North America is a large continent with extensive climatic, geological, soil, and biological diversity. As biota faces threat from habitat destruction and climate change, making a quantitative assessment of biodiversity becomes critically important. Rapid digitization of plant specimen records and accumulation of DNA sequence data enable a much‐needed broad synthesis of species occurrences with phylogenetic data. In this study, the first such synthesis of a flora from such a large and diverse part of the world is attempted, all seed plants from the North American continent (here defined to include Canada, United States, and Mexico), with a focus on examining phylogenetic diversity and endemism. We collected digitized plant specimen records and chose a coarse grain for analysis, recognizing that this grain is currently necessary for reasonable completeness per sampling unit. We found that raw richness and endemism patterns largely support previous hypotheses of biodiversity hotspots. The application of phylogenetic metrics and a randomization test revealed novel results, including a significant phylogenetic clustering across the continent, a striking east–west geographical difference in the distribution of branch lengths, and the discovery of centers of neo‐ and paleoendemism in Mexico, the southwestern USA, and the southeastern USA. Finally, our examination of phylogenetic beta diversity provides a new approach to compare centers of endemism. We discuss the empirical challenges of working at the continental scale and the need for more sampling across large parts of the continent, for both DNA data for terminal taxa and spatial data for poorly understood regions, to confirm and extend these results.

中文翻译：

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北美植物群的空间系统发育

北美洲是一个拥有广泛气候、地质、土壤和生物多样性的大洲。由于生物群面临栖息地破坏和气候变化的威胁，对生物多样性进行定量评估变得至关重要。植物标本记录的快速数字化和 DNA 序列数据的积累使得急需的物种发生与系统发育数据的广泛合成成为可能。在这项研究中，首次尝试合成来自世界如此大而多样的地区的植物群，所有来自北美大陆（此处定义为包括加拿大、美国和墨西哥）的种子植物，重点是检查系统发育多样性和地方性。我们收集了数字化的植物标本记录，并选择了粗粒进行分析，认识到目前这种谷物对于每个抽样单位的合理完整性是必要的。我们发现原始丰富度和特有模式在很大程度上支持了先前关于生物多样性热点的假设。系统发育指标和随机测试的应用揭示了新的结果，包括整个大陆显着的系统发育聚类，分支长度分布的显着东西地理差异，以及在墨西哥发现的新和古地方性中心，美国西南部和美国东南部。最后，我们对系统发育β多样性的检查提供了一种比较特有中心的新方法。我们讨论了在大陆范围内工作的经验挑战以及对大陆大部分地区进行更多采样的必要性，