Abstract The breakup of Gondwana and the associated climatic changes led to the fragmentation of floras that were once connected across the Southern lands. The diversity of the Gondwanan remnants has long been assumed to have fluctuated in Patagonia across the Cenozoic, although it has never been quantified so far. Here we address when the major floristic members of the Gondwanan legacy (e.g., southern beeches, proteas, podocarps, gumtrees) expanded, contracted, or became extinct during the Patagonian biogeographic isolation (Eocene–Miocene) on the basis of the re-assessment of the fossil record (i.e., woods, leaves, and spore-pollen grains). We found that the Patagonian floras experienced moderate to severe shifts in the diversity of the Gondwanan component —relative to the total flora— with the highest estimates in the late Eocene–early Oligocene (∼50%) and the lowest estimates in the late Miocene (∼20%) according to the fossil pollen record. The most important floristic changes include two major replacements: 1) tropical Gondwanan taxa (e.g., Akania, Eucalyptus, Gymnostoma) by typically cool-temperate taxa (e.g., Nothofagaceae) in the Eocene, and 2) humid taxa (e.g., Podocarpaceae) by arid-adapted floras, mostly of non-Gondwanan affinity, across the Miocene. The variation in diversity of the Gondwanan component from Patagonia shows a striking resemblance to that from Australia for the same period, probably indicating a global-scale driver of floristic turnover (e.g., global cooling conditions). Today, the Patagonian subantarctic forests harbor only about ∼15% of the Gondwanan diversity, representing a three-fold decrease from its climax in the late Eocene–early Oligocene.

中文翻译：

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始新世-中新世巴塔哥尼亚植物群的冈瓦纳遗产

摘要 冈瓦纳大陆的分裂和相关的气候变化导致曾经在南方土地上相连的植物群破碎。长期以来，人们一直认为巴塔哥尼亚的冈瓦纳遗迹的多样性在整个新生代都存在波动，尽管迄今为止尚未对其进行量化。在这里，我们根据对巴塔哥尼亚生物地理隔离（始新世-中新世）的重新评估，讨论了冈瓦纳遗产的主要植物区系成员（例如，南方山毛榉、普罗泰斯、罗汉松、桉树）何时扩张、收缩或灭绝。化石记录（即木材、树叶和孢子花粉粒）。我们发现巴塔哥尼亚植物群经历了冈瓦纳组件多样性的中度至重度变化——相对于总植物群——在始新世晚期 - 渐新世早期（~50%）估计最高，在中新世晚期估计最低。 ∼20%) 根据化石花粉记录。最重要的植物区系变化包括两个主要替代：1) 始新世典型的冷温带类群（例如，Nothofagaceae）将热带冈瓦纳类群（例如，阿卡尼亚、桉树、裸口藻）和 2）潮湿的类群（例如，罗汉果科）由整个中新世适应干旱的植物群，主要是非冈瓦纳亲缘关系。来自巴塔哥尼亚的冈瓦纳组件多样性的变化与来自澳大利亚的同一时期的差异惊人地相似，这可能表明植物群更替的全球规模驱动因素（例如，全球冷却条件）。今天，巴塔哥尼亚亚南极森林仅拥有约 15% 的冈瓦纳多样性，与始新世晚期至渐新世早期的高潮相比减少了三倍。