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（Metazoans）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构成的复杂生活史。就此而言，生活史复杂度的演化可推动表型多样性的产生。然而，生活史各阶段间的关联会对部分结构与功能的演化形成制约。尽管生活史演化具备潜在的宏演化后果，但目前鲜有研究检验生活史演化对跨类群性状分化格局的影响。本研究发现，相较于拥有复杂水生-陆生双相型（biphasic）生活史的支系，具备简单专水生幼态持续型（paedomorphic）生活史的蝾螈幼体和成体，其脊柱与体型形态的演化速率显著提升。相较于幼体生态，生活史复杂度的差异能更好地解释脊柱数量与成体体型形态的变异。此外，本研究还发现，拥有简单专陆生直接发育型（direct developing）生活史的支系，其成体体型形态的演化速率同样高于双相型支系，但仍仅为专水生支系的十分之一。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变，这一现象或反映了潜藏的阶段依赖性制约机制。