Hagen Oskar, Hartmann Klaas, Steel Mike, Stadler Tanja
Institute of Integrative Biology, ETH Zürich, Universitätsstr. 16, 8092 Zürich, Switzerland; Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, Tasmania 7001, Australia; Allan Wilson Centre for Molecular Ecology and Evolution, Biomathematics Research Centre, University of Canterbury, Christchurch 8140, New Zealand; and Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.
Institute of Integrative Biology, ETH Zürich, Universitätsstr. 16, 8092 Zürich, Switzerland; Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, Tasmania 7001, Australia; Allan Wilson Centre for Molecular Ecology and Evolution, Biomathematics Research Centre, University of Canterbury, Christchurch 8140, New Zealand; and Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland Institute of Integrative Biology, ETH Zürich, Universitätsstr. 16, 8092 Zürich, Switzerland; Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 49, Hobart, Tasmania 7001, Australia; Allan Wilson Centre for Molecular Ecology and Evolution, Biomathematics Research Centre, University of Canterbury, Christchurch 8140, New Zealand; and Department of Biosystems Science and Engineering, ETH Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
Syst Biol. 2015 May;64(3):432-40. doi: 10.1093/sysbio/syv001. Epub 2015 Jan 8.
Tens of thousands of phylogenetic trees, describing the evolutionary relationships between hundreds of thousands of taxa, are readily obtainable from various databases. From such trees, inferences can be made about the underlying macroevolutionary processes, yet remarkably these processes are still poorly understood. Simple and widely used evolutionary null models are problematic: Empirical trees show very different imbalance between the sizes of the daughter clades of ancestral taxa compared to what models predict. Obtaining a simple evolutionary model that is both biologically plausible and produces the imbalance seen in empirical trees is a challenging problem, to which none of the existing models provide a satisfying answer. Here we propose a simple, biologically plausible macroevolutionary model in which the rate of speciation decreases with species age, whereas extinction rates can vary quite generally. We show that this model provides a remarkable fit to the thousands of trees stored in the online database TreeBase. The biological motivation for the identified age-dependent speciation process may be that recently evolved taxa often colonize new regions or niches and may initially experience little competition. These new taxa are thus more likely to give rise to further new taxa than a taxon that has remained largely unchanged and is, therefore, well adapted to its niche. We show that age-dependent speciation may also be the result of different within-species populations following the same laws of lineage splitting to produce new species. As the fit of our model to the tree database shows, this simple biological motivation provides an explanation for a long standing problem in macroevolution.
数以万计描述了数十万分类单元之间进化关系的系统发育树，可从各种数据库中轻松获取。从这些树中，可以推断出潜在的宏观进化过程，但值得注意的是，这些过程仍然知之甚少。简单且广泛使用的进化零模型存在问题：与模型预测相比，实证树显示出祖先分类单元的子分支大小之间的不平衡非常不同。获得一个既具有生物学合理性又能产生实证树中所见不平衡的简单进化模型是一个具有挑战性的问题，现有模型均未对此提供令人满意的答案。在此，我们提出一个简单且具有生物学合理性的宏观进化模型，其中物种形成速率随物种年龄降低，而灭绝速率则可能普遍变化。我们表明，该模型与在线数据库TreeBase中存储的数千棵树非常吻合。所确定的年龄依赖性物种形成过程的生物学动机可能是，最近进化的分类单元通常会开拓新的区域或生态位，并且最初可能几乎没有竞争。因此，这些新分类单元比一个基本保持不变且因此很好地适应其生态位的分类单元更有可能产生更多新的分类单元。我们还表明，年龄依赖性物种形成也可能是同一物种内不同种群遵循相同的谱系分裂规律以产生新物种的结果。正如我们的模型与树数据库的拟合所示，这种简单的生物学动机为宏观进化中一个长期存在的问题提供了解释。
