Elevation gradients are drivers of species diversity, and, recently, studies have considered the evolutionary process in shaping community assembly patterns. Patterns of plant species richness across elevational gradients have been studied in different parts of the Atlantic Forest; however, little is known about plant phylogenetic diversity patterns. Thus, we aimed to analyse the phylogenetic diversity of angiosperm trees along an elevation gradient in southern Brazilian Plateau, in the subtropical portion of the Atlantic Forest. We expected a decrease in phylogenetic diversity along the elevation gradient, from lowlands towards to highlands, where species may be evolutionary closely related as many tropical lineages are not capable to inhabit colder conditions. We also investigated the distribution of phylogenetic clades along the elevation gradient through principal coordinates of phylogenetic structure. Data were obtained from 28 phytosociological surveys distributed across different elevation levels, ranging from 40 to 975 m. We found a negative association between phylogenetic diversity and the elevation gradient. The representativeness of families Myrtaceae and Lauraceae increased with elevation, while most of the families decreased in species richness and are replaced by temperate families such as Winteraceae (Drimys) in higher elevations. The decrease in phylogenetic diversity with increasing elevation may be linked to niche conservatism of tropical lineages that retain their historical climatic niches and thus many species are not capable to inhabit colder environments. Most tropical clades are restricted to lower elevations; however, Myrtaceae and Lauraceae probably evolved tolerance to colder temperatures during glacial cycles. Furthermore, the probably long‐term climate stability in lowlands than highland areas may have promoted the co‐occurrence of distantly related species, resulting in higher phylogenetic diversity. Finally, we observed how historical imprints and current environmental conditions shape the phylogenetic diversity of angiosperm tree species in subtropical Atlantic Forest.

中文翻译：

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亚热带巴西大西洋森林中被子植物树系进化多样性的高度变化

海拔梯度是物种多样性的驱动力，最近，研究已经考虑到了塑造社区聚集模式的进化过程。已经在大西洋森林的不同地区研究了海拔梯度上植物物种丰富度的模式。但是，关于植物系统发育多样性模式知之甚少。因此，我们旨在分析大西洋南部亚热带地区巴西南部高原海拔高度梯度上被子植物的系统发育多样性。我们预计随着海拔的升高，从低地到高地，系统发育多样性将下降，因为许多热带世系无法适应较冷的条件，物种在进化上可能密切相关。我们还通过系统发育结构的主坐标研究了系统进化枝沿海拔梯度的分布。数据是从分布在40至975 m范围内不同海拔高度的28项植物社会学调查获得的。我们发现系统发育多样性和海拔梯度之间存在负相关关系。桃金娘科和月桂科的代表性随着海拔的升高而增加，而大多数科的物种丰富度下降，被温带科取代，例如温带菌科（Drimys）在较高的高度。随着海拔的升高，系统发育多样性的减少可能与保留其历史气候生态位的热带谱系的生态位保守性有关，因此许多物种无法在较冷的环境中栖息。大多数热带进化枝只限于较低的海拔。然而，桃金娘科和月桂科可能在冰川周期中发展了对较冷温度的耐受性。此外，与高地相比，低地可能具有长期的气候稳定性，这可能促进了远缘物种的共生，从而导致更高的系统发育多样性。最后，我们观察到历史烙印和当前环境条件如何塑造亚热带大西洋森林中被子植物树种的系统发育多样性。