Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94766, 1090 GT Amsterdam, The Netherlands.
Integr Comp Biol. 2003 Feb;43(1):207-18. doi: 10.1093/icb/43.1.207.
The accumulation of multiple phylogenetic hypotheses for the Metazoa invites an evaluation of current progress in the field. I discuss three case studies from the recent literature to assess how cladistic analyses of metazoan morphology have contributed to our understanding of animal evolution. The first case study on cleavage cross patterns examines whether a decade of unanimous character scoring across different cladistic studies can be considered a reliable indicator of accumulated wisdom. The two remaining case studies illustrate how the unique strength of cladistic analyses to arbitrate between competing hypotheses can be crippled when insufficient attention is directed towards the construction of the data matrix. The second case study discusses a recent morphological cladistic analysis aimed at providing insight into the evolution of larval ciliary bands (prototrochs) in the Spiralia, and the third case study evaluates how four subsequent morphological cladistic analyses have contributed to our understanding of the phylogenetic placement of a problematicum, the Myzostomida. I conclude that current phylogenetic analyses of the Metazoa have not fully exploited the power of cladistics to test available alternative hypotheses. If our goal is to generate genuine progress in understanding rather than stochastic variation of opinions through time, we have to shift our attention from using cladistics as an easy tool to generate "novel" hypotheses of metazoan relationships, towards employing cladistics more critically as an effective instrument to test the relative merit of available multiple alternative hypotheses.
后生动物多个系统发育假说的积累促使人们对该领域的当前进展进行评估。我将讨论最近文献中的三个案例研究，以评估后生动物形态的分支分析如何有助于我们理解动物进化。第一个关于卵裂横缢模式的案例研究检验了在不同分支分析研究中一致的特征评分是否可以被认为是积累智慧的可靠指标。其余两个案例研究说明了分支分析在解决相互竞争的假说方面的独特优势如何会因对数据矩阵构建的重视不足而受到限制。第二个案例研究讨论了最近进行的旨在深入了解螺旋动物幼虫纤毛带（原担轮）进化的形态分支分析，第三个案例研究评估了随后的四个形态分支分析如何有助于我们理解一个有争议的 Myzostomida 的系统发育位置。我得出结论，后生动物的当前分支分析尚未充分利用分支分析来检验现有替代假说的力量。如果我们的目标是通过时间产生真正的理解进展，而不是随机变化的意见，我们必须将注意力从将分支分析作为生成后生动物关系“新颖”假说的简单工具转移到更批判性地使用分支分析作为检验现有多个替代假说的相对价值的有效工具。
