PREMISE Perhaps the most rapid period of vascular plant evolution occurred during the Silurian-Devonian time interval. Yet, few quantitative analyses have established the extent to which anatomical, morphological, or reproductive features contributed to this episode of tracheophyte diversification. METHODS Phylogenetic analyses were performed using a newly revised matrix of 54 characters (with 158 character states) of 37 of the best-preserved Paleozoic (predominantly Devonian) plants. Equisetum was included to determine whether it aligns with fossil sphenopsids or taxa collectively considered "ferns". The topology of the 54-character consensus tree was then compared to the topologies generated using only reproductive features (18 characters; 47 character states), only anatomical features (14 characters; 54 character states), only morphological features (22 characters; 57 character states), and the three pairwise combinations (e.g., anatomical and morphological characters). RESULTS The new 54-character tree topology continued to identify a trimerophyte-euphyllophyte clade and a zosterophyllophyte-lycophyte clade emerging from a Cooksonia-rhyniophyte plexus. Equisetum aligned with fossil sphenopsids rather than fern-like fossil taxa. Reproductive characters or anatomical characters analyzed in isolation resulted in nearly complete polytomy. Among the various permutations of the three categories, anatomical and morphological characters when combined provided the best restoration of the 54-character tree topology. CONCLUSIONS The phylogenetic relationships among the canonical fossil taxa used in this analysis predominantly reflect morphological trends. Reproductive and anatomical features taken in isolation appear to be evolutionarily conservative characters, i.e., natural selection "sees" the external phenotype.

中文翻译：

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形态学（而非解剖学或生殖学）特征定义了早期维管植物系统发育关系

前提也许维管植物进化的最快速时期发生在志留纪-泥盆纪时期。然而，很少有定量分析确定解剖学、形态学或生殖特征对这一气管植物多样化事件的贡献程度。方法 系统发育分析是使用新修订的矩阵进行的，该矩阵包含 37 种保存最完好的古生代（主要是泥盆纪）植物的 54 个特征（具有 158 个特征状态）。包括木贼属以确定它是否与化石蝶形纲或统称为“蕨类植物”的分类群一致。然后将 54 个字符的共识树的拓扑结构与仅使用再生特征（18 个字符；47 个字符状态）、仅使用解剖特征（14 个字符；54 个字符状态）生成的拓扑结构进行比较，只有形态特征（22 个字符；57 个字符状态）和三个成对组合（例如，解剖和形态特征）。结果 新的 54 个字符的树状拓扑结构继续识别出来自 Cooksonia-rhyniophyte 丛的三叶植物-真叶植物进化枝和带状叶植物-石松植物进化枝。木贼与化石蝶形纲而不是蕨类化石分类群对齐。孤立分析的生殖特征或解剖特征导致几乎完全的多聚体。在三个类别的各种排列中，结合解剖学和形态学特征提供了对 54 字符树拓扑结构的最佳恢复。结论 本分析中使用的典型化石类群之间的系统发育关系主要反映了形态趋势。