Kerguelen sedaDNA

While the Antarctic region has experienced significant climatic changes over the Holocene, few high-resolution records have examined their effects on the local biota. The windy Kerguelen Archipelago in the subantarctic Indian Ocean is covered by relatively sparse vegetation which grows close to the ground. We use sedimentary ancient DNA (sedaDNA) metabarcoding to characterise the local flora on the island of Grande Terre over the past 11,080 years. We identify a shift in vegetation composition at approximately 8,700 cal years BP, similar to the northward shift of the Southern Hemisphere Westerlies (SHW) inferred from a previous pollen record, when a dynamic Azorella- and other forb-dominated Early Holocene flora shifted toward one dominated by Azorella and bryophytes. This suggests a shift from a warmer Early Holocene to a colder Mid- to Late-Holocene. The high representation of bryophytes in the flora was revealed by the local record provided by sedaDNA, which are difficult to detect using traditional proxies. We discuss potential climate drivers based on vegetation changes throughout the core, including the effects that changes in the SHW and glacial dynamics may have had. Overall, our sedaDNA record provides an example of a dynamic Early Holocene followed by a relatively stable flora on a subantarctic island prior to human impact, enriches our knowledge of this unique and isolated archipelago over time, and showcases the potential of using sedaDNA to reveal past bryophyte communities.

南极地区在全新世（Holocene）期间经历了显著的气候变化，但目前鲜有高分辨率记录探究这些变化对当地生物群的影响。多风的凯尔盖朗群岛（Kerguelen Archipelago）坐落于亚南极印度洋海域，岛上分布着贴近地面生长的相对稀疏植被。本研究采用沉积物古DNA（sedimentary ancient DNA, sedaDNA）宏条形码技术，对格兰德特雷岛（Grande Terre）过去11080年的本地植物群进行特征解析。研究发现在约8700个校正碳十四距今年（cal years BP）时，植被组成发生转变——这与此前花粉记录中推断的南半球西风带（Southern Hemisphere Westerlies, SHW）北移事件相吻合；彼时以阿祖雷拉属（Azorella）和其他杂类草为主的全新世早期植物群，逐渐转变为以阿祖雷拉属和苔藓植物（bryophytes）为主的植物群。这表明植被群落经历了从温暖全新世早期向寒冷中晚全新世的转变。沉积物古DNA记录揭示了苔藓植物在该区域植物群中的高占比，而这一信息难以通过传统代用指标检测到。本研究基于岩芯记录中的植被变化，探讨了可能的气候驱动因子，包括南半球西风带变动与冰川动力学变化所产生的影响。总体而言，本研究的沉积物古DNA记录展现了亚南极岛屿在人类活动影响前，全新世早期植被动态活跃、中晚全新世后植被相对稳定的演化特征；同时丰富了我们对这一独特孤立群岛随时间变化的认知，并证明了利用沉积物古DNA解析史前苔藓植物群落的应用潜力。