Cladistic datasets of morphological characters are comprised of observations that exhibit varying degrees of consistency with underlying phylogenetic hypotheses, reflecting the acquisition and retention of character states (highly consistent characters), or the convergent evolution and loss of character states (less consistent characters). The consistency between phylogenetic history and individual character histories has a bearing both on the evolutionary process and on the relative ease with which phylogenetic history may be inferred from morphological data. We surveyed 486 tetrapod morphological cladistic datasets to establish an empirical distribution of consistency among characters and datasets. Average dataset size has increased in the number of characters and taxa through time. The Consistency Index measure of homoplasy decreases as more characters are added but the most significant decreases result from the addition of taxa. Retention Index and Homoplasy Excess Ratio remain relatively constant with changes in taxa and character number. Our sampling of larger datasets confirms that the positive relationship between dataset size and homoplasy is primarily caused by an increase in taxa, not an increase in characters. Genealogies of cladistic data matrices for early vertebrates, scalidophorans and crocodilians, which have been modified in succession, show a trend of generally consistent quality through research time. Thus, we find no support for the widely shared conjecture that in the search for phylogenetic resolution, high quality phylogenetic characters are quickly exhausted, with subsequent research leading to the inclusion of potentially misleading characters exhibiting high levels of homoplasy.

中文翻译：

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形态学数据中同质性的经验分布

形态特征的分支数据集由与潜在系统发育假设表现出不同程度一致性的观察组成，反映了特征状态（高度一致的特征）的获取和保留，或特征状态的收敛进化和丢失（不太一致的特征）。系统发育历史和个体特征历史之间的一致性与进化过程和从形态学数据推断系统发育历史的相对容易程度有关。我们调查了 486 个四足动物形态分支数据集，以建立字符和数据集之间一致性的经验分布。随着时间的推移，平均数据集大小在字符数和分类群方面有所增加。随着更多字符的添加，同质性的一致性指数测量值下降，但最显着的下降是由于添加了分类群。随着分类群和特征数量的变化，保留指数和同质性过剩率保持相对恒定。我们对较大数据集的抽样证实，数据集大小和同质性之间的正相关主要是由分类群的增加而不是字符的增加引起的。早期脊椎动物、鳞甲类和鳄鱼类的分支数据矩阵的谱系经过连续修改，显示出随着研究时间的推移质量普遍一致的趋势。因此，我们发现没有支持广泛共享的猜想，即在寻找系统发育分辨率时，高质量的系统发育特征很快就会耗尽，