Tabachnick R Elena, Bookstein Fred L
Department of Geological Sciences and Museum of Paleontology, University of Michigan, Ann Arbor, MI, 48109.
Center for Human Growth and Development, University of Michigan, Ann Arbor, MI, 48109.
Evolution. 1990 Mar;44(2):416-434. doi: 10.1111/j.1558-5646.1990.tb05209.x.
Analysis of probability distributions of individual organisms provides a common language to describe synchronic and diachronic diversity. When based on an appropriate quantitative description of morphology, this language can be used to explore the temporal component of diversity embedded in the fossil record. Miocene Globorotalia (planktonic foraminifera) from Deep Sea Drilling Project site 593 are described using two-point registration of landmarks in two views (spiral and apertural) and medial-axis analysis of the shape of the final chamber. The equiangular spiral parameters Θ (the angle of increment), r (the expansion rate), and t (the rate of translation down the spiral axis) appear as principal components of the landmark data. Chamber shape variation is described by three principal components of medial-axis curvature. Partial-least-squares analysis demonstrates that the first components of within-morphospace variation also explain the patterns of correlation between the landmark and chamber-shape morphospaces. In the landmark morphospaces, the distribution of sampled individuals is continuous and roughly elliptical with few stratigraphic changes. In the chamber-shape morphospace, the distribution is continuous but shows complex features beyond the elliptical; the occupied morphospace changes stratigraphically, but neither strict cladogenesis nor strict anagenesis explains the derivation of new morphologies. Exemplars of named morphospecies are scattered across these spaces with continuous variation among all forms. These names cannot be assumed to represent discrete entities.
对个体生物概率分布的分析提供了一种描述同步和历时多样性的通用语言。当基于对形态的适当定量描述时，这种语言可用于探索化石记录中所蕴含的多样性的时间成分。利用两个视图（螺旋视图和开口视图）中的地标两点配准以及末室形状的中轴线分析，对深海钻探计划593站点的中新世环球圆扁螺（浮游有孔虫）进行了描述。等角螺旋参数Θ（增量角）、r（膨胀率）和t（沿螺旋轴向下平移的速率）表现为地标数据的主成分。室形状变化由中轴线曲率的三个主成分来描述。偏最小二乘分析表明，形态空间内变异的第一主成分也解释了地标形态空间和室形状形态空间之间的相关模式。在地标形态空间中，采样个体的分布是连续的，大致呈椭圆形，地层变化较少。在室形状形态空间中，分布是连续的，但呈现出超出椭圆形的复杂特征；占据的形态空间随地层变化，但严格的分支发生或严格的前进演化都无法解释新形态的衍生。命名形态种的标本散布在这些空间中，所有形态之间存在连续变异。不能假定这些名称代表离散的实体。
