Holocene vegetation dynamics of Grande Terre (Kerguelen Islands) inferred from sedimentary ancient DNA

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ABSTRACT While the Antarctic region has experienced significant climatic changes over the Holocene, few high‐resolution records have examined their effects on the local biota. In order to understand past ecological shifts and forecast future changes, it is important to obtain high‐resolution palaeoecological records from this region. The windy Kerguelen Archipelago in the subantarctic Indian Ocean is covered by relatively sparse vegetation that grows close to the ground. We characterise the local flora on the island of Grande Terre over the past 11 080 years using sedimentary ancient DNA ( sed aDNA) metabarcoding with a general plant primer targeting the P6 loop minibarcode. We identify a shift in vegetation composition at approximately 8700 calibrated years before present (cal a BP), similar to the northward shift of the Southern Hemisphere Westerlies (SHWs) inferred from a previous pollen record, when a dynamic Azorella ‐ and other forb‐dominated Early Holocene flora shifted towards 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 sed aDNA, which are difficult to detect using traditional proxies, and even more could have been detected with increased DNA reference libraries and using bryophyte‐specific primers. 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 sed aDNA 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 sed aDNA to reveal past bryophyte communities.

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