Institute for Genomics and Evolutionary Medicine, Temple University, Philadelphia, PA, 19122, USA.
Department of Biology, Temple University, Philadelphia, PA, 19122, USA.
BMC Ecol Evol. 2021 May 12;21(1):83. doi: 10.1186/s12862-021-01798-6.
Matrices of morphological characters are frequently used for dating species divergence times in systematics. In some studies, morphological and molecular character data from living taxa are combined, whereas others use morphological characters from extinct taxa as well. We investigated whether morphological data produce time estimates that are concordant with molecular data. If true, it will justify the use of morphological characters alongside molecular data in divergence time inference.
We systematically analyzed three empirical datasets from different species groups to test the concordance of species divergence dates inferred using molecular and discrete morphological data from extant taxa as test cases. We found a high correlation between their divergence time estimates, despite a poor linear relationship between branch lengths for morphological and molecular data mapped onto the same phylogeny. This was because node-to-tip distances showed a much higher correlation than branch lengths due to an averaging effect over multiple branches. We found that nodes with a large number of taxa often benefit from such averaging. However, considerable discordance between time estimates from molecules and morphology may still occur as some intermediate nodes may show large time differences between these two types of data.
Our findings suggest that node- and tip-calibration approaches may be better suited for nodes with many taxa. Nevertheless, we highlight the importance of evaluating the concordance of intrinsic time structure in morphological and molecular data before any dating analysis using combined datasets.
形态特征矩阵常用于系统发育学中的物种分歧时间估计。在一些研究中，将来自活体分类群的形态和分子特征数据结合在一起，而另一些研究则使用已灭绝分类群的形态特征。我们研究了形态数据是否产生与分子数据一致的时间估计。如果是这样，它将证明在分歧时间推断中使用形态特征与分子数据是合理的。
我们系统地分析了来自不同物种群的三个经验数据集，以检验使用来自现存分类群的分子和离散形态数据推断物种分歧日期的一致性，作为测试案例。尽管映射到同一系统发育树上的形态和分子数据的分支长度之间存在较差的线性关系，但我们发现它们的分歧时间估计值高度相关。这是因为由于多个分支的平均效应，节点到尖端的距离比分支长度显示出更高的相关性。我们发现，具有大量分类群的节点通常受益于这种平均化。然而，分子和形态之间的时间估计可能仍然存在相当大的差异，因为在这两种数据类型之间，一些中间节点可能显示出较大的时间差异。
我们的研究结果表明，节点和尖端校准方法可能更适合具有大量分类群的节点。然而，我们强调在使用组合数据集进行任何约会分析之前，评估形态和分子数据中内在时间结构的一致性的重要性。
