Department of Biological Science, University of Tulsa, Tulsa, OK 74104
Department of Biological Science, University of Tulsa, Tulsa, OK 74104.
Proc Natl Acad Sci U S A. 2017 Sep 12;114(37):9936-9941. doi: 10.1073/pnas.1703877114. Epub 2017 Aug 29.
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.
后生动物表现出极大的发育模式多样性，包括由形态不同的阶段组成的复杂生命周期。在这方面，生命周期复杂性的进化促进了表型多样性。然而，生命周期阶段之间的相关性可能会限制某些结构和功能的进化。尽管具有潜在的宏观进化后果，但很少有研究测试生命周期进化对特征多样化的广泛模式的影响。在这里，我们表明，具有简单的、仅水生（幼态成熟的）生命周期的幼虫和成年蝾螈与具有复杂的、水生-陆生（双相的）生命周期的谱系相比，具有更高的脊柱和身体形态多样化的速度。生命周期复杂性的这些差异比幼虫生态更好地解释了椎骨数量和成年身体形态的变化。此外，我们发现，具有简单的仅陆生（直接发育）生命周期的谱系的成年身体形态进化速度也高于双相谱系，但仍比仅水生谱系低 10 倍。我们的分析表明，表型进化的显著转变可以遵循生命周期复杂性的长期转变，这可能反映了潜在的阶段依赖性限制。
