The climatic impacts of the Tibetan Plateau since the Neogene and the phytogeographic pattern changes of formerly widely-distributed forest communities on the plateau remain poorly constrained. Today, Cercis L. (Fabaceae) is a well-known arborescent genus typically distributed in subtropical to warm temperate zones of the Northern Hemisphere, and Paleogene fossil occurrences from Eurasia and North America show a long history of the genus in mid-low latitudes of the Northern Hemisphere. Here, we describe a fossil species, Cercis zekuensis sp. nov. based on well-preserved fruits from the early Miocene of the northeastern Tibetan Plateau. Detailed morphological comparison (e.g., ventral margin with a veinless wing) of extant and fossil members of Cercis and other genera confirmed validity of the present taxonomic identity. Based on the comparison with extant relatives and their climate preferences, this unexpected occurrence of thermophilic Cercis in northeastern Tibetan Plateau indicates this area had higher temperature and precipitation in the Miocene than today. Integrated with inferred (paleo-)temperature lapse rates, this indicates a low paleoelevation of less than 2.4 km. In contrast with the present-day alpine climate here (~3.7 km), such a low elevation facilitated a more favorable habitat with comparatively high biodiversity and warm temperate forests at that time, as were evidenced by co-occurring megafossils. Moreover, the present existence of Cercis implies the genus was widespread in interior Asia during the early Neogene and shows its modern disjunction or diversification between eastern and central Asia was possibly shaped by the late Cenozoic regional tectonic uplift and consequential environmental deterioration.

中文翻译：

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亚洲内陆早中新世晚期紫荆的独特记录及其对古环境和古植物地理学的意义

新近纪以来青藏高原的气候影响和原先广泛分布的高原森林群落的植物地理格局变化仍然缺乏约束。今天，紫荆（豆科）是著名的乔木属，通常分布在北半球的亚热带至暖温带地区，欧亚大陆和北美的古近纪化石出现表明该属在中低纬度地区有着悠久的历史。北半球。在这里，我们描述了一种化石物种，Cercis zekuensis sp。十一月 以青藏高原东北部早中新世保存完好的水果为基础。紫荆现存成员和化石成员的详细形态比较（例如，无脉翼的腹侧边缘）和其他属证实了当前分类学身份的有效性。根据与现存近缘种及其气候偏好的比较，青藏高原东北部意外出现嗜热紫荆，表明该地区在中新世的温度和降水量高于今天。结合推断的（古）温度递减率，这表明低于 2.4 公里的低古高程。与这里今天的高山气候（~3.7 公里）相比，如此低的海拔促进了更有利的栖息地，当时生物多样性相对较高，温暖的温带森林，同时出现的巨型化石证明了这一点。此外，紫荆现在的存在 暗示该属在新近纪早期广泛分布于亚洲内陆，表明其在东亚和中亚之间的现代分离或多样化可能是由晚新生代区域构造隆升和随之而来的环境恶化所形成的。