Sepkoski J J, Kendrick D C
Department of the Geophysical Sciences, University of Chicago, Illinois 60637, USA.
Paleobiology. 1993;19(2):168-84. doi: 10.1017/s0094837300015852.
The problem of how accurately paraphyletic taxa versus monophyletic (i.e., holophyletic) groups (clades) capture underlying species patterns of diversity and extinction is explored with Monte Carlo simulations. Phylogenies are modeled as stochastic trees. Paraphyletic taxa are defined in an arbitrary manner by randomly choosing progenitors and clustering all descendants not belonging to other taxa. These taxa are then examined to determine which are clades, and the remaining paraphyletic groups are dissected to discover monophyletic subgroups. Comparisons of diversity patterns and extinction rates between modeled taxa and lineages indicate that paraphyletic groups can adequately capture lineage information under a variety of conditions of diversification and mass extinction. This suggests that these groups constitute more than mere "taxonomic noise" in this context. But, strictly monophyletic groups perform somewhat better, especially with regard to mass extinctions. However, when low levels of paleontologic sampling are simulated, the veracity of clades deteriorates, especially with respect to diversity, and modeled paraphyletic taxa often capture more information about underlying lineages. Thus, for studies of diversity and taxic evolution in the fossil record, traditional paleontologic genera and families need not be rejected in favor of cladistically-defined taxa.
通过蒙特卡罗模拟，探讨了并系分类群与单系（即全系）类群（分支）在多大程度上准确反映了潜在的物种多样性和灭绝模式的问题。系统发育被建模为随机树。并系分类群通过随机选择祖先并将所有不属于其他分类群的后代聚类，以任意方式定义。然后检查这些分类群，以确定哪些是分支，其余的并系类群被剖析以发现单系亚群。对建模的分类群和谱系之间的多样性模式和灭绝率进行比较表明，在各种多样化和大规模灭绝的条件下，并系类群能够充分捕捉谱系信息。这表明在这种情况下，这些类群不仅仅构成单纯的“分类噪声”。但是，严格的单系类群表现稍好一些，尤其是在大规模灭绝方面。然而，当模拟低水平的古生物学采样时，分支的准确性会下降，尤其是在多样性方面，并且建模的并系分类群通常能捕捉到更多关于潜在谱系的信息。因此，对于化石记录中的多样性和分类演化研究，传统的古生物学属和科不必被摒弃而支持基于分支定义的分类群。
