Nees Institute for Biodiversity of Plants, University of Bonn, Bonn, Germany.
Centro de Estudios Avanzados en Zonas Áridas, CEAZA, La Serena, Chile.
PLoS One. 2020 May 29;15(5):e0233729. doi: 10.1371/journal.pone.0233729. eCollection 2020.
Extreme arid conditions in the Atacama Desert in northern Chile have created a unique vegetation almost entirely restricted to the desert margins along the coast of the Pacific Ocean and the Andean range. In this study we provide data on the desert vegetation along elevational gradients at four localities from the western Andean slopes, between 19° and 21° S. Additionally, zonation of floristic data was explored. Three altitudinal zones could be classified and described in detail for each locality. Conspicuously divergent floras in the Atacama Desert have been recorded in the coastal 'lomas formations' and in the Andean desert vegetation, separated by a narrow band of absolute desert. In this study, we investigate the floristic relationships between both regions by implementing similarity analyses for 21 localities from the coastal and Andean deserts in northern Chile. Our results show a drastic east-west divergence in pairwise floristic similarity, which is in stark contrast to a weaker north-south divergence. A biotic barrier, preventing plant exchange from east to west and vice versa, imposed by the hyperarid conditions of the absolute desert, is one possible explanation for this finding. Moreover, the coastal and Andean deserts likely represent ecologically divergent habitats, e.g., in rainfall seasonality. Essential differences in factors determining plant life between both regions have probably contributed to a divergent evolution of the floras. Both explanations-ecological divergence and ecogeographical isolation-are not mutually exclusive, but likely complementary. We also combined floristic data from northern Chile and southern Peru. Similarity analyses of this combined dataset provide first floristic evidence for the existence of a biotic north-south corridor along the western slope of the Andes. Sub-Andean distributions of several species are discussed in the light of floristic connectivity between the Peruvian and Chilean Andean floristic clusters.
智利北部阿塔卡马沙漠的极端干旱条件创造了一种独特的植被，这种植被几乎完全局限于沿太平洋和安第斯山脉海岸的沙漠边缘。在这项研究中，我们提供了来自西安第斯山坡四个地点沿海拔梯度的沙漠植被数据，地点位于南纬 19°至 21°之间。此外，还探讨了植物区系数据的分带情况。可以为每个地点的详细描述和分类三个海拔带。在沿海的“洛马斯形成”和安第斯沙漠植被中记录到了阿塔卡马沙漠中明显不同的植物群，两者之间被一条狭窄的绝对沙漠带隔开。在这项研究中，我们通过对智利北部沿海和安第斯沙漠的 21 个地点实施相似性分析，研究了这两个地区的植物区系关系。我们的结果显示，在成对植物相似性方面，存在明显的东西分歧，这与较弱的南北分歧形成鲜明对比。由于绝对沙漠的极度干旱条件，形成了一个生物障碍，阻止了植物从东向西和从西向东的交换，这是造成这种现象的一个可能原因。此外，沿海和安第斯沙漠可能代表了生态上不同的栖息地，例如在降雨量季节性方面。这两个地区决定植物生命的因素之间的基本差异可能导致了植物区系的趋异进化。这两种解释——生态分歧和生态地理隔离——并非相互排斥，而是可能互补的。我们还结合了智利北部和秘鲁南部的植物区系数据。对这个综合数据集的相似性分析首次提供了沿安第斯山西坡存在生物南北走廊的植物区系证据。根据秘鲁和智利安第斯植物区系聚类之间的植物区系连通性，讨论了几种物种的亚安第斯分布。
