Sánchez-Reyes Luna L, Morlon Hélène, Magallón Susana
Instituto de Biología, Universidad Nacional Autónoma de México, 3er Circuito de Ciudad Universitaria, Coyoacán, Ciudad de México 04510, México.
Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Av. Universidad 3000, Coyoacán, Ciudad de México 04510, México.
Syst Biol. 2017 May 1;66(3):367-378. doi: 10.1093/sysbio/syw088.
The relationship between clade age and species richness has been increasingly used in macroevolutionary studies as evidence for ecologically versus time-dependent diversification processes. However, theory suggests that phylogenetic structure, age type (crown or stem age), and taxonomic delimitation can affect estimates of the age-richness correlation (ARC) considerably. We currently lack an integrative understanding of how these different factors affect ARCs, which in turn, obscures further interpretations. To assess its informative breadth, we characterize ARC behavior with simulated and empirical phylogenies, considering phylogenetic structure and both crown and stem ages. First, we develop a two-state birth-death model to simulate phylogenies including the origin of higher taxa and a hierarchical taxonomy to determine ARC expectations under ecologically and time-dependent diversification processes. Then, we estimate ARCs across various taxonomic ranks of extant amphibians, squamate reptiles, mammals, birds, and flowering plants. We find that our model reproduces the general ARC trends of a wide range of biological systems despite the particularities of taxonomic practice within each, suggesting that the model is adequate to establish a framework of ARC null expectations for different diversification processes when taxa are defined with a hierarchical taxonomy. ARCs estimated with crown ages were positive in all the scenarios we studied, including ecologically dependent processes. Negative ARCs were only found at less inclusive taxonomic ranks, when considering stem age, and when rates varied among clades. This was the case both in ecologically and time-dependent processes. Together, our results warn against direct interpretations of single ARC estimates and advocate for a more integrative use of ARCs across age types and taxonomic ranks in diversification studies. [Birth-Death models; crown age; diversity dependence; extinction; phylogenetic structure; speciation; stem age; taxonomy; time dependence; tree simulations.].
进化枝年龄与物种丰富度之间的关系在宏观进化研究中越来越多地被用作生态与时间依赖性多样化过程的证据。然而，理论表明系统发育结构、年龄类型（冠龄或茎龄）和分类界定会显著影响年龄-丰富度相关性（ARC）的估计。我们目前缺乏对这些不同因素如何影响ARC的综合理解，这反过来又阻碍了进一步的解释。为了评估其信息广度，我们通过模拟和实证系统发育来刻画ARC行为，同时考虑系统发育结构以及冠龄和茎龄。首先，我们开发了一个两状态生死模型来模拟包括高级分类单元起源的系统发育，并构建一个层次分类法来确定生态和时间依赖性多样化过程下的ARC预期。然后，我们估计现存两栖动物、有鳞类爬行动物、哺乳动物、鸟类和开花植物在不同分类等级上的ARC。我们发现，尽管每个分类体系内存在分类实践的特殊性，但我们的模型再现了广泛生物系统的一般ARC趋势，这表明当用层次分类法定义分类单元时，该模型足以建立不同多样化过程的ARC零预期框架。在我们研究的所有情景中，包括生态依赖过程，用冠龄估计的ARC都是正的。只有在考虑茎龄、分类等级较低且各进化枝速率不同时，才会发现负的ARC。在生态和时间依赖性过程中都是如此。总之，我们的结果警示不要直接解读单个ARC估计值，并提倡在多样化研究中更综合地使用不同年龄类型和分类等级的ARC。[生死模型；冠龄；多样性依赖性；灭绝；系统发育结构；物种形成；茎龄；分类学；时间依赖性；树模拟。]
