PHENETIC CLASSIFICATION OF LEAF FLORAS: A COMPARATIVE EXPERIMENT

Classification of plant ecosystems is a difficult task that has occupied many of the great plant ecologists of the early twentieth century, and the proliferation of personal computers since the 1980s has not yet had nearly the impact upon ecological classification that is has upon systematics. This paper describes a comparative experiment that applies a number of phenetic (clustering) algorithms to modern and fossil leaf floras numerically described by two sets of leaf architectural variables, one from the Climate Leaf Analysis Multivariate Program (Wolfe, 1993), and one from the cataloging system of the Compendium Index of North American Fossil Plants at Yale University (Ash et al., 1999). The classifications produced by these different sets of variables are similar and reflect what is known about the ecologies of the floras analyzed. This implies that the ecological signal from leaf architecture is insensitive to the method of quantitative leaf description and strong enough to be heard despite taphonomic or methodological biases.

References: Ash, A., B. Ellis, L. J. Hickey, K. Johnson, P. Wilf, and S. Wing (1999) Manual of Leaf Architecture: Morphological Description of Dicotyledonous and Net-Veined Monocotyledonous Angiosperms. Privately published and distributed. Washington, D.C.: Smithsonian Institution. Wolfe, J. A. (1993) A method of obtaining climatic parameters from leaf assemblages. U.S. Geol. Surv. Bull. 2040:1-73.