Data from: The evolutionary root of flowering plants

Correct rooting of the angiosperm radiation is both challenging and necessary for understanding the origins and evolution of physiological and phenotypic traits in flowering plants. The problem is known to be difficult due to the large genetic distance separating flowering plants from other seed plants and the sparse taxon sampling among basal angiosperms. Here we provide further evidence for concern over substitution model misspecification in analyses of chloroplast DNA sequences. We show that support for Amborella as the sole representative of the most basal angiosperm lineage is founded on sequence site patterns poorly described by time reversible substitution models. Improving the fit between sequence data and substitution model identifies Trithuria, Nymphaeales and Amborella as surviving relatives of the most basal lineage of flowering plants. This finding indicates that aquatic and herbaceous species dominate the earliest extant lineage of flowering plants.确定被子植物辐射演化的正确系统发育根结，对于解析开花植物生理与表型性状的起源及演化过程，兼具挑战性与必要性。该问题历来棘手，究其原因，在于开花植物与其他种子植物间存在显著遗传距离，且基部被子植物的类群采样较为匮乏。本研究针对叶绿体DNA序列分析中存在的替换模型误设问题，提供了进一步的佐证证据。研究表明，认为无油樟（Amborella）是最基部被子植物支系唯一代表类群的支持依据，源于时间可逆替换模型无法良好拟合的序列位点模式。通过优化序列数据与替换模型的拟合程度，本研究确认三柱草属（Trithuria）、睡莲目（Nymphaeales）与无油樟均为开花植物最基部支系的现存近缘类群。该发现暗示，水生与草本类群构成了开花植物最早现存支系的主体类群。