The importance of phylogenetic analysis for the assessment of species turnover: a case history of Paleocene mammals in North America
The importance of phylogenetic analysis for the assessment of species turnover: a case history of Paleocene mammals in North America
复制标题
系统发育分析对于评估物种更替的重要性：北美古新世哺乳动物的案例史
作者：
J. Archibald
在白垩纪末和古新世期间，北美洲西部哺乳动物的消失率与出现率相同，两者都在古新世早期（Puercan）非鸟类恐龙灭绝后达到顶峰。在此期间的一些消失是由于祖先物种在物种形成过程中消失而导致的伪灭绝。物种水平的分支分析和约束良好的生物地层学框架需要研究这种形式的假灭绝。分支系统学分析表明，单系不能建立或拒绝一些物种，因为这些物种缺乏autapomorphies（唯一衍生的字符状态），团结他们的组成成员。这样的分类群，被称为元种，是物种和更高分支的潜在祖先，它们在分支图中共享一个节点。一个假设的物种水平的支序分析加上三个不同的假设生物地层显示不同的模式的物种形成（分叉，萌芽，或anagenesis）的结果非常不同的模式，真正与假灭绝。根据物种形成模型，真正的灭绝可能被高估了四倍，从而引发了大规模灭绝的幽灵。物种水平的研究，三个早期第三纪哺乳动物类群带齿真兽，taeniolabidid multituberculates，和periptychid有蹄类动物使用相同的程序。他们表明，在古新世早期（Puercan）的物种分析中，几乎25%的消失是metaspecies的伪灭绝。在这三个例子中，我们看到了萌芽和无性生殖样的周边物种形成，但没有分叉。将消失等同于真正的灭绝会深刻影响对动物更替的解释，特别是在大规模灭绝或重大动物重组期间。一些作者用假灭绝来描述非单系类群在分类学上而不是进化上的消失。这里所说的假绝灭，仅仅是指通过物种形成而导致的元种的进化消失。这两种用法似乎都很恰当，但不应混淆。
During the latest Cretaceous and the Paleocene in western North America, disappearance rates for mammalian genera track appearance rates, both reaching their peak in the early Paleocene (Puercan) following the extinction of non-avian dinosaurs. Some of the disappearances during this time were pseudoextinctions that resulted when ancestral species disappeared during speciation. Species-level cladistic analyses and a well-constrained biostratigraphic framework are required to study this form of pseudoextinction. Cladistic analyses show that monophyly cannot be established or rejected for some species because these species lack autapomorphies (uniquely derived character states) that unite their constituent members. Such taxa, termed metaspecies, are potential ancestors to species and higher clades with which they share a node in the cladogram. A hypothetical species-level cladistic analysis coupled with three different hypothetical biostratigraphies shows how different models of speciation (bifurcation, budding, or anagenesis) result in very different patterns of true versus pseudoextinction. Depending on the speciation model, true extinction can be overestimated by as much as a factor of four, raising the specter of mass extinction. Species-level studies for three early Tertiary mammalian taxa—taeniodont eutherians, taeniolabidid multituberculates, and periptychid ungulates—use the same procedures. They show that almost 25% of disappearances during the early Paleocene (Puercan) for species in the analysis were pseudoextinctions of metaspecies. Budding and anagenetic-like peripatric speciation, but not bifurcation, are seen in the three examples. Equating disappearance to true extinction can profoundly affect interpretations of faunal turnover, especially during mass extinctions or major faunal reorganizations. Some authors use pseudoextinction to describe the taxonomic rather than evolutionary disappearance of nonmonophyletic groups. Pseudoextinction, as used here refers only to the evolutionary disappearance of metaspecies via speciation. Both usages seem appropriate but should not be confounded.