Data from: Evidence for complex life cycle constraints on salamander body form diversification

Metazoans display a tremendous diversity of developmental patterns, including complex life cycles composed of morphologically disparate stages. In this regard, the evolution of life cycle complexity promotes phenotypic diversity. However, correlations between life cycle stages can constrain the evolution of some structures and functions. Despite the potential macroevolutionary consequences, few studies have tested the impacts of life cycle evolution on broad-scale patterns of trait diversification. Here we show that larval and adult salamanders with a simple, aquatic-only (paedomorphic) life cycle had an increased rate of vertebral column and body form diversification compared to lineages with a complex, aquatic-terrestrial (biphasic) life cycle. These differences in life cycle complexity explain the variations in vertebral number and adult body form better than larval ecology. In addition, we found that lineages with a simple terrestrial-only (direct developing) life cycle also had a higher rate of adult body form evolution than biphasic lineages, but still 10-fold lower than aquatic-only lineages. Our analyses demonstrate that prominent shifts in phenotypic evolution can follow long-term transitions in life cycle complexity, which may reflect underlying stage-dependent constraints.

后生动物（Metazoa）展现出极为丰富的发育模式多样性，涵盖由形态迥异的发育阶段组成的复杂生活史周期。在此背景下，生活史复杂度的演化可推动表型多样性的形成。然而，生活史各阶段间的关联性可能会限制部分结构与功能的演化。尽管生活史演化具备潜在的宏观演化效应，但目前鲜有研究检验其对性状分化大尺度格局的影响。本研究显示，相较于具有复杂水-陆双相型（biphasic）生活史的支系，仅营水生生活的幼态持续型（paedomorphic）生活史蝾螈，其脊柱与体型的演化速率显著更高。相较于幼体生态，生活史复杂度的差异能够更有效地解释脊柱数量与成体体型的变异。此外，本研究发现仅营陆生生活的直接发育型（direct developing）生活史支系，其成体体型的演化速率同样高于双相型支系，但仍仅为仅水生支系的1/10。本研究的分析结果表明，表型演化的显著转变可伴随生活史复杂度的长期转型，这一现象或反映了潜藏的阶段依赖性约束机制。