title: Reading the leaves: A comparison of leaf rank and automated areole measurement for quantifying aspects of leaf venation.
abstract: The reticulate venation that is characteristic of a dicot leaf has excited interest from systematists for more than a century, and from physiological and developmental botanists for decades. The tools of digital image acquisition and computer image analysis, however, are only now approaching the sophistication needed to quantify aspects of the venation network found in real leaves quickly, easily, accurately, and reliably enough to produce biologically meaningful data. In this paper, we examine 120 leaves distributed across vascular plants (representing 118 genera and 80 families) using two approaches: a semiquantitative scoring system called "leaf ranking," devised by the late Leo Hickey, and an automated image-analysis protocol. In the process of comparing these approaches, we review some methodological issues that arise in trying to quantify a vein network, and discuss the strengths and weaknesses of automatic data collection and human pattern recognition. We conclude that subjective leaf rank provides a relatively consistent, semiquantitative measure of areole size among other variables; that modal areole size is generally consistent across large sections of a leaf lamina; and that both approaches-semiquantitative, subjective scoring; and fully quantitative, automated measurement-have appropriate places in the study of leaf venation.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138 USA.
authors.forename: Walton A
authors.initials: WA
authors.lastname: Green
authors.affiliation: Department of Plant Sciences, University of California, Davis, One Shields Avenue, Davis, California 95616 USA.
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Little
authors.affiliation: School of Plant Biology, University of Western Australia (M084), 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Price
authors.affiliation: Department of Paleobiology, Natural Museum of Natural History, Smithsonian Institution, P.O. Box 37012 MRC 121, Washington, D.C. 20013-7012 USA.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Wing
authors.affiliation: Department of Earth and Environmental Sciences and Museum of Paleontology, University of Michigan, 2534 CC Little Bldg., 1100 North University Ave., Ann Arbor, Michigan 48109-1005 USA.
authors.forename: Selena Y
authors.initials: SY
authors.lastname: Smith
authors.affiliation: Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Kotrc
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, Connecticut 06511 USA.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Doria
keywords: automated image quantification; leaf architecture; leaf rank; leaf venation; repeatability