Despite warm polar climates and low meridional temperature gradients, a number of different high-latitude plankton assemblages were, to varying extents, dominated by endemic species during most of the Paleogene. To better understand the evolution of Paleogene plankton endemism in the high southern latitudes, we investigate the spatiotemporal distribution of the fossil remains of dinoflagellates, i.e., organic-walled cysts (dinocysts), and their response to changes in regional sea surface temperature (SST). We show that Paleocene and early Eocene (～65-50 Ma) Southern Ocean dinocyst assemblages were largely cosmopolitan in nature but that a distinct switch from cosmopolitan-dominated to endemic-dominated assemblages (the so-called "transantarctic flora") occurred around the early-middle Eocene boundary (～50 Ma). The spatial distribution and relative abundance patterns of this transantarctic flora correspond well with surface water circulation patterns as reconstructed through general circulation model experiments throughout the Eocene. We quantitatively compare dinocyst assemblages with previously published TEX86-based SST reconstructions through the early and middle Eocene from a key locality in the southwest Pacific Ocean, ODP Leg 189 Site 1172 on the East Tasman Plateau. We conclude that the middle Eocene onset of the proliferation of the transantarctic flora is not linearly correlated with regional SST records and that only after the transantarctic flora became fully established later in the middle Eocene, possibly triggered by large-scale changes in surface-ocean nutrient availability, were abundances of endemic dinocysts modulated by regional SST variations.
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机译：尽管极地气候温暖，子午线温度梯度低，但在大多数古近纪中，许多不同的高纬度浮游生物组合在不同程度上受特有物种的控制。为了更好地了解南部高纬度地区古近纪浮游生物的特有性，我们调查了鞭毛藻化石遗体的时空分布，即有机壁囊肿（恐龙囊肿）及其对区域海表温度变化的响应（SST） 。我们发现，古新世和始新世（〜65-50 Ma）南大洋的藻类组合在本质上是世界性的，但在世界各地发生了从世界性的组合到地方性的组合（所谓的“跨南极植物群”）的明显转变。始新世中早界线（〜50 Ma）。通过整个始新世的一般环流模型实验重建的该跨南极植物区系的空间分布和相对丰度模式与地表水环流模式非常吻合。我们通过西南太平洋的一个关键地点，东塔斯曼高原的ODP Leg 189 Site 1172上的始新世和中期始新世，定量比较了恐龙囊与先前发布的基于TEX86的SST重建。我们得出的结论是，越洋微生物群落的中新世中期开始与区域SST记录不线性相关，并且只有在越洋微生物群在晚始新世完全建立之后，这可能是由表层海洋营养物的大规模变化触发的可用性，是地方性SST变异调节的地方性单囊藻的数量。
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