Wills Matthew A, Barrett Paul M, Heathcote Julia F
Department of Biology and Biochemistry, The University of Bath, Claverton Down, Bath, UK.
Syst Biol. 2008 Dec;57(6):891-904. doi: 10.1080/10635150802570809.
Palaeontologists routinely map their cladograms onto what is known of the fossil record. Where sister taxa first appear as fossils at different times, a ghost range is inferred to bridge the gap between these dates. Some measure of the total extent of ghost ranges across the tree underlies several indices of cladistic/stratigraphic congruence. We investigate this congruence for 19 independent, published cladograms of major dinosaur groups and report exceptional agreement between the phylogenetic and stratigraphic patterns, evidenced by sums of ghost ranges near the theoretical minima. This implies that both phylogenetic and stratigraphic data reflect faithfully the evolutionary history of dinosaurs, at least for the taxa included in this study. We formally propose modifications to an existing index of congruence (the gap excess ratio; GER), designed to remove a bias in the range of values possible with trees of different shapes. We also propose a more informative index of congruence--GER*--that takes account of the underlying distribution of sums of ghost ranges possible when permuting stratigraphic range data across the tree. Finally, we incorporate data on the range of possible first occurrence dates into our estimates of congruence, extending a procedure originally implemented with the modified Manhattan stratigraphic measure and GER to our new indices. Most dinosaur data sets maintain extremely high congruence despite such modifications.
古生物学家通常会将他们的分支图映射到已知的化石记录上。当姊妹分类单元首次作为化石出现在不同时间时，就会推断出一个幽灵区间来填补这些日期之间的空白。整个分支图中幽灵区间的某种总量度量是几种分支/地层一致性指标的基础。我们研究了19个已发表的主要恐龙类群独立分支图的这种一致性，并报告了系统发育模式和地层模式之间的高度一致性，这由幽灵区间总和接近理论最小值所证明。这意味着系统发育数据和地层数据都忠实地反映了恐龙的进化历史，至少对于本研究中包含的分类单元是这样。我们正式提议对现有的一致性指标（间隙过剩比率；GER）进行修改，旨在消除不同形状的分支图可能出现的值范围中的偏差。我们还提出了一个更具信息量的一致性指标——GER*——它考虑了在整个分支图中排列地层范围数据时幽灵区间总和的潜在分布。最后，我们将可能的首次出现日期范围的数据纳入我们的一致性估计中，将最初用修改后的曼哈顿地层度量和GER实施的程序扩展到我们的新指标。尽管有这些修改，大多数恐龙数据集仍保持着极高的一致性。
