Abstract Contemporary methods for visualizing phenotypic evolution, such as phylomorphospaces, often reveal patterns which depart strongly from a naïve expectation of consistently divergent branching and expansion. Instead, branches regularly crisscross as convergence, reversals, or other forms of homoplasy occur, forming patterns described as “birds’ nests”, “flies in vials”, or less elegantly, “a mess”. In other words, the phenotypic tree of life often appears highly tangled. Various explanations are given for this, such as differential degrees of developmental constraint, adaptation, or lack of adaptation. However, null expectations for the magnitude of disorder or “tangling” have never been established, so it is unclear which or even whether various evolutionary factors are required to explain messy patterns of evolution. I simulated evolution along phylogenies under a number of varying parameters (number of taxa and number of traits) and models (Brownian motion, Ornstein–Uhlenbeck (OU)-based, early burst, and character displacement (CD)] and quantified disorder using 2 measures. All models produce substantial amounts of disorder. Disorder increases with tree size and the number of phenotypic traits. OU models produced the largest amounts of disorder—adaptive peaks influence lineages to evolve within restricted areas, with concomitant increases in crossing of branches and density of evolution. Large early changes in trait values can be important in minimizing disorder. CD consistently produced trees with low (but not absent) disorder. Overall, neither constraints nor a lack of adaptation is required to explain messy phylomorphospaces—both stochastic and deterministic processes can act to produce the tantalizingly tangled phenotypic tree of life.

中文翻译：

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我们的系统形态空间图是否如此错综复杂？自适应和非自适应模型下模拟数据的无序调查

摘要 用于可视化表型进化的当代方法，例如系统形态空间，通常揭示出的模式与持续发散分支和扩展的天真预期强烈背离。取而代之的是，随着收敛、反转或其他形式的同质性发生，分支会定期交叉，形成被描述为“鸟巢”、“小瓶中的苍蝇”或不那么优雅的“一团糟”的模式。换句话说，生命的表型树经常显得高度纠结。对此给出了各种解释，例如不同程度的发展约束、适应或缺乏适应。然而，对于无序或“缠结”程度的零预期从未建立，因此尚不清楚需要哪些甚至是否需要各种进化因素来解释混乱的进化模式。