AMOC-stabilizing mechanisms with implications for past and future AMOC changes, and hence for ecosystems and ocean biogeochemistry. They suggest that better understanding and estimates of the Southern Ocean and Indo-Pacific circulations are urgently needed to accurately predict future AMOC change.
Warming and cooling catalyse widespread temporal turnover in biodiversity
變暖與降溫催化了生物多樣性的廣泛時間更替
▲ 作者：Malin L. Pinsky, Helmut Hillebrand et al.
▲ 鏈接：https://www.nature.com/articles/s41586-024-08456-z
▲摘要：我們分析了來自海洋、陸地和淡水群落的42225個物種組成的時間序列。結果表明，在經歷更快溫度變化（包括變暖和降溫）的地點，時間更替率始終更快。
此外，那些難以進入微氣候避難所或面臨更強人類影響的陸生群落對溫度變化尤為敏感，每十年物種更替率高達48%。
這些結果揭示了對持續氣候變化的廣泛脆弱性信號，并突出了哪些生態群落最為敏感，從而引發了對生態系統完整性的擔憂，因為氣候變化和其他人類影響正在加速。
▲ Abstract：Here we analyse 42,225 time series of species composition from marine, terrestrial and freshwater assemblages, and show that temporal rates of turnover were consistently faster in locations that experienced faster temperature change, including both warming and cooling. In addition, assemblages with limited access to microclimate refugia or that faced stronger human impacts on land were especially responsive to temperature change, with up to 48% of species replaced per decade. These results reveal a widespread signal of vulnerability to continuing climate change and highlight which ecological communities are most sensitive, raising concerns about ecosystem integrity as climate change and other human impacts accelerate.
生物學Biology
Widespread occurrence and relevance of phosphate storage in foraminifera
磷酸鹽在有孔蟲中儲存的廣泛性及相關性
▲ 作者：Nicolaas Glock, Julien Richirt et al.
▲ 鏈接：https://www.nature.com/articles/s41586-024-08431-8
▲ 摘要：我們展示了磷酸鹽儲存在有孔蟲中是廣泛存在的，從潮灘到深海均有發現。在瓦登海里，底棲有孔蟲Ammonia confertitesta在水華期間細胞內儲存的磷酸鹽總量高達德國每年磷肥消耗量的約5%。對南北海和秘魯氧最小區的預算計算表明，底棲有孔蟲可能在南北海緩沖河流磷徑流約37天，在秘魯邊緣緩沖約21天。
這表明這些生物可能對海洋磷循環具有重要意義——它們可能在沿海環境中為人為富營養化的情況進行緩沖。磷酸鹽以多聚磷酸鹽的形式儲存在細胞器中，這些細胞器可能是酸性鈣化體。
它們的代謝功能可能包括調節滲透壓、細胞內pH值以及鈣和能量儲存。此外，儲存高能磷化合物（如磷酸肌酸和多磷酸）可能是有孔蟲對氧氣耗竭的一種適應機制。
▲ Abstract：Here we show that phosphate storage in foraminifera is widespread, from tidal flats to the deep sea. The total amount of intracellular phosphate stored in the benthic foraminifer Ammonia confertitesta in the Wadden Sea during a bloom is as high as around 5% of the annual consumption of phosphorus (P) fertilizer in Germany. Budget calculations for the Southern North Sea and the Peruvian Oxygen Minimum Zone indicate that benthic foraminifera may buffer riverine P runoff for approximately 37?days at the Southern North Sea and for about 21?days at the Peruvian margin. This indicates that these organisms are probably relevant for marine P cycling—they potentially buffer anthropogenic eutrophication in coastal environments. Phosphate is stored as polyphosphate in cell organelles that are potentially acidocalcisomes. Their metabolic functions can range from regulation of osmotic pressure and intracellular pH to calcium and energy storage. In addition, storage of energetic P compounds, such as creatine phosphate and polyphosphate, is probably an adaptation of foraminifera to O2 depletion.
Learned magnetic map cues and two mechanisms of magnetoreception in turtles
海龜學習磁地圖的線索與兩種磁感應機制
▲ 作者：Kayla M. Goforth, Catherine M. F. Lohmann et al.
▲ 鏈接：https://www.nature.com/articles/s41586-024-08554-y
▲摘要：長期以來，人們一直認為，動物要利用地磁地圖進行導航，必須了解目的地的地磁坐標。然而，關于動物能夠學習地理區域地磁特征的關鍵假設尚未得到驗證。
我們報告一種標志性的導航物種——紅海龜（Caretta caretta）能夠學習此類信息。當在模擬特定海洋位置地磁場的磁場中被反復喂食時，幼年海龜學會了區分它們遇到食物的磁場與其他地方的磁場，這種能力可能是其覓食地點忠誠性的基礎。
在這種新的地磁地圖測試中，條件反射不受射頻振蕩磁場的影響，而射頻振蕩磁場應該會破壞基于自由基對的化學磁感受機制，這表明海龜的地磁地圖感知并不依賴這種機制。相比之下，需要利用磁羅盤的定向行為則會被射頻振蕩磁場干擾。這些發現提供了證據，表明海龜的地磁地圖和“磁羅盤”依賴于兩種不同的磁感應機制。
▲ Abstract：It has long been proposed that, to navigate using a magnetic map, animals must learn the magnetic coordinates of the destination, yet the pivotal hypothesis that animals can learn magnetic signatures of geographical areas has, to our knowledge, yet to be tested. Here we report that an iconic navigating species, the loggerhead turtle (Caretta caretta), can learn such information. When fed repeatedly in magnetic fields replicating those that exist in particular oceanic locations, juvenile turtles learned to distinguish magnetic fields in which they encountered food from magnetic fields that exist elsewhere, an ability that might underlie foraging site fidelity. Conditioned responses in this new magnetic map assay were unaffected by radiofrequency oscillating magnetic fields, a treatment expected to disrupt radical-pair-based chemical magnetoreception, suggesting that the magnetic map sense of the turtle does not rely on this mechanism. By contrast, orientation behaviour that required use of the magnetic compass was disrupted by radiofrequency oscillating magnetic fields. The findings provide evidence that two different mechanisms of magnetoreception underlie the magnetic map and magnetic compass in sea turtles.
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